Nature-based solutions

From Wikipedia, the free encyclopedia

 

Multiple rows of trees and shrubs, as well as a native grass strip, combine in a riparian buffer to protect Bear Creek in Story County, Iowa, United States.

 

Nature-based solutions (NBS) refers to the sustainable management and use of nature for tackling socio-environmental challenges. The challenges include issues such as climate change, water security, water pollution, food security, human health, and disaster risk management. 

A definition by the European Union states that these solutions are "inspired and supported by nature, which are cost-effective, simultaneously provide environmental, social and economic benefits and help build resilience. The Nature-based Solutions Initiative meanwhile defines them as "actions that work with and enhance nature so as to help people adapt to change and disasters". Such solutions bring more, and more diverse, nature and natural features and processes into cities, landscapes and seascapes, through locally adapted, resource-efficient and systemic interventions". With NBS, healthy, resilient and diverse ecosystems (whether natural, managed or newly created) can provide solutions for the benefit of societies and overall biodiversity. 

For instance, the restoration or protection of mangroves along coastlines utilizes a nature-based solution to accomplish several things. Mangroves moderate the impact of waves and wind on coastal settlements or cities and sequester CO_2. . They also provide safe nurseries for marine life that can be the basis for sustaining populations of fish that local populations may depend on. Additionally, the mangrove forests can help control coastal erosion resulting from sea level rise. Similarly, in cities green roofs or walls are nature-based solutions that can be used to moderate the impact of high temperatures, capture storm water, abate pollution, and act as carbon sinks, while enhancing biodiversity. 

Conservation approaches and environment management initiatives have been carried out for decades. What is new is that the benefits of such nature-based solutions to human well-being have been articulated well more recently. Even if the term itself is still being framed, examples of nature-based solutions can be found all over the world, and imitated. Nature-based solutions are on their way to being mainstreamed in national and international policies and programmes (e.g. climate change policy, law, infrastructure investment and financing mechanisms). For example, the theme for World Water Day 2018 was "Nature for water" and by UN-Water's accompanying UN World Water Development Report had the title "Nature-based Solutions for Water".

Background

Chicago City Hall green roof

 

Construction sample of a green roof system

 

Mangroves protect coastlines against erosion (Cape Coral, Florida, United States)

 

Coastal habitat protection at Morro Strand State Beach in San Luis Obispo County, California

 

Constructed wetland for wastewater treatment at an ecological housing estate in Flintenbreite, Germany

 

Societies increasingly face challenges such as climate change, urbanization, jeopardized food security and water resource provision, and disaster risk. One approach to answer these challenges is to singularly rely on technological strategies. An alternative approach is to manage the (socio-)ecological systems in a comprehensive way in order to sustain and potentially increase the delivery of ecosystem services to humans. In this context, nature-based solutions (NBS) have recently been put forward by practitioners and quickly thereafter by policymakers. These solutions stress the sustainable use of nature in solving coupled environmental-social-economic challenges.

While ecosystem services are often valued in terms of immediate benefits to human well-being and economy, NBS focus on the benefits to people and the environment itself, to allow for sustainable solutions that are able to respond to environmental change and hazards in the long-term. NBS go beyond the traditional biodiversity conservation and management principles by "re-focusing" the debate on humans and specifically integrating societal factors such as human well-being and poverty reduction, socio-economic development, and governance principles.

With respect to water issues, NBS can achieve the following, according to the World Water Development Report 2018 by UN-Water:

• Use natural processes to enhance water availability (e.g., soil moisture retention, groundwater recharge),
• Improve water quality (e.g., natural wetlands and constructed wetlands to treat wastewater, riparian buffer strips), and
• Reduce risks associated with water‐related disasters and climate change (e.g., floodplain restoration, green roofs).

Related concepts

In 2015, the European network BiodivERsA highlighted how NBS relate to concepts like ecosystem approaches and ecological engineering. NBS are strongly connected to ideas such as natural systems agriculture, natural solutions, ecosystem-based approaches, adaptation services, natural infrastructure, green infrastructure and ecological engineering. For instance, ecosystem-based approaches are increasingly promoted for climate change adaptation and mitigation by organisations like United Nations Environment Programme and non-governmental organisations such as The Nature Conservancy. These organisations refer to "policies and measures that take into account the role of ecosystem services in reducing the vulnerability of society to climate change, in a multi-sectoral and multi-scale approach".

Likewise, natural infrastructure is defined as a "strategically planned and managed network of natural lands, such as forests and wetlands, working landscapes, and other open spaces that conserves or enhances ecosystem values and functions and provides associated benefits to human populations"; and green infrastructure refers to an "interconnected network of green spaces that conserves natural systems and provides assorted benefits to human populations".

Similarly, the concept of ecological engineering generally refers to "protecting, restoring (i.e. ecosystem restoration) or modifying ecological systems to increase the quantity, quality and sustainability of particular services they provide, or to build new ecological systems that provide services that would otherwise be provided through more conventional engineering, based on non-renewable resources".

Definitions

The International Union for the Conservation of Nature (IUCN) defines NBS as actions to protect, sustainably manage, and restore natural or modified ecosystems, that address societal challenges effectively and adaptively, simultaneously providing human well-being and biodiversity benefits,^[15] with climate change, food security, disaster risks, water security, social and economic development as well as human health being the common societal challenges.

