Tundra

From Wikipedia, the free encyclopedia

Tundra
Tundra in Greenland
Map showing Arctic tundra
Geography
Area	11,563,300 km2 (4,464,600 sq mi)
Climate type	ET

In physical geography, tundra (/ˈtʌndrə, ˈtʊn-/) is a type of biome where the tree growth is hindered by low temperatures and short growing seasons. The term tundra comes through Russian тундра (tûndra) from the Kildin Sami word тӯндар (tūndâr) meaning "uplands", "treeless mountain tract". There are three types of tundra: Arctic tundra, alpine tundra, and Antarctic tundra. In tundra, the vegetation is composed of dwarf shrubs, sedges and grasses, mosses, and lichens. Scattered trees grow in some tundra regions. The ecotone (or ecological boundary region) between the tundra and the forest is known as the tree line or timberline.

Arctic

Arctic tundra occurs in the far Northern Hemisphere, north of the taiga belt. The word "tundra" usually refers only to the areas where the subsoil is permafrost, or permanently frozen soil. (It may also refer to the treeless plain in general, so that northern Sápmi would be included.) Permafrost tundra includes vast areas of northern Russia and Canada.^[2] The polar tundra is home to several peoples who are mostly nomadic reindeer herders, such as the Nganasan and Nenets in the permafrost area (and the Sami in Sápmi).

Tundra in Siberia

Arctic tundra contains areas of stark landscape and is frozen for much of the year. The soil there is frozen from 25 to 90 cm (10 to 35 in) down, and it is impossible for trees to grow. Instead, bare and sometimes rocky land can only support low growing plants such as moss, heath (Ericaceae varieties such as crowberry and black bearberry), and lichen. There are two main seasons, winter and summer, in the polar tundra areas. During the winter it is very cold and dark, with the average temperature around −28 °C (−18 °F), sometimes dipping as low as −50 °C (−58 °F). However, extreme cold temperatures on the tundra do not drop as low as those experienced in taiga areas further south (for example, Russia's and Canada's lowest temperatures were recorded in locations south of the tree line). During the summer, temperatures rise somewhat, and the top layer of seasonally-frozen soil melts, leaving the ground very soggy. The tundra is covered in marshes, lakes, bogs and streams during the warm months. Generally daytime temperatures during the summer rise to about 12 °C (54 °F) but can often drop to 3 °C (37 °F) or even below freezing. Arctic tundras are sometimes the subject of habitat conservation programs. In Canada and Russia, many of these areas are protected through a national Biodiversity Action Plan.

Vuntut National Park in Canada

Tundra tends to be windy, with winds often blowing upwards of 50–100 km/h (30–60 mph). However, in terms of precipitation, it is desert-like, with only about 15–25 cm (6–10 in) falling per year (the summer is typically the season of maximum precipitation). Although precipitation is light, evaporation is also relatively minimal. During the summer, the permafrost thaws just enough to let plants grow and reproduce, but because the ground below this is frozen, the water cannot sink any lower, and so the water forms the lakes and marshes found during the summer months. There is a natural pattern of accumulation of fuel and wildfire which varies depending on the nature of vegetation and terrain. Research in Alaska has shown fire-event return intervals (FRIs) that typically vary from 150 to 200 years, with dryer lowland areas burning more frequently than wetter highland areas.^[4]
 

A group of muskoxen in Alaska

The biodiversity of tundra is low: 1,700 species of vascular plants and only 48 species of land mammals can be found, although millions of birds migrate there each year for the marshes.^[5] There are also a few fish species. There are few species with large populations. Notable animals in the Arctic tundra include caribou (reindeer), musk ox, Arctic hare, Arctic fox, snowy owl, lemmings, and polar bears (only near ocean-fed bodies of water).^[6] Tundra is largely devoid of poikilotherms such as frogs or lizards.

Due to the harsh climate of Arctic tundra, regions of this kind have seen little human activity, even though they are sometimes rich in natural resources such as oil and uranium. In recent times this has begun to change in Alaska, Russia, and some other parts of the world.

