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Wednesday, February 2, 2022

Ecosystem service

From Wikipedia, the free encyclopedia
 
Honey bee on Avocado crop. Pollination is just one type of ecosystem service.
 
Upland bog in Wales, forming the official source of the River Severn. Healthy bogs sequester carbon, hold back water thereby reducing flood risk, and supply cleaned water better than degraded habitats do.
 
Social forestry in Andhra Pradesh, India, providing fuel, soil protection, shade and even well-being to travellers.

Ecosystem services are the many and varied benefits to humans provided by the natural environment and from healthy ecosystems. Such ecosystems include, for example, agroecosystems, forest ecosystems, grassland ecosystems and aquatic ecosystems. These ecosystems, functioning in healthy relationship, offer such things like natural pollination of crops, clean air, extreme weather mitigation, and human mental and physical well-being. Collectively, these benefits are becoming known as 'ecosystem services', and are often integral to the provisioning of clean drinking water, the decomposition of wastes, and resilience and productivity of food ecosystems.

While scientists and environmentalists have discussed ecosystem services implicitly for decades, the Millennium Ecosystem Assessment (MA) in the early 2000s popularized this concept. There, ecosystem services are grouped into four broad categories: provisioning, such as the production of food and water; regulating, such as the control of climate and disease; supporting, such as nutrient cycles and oxygen production; and cultural, such as spiritual and recreational benefits. To help inform decision-makers, many ecosystem services are being valuated in order to draw equivalent comparisons to human engineered infrastructure and services.

Estuarine and coastal ecosystems are both marine ecosystems. Together, these ecosystems perform the four categories of ecosystem services in a variety of ways: "Regulating services" include climate regulation as well as waste treatment and disease regulation and buffer zones. The "provisioning services" include forest products, marine products, fresh water, raw materials, biochemical and genetic resources. "Cultural services" of coastal ecosystems include inspirational aspects, recreation and tourism, science and education. "Supporting services" of coastal ecosystems include nutrient cycling, biologically mediated habitats and primary production.

Definition

Ecosystem services are defined as the gains acquired by humankind from surroundings ecosystems. Per the 2006 Millennium Ecosystem Assessment (MA), ecosystem services are "the benefits people obtain from ecosystems". The MA also delineated the four categories of ecosystem services—supporting, provisioning, regulating and cultural—discussed below.

By 2010, there had evolved various working definitions and descriptions of ecosystem services in the literature. To prevent double counting in ecosystem services audits, for instance, The Economics of Ecosystems and Biodiversity (TEEB) replaced "Supporting Services" in the MA with "Habitat Services" and "ecosystem functions", defined as "a subset of the interactions between ecosystem structure and processes that underpin the capacity of an ecosystem to provide goods and services".

Categories

Detritivores like this dung beetle help to turn animal wastes into organic material that can be reused by primary producers.

Four different types of ecosystem services have been distinguished by the scientific body: regulating services, provisioning services, cultural services and supporting services. An ecosystem does not necessarily offer all four types of services simultaneously; but given the intricate nature of any ecosystem, it is usually assumed that humans benefit from a combination of these services. The services offered by diverse types of ecosystems (forests, seas, coral reefs, mangroves, etc.) differ in nature and in consequence. In fact, some services directly affect the livelihood of neighboring human populations (such as fresh water, food or aesthetic value, etc.) while other services affect general environmental conditions by which humans are indirectly impacted (such as climate change, erosion regulation or natural hazard regulation, etc.).

The Millennium Ecosystem Assessment report 2005 defined ecosystem services as benefits people obtain from ecosystems and distinguishes four categories of ecosystem services, where the so-called supporting services are regarded as the basis for the services of the other three categories.

Regulating services

Provisioning services

The following services are also known as ecosystem goods:

  • food (including seafood and game), crops, wild foods, and spices
  • raw materials (including lumber, skins, fuel wood, organic matter, fodder, and fertilizer)
  • genetic resources (including crop improvement genes, and health care)
  • biogenic minerals
  • medicinal resources (including pharmaceuticals, chemical models, and test and assay organisms)
  • energy (hydropower, biomass fuels)
  • ornamental resources (including fashion, handicraft, jewelry, pets, worship, decoration and souvenirs like furs, feathers, ivory, orchids, butterflies, aquarium fish, shells, etc.)

Cultural services

  • cultural (including use of nature as motif in books, film, painting, folklore, national symbols, advertising, etc.)
  • spiritual and historical (including use of nature for religious or heritage value or natural)
  • recreational experiences (including ecotourism, outdoor sports, and recreation)
  • science and education (including use of natural systems for school excursions, and scientific discovery)
  • Therapeutic (including Ecotherapy, social forestry and animal assisted therapy)

As of 2012, there was a discussion as to how the concept of cultural ecosystem services could be operationalized, how landscape aesthetics, cultural heritage, outdoor recreation, and spiritual significance to define can fit into the ecosystem services approach. who vote for models that explicitly link ecological structures and functions with cultural values and benefits. Likewise, there has been a fundamental critique of the concept of cultural ecosystem services that builds on three arguments:

  1. Pivotal cultural values attaching to the natural/cultivated environment rely on an area's unique character that cannot be addressed by methods that use universal scientific parameters to determine ecological structures and functions.
  2. If a natural/cultivated environment has symbolic meanings and cultural values the object of these values are not ecosystems but shaped phenomena like mountains, lakes, forests, and, mainly, symbolic landscapes.
  3. Cultural values do result not from properties produced by ecosystems but are the product of a specific way of seeing within the given cultural framework of symbolic experience.

The Common International Classification of Ecosystem Services (CICES) is a classification scheme developed to accounting systems (like National counts etc.), in order to avoid double-counting of Supporting Services with others Provisioning and Regulating Services.

Supporting services

These may be redundant with regulating services in some categorisations, but include services such as, but not limited to, nutrient cycling, primary production, soil formation, habitat provision. These services make it possible for the ecosystems to continue providing services such as food supply, flood regulation, and water purification. Slade et al. outline the situation where a greater number of species would maximize more ecosystem services

Ecology

Understanding of ecosystem services requires a strong foundation in ecology, which describes the underlying principles and interactions of organisms and the environment. Since the scales at which these entities interact can vary from microbes to landscapes, milliseconds to millions of years, one of the greatest remaining challenges is the descriptive characterization of energy and material flow between them. For example, the area of a forest floor, the detritus upon it, the microorganisms in the soil, and characteristics of the soil itself will all contribute to the abilities of that forest for providing ecosystem services like carbon sequestration, water purification, and erosion prevention to other areas within the watershed. Note that it is often possible for multiple services to be bundled together and when benefits of targeted objectives are secured, there may also be ancillary benefits—the same forest may provide habitat for other organisms as well as human recreation, which are also ecosystem services.

The complexity of Earth's ecosystems poses a challenge for scientists as they try to understand how relationships are interwoven among organisms, processes and their surroundings. As it relates to human ecology, a suggested research agenda for the study of ecosystem services includes the following steps:

  1. identification of ecosystem service providers (ESPs)—species or populations that provide specific ecosystem services—and characterization of their functional roles and relationships;
  2. determination of community structure aspects that influence how ESPs function in their natural landscape, such as compensatory responses that stabilize function and non-random extinction sequences which can erode it;
  3. assessment of key environmental (abiotic) factors influencing the provision of services;
  4. measurement of the spatial and temporal scales ESPs and their services operate on.

Recently, a technique has been developed to improve and standardize the evaluation of ESP functionality by quantifying the relative importance of different species in terms of their efficiency and abundance. Such parameters provide indications of how species respond to changes in the environment (i.e. predators, resource availability, climate) and are useful for identifying species that are disproportionately important at providing ecosystem services. However, a critical drawback is that the technique does not account for the effects of interactions, which are often both complex and fundamental in maintaining an ecosystem and can involve species that are not readily detected as a priority. Even so, estimating the functional structure of an ecosystem and combining it with information about individual species traits can help us understand the resilience of an ecosystem amidst environmental change.

Many ecologists also believe that the provision of ecosystem services can be stabilized with biodiversity. Increasing biodiversity also benefits the variety of ecosystem services available to society. Understanding the relationship between biodiversity and an ecosystem's stability is essential to the management of natural resources and their services.

Redundancy hypothesis

The concept of ecological redundancy is sometimes referred to as functional compensation and assumes that more than one species performs a given role within an ecosystem. More specifically, it is characterized by a particular species increasing its efficiency at providing a service when conditions are stressed in order to maintain aggregate stability in the ecosystem. However, such increased dependence on a compensating species places additional stress on the ecosystem and often enhances its susceptibility to subsequent disturbance. The redundancy hypothesis can be summarized as "species redundancy enhances ecosystem resilience".

Another idea uses the analogy of rivets in an airplane wing to compare the exponential effect the loss of each species will have on the function of an ecosystem; this is sometimes referred to as rivet popping. If only one species disappears, the loss of the ecosystem's efficiency as a whole is relatively small; however, if several species are lost, the system essentially collapses—similar to an airplane that lost too many rivets. The hypothesis assumes that species are relatively specialized in their roles and that their ability to compensate for one another is less than in the redundancy hypothesis. As a result, the loss of any species is critical to the performance of the ecosystem. The key difference is the rate at which the loss of species affects total ecosystem functioning.