Categories

IUCN proposes to consider NBS as an umbrella concept. Categories and examples of NBS approaches according to IUCN include:

Category of NBS approaches	Examples
Ecosystem restoration approaches	Ecological restoration; Ecological engineering; Forest landscape restoration
Issue-specific ecosystem-related approaches	Ecosystem-based adaptation; Ecosystem-based mitigation; Climate adaptation services; Ecosystem-based disaster risk reduction
Infrastructure-related approaches	Natural infrastructure; Green infrastructure
Ecosystem-based management approaches	Integrated coastal zone management; Integrated water resources management
Ecosystem protection approaches	Area-based conservation approaches including protected area management

Objectives and framing

The general objective of NBS is clear, namely the sustainable management and use of nature for tackling societal challenges. However, different stakeholders view NBS from other perspectives. For instance, IUCN defines NBS as "actions to protect, sustainably manage and restore natural or modified ecosystems, which address societal challenges effectively and adaptively, while simultaneously providing human well-being and biodiversity benefits". This framing puts the need for well-managed and restored ecosystems at the heart of NBS, with the overarching goal of "Supporting the achievement of society's development goals and safeguard human well-being in ways that reflect cultural and societal values and enhance the resilience of ecosystems, their capacity for renewal and the provision of services". 

In the context of the ongoing political debate on jobs and growth (main drivers of the current EU policy agenda), the European Commission underlines that NBS can transform environmental and societal challenges into innovation opportunities, by turning natural capital into a source for green growth and sustainable development. In their view, NBS to societal challenges are "solutions that are inspired and supported by nature, which are cost-effective, simultaneously provide environmental, social and economic benefits and help build resilience. Such solutions bring more, and more diverse, nature and natural features and processes into cities, landscapes and seascapes, through locally adapted, resource-efficient and systemic interventions."

This framing is somewhat broader, and puts economy and social assets at the heart of NBS as importantly as sustaining environmental conditions. It shares similarities with the definition proposed by Maes and Jacobs (2015) defining NBS as "any transition to a use of ES with decreased input of non-renewable natural capital and increased investment in renewable natural processes". In their view, development and evaluation of NBS spans three basic requirements: (1) decrease of fossil fuel input per produced unit; (2) lowering of systemic trade-offs and increasing synergies between ES; and (3) increasing labor input and jobs. Here, nature is seen as a tool to inspire more systemic solutions to societal problems. 

Whatever definition used, promoting sustainability and the increased role of natural, self-sustained processes relying on biodiversity, are inherent to NBS. They constitute actions easily seen as positive for a wide range of stakeholders, as they bring about benefits at environmental, economic and social levels. As a consequence, the concept of NBS is gaining acceptance outside the conservation community (e.g. urban planning) and is now on its way to be mainstreamed into policies and programmes (climate change policy, law, infrastructure investment and financing mechanisms).

Types

Schematic presentation of the NBS typology.

 

In 2014-2015, the European network BiodivERsA mobilized a range of scientists, research donors and stakeholders and proposed a typology characterizing NBS along two gradients. 1. "how much engineering of biodiversity and ecosystems is involved in NBS", and 2. "how many ecosystem services and stakeholder groups are targeted by a given NBS". The typology highlights that NBS can involve very different actions on ecosystems (from protection to management and even creation of new ecosystems) and is based on the assumption that the higher the number of services and stakeholder groups targeted, the lower the capacity to maximize the delivery of each service and simultaneously fulfil the specific needs of all stakeholder groups. As such, three types of NBS are distinguished (Figure 2):

Type 1 – Minimal intervention in ecosystems

Type 1 NBS consists of no or minimal intervention in ecosystems, with the objectives of maintaining or improving the delivery of a range of ES both inside and outside of these conserved ecosystems. Examples include the protection of mangroves in coastal areas to limit risks associated to extreme weather conditions and provide benefits and opportunities to local populations; and the establishment of marine protected areas to conserve biodiversity within these areas while exporting biomass into fishing grounds. This type of NBS is connected to, for example, the concept of biosphere reserves which incorporates core protected areas for nature conservation and buffer zones and transition areas where people live and work in a sustainable way.

Type 2 – Some interventions in ecosystems and landscapes

Type 2 NBS corresponds to management approaches that develop sustainable and multifunctional ecosystems and landscapes (extensively or intensively managed). These types improve the delivery of selected ES compared to what would be obtained with a more conventional intervention. Examples include innovative planning of agricultural landscapes to increase their multi-functionality; and approaches for enhancing tree species and genetic diversity to increase forest resilience to extreme events. This type of NBS is strongly connected to concepts like natural systems agriculture, agro-ecology, and evolutionary-orientated forestry.

Type 3 – Managing ecosystems in extensive ways

Type 3 NBS consists of managing ecosystems in very extensive ways or even creating new ecosystems (e.g., artificial ecosystems with new assemblages of organisms for green roofs and walls to mitigate city warming and clean polluted air). Type 3 is linked to concepts like green and blue infrastructures and objectives like restoration of heavily degraded or polluted areas and greening cities. 

Type 1 and 2 would typically fall within the IUCN NBS framework, whereas Type 2 and moreover Type 3 are often exemplified by EC for turning natural capital into a source for green growth and sustainable development.

Hybrid solutions

Hybrid solutions exist along this gradient both in space and time. For instance, at landscape scale, mixing protected and managed areas could be needed to fulfil multi-functionality and sustainability goals. Similarly, a constructed wetland can be developed as a type 3 but, when well established, may subsequently be preserved and surveyed as a type 1.

Examples

Demonstrating the benefits of nature and healthy ecosystems and showcasing the return on investment they can offer is necessary in order to increase awareness, but also to provide support and guidance on how to implement NBS. A large number of initiatives around the world already highlight the effectiveness of NBS approaches to address a wide range of societal challenges.