Relationship with global warming

A severe threat to tundra is global warming, which causes permafrost to melt. The melting of the permafrost in a given area on human time scales (decades or centuries) could radically change which species can survive there.^[7]

Another concern is that about one third of the world's soil-bound carbon is in taiga and tundra areas. When the permafrost melts, it releases carbon in the form of carbon dioxide and methane,^[8] both of which are greenhouse gases. The effect has been observed in Alaska. In the 1970s the tundra was a carbon sink, but today, it is a carbon source.^[9] Methane is produced when vegetation decays in lakes and wetlands.^[10]

The amount of greenhouse gases which will be released under projected scenarios for global warming have not been reliably quantified by scientific studies, although a few studies were reported to be underway in 2011. It is uncertain whether the impact of increased greenhouse gases from this source will be minimal or massive.^[10]

In locations where dead vegetation and peat has accumulated there is a risk of wildfire such as the 1,039 km² (401 sq mi) of tundra which burned in 2007 on the north slope of the Brooks Range in Alaska.^[10] Such events may both result from and contribute to global warming.^[11]

Antarctic

Tundra on the Péninsule Rallier du Baty, Kerguelen Islands.

Antarctic tundra occurs on Antarctica and on several Antarctic and subantarctic islands, including South Georgia and the South Sandwich Islands and the Kerguelen Islands. Most of Antarctica is too cold and dry to support vegetation, and most of the continent is covered by ice fields. However, some portions of the continent, particularly the Antarctic Peninsula, have areas of rocky soil that support plant life. The flora presently consists of around 300–400 lichens, 100 mosses, 25 liverworts, and around 700 terrestrial and aquatic algae species, which live on the areas of exposed rock and soil around the shore of the continent. Antarctica's two flowering plant species, the Antarctic hair grass (Deschampsia antarctica) and Antarctic pearlwort (Colobanthus quitensis), are found on the northern and western parts of the Antarctic Peninsula.^[12] In contrast with the Arctic tundra, the Antarctic tundra lacks a large mammal fauna, mostly due to its physical isolation from the other continents. Sea mammals and sea birds, including seals and penguins, inhabit areas near the shore, and some small mammals, like rabbits and cats, have been introduced by humans to some of the subantarctic islands. The Antipodes Subantarctic Islands tundra ecoregion includes the Bounty Islands, Auckland Islands, Antipodes Islands, the Campbell Island group, and Macquarie Island.^[13] Species endemic to this ecoregion include Nematoceras dienemum and Nematoceras sulcatum, the only subantarctic orchids; the royal penguin; and the Antipodean albatross.^[13]

There is some ambiguity on whether Magellanic moorland, on the west coast of Patagonia, should be considered tundra or not.^[14] Phytogeographer Edmundo Pisano called it tundra (Spanish: tundra Magallánica) since he considered the low temperatures key to restrict plant growth.^[14]

The flora and fauna of Antarctica and the Antarctic Islands (south of 60° south latitude) are protected by the Antarctic Treaty.^[15]

Alpine

Alpine tundra at Venezuelan Andes

Alpine tundra does not contain trees because the climate and soils at high altitude block tree growth. Alpine tundra is distinguished from arctic tundra in that alpine tundra typically does not have permafrost, and alpine soils are generally better drained than arctic soils. Alpine tundra transitions to subalpine forests below the tree line; stunted forests occurring at the forest-tundra ecotone (the treeline) are known as Krummholz.

Alpine tundra occurs in mountains worldwide. The flora of the alpine tundra is characterized by dwarf shrubs close to the ground. The cold climate of the alpine tundra is caused by the low air temperatures, and is similar to polar climate.

Climatic classification

Tundra region with fjords, glaciers and mountains. Kongsfjorden, Spitsbergen.