Portfolio effect

A third explanation, known as the portfolio effect, compares biodiversity to stock holdings, where diversification minimizes the volatility of the investment, or in this case, the risk of instability of ecosystem services. This is related to the idea of response diversity where a suite of species will exhibit differential responses to a given environmental perturbation. When considered together, they create a stabilizing function that preserves the integrity of a service.

Several experiments have tested these hypotheses in both the field and the lab. In ECOTRON, a laboratory in the UK where many of the biotic and abiotic factors of nature can be simulated, studies have focused on the effects of earthworms and symbiotic bacteria on plant roots. These laboratory experiments seem to favor the rivet hypothesis. However, a study on grasslands at Cedar Creek Reserve in Minnesota supports the redundancy hypothesis, as have many other field studies.

Estuarine and coastal ecosystem services

Estuarine and coastal ecosystems are both marine ecosystems. Together, these ecosystems perform the four categories of ecosystem services in a variety of ways: "Regulating services" include climate regulation as well as waste treatment and disease regulation and buffer zones. The "provisioning services" include forest products, marine products, fresh water, raw materials, biochemical and genetic resources. "Cultural services" of coastal ecosystems include inspirational aspects, recreation and tourism, science and education. "Supporting services" of coastal ecosystems include nutrient cycling, biologically mediated habitats and primary production.

Coasts and their adjacent areas on and offshore are an important part of a local ecosystem. The mixture of fresh water and salt water (brackish water) in estuaries provides many nutrients for marine life. Salt marshes, mangroves and beaches also support a diversity of plants, animals and insects crucial to the food chain. The high level of biodiversity creates a high level of biological activity, which has attracted human activity for thousands of years. Coasts also create essential material for organisms to live by, including estuaries, wetland, seagrass, coral reefs, and mangroves. Coasts provide habitats for migratory birds, sea turtles, marine mammals, and coral reefs.

Regulating services

Regulating services are the "benefits obtained from the regulation of ecosystem processes". In the case of coastal and estuarine ecosystems, these services include climate regulation, waste treatment and disease control and natural hazard regulation.

Climate regulation

Both the biotic and abiotic ensembles of marine ecosystems play a role in climate regulation. They act as sponges when it comes to gases in the atmosphere, retaining large levels of CO2 and other greenhouse gases (methane and nitrous oxide). Marine plants also use CO2 for photosynthesis purposes and help in reducing the atmospheric CO2. The oceans and seas absorb the heat from the atmosphere and redistribute it through the means of water currents, and atmospheric processes, such as evaporation and the reflection of light allow for the cooling and warming of the overlying atmosphere. The ocean temperatures are thus imperative to the regulation of the atmospheric temperatures in any part of the world: "without the ocean, the Earth would be unbearably hot during the daylight hours and frigidly cold, if not frozen, at night".

Waste treatment and disease regulation

Another service offered by marine ecosystem is the treatment of wastes, thus helping in the regulation of diseases. Wastes can be diluted and detoxified through transport across marine ecosystems; pollutants are removed from the environment and stored, buried or recycled in marine ecosystems: "Marine ecosystems break down organic waste through microbial communities that filter water, reduce/limit the effects of eutrophication, and break down toxic hydrocarbons into their basic components such as carbon dioxide, nitrogen, phosphorus, and water". The fact that waste is diluted with large volumes of water and moves with water currents leads to the regulation of diseases and the reduction of toxics in seafood.

Buffer zones

Coastal and estuarine ecosystems act as buffer zones against natural hazards and environmental disturbances, such as floods, cyclones, tidal surges and storms. The role they play is to "[absorb] a portion of the impact and thus [lessen] its effect on the land". Wetlands (which include saltwater swamps, salt marshes, ...) and the vegetation it supports – trees, root mats, etc. – retain large amounts of water (surface water, snowmelt, rain, groundwater) and then slowly releases them back, decreasing the likeliness of floods. Mangrove forests protect coastal shorelines from tidal erosion or erosion by currents; a process that was studied after the 1999 cyclone that hit India. Villages that were surrounded with mangrove forests encountered less damages than other villages that weren't protected by mangroves.

Provisioning services

Provisioning services consist of all "the products obtained from ecosystems".

Forest products

Forests produce a large type and variety of timber products, including roundwood, sawnwood, panels, and engineered wood, e.g., cross-laminated timber, as well as pulp and paper. Besides the production of timber, forestry activities may also result in products that undergo little processing, such as fire wood, charcoal, wood chips and roundwood used in an unprocessed form. Global production and trade of all major wood-based products recorded their highest ever values in 2018. Production, imports and exports of roundwood, sawnwood, wood-based panels, wood pulp, wood charcoal and pellets reached their maximum quantities since 1947 when FAO started reporting global forest product statistics. In 2018, growth in production of the main wood-based product groups ranged from 1 percent (woodbased panels) to 5 percent (industrial roundwood). The fastest growth occurred in the Asia-Pacific, Northern American and European regions, likely due to positive economic growth in these areas.

Forests also provide non-wood forest products, including fodder, aromatic and medicinal plants, and wild foods. Worldwide, around 1 billion people depend to some extent on wild foods such as wild meat, edible insects, edible plant products, mushrooms and fish, which often contain high levels of key micronutrients. The value of forest foods as a nutritional resource is not limited to low- and middle-income countries; more than 100 million people in the European Union (EU) regularly consume wild food. Some 2.4 billion people – in both urban and rural settings – use wood-based energy for cooking.

Marine products

Marine ecosystems provide people with: wild & cultured seafood, fresh water, fiber & fuel and biochemical & genetic resources.

Humans consume a large number of products originating from the seas, whether as a nutritious product or for use in other sectors: "More than one billion people worldwide, or one-sixth of the global population, rely on fish as their main source of animal protein. In 2000, marine and coastal fisheries accounted for 12 per cent of world food production". Fish and other edible marine products – primarily fish, shellfish, roe and seaweeds – constitute for populations living along the coast the main elements of the local cultural diets, norms and traditions. A very pertinent example would be sushi, the national food of Japan, which consists mostly of different types of fish and seaweed.

Fresh water

Water bodies that are not highly concentrated in salts are referred to as 'fresh water' bodies. Fresh water may run through lakes, rivers and streams, to name a few; but it is most prominently found in the frozen state or as soil moisture or buried deep underground. Fresh water is not only important for the survival of humans, but also for the survival of all the existing species of animals, plants.

Raw materials

Marine creatures provide us with the raw materials needed for the manufacturing of clothing, building materials (lime extracted from coral reefs), ornamental items and personal-use items (luffas, art and jewelry): "The skin of marine mammals for clothing, gas deposits for energy production, lime (extracted from coral reefs) for building construction, and the timber of mangroves and coastal forests for shelter are some of the more familiar uses of marine organisms. Raw marine materials are utilized for non-essential goods as well, such as shells and corals in ornamental items". Humans have also referred to processes within marine environments for the production of renewable energy: using the power of waves – or tidal power – as a source of energy for the powering of a turbine, for example. Oceans and seas are used as sites for offshore oil and gas installations, and offshore wind farms.

Biochemical and genetic resources

Biochemical resources are compounds extracted from marine organisms for use in medicines, pharmaceuticals, cosmetics, and other biochemical products. Genetic resources are the genetic information found in marine organisms that would later on be used for animal and plant breeding and for technological advances in the biological field. These resources are either directly taken out from an organism – such as fish oil as a source of omega3 –, or used as a model for innovative man-made products: "such as the construction of fiber optics technology based on the properties of sponges. ... Compared to terrestrial products, marine-sourced products tend to be more highly bioactive, likely due to the fact that marine organisms have to retain their potency despite being diluted in the surrounding sea-water".

Cultural services

Cultural services relate to the non-material world, as they benefit the benefit recreational, aesthetic, cognitive and spiritual activities, which are not easily quantifiable in monetary terms.

Inspirational

Marine environments have been used by many as an inspiration for their works of art, music, architecture, traditions... Water environments are spiritually important as a lot of people view them as a means for rejuvenation and change of perspective. Many also consider the water as being a part of their personality, especially if they have lived near it since they were kids: they associate it to fond memories and past experiences. Living near water bodies for a long time results in a certain set of water activities that become a ritual in the lives of people and of the culture in the region.

Recreation and tourism

Sea sports are very popular among coastal populations: surfing, snorkeling, whale watching, kayaking, recreational fishing...a lot of tourists also travel to resorts close to the sea or rivers or lakes to be able to experience these activities, and relax near the water. The United Nations Sustainable Development Goal 14 also has targets aimed at enhancing the use of ecosystem services for sustainable tourism especially in Small Island Developing States.

Beach accommodated into a recreational area.

Science and education

A lot can be learned from marine processes, environments and organisms – that could be implemented into our daily actions and into the scientific domain. Although much is still yet to still be known about the ocean world: "by the extraordinary intricacy and complexity of the marine environment and how it is influenced by large spatial scales, time lags, and cumulative effects".

Supporting services

Supporting services are the services that allow for the other ecosystem services to be present. They have indirect impacts on humans that last over a long period of time. Several services can be considered as being both supporting services and regulating/cultural/provisioning services.