India

East Kolkata wetlands

In 2018, The Hindu reported that the East Kolkata wetlands, the world's largest organic sewage treatment facility had been used to clean the sewage of Kolkata in an organic manner by using algae for several decades. In use since the 1930s, the natural system was discovered by Dhrubajyoti Ghosh, an ecologist and a municipal engineer in the 1970s while working in the region. Ghosh worked for decades to protect the wetlands. It had been a practice in Kolkata, one of the five largest cities in India, for the municipal authorities to pump sewage into shallow ponds (bheris). Under the heat of the tropical sun, algae proliferated in them, converting the sewage into clean water, which in turn was used by villagers to grow paddy and vegetables. This system has been in use in the region since the 1930s and treats 750 million litres of wastewater per day, giving livelihood to 100,000 people in the vicinity. For his work, Ghosh was included in the UN Global 500 Roll of Honour in 1990 and received the Luc Hoffmann award in 2016.

Practical implementation

There is currently no accepted basis on which a government agency, municipality or private company can systematically assess the efficiency, effectiveness and sustainability of a particular nature-based solution. However, a series of principles are proposed to guide effective and appropriate implementation, and thus to upscale NBS in practice. For example, NBS embrace and are not meant to replace nature conservation norms. Also, NBS are determined by site-specific natural and cultural contexts that include traditional, local and scientific knowledge. NBS are an integral part of the overall design of policies, and measure or actions, to address a specific challenges. Finally, NBS can be implemented alone or in an integrated manner with other solutions to societal challenges (e.g. technological and engineering solutions) and they are applied at the landscape scale. 

Implementing NBS requires political, economic, and scientific challenges to be tackled. First and foremost, private sector investment is needed, not to replace but to supplement traditional sources of capital such as public funding or philanthropy. The challenge is therefore to provide a robust evidence base for the contribution of nature to economic growth and jobs, and to demonstrate the economic viability of these solutions – compared to technological ones – on a timescale compatible with that of global change. Furthermore, it requires measures like adaptation of economic subsidy schemes, and the creation of opportunities for conservation finance, to name a few. Indeed, such measures will be needed to scale up NBS interventions, and strengthen their impact in mitigating the world's most pressing challenges.

Projects supported by the European Union

Since 2016, the EU is supporting a multi-stakeholder dialogue platform (called ThinkNature) to promote the co-design, testing and deployment of improved and innovative NBS in an integrated way. Creation of such science-policy-business-society interfaces could promote the market uptake of NBS. The project is part of the EU’s Horizon 2020 – Research and Innovation programme, and will last for 3 years. There are a total of 17 international partners involved, including the Technical University of Crete (Project Leader), the University of Helsinki and BiodivERsA. 

In 2017, as part of the Presidency of the Estonian Republic of the Council of the European Union, a conference called “Nature-based Solutions: From Innovation to Common-use” was organized by the Ministry of the Environment of Estonia and the University of Tallinn. This conference aimed to strengthen synergies among various recent initiatives and programs related to NBS launched by the European Commission and by the EU Member States, focusing on policy and governance of NBS, and on research and innovation.

Nature-based Solutions in the Paris Agreement

In recognition of the importance of natural ecosystems for mitigation and adaptation, the Paris Agreement calls on all Parties to acknowledge “the importance of the conservation and enhancement, as appropriate, of sinks and reservoirs of the greenhouse gases” and to “note the importance of ensuring the integrity of all ecosystems, including oceans, and the protection of biodiversity, recognized by some cultures as Mother Earth”. It then includes in its Articles several references to nature-based solutions. For example, Article 5.2 encourages Parties to adopt “…policy approaches and positive incentives for activities relating to reducing emissions from deforestation and forest degradation, and the role of conservation and sustainable management of forests and enhancement of forest carbon stocks in developing countries; and alternative policy approaches, such as joint mitigation and adaptation approaches for the integral and sustainable management of forests, while reaffirming the importance of incentivizing, as appropriate, non-carbon benefits associated with such approaches”. Article 7.1 further encourages Parties to build the resilience of socioeconomic and ecological systems, including through economic diversification and sustainable management of natural resources. In total, the Agreement refers to nature (ecosystems, natural resources, forests) in 13 distinct places. An in-depth analysis of all Nationally Determined Contributions submitted to UNFCCC, revealed that around 130 NDCs or 65% of signatories commit to nature-based solutions in their climate pledges, suggesting broad consensus for the role of nature in helping meet climate change goals. However, high-level commitments rarely translate into robust, measurable actions on-the-ground.

History

The term NBS was put forward by practitioners in the late 2000s (in particular the International Union for the Conservation of Nature and the World Bank) and thereafter by policymakers in Europe (most notably the European Commission).

The term "nature-based solutions" was first used in the late 2000s. It was used in the context of finding new solutions to mitigate and adapt to climate change effects, whilst simultaneously protecting biodiversity and improving sustainable livelihoods. 

The IUCN referred to NBS in a position paper for the United Nations Framework Convention on Climate Change. The term was also adopted by European policymakers, in particular by the European Commission in a report stressing that NBS can offer innovative means to create jobs and growth as part of a green economy. The term started to make appearances in the mainstream media around the time of the Global Climate Action Summit in California in September 2018 

Nutrient cycle

From Wikipedia, the free encyclopedia

Composting within agricultural systems capitalizes upon the natural services of nutrient recycling in ecosystems. Bacteria, fungi, insects, earthworms, bugs, and other creatures dig and digest the compost into fertile soil. The minerals and nutrients in the soil is recycled back into the production of crops.

 

A nutrient cycle (or ecological recycling) is the movement and exchange of organic and inorganic matter back into the production of matter. Energy flow is a unidirectional and noncyclic pathway, whereas the movement of mineral nutrients is cyclic. Mineral cycles include the carbon cycle, sulfur cycle, nitrogen cycle, water cycle, phosphorus cycle, oxygen cycle, among others that continually recycle along with other mineral nutrients into productive ecological nutrition.

Outline

Fallen logs are critical components of the nutrient cycle in terrestrial forests. Nurse logs form habitats for other creatures that decompose the materials and recycle the nutrients back into production.

 

The nutrient cycle is nature's recycling system. All forms of recycling have feedback loops that use energy in the process of putting material resources back into use. Recycling in ecology is regulated to a large extent during the process of decomposition. Ecosystems employ biodiversity in the food webs that recycle natural materials, such as mineral nutrients, which includes water. Recycling in natural systems is one of the many ecosystem services that sustain and contribute to the well-being of human societies.

A nutrient cycle of a typical terrestrial ecosystem.

 

There is much overlap between the terms for the biogeochemical cycle and nutrient cycle. Most textbooks integrate the two and seem to treat them as synonymous terms. However, the terms often appear independently. Nutrient cycle is more often used in direct reference to the idea of an intra-system cycle, where an ecosystem functions as a unit. From a practical point, it does not make sense to assess a terrestrial ecosystem by considering the full column of air above it as well as the great depths of Earth below it. While an ecosystem often has no clear boundary, as a working model it is practical to consider the functional community where the bulk of matter and energy transfer occurs. Nutrient cycling occurs in ecosystems that participate in the "larger biogeochemical cycles of the earth through a system of inputs and outputs."

Complete and closed loop

All systems recycle. The biosphere is a network of continually recycling materials and information in alternating cycles of convergence and divergence. As materials converge or become more concentrated they gain in quality, increasing their potentials to drive useful work in proportion to their concentrations relative to the environment. As their potentials are used, materials diverge, or become more dispersed in the landscape, only to be concentrated again at another time and place.

Ecosystems are capable of complete recycling. Complete recycling means that 100% of the waste material can be reconstituted indefinitely. This idea was captured by Howard T. Odum when he penned that "it is thoroughly demonstrated by ecological systems and geological systems that all the chemical elements and many organic substances can be accumulated by living systems from background crustal or oceanic concentrations without limit as to concentration so long as there is available solar or another source of potential energy" In 1979 Nicholas Georgescu-Roegen proposed the fourth law of entropy stating that complete recycling is impossible. Despite Georgescu-Roegen's extensive intellectual contributions to the science of ecological economics, the fourth law has been rejected in line with observations of ecological recycling. However, some authors state that complete recycling is impossible for technological waste.

A simplified food web illustrating a three-trophic food chain (producers-herbivores-carnivores) linked to decomposers. The movement of mineral nutrients through the food chain, into the mineral nutrient pool, and back into the trophic system illustrates ecological recycling. The movement of energy, in contrast, is unidirectional and noncyclic.

 

Ecosystems execute closed loop recycling where demand for the nutrients that adds to the growth of biomass exceeds supply within that system. There are regional and spatial differences in the rates of growth and exchange of materials, where some ecosystems may be in nutrient debt (sinks) where others will have extra supply (sources). These differences relate to climate, topography, and geological history leaving behind different sources of parent material. In terms of a food web, a cycle or loop is defined as "a directed sequence of one or more links starting from, and ending at, the same species." An example of this is the microbial food web in the ocean, where "bacteria are exploited, and controlled, by protozoa, including heterotrophic microflagellates which are in turn exploited by ciliates. This grazing activity is accompanied by excretion of substances which are in turn used by the bacteria so that the system more or less operates in a closed circuit."

Ecological recycling

A large fraction of the elements composing living matter reside at any instant of time in the world’s biota. Because the earthly pool of these elements is limited and the rates of exchange among the various components of the biota are extremely fast with respect to geological time, it is quite evident that much of the same material is being incorporated again and again into different biological forms. This observation gives rise to the notion that, on the average, matter (and some amounts of energy) are involved in cycles.

An example of ecological recycling occurs in the enzymatic digestion of cellulose. "Cellulose, one of the most abundant organic compounds on Earth, is the major polysaccharide in plants where it is part of the cell walls. Cellulose-degrading enzymes participate in the natural, ecological recycling of plant material." Different ecosystems can vary in their recycling rates of litter, which creates a complex feedback on factors such as the competitive dominance of certain plant species. Different rates and patterns of ecological recycling leaves a legacy of environmental effects with implications for the future evolution of ecosystems.

Ecological recycling is common in organic farming, where nutrient management is fundamentally different compared to agri-business styles of soil management. Organic farms that employ ecosystem recycling to a greater extent support more species (increased levels of biodiversity) and have a different food web structure. Organic agricultural ecosystems rely on the services of biodiversity for the recycling of nutrients through soils instead of relying on the supplementation of synthetic fertilizers. The model for ecological recycling agriculture adheres to the following principals:

• Protection of biodiversity.
• Use of renewable energy.
• Recycling of plant nutrients.

Where produce from an organic farm leaves the farm gate for the market the system becomes an open cycle and nutrients may need to be replaced through alternative methods.

Ecosystem engineers

An illustration of an earthworm casting taken from Charles Darwin's publication on the movement of organic matter in soils through the ecological activities of worms.

 

From the largest to the smallest of creatures, nutrients are recycled by their movement, by their wastes, and by their metabolic activities. This illustration shows an example of the whale pump that cycles nutrients through the layers of the oceanic water column. Whales can migrate to great depths to feed on bottom fish (such as sand lance Ammodytes spp.) and surface to feed on krill and plankton at shallower levels. The whale pump enhances growth and productivity in other parts of the ecosystem.