Nutrient cycling

Nutrient cycling is the movement of nutrients through an ecosystem by biotic and abiotic processes. The ocean is a vast storage pool for these nutrients, such as carbon, nitrogen and phosphorus. The nutrients are absorbed by the basic organisms of the marine food web and are thus transferred from one organism to the other and from one ecosystem to the other. Nutrients are recycled through the life cycle of organisms as they die and decompose, releasing the nutrients into the neighboring environment. "The service of nutrient cycling eventually impacts all other ecosystem services as all living things require a constant supply of nutrients to survive".

Biologically mediated habitats

Biologically mediated habitats are defined as being the habitats that living marine structures offer to other organisms. These need not to have evolved for the sole purpose of serving as a habitat, but happen to become living quarters whilst growing naturally. For example, coral reefs and mangrove forests are home to numerous species of fish, seaweed and shellfish... The importance of these habitats is that they allow for interactions between different species, aiding the provisioning of marine goods and services. They are also very important for the growth at the early life stages of marine species (breeding and bursary spaces), as they serve as a food source and as a shelter from predators.

Coral and other living organisms serve as habitats for many marine species.

Primary production

Primary production refers to the production of organic matter, i.e., chemically bound energy, through processes such as photosynthesis and chemosynthesis. The organic matter produced by primary producers forms the basis of all food webs. Further, it generates oxygen (O2), a molecule necessary to sustain animals and humans. On average, a human consumes about 550 liter of oxygen per day, whereas plants produce 1,5 liter of oxygen per 10 grams of growth.

Economics

Sustainable urban drainage pond near housing in Scotland. The filtering and cleaning of surface and waste water by natural vegetation is a form of ecosystem service.

There are questions regarding the environmental and economic values of ecosystem services. Some people may be unaware of the environment in general and humanity's interrelatedness with the natural environment, which may cause misconceptions. Although environmental awareness is rapidly improving in our contemporary world, ecosystem capital and its flow are still poorly understood, threats continue to impose, and we suffer from the so-called 'tragedy of the commons'. Many efforts to inform decision-makers of current versus future costs and benefits now involve organizing and translating scientific knowledge to economics, which articulate the consequences of our choices in comparable units of impact on human well-being. An especially challenging aspect of this process is that interpreting ecological information collected from one spatial-temporal scale does not necessarily mean it can be applied at another; understanding the dynamics of ecological processes relative to ecosystem services is essential in aiding economic decisions. Weighting factors such as a service's irreplaceability or bundled services can also allocate economic value such that goal attainment becomes more efficient.

The economic valuation of ecosystem services also involves social communication and information, areas that remain particularly challenging and are the focus of many researchers. In general, the idea is that although individuals make decisions for any variety of reasons, trends reveal the aggregated preferences of a society, from which the economic value of services can be inferred and assigned. The six major methods for valuing ecosystem services in monetary terms are:

  • Avoided cost: Services allow society to avoid costs that would have been incurred in the absence of those services (e.g. waste treatment by wetland habitats avoids health costs)
  • Replacement cost: Services could be replaced with man-made systems (e.g. restoration of the Catskill Watershed cost less than the construction of a water purification plant)
  • Factor income: Services provide for the enhancement of incomes (e.g. improved water quality increases the commercial take of a fishery and improves the income of fishers)
  • Travel cost: Service demand may require travel, whose costs can reflect the implied value of the service (e.g. value of ecotourism experience is at least what a visitor is willing to pay to get there)
  • Hedonic pricing: Service demand may be reflected in the prices people will pay for associated goods (e.g. coastal housing prices exceed that of inland homes)
  • Contingent valuation: Service demand may be elicited by posing hypothetical scenarios that involve some valuation of alternatives (e.g. visitors willing to pay for increased access to national parks)

A peer-reviewed study published in 1997 estimated the value of the world's ecosystem services and natural capital to be between US$16–54 trillion per year, with an average of US$33 trillion per year. However, Salles (2011) indicated 'The total value of biodiversity is infinite, so having debate about what is the total value of nature is actually pointless because we can't live without it'.

As of 2012, many companies were not fully aware of the extent of their dependence and impact on ecosystems and the possible ramifications. Likewise, environmental management systems and environmental due diligence tools are more suited to handle "traditional" issues of pollution and natural resource consumption. Most focus on environmental impacts, not dependence. Several tools and methodologies can help the private sector value and assess ecosystem services, including Our Ecosystem, the 2008 Corporate Ecosystem Services Review, the Artificial Intelligence for Environment & Sustainability (ARIES) project from 2007, the Natural Value Initiative (2012) and InVEST (Integrated Valuation of Ecosystem Services & Tradeoffs, 2012)

Management and policy

Although monetary pricing continues with respect to the valuation of ecosystem services, the challenges in policy implementation and management are significant and multitudinous. The administration of common pool resources has been a subject of extensive academic pursuit. From defining the problems to finding solutions that can be applied in practical and sustainable ways, there is much to overcome. Considering options must balance present and future human needs, and decision-makers must frequently work from valid but incomplete information. Existing legal policies are often considered insufficient since they typically pertain to human health-based standards that are mismatched with necessary means to protect ecosystem health and services. In 2000, to improve the information available, the implementation of an Ecosystem Services Framework has been suggested (ESF), which integrates the biophysical and socio-economic dimensions of protecting the environment and is designed to guide institutions through multidisciplinary information and jargon, helping to direct strategic choices.

As of 2005 Local to regional collective management efforts were considered appropriate for services like crop pollination or resources like water. Another approach that has become increasingly popular during the 1990s is the marketing of ecosystem services protection. Payment and trading of services is an emerging worldwide small-scale solution where one can acquire credits for activities such as sponsoring the protection of carbon sequestration sources or the restoration of ecosystem service providers. In some cases, banks for handling such credits have been established and conservation companies have even gone public on stock exchanges, defining an evermore parallel link with economic endeavors and opportunities for tying into social perceptions. However, crucial for implementation are clearly defined land rights, which are often lacking in many developing countries. In particular, many forest-rich developing countries suffering deforestation experience conflict between different forest stakeholders. In addition, concerns for such global transactions include inconsistent compensation for services or resources sacrificed elsewhere and misconceived warrants for irresponsible use. As of 2001, another approach focused on protecting ecosystem service biodiversity hotspots. Recognition that the conservation of many ecosystem services aligns with more traditional conservation goals (i.e. biodiversity) has led to the suggested merging of objectives for maximizing their mutual success. This may be particularly strategic when employing networks that permit the flow of services across landscapes, and might also facilitate securing the financial means to protect services through a diversification of investors.

For example, as of 2013, there had been interest in the valuation of ecosystem services provided by shellfish production and restoration. A keystone species, low in the food chain, bivalve shellfish such as oysters support a complex community of species by performing a number of functions essential to the diverse array of species that surround them. There is also increasing recognition that some shellfish species may impact or control many ecological processes; so much so that they are included on the list of "ecosystem engineers"—organisms that physically, biologically or chemically modify the environment around them in ways that influence the health of other organisms. Many of the ecological functions and processes performed or affected by shellfish contribute to human well-being by providing a stream of valuable ecosystem services over time by filtering out particulate materials and potentially mitigating water quality issues by controlling excess nutrients in the water. As of 2018, the concept of ecosystem services had not been properly implemented into international and regional legislation yet.

Notwithstanding, the United Nations Sustainable Development Goal 15 has a target to ensure the conservation, restoration, and sustainable use of ecosystem services.

Ecosystem-based adaptation (EbA)

Ecosystem-based adaptation or EbA is a strategy for community development and environmental management that seeks to use an ecosystem services framework to help communities adapt to the effects of climate change. The Convention on Biological Diversity defines it as "the use of biodiversity and ecosystem services to help people adapt to the adverse effects of climate change", which includes the use of "sustainable management, conservation and restoration of ecosystems, as part of an overall adaptation strategy that takes into account the multiple social, economic and cultural co-benefits for local communities".

In 2001, the Millennium Ecosystem Assessment announced that humanity's impact on the natural world was increasing to levels never before seen, and that the degradation of the planet's ecosystems would become a major barrier to achieving the Millennium Development Goals. In recognition of this fact, Ecosystem-Based Adaptation sought to use the restoration of ecosystems as a stepping-stone to improve the quality of life in communities experiencing the impacts of climate change. Specifically, it involved the restoration of such ecosystems that provide food and water and protection from storm surges and flooding. EbA interventions combine elements of both climate change mitigation and adaptation to global warming to help address the community's current and future needs.

Collaborative planning between scientists, policy makers, and community members is an essential element of Ecosystem-Based Adaptation. By drawing on the expertise of outside experts and local residents alike, EbA seeks to develop unique solutions to unique problems, rather than simply replicating past projects.

Land use change decisions

Ecosystem services decisions require making complex choices at the intersection of ecology, technology, society, and the economy. The process of making ecosystem services decisions must consider the interaction of many types of information, honor all stakeholder viewpoints, including regulatory agencies, proposal proponents, decision makers, residents, NGOs, and measure the impacts on all four parts of the intersection. These decisions are usually spatial, always multi-objective, and based on uncertain data, models, and estimates. Often it is the combination of the best science combined with the stakeholder values, estimates and opinions that drive the process.