 

The persistent legacy of environmental feedback that is left behind by or as an extension of the ecological actions of organisms is known as niche construction or ecosystem engineering. Many species leave an effect even after their death, such as coral skeletons or the extensive habitat modifications to a wetland by a beaver, whose components are recycled and re-used by descendants and other species living under a different selective regime through the feedback and agency of these legacy effects. Ecosystem engineers can influence nutrient cycling efficiency rates through their actions. 

Earthworms, for example, passively and mechanically alter the nature of soil environments. Bodies of dead worms passively contribute mineral nutrients to the soil. The worms also mechanically modify the physical structure of the soil as they crawl about (bioturbation), digest on the molds of organic matter they pull from the soil litter. These activities transport nutrients into the mineral layers of soil. Worms discard wastes that create worm castings containing undigested materials where bacteria and other decomposers gain access to the nutrients. The earthworm is employed in this process and the production of the ecosystem depends on their capability to create feedback loops in the recycling process.

Shellfish are also ecosystem engineers because they: 1) Filter suspended particles from the water column; 2) Remove excess nutrients from coastal bays through denitrification; 3) Serve as natural coastal buffers, absorbing wave energy and reducing erosion from boat wakes, sea level rise and storms; 4) Provide nursery habitat for fish that are valuable to coastal economies.

Fungi contribute to nutrient cycling and nutritionally rearrange patches of ecosystem creating niches for other organisms. In that way fungi in growing dead wood allow xylophages to grow and develop and xylophages, in turn, affect dead wood, contributing to wood decomposition and nutrient cycling in the forest floor.

History

Nutrient cycling has a historical foothold in the writings of Charles Darwin in reference to the decomposition actions of earthworms. Darwin wrote about "the continued Following the Greeks, the idea of a hydrological cycle (water is considered a nutrient) was validated and quantified by Halley in 1687.

Variations in terminology

In 1926 Vernadsky coined the term biogeochemistry as a sub-discipline of geochemistry. However, the term nutrient cycle pre-dates biogeochemistry in a pamphlet on silviculture in 1899: "These demands by no means pass over the fact that at places where sufficient quantities of humus are available and where, in case of continuous decomposition of litter, a stable, nutrient humus is present, considerable quantities of nutrients are also available from the biogenic nutrient cycle for the standing timber. In 1898 there is a reference to the nitrogen cycle in relation to nitrogen fixing microorganisms. Other uses and variations on the terminology relating to the process of nutrient cycling appear throughout history:

• The term mineral cycle appears early in a 1935 in reference to the importance of minerals in plant physiology: "...ash is probably either built up into its permanent structure, or deposited in some way as waste in the cells, and so may not be free to re-enter the mineral cycle."
• The term nutrient recycling appears in a 1964 paper on the food ecology of the wood stork: "While the periodic drying up and reflooding of the marshes creates special survival problems for organisms in the community, the fluctuating water levels favor rapid nutrient recycling and subsequent high rates of primary and secondary production"
• The term natural cycling appears in a 1968 paper on the transportation of leaf litter and its chemical elements for consideration in fisheries management: "Fluvial transport of tree litter from drainage basins is a factor in natural cycling of chemical elements and in degradation of the land."
• The term ecological recycling appears in a 1968 publication on future applications of ecology for the creation of different modules designed for living in extreme environments, such as space or under sea: "For our basic requirement of recycling vital resources, the oceans provide much more frequent ecological recycling than the land area. Fish and other organic populations have higher growth rates, vegetation has less capricious weather problems for sea harvesting."
• The term bio-recycling appears in a 1976 paper on the recycling of organic carbon in oceans: "Following the actualistic assumption, then, that biological activity is responsible for the source of dissolved organic material in the oceans, but is not important for its activities after death of the organisms and subsequent chemical changes which prevent its bio-recycling, we can see no major difference in the behavior of dissolved organic matter between the prebiotic and post-biotic oceans."

Water is also a nutrient. In this context, some authors also refer to precipitation recycling, which "is the contribution of evaporation within a region to precipitation in that same region." These variations on the theme of nutrient cycling continue to be used and all refer to processes that are part of the global biogeochemical cycles. However, authors tend to refer to natural, organic, ecological, or bio-recycling in reference to the work of nature, such as it is used in organic farming or ecological agricultural systems.

Recycling in novel ecosystems

An endless stream of technological waste accumulates in different spatial configurations across the planet and turns into a predator in our soils, our streams, and our oceans. This idea was similarly expressed in 1954 by ecologist Paul Sears: "We do not know whether to cherish the forest as a source of essential raw materials and other benefits or to remove it for the space it occupies. We expect a river to serve as both vein and artery carrying away waste but bringing usable material in the same channel. Nature long ago discarded the nonsense of carrying poisonous wastes and nutrients in the same vessels." Ecologists use population ecology to model contaminants as competitors or predators. Rachel Carson was an ecological pioneer in this area as her book Silent Spring inspired research into biomagification and brought to the worlds attention the unseen pollutants moving into the food chains of the planet.

In contrast to the planets natural ecosystems, technology (or technoecosystems) is not reducing its impact on planetary resources. Only 7% of total plastic waste (adding up to millions upon millions of tons) is being recycled by industrial systems; the 93% that never makes it into the industrial recycling stream is presumably absorbed by natural recycling systems In contrast and over extensive lengths of time (billions of years) ecosystems have maintained a consistent balance with production roughly equaling respiratory consumption rates. The balanced recycling efficiency of nature means that production of decaying waste material has exceeded rates of recyclable consumption into food chains equal to the global stocks of fossilized fuels that escaped the chain of decomposition.

Pesticides soon spread through everything in the ecosphere-both human technosphere and nonhuman biosphere-returning from the 'out there' of natural environments back into plant, animal, and human bodies situated at the 'in here' of artificial environments with unintended, unanticipated, and unwanted effects. By using zoological, toxicological, epidemiological, and ecological insights, Carson generated a new sense of how 'the environment' might be seen.

Microplastics and nanosilver materials flowing and cycling through ecosystems from pollution and discarded technology are among a growing list of emerging ecological concerns. For example, unique assemblages of marine microbes have been found to digest plastic accumulating in the worlds oceans. Discarded technology is absorbed into soils and creates a new class of soils called technosols. Human wastes in the Anthropocene are creating new systems of ecological recycling, novel ecosystems that have to contend with the mercury cycle and other synthetic materials that are streaming into the biodegradation chain. Microorganisms have a significant role in the removal of synthetic organic compounds from the environment empowered by recycling mechanisms that have complex biodegradation pathways. The effect of synthetic materials, such as nanoparticles and microplastics, on ecological recycling systems is listed as one of the major concerns for ecosystem in this century.

Technological recycling

Recycling in human industrial systems (or technoecosystems) differs from ecological recycling in scale, complexity, and organization. Industrial recycling systems do not focus on the employment of ecological food webs to recycle waste back into different kinds of marketable goods, but primarily employ people and technodiversity instead. Some researchers have questioned the premise behind these and other kinds of technological solutions under the banner of 'eco-efficiency' are limited in their capability, harmful to ecological processes, and dangerous in their hyped capabilities. Many technoecosystems are competitive and parasitic toward natural ecosystems. Food web or biologically based "recycling includes metabolic recycling (nutrient recovery, storage, etc.) and ecosystem recycling (leaching and in situ organic matter mineralization, either in the water column, in the sediment surface, or within the sediment."

Scandium

From Wikipedia, the free encyclopedia

Scandium,  ₂₁Sc

Scandium
Pronunciation	/ˈskændiəm/ ​(SKAN-dee-əm)
Appearance	silvery white
Standard atomic weight Ar, std(Sc)	44.955908(5)
Scandium in the periodic table
Hydrogen Helium Lithium Beryllium Boron Carbon Nitrogen Oxygen Fluorine Neon Sodium Magnesium Aluminium Silicon Phosphorus Sulfur Chlorine Argon Potassium Calcium Scandium Titanium Vanadium Chromium Manganese Iron Cobalt Nickel Copper Zinc Gallium Germanium Arsenic Selenium Bromine Krypton Rubidium Strontium Yttrium Zirconium Niobium Molybdenum Technetium Ruthenium Rhodium Palladium Silver Cadmium Indium Tin Antimony Tellurium Iodine Xenon Caesium Barium Lanthanum Cerium Praseodymium Neodymium Promethium Samarium Europium Gadolinium Terbium Dysprosium Holmium Erbium Thulium Ytterbium Lutetium Hafnium Tantalum Tungsten Rhenium Osmium Iridium Platinum Gold Mercury (element) Thallium Lead Bismuth Polonium Astatine Radon Francium Radium Actinium Thorium Protactinium Uranium Neptunium Plutonium Americium Curium Berkelium Californium Einsteinium Fermium Mendelevium Nobelium Lawrencium Rutherfordium Dubnium Seaborgium Bohrium Hassium Meitnerium Darmstadtium Roentgenium Copernicium Nihonium Flerovium Moscovium Livermorium Tennessine Oganesson – ↑ Sc ↓ Y calcium ← scandium → titanium
Atomic number (Z)	21
Group	group 3
Period	period 4
Block	d-block
Element category	transition metal
Electron configuration	[Ar] 3d1 4s2
Electrons per shell	2, 8, 9, 2
Physical properties
Phase at STP	solid
Melting point	1814 K ​(1541 °C, ​2806 °F)
Boiling point	3109 K ​(2836 °C, ​5136 °F)
Density (near r.t.)	2.985 g/cm3
when liquid (at m.p.)	2.80 g/cm3
Heat of fusion	14.1 kJ/mol
Heat of vaporization	332.7 kJ/mol
Molar heat capacity	25.52 J/(mol·K)
Vapor pressure P (Pa) 1 10 100 1 k 10 k 100 k at T (K) 1645 1804 (2006) (2266) (2613) (3101)
Atomic properties
Oxidation states	+1, +2, +3 (an amphoteric oxide)
Electronegativity	Pauling scale: 1.36
Ionization energies	1st: 633.1 kJ/mol 2nd: 1235.0 kJ/mol 3rd: 2388.6 kJ/mol
Atomic radius	empirical: 162 pm
Covalent radius	170±7 pm
Van der Waals radius	211 pm
Spectral lines of scandium
Other properties
Natural occurrence	primordial
Crystal structure	​hexagonal close-packed (hcp)
Thermal expansion	α, poly: 10.2 µm/(m·K) (at r.t.)
Thermal conductivity	15.8 W/(m·K)
Electrical resistivity	α, poly: 562 nΩ·m (at r.t., calculated)
Magnetic ordering	paramagnetic
Magnetic susceptibility	+315.0·10−6 cm3/mol (292 K)[4]
Young's modulus	74.4 GPa
Shear modulus	29.1 GPa
Bulk modulus	56.6 GPa
Poisson ratio	0.279
Brinell hardness	736–1200 MPa
CAS Number	7440-20-2
History
Naming	after Scandinavia
Prediction	Dmitri Mendeleev (1871)
Discovery and first isolation	Lars Fredrik Nilson (1879)
Main isotopes of scandium
Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct 44m2Sc syn 58.61 h IT 44Sc γ 44Sc ε 44Ca 45Sc 100% stable 46Sc syn 83.79 d β− 46Ti γ – 47Sc syn 80.38 d β− 47Ti γ – 48Sc syn 43.67 h β− 48Ti γ –

Scandium is a chemical element with the symbol Sc and atomic number 21. A silvery-white metallic d-block element, it has historically been classified as a rare-earth element, together with yttrium and the lanthanides. It was discovered in 1879 by spectral analysis of the minerals euxenite and gadolinite from Scandinavia.