One analytical study modeled the stakeholders as agents to support water resource management decisions in the Middle Rio Grande basin of New Mexico. This study focused on modeling the stakeholder inputs across a spatial decision, but ignored uncertainty. Another study used Monte Carlo methods to exercise econometric models of landowner decisions in a study of the effects of land-use change. Here the stakeholder inputs were modeled as random effects to reflect the uncertainty. A third study used a Bayesian decision support system to both model the uncertainty in the scientific information Bayes Nets and to assist collecting and fusing the input from stakeholders. This study was about siting wave energy devices off the Oregon Coast, but presents a general method for managing uncertain spatial science and stakeholder information in a decision making environment. Remote sensing data and analyses can be used to assess the health and extent of land cover classes that provide ecosystem services, which aids in planning, management, monitoring of stakeholders' actions, and communication between stakeholders.

In Baltic countries scientists, nature conservationists and local authorities are implementing integrated planning approach for grassland ecosystems. They are developing an integrated planning tool based on GIS (geographic information system) technology and put online that will help for planners to choose the best grassland management solution for concrete grassland. It will look holistically at the processes in the countryside and help to find best grassland management solutions by taking into account both natural and socioeconomic factors of the particular site.

History

While the notion of human dependence on Earth's ecosystems reaches to the start of Homo sapiens' existence, the term 'natural capital' was first coined by E.F. Schumacher in 1973 in his book Small is Beautiful. Recognition of how ecosystems could provide complex services to humankind date back to at least Plato (c. 400 BC) who understood that deforestation could lead to soil erosion and the drying of springs. Modern ideas of ecosystem services probably began when Marsh challenged in 1864 the idea that Earth's natural resources are unbounded by pointing out changes in soil fertility in the Mediterranean. It was not until the late 1940s that three key authors—Henry Fairfield Osborn, Jr, William Vogt, and Aldo Leopold—promoted recognition of human dependence on the environment.

In 1956, Paul Sears drew attention to the critical role of the ecosystem in processing wastes and recycling nutrients. In 1970, Paul Ehrlich and Rosa Weigert called attention to "ecological systems" in their environmental science textbook and "the most subtle and dangerous threat to man's existence... the potential destruction, by man's own activities, of those ecological systems upon which the very existence of the human species depends".

The term "environmental services" was introduced in a 1970 report of the Study of Critical Environmental Problems, which listed services including insect pollination, fisheries, climate regulation and flood control. In following years, variations of the term were used, but eventually 'ecosystem services' became the standard in scientific literature.

The ecosystem services concept has continued to expand and includes socio-economic and conservation objectives, which are discussed below. A history of the concepts and terminology of ecosystem services as of 1997, can be found in Daily's book "Nature's Services: Societal Dependence on Natural Ecosystems".

While Gretchen Daily's original definition distinguished between ecosystem goods and ecosystem services, Robert Costanza and colleagues' later work and that of the Millennium Ecosystem Assessment lumped all of these together as ecosystem services.

Examples

The following examples illustrate the relationships between humans and natural ecosystems through the services derived from them:

  • The US military has funded research through the Pacific Northwest National Laboratory, which claims that Department of Defense lands and military installations provide substantial ecosystem services to local communities, including benefits to carbon storage, resiliency to climate, and endangered species habitat. As of 2020, research from Duke University claims for example Eglin Air Force Base provides about $110 million in ecosystem services per year, $40 million more than if no base was present.
  • In New York City, where the quality of drinking water had fallen below standards required by the U.S. Environmental Protection Agency (EPA), authorities opted to restore the polluted Catskill Watershed that had previously provided the city with the ecosystem service of water purification. Once the input of sewage and pesticides to the watershed area was reduced, natural abiotic processes such as soil absorption and filtration of chemicals, together with biotic recycling via root systems and soil microorganisms, water quality improved to levels that met government standards. The cost of this investment in natural capital was estimated between $1–1.5 billion, which contrasted dramatically with the estimated $6–8 billion cost of constructing a water filtration plant plus the $300 million annual running costs.
  • Pollination of crops by bees is required for 15–30% of U.S. food production; most large-scale farmers import non-native honey bees to provide this service. A 2005 study reported that in California's agricultural region, it was found that wild bees alone could provide partial or complete pollination services or enhance the services provided by honey bees through behavioral interactions. However, intensified agricultural practices can quickly erode pollination services through the loss of species. The remaining species are unable to compensate this. The results of this study also indicate that the proportion of chaparral and oak-woodland habitat available for wild bees within 1–2 km of a farm can stabilize and enhance the provision of pollination services. The presence of such ecosystem elements functions almost like an insurance policy for farmers.
  • In watersheds of the Yangtze River China, spatial models for water flow through different forest habitats were created to determine potential contributions for hydroelectric power in the region. By quantifying the relative value of ecological parameters (vegetation-soil-slope complexes), researchers were able to estimate the annual economic benefit of maintaining forests in the watershed for power services to be 2.2 times that if it were harvested once for timber.
  • In the 1980s, mineral water company Vittel now a brand of Nestlé Waters) faced the problem that nitrate and pesticides were entering the company's springs in northeastern France. Local farmers had intensified agricultural practices and cleared native vegetation that previously had filtered water before it seeped into the aquifer used by Vittel. This contamination threatened the company's right to use the "natural mineral water" label under French law. In response to this business risk, Vittel developed an incentive package for farmers to improve their agricultural practices and consequently reduce water pollution that had affected Vittel's product. For example, Vittel provided subsidies and free technical assistance to farmers in exchange for farmers' agreement to enhance pasture management, reforest catchments, and reduce the use of agrochemicals, an example of a payment for ecosystem services program.
  • In 2016, it was counted that to plant 15 000 ha new woodland in the UK, considering only the value of timber, it would cost £79 000 000, which is more than the benefit of £65 000 000. If, however, all other benefits the trees in lowland could provide (like soil stabilization, wind deflection, recreation, food production, air purification, carbon storage, wildlife habitat, fuel production, cooling, flood prevention) were included, the costs will increase due to displacing the profitable farmland (would be around £231 000 000) but would be overweight by benefits of £546 000 000.
  • In Europe, various projects are implemented in order to define the values of concrete ecosystems and to implement this concept into decision making process. For example, "LIFE Viva grass" project aims to do this with grasslands in Baltics.

Crop diversity

From Wikipedia, the free encyclopedia

Crop diversity is the variance in genetic and phenotypic characteristics of plants used in agriculture. Over the past 50 years, there has been a major decline in two components of crop diversity; genetic diversity within each crop and the number of species commonly grown.

Crop diversity loss threatens global food security, as the world's human population depends on a diminishing number of varieties of a diminishing number of crop species. Crops are increasingly grown in monoculture, meaning that if, as in the historic Great Famine of Ireland, a single disease overcomes a variety's resistance, it may destroy an entire harvest, or as in the case of the 'Gros Michel' banana, may cause the commercial extinction of an entire variety. With the help of seed banks, international organizations are working to preserve crop diversity.

Biodiversity loss

Geographic hotspots of distributions of crop wild relatives not represented in genebanks

Crop diversity is an aspect of biodiversity important for food security. The loss of biodiversity is considered one of today’s most serious environmental concerns by the Food and Agriculture Organization. If current trends persist, as many as half of all plant species could face extinction. Some 6% of wild relatives of cereal crops such as wheat, maize, rice, and sorghum are under threat, as are 18% of legumes (Fabaceae), the wild relatives of beans, peas and lentils, and 13% of species within the botanical family (Solanaceae) that includes potato, tomato, eggplant (aubergine), and peppers (Capsicum).

Within-crop diversity

Traditional mixed crop (polyculture) cultivation of cacao and banana, Trinidad, 1903

Within-crop diversity, a specific crop can result from various growing conditions, for example a crop growing in nutrient-poor soil is likely to have stunted growth than a crop growing in more fertile soil. The availability of water, soil pH level, and temperature similarly influence crop growth.

 

Within-crop diversity: maize cobs of differing colours

In addition, diversity of a harvested plant can be the result of genetic differences: a crop may have genes conferring early maturity or disease resistance. Such traits collectively determine a crop's overall characteristics and their future potential. Diversity within a crop includes genetically-influenced attributes such as seed size, branching pattern, height, flower color, fruiting time, and flavor. Crops can also vary in less obvious characteristics such as their response to heat, cold, a drought, or their ability to resist specific diseases and pests.

Modern plant breeders develop new crop varieties to meet specific conditions. A new variety might, for example, be higher yielding, more disease resistant or have a longer shelf life than the varieties from which it was bred. The practical use of crop diversity goes back to early agricultural methods of crop rotation and fallow fields, where planting and harvesting one type of crop on a plot of land one year, and planting a different crop on that same plot the next year. This takes advantage of differences in a plant's nutrient needs, but more importantly reduces the buildup of pathogens.

Both farmers and scientists must continually draw on the irreplaceable resource of genetic diversity to ensure productive harvests. While genetic variability provides farmers with plants that have a higher resilience to pests and diseases and allows scientists access to a more diverse genome than can be found in highly selected crops. The breeding of high performing crops steadily reduces genetic diversity as desirable traits are selected, and undesirable traits are removed. Farmers can increase within-crop diversity to some extent by planting mixtures of crop varieties.