Scandium is present in most of the deposits of rare-earth and uranium compounds, but it is extracted from these ores in only a few mines worldwide. Because of the low availability and the difficulties in the preparation of metallic scandium, which was first done in 1937, applications for scandium were not developed until the 1970s. The positive effects of scandium on aluminium alloys were discovered in the 1970s, and its use in such alloys remains its only major application. The global trade of scandium oxide is about 10 tonnes per year.

The properties of scandium compounds are intermediate between those of aluminium and yttrium. A diagonal relationship exists between the behavior of magnesium and scandium, just as there is between beryllium and aluminium. In the chemical compounds of the elements in group 3, the predominant oxidation state is +3.

Properties

Chemical characteristics

Scandium is a soft metal with a silvery appearance. It develops a slightly yellowish or pinkish cast when oxidized by air. It is susceptible to weathering and dissolves slowly in most dilute acids. It does not react with a 1:1 mixture of nitric acid (HNO₃) and 48% hydrofluoric acid (HF), possibly due to the formation of an impermeable passive layer. Scandium turnings ignite in air with a brilliant yellow flame to form scandium oxide.

Isotopes

In nature, scandium is found exclusively as the isotope ⁴⁵Sc, which has a nuclear spin of 7/2; this is its only stable isotope. Thirteen radioisotopes have been characterized with the most stable being ⁴⁶Sc, which has a half-life of 83.8 days; ⁴⁷Sc, 3.35 days; the positron emitter ⁴⁴Sc, 4 h; and ⁴⁸Sc, 43.7 hours. All of the remaining radioactive isotopes have half-lives less than 4 hours, and the majority of these have half-lives less than 2 minutes. This element also has five nuclear isomers, with the most stable being ^44mSc (t_1/2 = 58.6 h).

The isotopes of scandium range from ³⁶Sc to ⁶⁰Sc. The primary decay mode at masses lower than the only stable isotope, ⁴⁵Sc, is electron capture, and the primary mode at masses above it is beta emission. The primary decay products at atomic weights below ⁴⁵Sc are calcium isotopes and the primary products from higher atomic weights are titanium isotopes.

Occurrence

In Earth's crust, scandium is not rare. Estimates vary from 18 to 25 ppm, which is comparable to the abundance of cobalt (20–30 ppm). Scandium is only the 50th most common element on Earth (35th most abundant in the crust), but it is the 23rd most common element in the Sun. However, scandium is distributed sparsely and occurs in trace amounts in many minerals. Rare minerals from Scandinavia and Madagascar such as thortveitite, euxenite, and gadolinite are the only known concentrated sources of this element. Thortveitite can contain up to 45% of scandium in the form of scandium oxide.

The stable form of scandium is created in supernovas via the r-process.

Production

The world production of scandium is in the order of 15 tonnes per year, in the form of scandium oxide. The demand is about 50% higher, and both the production and demand keep increasing. In 2003, only three mines produced scandium: the uranium and iron mines in Zhovti Vody in Ukraine, the rare-earth mines in Bayan Obo, China, and the apatite mines in the Kola peninsula, Russia; since then many other countries have built scandium-producing facilities, including 5 tonnes/year (7.5 tonnes/year Sc₂O₃) by Nickel Asia Corporation and Sumitomo Metal Mining in the Philippines. In the US, NioCorp Development hopes to raise $1 billion toward opening a niobium mine at its Elk Creek site in southeast Nebraska which may be able to produce as much as 95 tonnes of scandium dioxide annually. In each case scandium is a byproduct from the extraction of other elements and is sold as scandium oxide.

To produce metallic scandium, the oxide is converted to scandium fluoride and then reduced with metallic calcium. 

Madagascar and the Iveland-Evje region in Norway have the only deposits of minerals with high scandium content, thortveitite (Sc,Y)₂(Si₂O₇) and kolbeckite ScPO₄·2H₂O, but these are not being exploited.

The absence of reliable, secure, stable, long-term production has limited the commercial applications of scandium. Despite this low level of use, scandium offers significant benefits. Particularly promising is the strengthening of aluminium alloys with as little as 0.5% scandium. Scandium-stabilized zirconia enjoys a growing market demand for use as a high-efficiency electrolyte in solid oxide fuel cells.

Price

Because of its rarity, scandium is among the most expensive elements. Price for pure scandium fluctuates between 4,000 and 20,000 US dollars per kilogram. Meanwhile, the limited market generates a variety of prices at any given time. In 2010, at the peak of the rare-earths shortage, the price of scandium rose to over 15,000 US dollars per kilogram, and the widely commercially used scandium oxide (Sc₂O₃) was selling above 7 000 US dollars per kilogram. Since then the limited demand coupled with steady production keeps the price at its 20-year average.

Compounds

Scandium chemistry is almost completely dominated by the trivalent ion, Sc³⁺. The radii of M³⁺ ions in the table below indicate that the chemical properties of scandium ions have more in common with yttrium ions than with aluminium ions. In part because of this similarity, scandium is often classified as a lanthanide-like element.

Ionic radii (pm)

Al	Sc	Y	La	Lu
53.5	74.5	90.0	103.2	86.1

Oxides and hydroxides

The oxide Sc
₂O
₃ and the hydroxide Sc(OH)
₃ are amphoteric:

Sc(OH)
₃ + 3 OH⁻ → [Sc(OH)
₆]³⁻ (scandate ion)

Sc(OH)
₃ + 3 H⁺ + 3 H
₂O → [Sc(H
₂O)
₆]³⁺

α- and γ-ScOOH are isostructural with their aluminium hydroxide oxide counterparts. Solutions of Sc³⁺ in water are acidic due to hydrolysis.

Halides and pseudohalides

The halides ScX₃, where X= Cl, Br, or I, are very soluble in water, but ScF₃ is insoluble. In all four halides, the scandium is 6-coordinated. The halides are Lewis acids; for example, ScF₃ dissolves in a solution containing excess fluoride ion to form [ScF₆]³⁻. The coordination number 6 is typical for Sc(III). In the larger Y³⁺ and La³⁺ ions, coordination numbers of 8 and 9 are common. Scandium triflate is sometimes used as a Lewis acid catalyst in organic chemistry.

Organic derivatives

Scandium forms a series of organometallic compounds with cyclopentadienyl ligands (Cp), similar to the behavior of the lanthanides. One example is the chlorine-bridged dimer, [ScCp₂Cl]₂ and related derivatives of pentamethylcyclopentadienyl ligands.

Uncommon oxidation states

Compounds that feature scandium in oxidation states other than +3 are rare but well characterized. The blue-black compound CsScCl₃ is one of the simplest. This material adopts a sheet-like structure that exhibits extensive bonding between the scandium(II) centers. Scandium hydride is not well understood, although it appears not to be a saline hydride of Sc(II). As is observed for most elements, a diatomic scandium hydride has been observed spectroscopically at high temperatures in the gas phase. Scandium borides and carbides are non-stoichiometric, as is typical for neighboring elements.

Lower oxidation states (+2, +1, 0) have also been observed in organoscandium compounds.

History

Dmitri Mendeleev, who is referred to as the father of the periodic table, predicted the existence of an element ekaboron, with an atomic mass between 40 and 48 in 1869. Lars Fredrik Nilson and his team detected this element in the minerals euxenite and gadolinite in 1879. Nilson prepared 2 grams of scandium oxide of high purity. He named the element scandium, from the Latin Scandia meaning "Scandinavia". Nilson was apparently unaware of Mendeleev's prediction, but Per Teodor Cleve recognized the correspondence and notified Mendeleev.

Metallic scandium was produced for the first time in 1937 by electrolysis of a eutectic mixture of potassium, lithium, and scandium chlorides, at 700–800 °C. The first pound of 99% pure scandium metal was produced in 1960. Production of aluminium alloys began in 1971, following a US patent. Aluminium-scandium alloys were also developed in the USSR.

Laser crystals of gadolinium-scandium-gallium garnet (GSGG) were used in strategic defense applications developed for the Strategic Defense Initiative (SDI) in the 1980s and 1990s.

Red giant stars near the Galactic Center

In early 2018, evidence was gathered from spectrometer data of significant scandium, vanadium and yttrium abundances in red giant stars in the Nuclear Star Cluster (NSC) in the Galactic Center. Further research showed that this was an illusion caused by the relatively low temperature (below 3,500 K) of these stars masking the abundance signals, and that this phenomenon was observable in other red giants.

Applications

Parts of the MiG-29 are made from Al-Sc alloy.

 

The addition of scandium to aluminium limits the grain growth in the heat zone of welded aluminium components. This has two beneficial effects: the precipitated Al₃Sc forms smaller crystals than in other aluminium alloys, and the volume of precipitate-free zones at the grain boundaries of age-hardening aluminium alloys is reduced. Both of these effects increase the usefulness of the alloy. However, titanium alloys, which are similar in lightness and strength, are cheaper and much more widely used.

The alloy Al₂₀Li₂₀Mg₁₀Sc₂₀Ti₃₀ is as strong as titanium, light as aluminium, and hard as ceramic.

The main application of scandium by weight is in aluminium-scandium alloys for minor aerospace industry components. These alloys contain between 0.1% and 0.5% of scandium. They were used in the Russian military aircraft, specifically the Mikoyan-Gurevich MiG-21 and MiG-29.

Some items of sports equipment, which rely on high-performance materials, have been made with scandium-aluminium alloys, including baseball bats and bicycle frames and components. Lacrosse sticks are also made with scandium. The American firearm manufacturing company Smith & Wesson produces semi-automatic pistols and revolvers with frames of scandium alloy and cylinders of titanium or carbon steel.

Dentists use erbium-chromium-doped yttrium-scandium-gallium garnet (Er,Cr:YSGG) lasers for cavity preparation and in endodontics.

The first scandium-based metal-halide lamps were patented by General Electric and initially made in North America, although they are now produced in all major industrialized countries. Approximately 20 kg of scandium (as Sc₂O₃) is used annually in the United States for high-intensity discharge lamps. One type of metal-halide lamp, similar to the mercury-vapor lamp, is made from scandium triiodide and sodium iodide. This lamp is a white-light source with high color rendering index that sufficiently resembles sunlight to allow good color-reproduction with TV cameras. About 80 kg of scandium is used in metal-halide lamps/light bulbs globally per year.

The radioactive isotope ⁴⁶Sc is used in oil refineries as a tracing agent. Scandium triflate is a catalytic Lewis acid used in organic chemistry.

Health and safety

Elemental scandium is considered non-toxic, though extensive animal testing of scandium compounds has not been done. The median lethal dose (LD₅₀) levels for scandium chloride for rats have been determined as 4 mg/kg for intraperitoneal and 755 mg/kg for oral administration. In the light of these results, compounds of scandium should be handled as compounds of moderate toxicity.