Ecological effects

Biodiverse agroecosystem: traditional potato harvesting high in the Andes, Manco Kapac Province, Bolivia, 2012

Agricultural ecosystems function effectively as self-regulating systems provided they have sufficient biodiversity of plants and animals. Apart from producing food, fuel, and fibre, agroecosystem functions include recycling nutrients, maintaining soil fertility, regulating microclimate, regulating water flow, controlling pests, and detoxification of waste products.

However, modern agriculture seriously reduces biodiversity. Traditional systems maintain diversity within a crop species, such as in the Andes mountains where up to 50 varieties of potato are grown. Strategies to raise genetic diversity can involve planting mixtures of crop varieties.

Genetic diversity of crops can be used to help protect the environment. Crop varieties that are resistant to pests and diseases can reduce the need for application of harmful pesticides.

Economic impact

Agriculture is the economic foundation of most countries, and for developing countries a likely source of economic growth. Growth in agriculture can benefit the rural poor, though it does not always do so. Profits from crops can increase from higher value crops, better marketing, value-adding activities such as processing, or expanded access for the public to markets. Profits can also decrease through reduced demand or increased production. Crop diversity can protect against crop failure, and can also offer higher returns.

Despite efforts to quantify them, the financial values of crop diversity sources remain entirely uncertain.

Disease threats

Loss of low-diversity crop to a single disease: the Great Famine, caused by the oomycete Phytophthora infestans. Starvation followed, as illustrated by James Mahony, 1847
 
 
Wheat stem rust is evolving new, virulent strains, threatening many low-diversity cultivars.

Along with insect pests, disease is a major cause of crop loss.  Wild species have a range of genetic variability that allows some individuals to survive should a disturbance occur. In agriculture, resistance through variability is compromised, since genetically uniform seeds are planted under uniform conditions. Monocultural agriculture thus causes low crop diversity, especially when the seeds are mass-produced or when plants (such as grafted fruit trees and banana plants) are cloned. A single pest or disease could threaten a whole crop due to this uniformity ("genetic erosion"). A well-known historic case was the Great Famine of Ireland of 1845-1847, where a vital crop with low diversity was destroyed by a single fungus. Another example is when a disease caused by a fungus affected the monocultured 1970 US corn crop, causing a loss of over one billion dollars in production.

A danger to agriculture is wheat rust, a pathogenic fungus causing reddish patches, coloured by its spores. A virulent form of the wheat disease, stem rust, strain Ug99, spread from Africa across to the Arabian Peninsula by 2007. In field trials in Kenya, more than 85% of wheat samples, including major cultivars, were susceptible, implying that higher crop diversity was required. The Nobel laureate Norman Borlaug argued for action to ensure global food security.

 

Low-diversity crop variety destroyed: the 'Gros Michel' banana was commercially destroyed by Panama disease, caused by the fungus Fusarium oxysporum (illustrated).

Reports from Burundi and Angola warn of a threat to food security caused by the African Cassava Mosaic Virus (ACMD). ACMD is responsible for the loss of a million tons of cassava each year. CMD is prevalent in all the main cassava-growing areas in the Great Lakes region of east Africa, causing between 20 and 90 percent crop losses in the Congo. The FAO emergency relief and rehabilitation program is assisting vulnerable returnee populations in the African Great Lakes Region through mass propagation and distribution of CMD resistant or highly tolerant cassava.

A well known occurrence of disease susceptibility in crops lacking diversity concerns the 'Gros Michel', a seedless banana that saw world marketing in the 1940s. As the market demand became high for this particular cultivar, growers and farmers began to use the Gros Michel banana almost exclusively. Genetically, these bananas are clones, and because of this lack of genetic diversity, are all susceptible to a single fungus, Fusarium oxysporum (Panama disease); large areas of the crop were destroyed by the fungus in the 1950s. 'Gros Michel' has been replaced by the current main banana on the market, the 'Cavendish', which in turn is (2015) at risk of total loss to a strain of the same fungus, 'Tropical Race 4'.

Such threats can be countered by strategies such as planting multi-line cultivars and cultivar mixes, in the hope that some of the cultivars will be resistant to any individual outbreak of disease.

Organizations and technologies

The implications of crop diversity are at both local and world levels. Global organizations that aim to support diversity include Bioversity International (formerly known as International Plant Genetic Resources Institute), the International Institute of Tropical Agriculture, the Borlaug Global Rust Initiative, and the International Network for Improvement of Banana and Plantain. Members of the United Nations, at the World Summit on Sustainable Development 2002 at Johannesburg, said that crop diversity is in danger of being lost if measures are not taken. One such step taken in the action against the loss of biodiversity among crops is gene banking. There are a number of organizations that enlist teams of local farmers to grow native varieties, particularly those that are threatened by extinction due to lack of modern-day use. There are also local, national and international efforts to preserve agricultural genetic resources through off-site methods such as seed and banks for further research and crop breeding. 

 

Six bean varieties at a gene bank

The Global Crop Diversity Trust is an independent international organisation which exists to ensure the conservation and availability of crop diversity for food security worldwide. It was established through a partnership between the United Nations Food and Agriculture Organization (FAO) and CGIAR acting through Bioversity International. The CGIAR is a consortium of international agriculture research centers (IARC) and others that each conduct research on and preserve germplasm from a particular crop or animal species. The genebanks of CGIAR centers hold some of the world's largest off site collections of plant genetic resources in trust for the world community. Collectively, the CGIAR genebanks contain more that 778,000 accessions of more than 3,000 crop, forage, and agroforestry species. The collection includes farmers' varieties and improved varieties and, in substantial measure, the wild species from which those varieties were created. National germplasm storage centers include the U.S. Department of Agriculture's National Center for Genetic Resources Preservation, India's National Bureau of Animal Genetic Resources, the Taiwan Livestock Research Institute, and the proposed Australian Network of Plant Genetic Resource Centers.

 

The World Resources Institute (WRI) and the World Conservation Union (IUCN) are non-profit organizations that provide funding and other support to off site and on site conservation efforts. The wise use of crop genetic diversity in plant breeding and genetic modification can also contribute significantly to protecting the biodiversity in crops. Crop varieties can be genetically modified to resist specific pests and diseases. For example, a gene from the soil bacterium Bacillus thuringiensis (Bt) produces a natural insecticide toxin. Genes from Bt can be inserted into crop plants to make them capable of producing an insecticidal toxin and therefore a resistance to certain pests. Bt corn (maize) can however adversely affect non-target insects closely related to the target pest, as with the monarch butterfly.

Bayesian probability

From Wikipedia, the free encyclopedia

Bayesian probability is an interpretation of the concept of probability, in which, instead of frequency or propensity of some phenomenon, probability is interpreted as reasonable expectation representing a state of knowledge or as quantification of a personal belief.

The Bayesian interpretation of probability can be seen as an extension of propositional logic that enables reasoning with hypotheses; that is, with propositions whose truth or falsity is unknown. In the Bayesian view, a probability is assigned to a hypothesis, whereas under frequentist inference, a hypothesis is typically tested without being assigned a probability.

Bayesian probability belongs to the category of evidential probabilities; to evaluate the probability of a hypothesis, the Bayesian probabilist specifies a prior probability. This, in turn, is then updated to a posterior probability in the light of new, relevant data (evidence). The Bayesian interpretation provides a standard set of procedures and formulae to perform this calculation.

The term Bayesian derives from the 18th-century mathematician and theologian Thomas Bayes, who provided the first mathematical treatment of a non-trivial problem of statistical data analysis using what is now known as Bayesian inference. Mathematician Pierre-Simon Laplace pioneered and popularized what is now called Bayesian probability.

Bayesian methodology

Bayesian methods are characterized by concepts and procedures as follows:

  • The use of random variables, or more generally unknown quantities, to model all sources of uncertainty in statistical models including uncertainty resulting from lack of information (see also aleatoric and epistemic uncertainty).
  • The need to determine the prior probability distribution taking into account the available (prior) information.
  • The sequential use of Bayes' formula: when more data become available, calculate the posterior distribution using Bayes' formula; subsequently, the posterior distribution becomes the next prior.
  • While for the frequentist, a hypothesis is a proposition (which must be either true or false) so that the frequentist probability of a hypothesis is either 0 or 1, in Bayesian statistics, the probability that can be assigned to a hypothesis can also be in a range from 0 to 1 if the truth value is uncertain.

Objective and subjective Bayesian probabilities

Broadly speaking, there are two interpretations of Bayesian probability. For objectivists, who interpret probability as an extension of logic, probability quantifies the reasonable expectation that everyone (even a "robot") who shares the same knowledge should share in accordance with the rules of Bayesian statistics, which can be justified by Cox's theorem. For subjectivists, probability corresponds to a personal belief. Rationality and coherence allow for substantial variation within the constraints they pose; the constraints are justified by the Dutch book argument or by decision theory and de Finetti's theorem. The objective and subjective variants of Bayesian probability differ mainly in their interpretation and construction of the prior probability.

History

The term Bayesian derives from Thomas Bayes (1702–1761), who proved a special case of what is now called Bayes' theorem in a paper titled "An Essay towards solving a Problem in the Doctrine of Chances". In that special case, the prior and posterior distributions were beta distributions and the data came from Bernoulli trials. It was Pierre-Simon Laplace (1749–1827) who introduced a general version of the theorem and used it to approach problems in celestial mechanics, medical statistics, reliability, and jurisprudence. Early Bayesian inference, which used uniform priors following Laplace's principle of insufficient reason, was called "inverse probability" (because it infers backwards from observations to parameters, or from effects to causes). After the 1920s, "inverse probability" was largely supplanted by a collection of methods that came to be called frequentist statistics.

In the 20th century, the ideas of Laplace developed in two directions, giving rise to objective and subjective currents in Bayesian practice. Harold Jeffreys' Theory of Probability (first published in 1939) played an important role in the revival of the Bayesian view of probability, followed by works by Abraham Wald (1950) and Leonard J. Savage (1954). The adjective Bayesian itself dates to the 1950s; the derived Bayesianism, neo-Bayesianism is of 1960s coinage. In the objectivist stream, the statistical analysis depends on only the model assumed and the data analysed. No subjective decisions need to be involved. In contrast, "subjectivist" statisticians deny the possibility of fully objective analysis for the general case.

In the 1980s, there was a dramatic growth in research and applications of Bayesian methods, mostly attributed to the discovery of Markov chain Monte Carlo methods and the consequent removal of many of the computational problems, and to an increasing interest in nonstandard, complex applications. While frequentist statistics remains strong (as demonstrated by the fact that much of undergraduate teaching is based on it ), Bayesian methods are widely accepted and used, e.g., in the field of machine learning.

Justification of Bayesian probabilities

The use of Bayesian probabilities as the basis of Bayesian inference has been supported by several arguments, such as Cox axioms, the Dutch book argument, arguments based on decision theory and de Finetti's theorem.

Axiomatic approach

Richard T. Cox showed that Bayesian updating follows from several axioms, including two functional equations and a hypothesis of differentiability. The assumption of differentiability or even continuity is controversial; Halpern found a counterexample based on his observation that the Boolean algebra of statements may be finite. Other axiomatizations have been suggested by various authors with the purpose of making the theory more rigorous.

Dutch book approach

The Dutch book argument was proposed by de Finetti; it is based on betting. A Dutch book is made when a clever gambler places a set of bets that guarantee a profit, no matter what the outcome of the bets. If a bookmaker follows the rules of the Bayesian calculus in the construction of his odds, a Dutch book cannot be made.

However, Ian Hacking noted that traditional Dutch book arguments did not specify Bayesian updating: they left open the possibility that non-Bayesian updating rules could avoid Dutch books. For example, Hacking writes "And neither the Dutch book argument, nor any other in the personalist arsenal of proofs of the probability axioms, entails the dynamic assumption. Not one entails Bayesianism. So the personalist requires the dynamic assumption to be Bayesian. It is true that in consistency a personalist could abandon the Bayesian model of learning from experience. Salt could lose its savour."

In fact, there are non-Bayesian updating rules that also avoid Dutch books (as discussed in the literature on "probability kinematics" following the publication of Richard C. Jeffreys' rule, which is itself regarded as Bayesian). The additional hypotheses sufficient to (uniquely) specify Bayesian updating are substantial and not universally seen as satisfactory.

Decision theory approach

A decision-theoretic justification of the use of Bayesian inference (and hence of Bayesian probabilities) was given by Abraham Wald, who proved that every admissible statistical procedure is either a Bayesian procedure or a limit of Bayesian procedures. Conversely, every Bayesian procedure is admissible.

Personal probabilities and objective methods for constructing priors

Following the work on expected utility theory of Ramsey and von Neumann, decision-theorists have accounted for rational behavior using a probability distribution for the agent. Johann Pfanzagl completed the Theory of Games and Economic Behavior by providing an axiomatization of subjective probability and utility, a task left uncompleted by von Neumann and Oskar Morgenstern: their original theory supposed that all the agents had the same probability distribution, as a convenience. Pfanzagl's axiomatization was endorsed by Oskar Morgenstern: "Von Neumann and I have anticipated ... [the question whether probabilities] might, perhaps more typically, be subjective and have stated specifically that in the latter case axioms could be found from which could derive the desired numerical utility together with a number for the probabilities (cf. p. 19 of The Theory of Games and Economic Behavior). We did not carry this out; it was demonstrated by Pfanzagl ... with all the necessary rigor".

Ramsey and Savage noted that the individual agent's probability distribution could be objectively studied in experiments. Procedures for testing hypotheses about probabilities (using finite samples) are due to Ramsey (1931) and de Finetti (1931, 1937, 1964, 1970). Both Bruno de Finetti and Frank P. Ramsey acknowledge their debts to pragmatic philosophy, particularly (for Ramsey) to Charles S. Peirce.

The "Ramsey test" for evaluating probability distributions is implementable in theory, and has kept experimental psychologists occupied for a half century. This work demonstrates that Bayesian-probability propositions can be falsified, and so meet an empirical criterion of Charles S. Peirce, whose work inspired Ramsey. (This falsifiability-criterion was popularized by Karl Popper.)

Modern work on the experimental evaluation of personal probabilities uses the randomization, blinding, and Boolean-decision procedures of the Peirce-Jastrow experiment. Since individuals act according to different probability judgments, these agents' probabilities are "personal" (but amenable to objective study).

Personal probabilities are problematic for science and for some applications where decision-makers lack the knowledge or time to specify an informed probability-distribution (on which they are prepared to act). To meet the needs of science and of human limitations, Bayesian statisticians have developed "objective" methods for specifying prior probabilities.

Indeed, some Bayesians have argued the prior state of knowledge defines the (unique) prior probability-distribution for "regular" statistical problems; cf. well-posed problems. Finding the right method for constructing such "objective" priors (for appropriate classes of regular problems) has been the quest of statistical theorists from Laplace to John Maynard Keynes, Harold Jeffreys, and Edwin Thompson Jaynes. These theorists and their successors have suggested several methods for constructing "objective" priors (Unfortunately, it is not clear how to assess the relative "objectivity" of the priors proposed under these methods):

Each of these methods contributes useful priors for "regular" one-parameter problems, and each prior can handle some challenging statistical models (with "irregularity" or several parameters). Each of these methods has been useful in Bayesian practice. Indeed, methods for constructing "objective" (alternatively, "default" or "ignorance") priors have been developed by avowed subjective (or "personal") Bayesians like James Berger (Duke University) and José-Miguel Bernardo (Universitat de València), simply because such priors are needed for Bayesian practice, particularly in science. The quest for "the universal method for constructing priors" continues to attract statistical theorists.

Thus, the Bayesian statistician needs either to use informed priors (using relevant expertise or previous data) or to choose among the competing methods for constructing "objective" priors.

Affordable housing

From Wikipedia, the free encyclopedia

Affordable housing is housing which is deemed affordable to those with a household income at or below the median as rated by the national government or a local government by a recognized housing affordability index. Most of the literature on affordable housing refers to mortgages and a number of forms that exist along a continuum – from emergency homeless shelters, to transitional housing, to non-market rental (also known as social or subsidized housing), to formal and informal rental, indigenous housing, and ending with affordable home ownership.

In Australia, the National Affordable Housing Summit Group developed their definition of affordable housing as housing that is "...reasonably adequate in standard and location for lower or middle income households and does not cost so much that a household is unlikely to be able to meet other basic needs on a sustainable basis." Affordable housing in the United Kingdom includes "social rented and intermediate housing, provided to specified eligible households whose needs are not met by the market."

Housing choice is a response to an extremely complex set of economic, social, and psychological impulses. For example, some households may choose to spend more on housing because they feel they can afford to, while others may not have a choice.

https://www.huduser.gov/portal/pdredge/pdr_edge_inpractice_090814.html
Legends Park West Mixed-Income and Affordable Housing Redevelopment in Memphis Tennessee, USA

Definition and measurement

There are several means of defining and measuring affordable housing. The definition and measurement may change in different nations, cities, or for specific policy goals. Several common means of measuring and defining affordable housing are found below.

Median multiple approaches

The median multiple indicator, recommended by the World Bank and the United Nations, rates affordability of housing by dividing the median house price by gross (before tax) annual median household income).

A common measure of community-wide affordability is the number of homes that a household with a certain percentage of median income can afford. For example, in a perfectly balanced housing market, the median household (the wealthier half of households) could officially afford the median housing option, while those poorer than the median income could not afford the median home. 50% affordability for the median home indicates a balanced market.

Some countries look at those living in relative poverty, which is usually defined as making less than 60% of the median household income. In their policy reports, they consider the presence or absence of housing for people making 60% of the median income.

Housing costs as percentage of gross income

Determining housing affordability is complex and the commonly used housing-expenditure-to-income-ratio tool has been challenged. In the United States and Canada, a commonly accepted guideline for housing affordability is a housing cost, including utilities, that does not exceed 30% of a household's gross income. Some definitions include maintenance costs as part of housing costs. Canada, for example, switched to a 25% rule from a 20% rule in the 1950s. In the 1980s this was replaced by a 30% rule. India uses a 40% rule.

Housing affordability index approaches

There are several types of housing affordability indexes that take a number of factors, not just income, into account when measuring housing affordability.

The American National Association of Realtors and other groups measure market housing through a housing affordability index which measures whether or not a typical family could qualify for a mortgage loan on a typical home. This index calculates affordability based on the national median-priced single family home, the typical family median income, and the prevailing mortgage interest rate to determine if the median income family can qualify for a mortgage on a typical home. To interpret the indices, a value of 100 means that a family with the median income has exactly enough income to qualify for a mortgage on a median-priced home. An index over 100 signifies that family earning the median income has more than enough income for a mortgage loan on the median-priced home (assuming they have a 20 percent down payment). For example, a composite HAI of 120.0 means a family earning the median family income has 120% of the income necessary to qualify for a conventional loan covering 80 percent of a median-priced existing single-family home. An increase in the HAI shows that this family is more able to afford the median-priced home.

The Massachusetts Institute of Technology (MIT) developed a housing affordability index that attempts to capture the total cost of housing by several factors include employment accessibility, amenities, transportation costs and transit access, quality of schools, etc. In computing the index the obvious cost of rents and mortgage payments are modified by the hidden costs of those choices. Other groups have also created amenity based housing affordability indexes.

The Center for Neighborhood Technology developed the Housing + Transportation (H+T) Affordability Index provides a comprehensive view of affordability that includes both the cost of housing and the cost of transportation at the neighborhood level. CNT notes that the 30% of household income affordability measurementment results in little over half (55%) of U.S. neighborhoods being considered “affordable” for the typical household. They note that such a measurement fails to take into account transportation costs (such as multiple cars, gas, maintenance), which are usually a household’s second-largest expenditure. When transportation costs are factored into the measurement, the number of affordable neighborhoods nationally drops to 26%, resulting in a net loss of 59,768 neighborhoods that Americans can truly afford. Per CNT's measurement, people who live in location-efficient neighborhoods that are compact, mixed-use, and have convenient access to jobs, services, transit and amenities tend to have lower transportation costs.

Household income and wealth approaches

Some analysts believe income is the primary factor – not price and availability, that determines housing affordability. In a market economy the distribution of income is the key determinant of the quantity and quality of housing obtained. Therefore, understanding affordable housing challenges requires understanding trends and disparities in income and wealth. Housing is often the single biggest expenditure of low and middle income families. For low and middle income families, their house is also the greatest source of wealth.

Another method of studying affordability looks at the regular hourly wage of full-time workers who are paid only the minimum wage (as set by their local, regional, or national government). This methods attempts to determine if workers at that income can afford adequate housing.

Differing parameters and limitations in approaches

Housing affordability can be measured by the changing relationships between house prices and rents, and between house prices and incomes. Housing affordability may be measured by various expenditures beyond the price of the actual housing stock itself, that are considered depending on the index being used.

Some organizations and agencies consider the cost of purchasing a single-family home; others look exclusively at the cost of renting an apartment. Many U.S. studies, for example, focus primarily on the median cost of renting a two-bedroom apartment in a large apartment complex for a new tenant. These studies often lump together luxury apartments and slums, as well as desirable and undesirable neighborhoods. While this practice is known to distort the true costs, it is difficult to provide accurate information for the wide variety of situations without the report being unwieldy.

Often, only legal, permitted, separate housing is considered when calculating the cost of housing. The low rent costs for a room in a single family home, or an illegal garage conversion, or a college dormitory are generally excluded from the calculation, no matter how many people in an area live in such situations. Because of this study methodology, median housing costs tend to be slightly inflated.

Costs are generally considered on a cash (not accrual) basis. Thus a person making the last payment on a large home mortgage might live in officially unaffordable housing one month, and very affordable housing the following month, when the mortgage is paid off. This distortion can be significant in areas where real estate costs are high, even if incomes are similarly high, because a high income allows a higher proportion of the income to be dedicated towards buying an expensive home without endangering the household's ability to buy food or other basic necessities.

Economics

Affordable housing, or low income housing, at the St. James Town neighborhood in Toronto, Ontario, Canada

Causes and consequences of rises in housing prices

Costs are being driven by a number of factors including:

  • demographic shifts
    • the declining number of people per dwelling
    • growing density convergence and regional urbanization
    • solid population growth (for example high prices in Australia and Canada as a rising population pushes up demand)
  • supply and demand
    • a shortfall in the number of dwellings to the number of households
      • smaller family size
      • strong psychological desire for home ownership
  • shifts in economic policies and innovations in financial instruments
    • reduced profitability of other forms of investment
    • availability of housing finance
    • low interest rates
    • mortgage market innovations
  • public policy
    • regulation
    • land use zoning
    • significant taxes, levies and fees by government on new housing (especially in Australia)

Supply and demand

In some countries, the market has been unable to meet the growing demand to supply housing stock at affordable prices. Although demand for affordable housing, particularly rental housing that is affordable for low and middle income earners, has increased, the supply has not. Potential home buyers are forced to turn to the rental market, which is also under pressure. An inadequate supply of housing stock increases demand on the private and social rented sector, and in worse case scenarios, homelessness.

Factors that affect supply and demand of housing stock

  • Demographic and behavioral factors
  • Migration (to cities and potential employment)
  • Increased life expectancy
  • Building codes
  • A greater propensity for people to live alone
  • Young adults delaying forming their own household (in advanced economies)
  • Exclusionary zoning

Factors that affect tenure choices (ex. owner occupier, private rented, social rented)

  • Employment rates
    • Rising unemployment rates increase demand for market rentals, social housing and homelessness.
  • Real household incomes
    • Household incomes have not kept up with rising housing prices
  • Affordability of rents and owner occupation
  • Interest rates
  • Availability of mortgages
  • Levels of confidence in the economy and housing market
    • Low confidence decreases demand for owner occupation.

Labour market performance

In both large metropolitan areas and regional towns where housing prices are high, a lack of affordable housing places local firms at a competitive disadvantage. They are placed under wage pressures as they attempt to decrease the income/housing price gap. Key workers have fewer housing choices if prices rise to non-affordable levels. Variations in affordability of housing between areas may create labour market impediments.

Potential workers are discouraged from moving to employment in areas of low affordability. They are also discouraged from migrating to areas of high affordability as the low house prices and rents indicate low capital gain potential and poor employment prospects.

Inequality and housing

A number of researchers argue that a shortage of affordable housing – at least in the US – is caused in part by income inequality. David Rodda noted that from 1984 and 1991, the number of quality rental units decreased as the demand for higher quality housing increased. Through gentrification of older neighbourhoods, for example, in East New York, rental prices increased rapidly as landlords found new residents willing to pay higher market rate for housing and left lower income families without rental units. The ad valorem property tax policy combined with rising prices made it difficult or impossible for low income residents to keep pace.

Lack of affordable housing places a particular burden on local economies. As well, individual consumers are faced with mortgage arrears and excessive debt and therefore cut back on consumption. A combination of high housing costs and high debt levels contributes to a reduction in savings. These factors can lead to decreased investment in sectors that are essential to the long-term growth of the economy.

Affordable housing and urbanization

The majority of the more than seven billion people on earth now live in cities (UN). There are more than 500 city regions of more than one million inhabitants in the world. Cities become megacities become megalopolitan city regions and even "galaxies" of more than 60 million inhabitants. The Yangtze Delta-Greater Shanghai region now surpasses 80 million. Tokyo-Yokohama adjacent to Osaka-Kobe-Kyoto have a combined population of 100 million. Rapid population growth leads to increased need for affordable housing in most cities. The availability of affordable housing in proximity of mass transit and linked to job distribution has become severely imbalanced in this period of rapid regional urbanization and growing density convergence.

"In addition to the distress it causes families who cannot find a place to live, lack of affordable housing is considered by many urban planners to have negative effects on a community's overall health."

Affordable housing challenges in inner cities range from the homeless who are forced to live on the street to the relative deprivation of vital workers like police officers, firefighters, teachers and nurses unable to find affordable accommodation near their place of work. These workers are forced to live in suburbia, commuting up to two hours each way to work. Lack of affordable housing can make low-cost labour scarcer (as workers travel longer distances) (Pollard and Stanley 2007).

Social and environmental impacts

Housing affordability is more than just a personal trouble experienced by individual households who cannot easily find a place to live. Lack of affordable housing is considered by many urban planners to have negative effects on a community's overall health.

Jobs, transportation, and affordable housing

Lack of affordable housing can make low-cost labor more scarce, and increase demands on transportation systems (as workers travel longer distances between jobs and affordable housing). Housing cost increases in U.S. cities have been linked to declines in enrollment at local schools. "Faced with few affordable options, many people attempt to find less expensive housing by buying or renting farther out, but long commutes often result in higher transportation costs that erase any savings on shelter." Pollard (2010) called this the "drive 'til you qualify" approach, which causes far-flung development and forces people to drive longer distances to get to work, to get groceries, to take children to school, or to engage in other activities. A well located dwelling might save significant household travel costs and therefore improve overall family economics, even if the rent is higher than a dwelling in a poorer location.

A household's inhabitants must decide whether to pay more for housing to keep commuting time and expense low, or to accept a long or expensive commute to obtain "better" housing. The absolute availability of housing is not generally considered in the calculation of affordable housing. In a depressed or sparsely settled rural area, for example, the predicted price of the canonical median two-bedroom apartment may be quite easily affordable even to a minimum-wage worker – if only any apartments had ever been built. Some affordable housing prototypes include Nano House and Affordable Green Tiny House Project.

Improving thermal comfort at home especially for houses without adequate warmth and for tenants with chronic respiratory disease may lead to improved health and promote social relationships.

Affordable housing and public policy

Background

Policy makers at all levels – global, national, regional, municipal, community associations – are attempting to respond to the issue of affordable housing, a highly complex crisis of global proportions, with a myriad of policy instruments. These responses range from stop-gap financing tools to long-term intergovernmental infrastructural changes. There has been an increase among policy makers in affordable housing as the price of housing has increased dramatically creating a crisis in affordable housing.

In the simplest of terms, affordability of housing refers to the amount of capital one has available in relation to the price of the goods to be obtained. Public policies are informed by underlying assumptions about the nature of housing itself. Is housing a basic need, a right, an entitlement, or a public good? Or is just another household-level consumer choice, a commodity or an investment within the free market system? "Housing Policies provide a remarkable litmus test for the values of politicians at every level of office and of the varied communities that influence them. Often this test measures simply the warmth or coldness of heart of the more affluent and secure towards families of a lower socio-economic status."

The growing gap between rich and poor since the 1980s manifests itself in a housing system where public policy decisions privilege the ownership sector to the disadvantage of the rental sector. The notion of housing affordability became widespread in the 1980s in Europe and North America. In the words of Alain Bertaud, of New York University and former principal planner at the World Bank,

It is time for planners to abandon abstract objectives and to focus their efforts on two measurable outcomes that have always mattered since the growth of large cities during the 19th century’s industrial revolution: workers' spatial mobility and housing affordability.

Ann Owen wonders if the housing market helped reduced poverty concentration in the National longitudinal data between the years of 1977–2008 with the concentration of the 100 largest metropolitan areas in the United States. Data information is to compare or intertwine with the differences of national housing subsidies, the entry, exit, and enhancement of low-income housing.

Affordable housing is a controversial reality of contemporary life, for gains in affordability often result from expanding land available for housing or increasing the density of housing units in a given area. Ensuring a steady supply of affordable housing means ensuring that communities weigh real and perceived livability impacts against the sheer necessity of affordability. The process of weighing the impacts of locating affordable housing is quite contentious and is laden with race and class implications. Recent research, however, suggests that proximity to low-income housing developments generally has a positive impact on neighborhood property conditions.

To combat slums, homelessness, and other social and economic impacts of a housing unaffordability, many groups have argued for a "right to housing". Article 25 of the Universal Declaration of Human Rights recognizes the right to housing as part of the right to an adequate standard of living. Article 11(1) of the International Covenant on Economic, Social and Cultural Rights (ICESCR) also guarantees the right to housing as part of the right to an adequate standard of living. Many housing rights groups also attempt to combat social and political issues which relate to access to quality affordable housing such as housing discrimination, redlining, and lack of access to amenities in areas with affordable housing including food deserts and transit deserts.

Market-based approaches

Affordable housing needs can be addressed through public policy instruments that focus on the demand side of the market, programs that help households reach financial benchmarks that make housing affordable. This can include approaches that simply promote economic growth in general – in the hope that a stronger economy, higher employment rates, and higher wages will increase the ability of households to acquire housing at market prices. Federal government policies define banking and mortgage lending practices, tax and regulatory measures affecting building materials, professional practices (ex. real estate transactions). The purchasing power of individual households can be enhanced through tax and fiscal policies that result in reducing the cost of mortgages and the cost of borrowing. Public policies may include the implementation of subsidy programs and incentive patterns for average households. For the most vulnerable groups, such as seniors, single-parent families, the disabled, etc. some form of publicly funded allowance strategy can be implemented providing individual households with adequate income to afford housing.

Currently, policies that facilitate production on the supply side include favorable land use policies such as inclusionary zoning, relaxation of environmental regulations, and the enforcement of affordable housing quotas in new developments.

In some countries, such as Canada and the United States, municipal governments began to play a greater role in developing and implementing policies regarding form and density of municipal housing in residential districts, as early as the 1950s. At the municipal level, promoted policy tools include zoning permissions for diverse housing types or missing middle housing types such as duplexes, cottages, rowhomes, fourplexes, and accessory dwelling units. Some municipalities have also reduced the of the amount of parking that must be built for a new structure in order to reduce land acquisition and construction costs. Other common strategies include reducing permitting costs and wait times for new housing, permitting small-lot development, multi-family tax exemptions, density bonuses, preserving existing affordable housing, and transit-oriented development.

Existing housing that is affordable may be used, instead of building new structures. This is called "Naturally Occurring Affordable Housing", or NOAH.

In a housing cooperative people join on a democratic basis to own or manage the housing facility in which they live. Generally these housing units are owned and controlled collectively by a corporation which is owned and controlled jointly by a group of individuals who have equal shares in that corporation. In market rate cooperatives owners can accumulate equity and sell their share of the corporation at market rate. In a limited-equity housing cooperative there are restrictions on the profits members can earn from selling their share (such as caps on sale price) to meant to maintain affordable housing.

Community land trusts are nonprofit corporation that holds land, housing, or other assets on behalf of a neighborhood or community. A community land trust acquires and maintains ownership of the land through a non-for-profit that holds the land in a trust. Homeowners then purchase or build a home on land trust property but do not purchase the land thus reducing costs. If the homeowner sells, they may be limited on what they may sell the home for or the family may earn only a portion of the increased property value with the remainder kept by the trust to preserve affordable housing There are over 225 community land trusts in the United States.

Right to build

An article by libertarian writer Virginia Postrel in the November 2007 issue of Atlantic Monthly reported on a study of the cost of obtaining the "right to build" (i.e. a building permit, red tape, bureaucracy, etc.) in different U.S. cities. The "right to build" cost does not include the cost of the land or the cost of constructing the house. The study was conducted by Harvard economists Edward Glaeser and Kristina Tobio. According to the chart accompanying the article, the cost of obtaining the "right to build" adds approximately $600,000 to the cost of each new house that is built in San Francisco. The study, cited, published by Ed Glaeser and Joseph Gyourko, reached its conclusion about the value of the right to build in different localities based on a methodology of comparing the cost of single-family homes on quarter-acre versus half-acre lots to get a marginal land price and then comparing the selling price of homes to construction costs to get a price for the land plus other costs, with the difference between the two being attributed to the cost of zoning and other local government permitting and regulations.

Government restrictions on affordable housing

Many governments put restrictions on the size or cost of a dwelling that people can live in, making it essentially illegal to live permanently in a house that is too small, low-cost or not compliant with other government-defined requirements. Generally, these laws are implemented in an attempt to raise the perceived "standard" of housing across the country. This can lead to thousands of houses across a country being left empty for much of the year even when there is a great need for more affordable housing; such is the case in countries like Sweden, Norway, Finland and Denmark, where there is a common tradition to have a summer house. This sometimes raises concerns for the respect of rights such as the right to utilize one's property.

As of 2013, in the United States, most cities have zoning codes that set the minimum size for a housing unit (often 400 square feet) as well as the number of non-related persons who can live together in one unit, resulting in having "outlawed the bottom end of the private housing market, driving up rents on everything above it."

In California in 2021, researchers estimated that parking requirements increase the cost of building affordable housing by up to $36,000 per unit, and up to $75,000 per unit in cities like Los Angeles and San Francisco.

Until 2018, in Los Angeles, for an affordable housing development to be allowed to be built, it required a "letter of acknowledgement" from the city councilperson in whose district it would be constructed. This allowed city council members to block affordable housing developments in their district without having to give any reason.

Subsidy-based approaches

Subsidized housing is government or non-for-profit sponsored economic assistance aimed towards alleviating housing costs and expenses, generally for people with low to moderate incomes. Subsidy-based approaches may take the form of government sponsored rental subsidies, government sponsored rental supplements, tax credits, or housing provided by a non-for-profit.

In a mutual-aid housing cooperative, a group of families forms a cooperative to collectively build, own, and manage land by participating in the process of constructing the housing for the cooperative. Each family is responsible for contributing labor towards the construction of the housing complex to reduce costs and members take on responsibilities before, during, and after the construction. The Uruguayan Federation of Mutual Aid Housing Cooperatives (FUCVAM) has completed nearly 500 housing cooperatives housing more than 25,000 families.

The George-Washington-Hof is protected public housing in Vienna

Public, state, or social housing approaches

Public housing is a form of housing tenure in which the property is usually built and owned by a government authority, either central or local. In some countries, public housing is focused on providing affordable housing for low-income earners while in others, such as Singapore, citizens across a wide range of incomes live in public housing. In Vienna, Austria, social housing may be completely government built and run or include a mixture of public land and private-sector construction and management. Combined, the two types of housing represent about 46 percent of the city’s housing stock (26% government owned and managed and 20% a public/private partnership) and house people with a wide variety of incomes. In South Korea the public Korea Land & Housing Corporation has provided homes to 2.9 million households which is 15% of the national total of 19.56 million households. This includes 2.7 million newly-built public housing units and 1.03 million rental homes of which 260,000 were purchased or rented by the Land and Housing Corporation.

Affordable housing by country

The challenges of promoting affordable housing varies by location.

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