Tundra climates ordinarily fit the Köppen climate classification ET, signifying a local climate in which at least one month has an average temperature high enough to melt snow (0 °C (32 °F)), but no month with an average temperature in excess of 10 °C (50 °F). The cold limit generally meets the EF climates of permanent ice and snows; the warm-summer limit generally corresponds with the poleward or altitudinal limit of trees, where they grade into the subarctic climates designated Dfd, Dwd and Dsd (extreme winters as in parts of Siberia), Dfc typical in Alaska, Canada, parts of Scandinavia, European Russia, and Western Siberia (cold winters with months of freezing), or even Cfc (no month colder than −3 °C (27 °F) as in parts of Iceland and southernmost South America). Tundra climates as a rule are hostile to woody vegetation even where the winters are comparatively mild by polar standards, as in Iceland.

Despite the potential diversity of climates in the ET category involving precipitation, extreme temperatures, and relative wet and dry seasons, this category is rarely subdivided. Rainfall and snowfall are generally slight due to the low vapor pressure of water in the chilly atmosphere, but as a rule potential evapotranspiration is extremely low, allowing soggy terrain of swamps and bogs even in places that get precipitation typical of deserts of lower and middle latitudes. The amount of native tundra biomass depends more on the local temperature than the amount of precipitation.

Mammoth steppe

From Wikipedia, the free encyclopedia

Ukok Plateau, one of the last remnants of the mammoth steppe^[1]

During the Last Glacial Maximum, the mammoth steppe was the Earth’s most extensive biome. It spanned from Spain eastwards across Eurasia to Canada and from the arctic islands southwards to China. It had a cold, dry climate, the vegetation was dominated by palatable high-productivity grasses, herbs and willow shrubs, and the animal biomass was dominated by the bison, horse, and the woolly mammoth. This ecosystem covered wide areas of the northern part of the globe, thrived for approximately 100,000 years without major changes, and then suddenly became all but extinct about 12,000 years ago.

Naming

At the end of the 19th century, Alfred Nehring (1890)^[9] and Iwan Dementjewitsch Chersky (Tscherski, 1891)^[10] proposed that during the last glacial period a major part of northern Europe had been populated by large herbivores and that a steppe climate had prevailed there.^[11] In 1982, the scientist R. Dale Guthrie coined the term "mammoth steppe" for this paleoregion.

Origin of the mammoth steppe

The last glacial period, commonly referred to as the 'Ice Age', spanned from 126,000 YBP–11,700 YBP^[13] and was the most recent glacial period within the current ice age which occurred during the last years of the Pleistocene era.^[14] It reached its peak during the last glacial maximum, when ice sheets commenced advancing from 33,000 years BP and reached their maximum positions 26,500 years BP. Deglaciation commenced in the Northern Hemisphere approximately 19,000 years BP, and in Antarctica approximately 14,500 years BP, which is consistent with evidence that it was the primary source for an abrupt rise in the sea level at that time.^[15]

During the peak of the last glacial maximum, a vast mammoth steppe stretched from Spain across Eurasia and over the Bering land bridge into Alaska and the Yukon where it was stopped by the Wisconsin glaciation. This land bridge existed because more of the planet's water was locked up in ice than now and therefore the sea levels were lower. When the sea levels began to rise this bridge was inundated around 11,000 years BP.^[16]

During glacial periods, there is clear evidence for intense aridity due to water being held in glaciers and their associated effects on climate.^[17][18][7] The mammoth steppe was like a huge 'inner court' that was surrounded on all sides by moisture-blocking features: massive continental glaciers, high mountains, and frozen seas. These kept rainfall low and created more days with clear skies than are seen today, which increased evaporation in the summer leading to aridity, and radiation of warmth from the ground into the black night sky in the winter leading to cold.^[7] This is thought to have been caused by seven factors:

1. The driving force for the core Asian steppe was an enormous and stable high-pressure system north of the Tibetan Plateau.
2. Deflection of the larger portion of the Gulf Stream southward, past southern Spain onto the coast of Africa, reduced temperatures (hence moisture and cloud cover) that the North Atlantic Current brings to Western Europe.
3. Growth of the Scandinavian ice sheet created a barrier to North Atlantic moisture.
4. Icing over of the North Atlantic sea surface with reduced flow of moisture from the east.
5. The winter (January) storm track seems to have swept across Eurasia on this axis.
6. Lowered sea levels exposed a large continental shelf to the north and east producing a vast northern plain which increased the size of the continent to the north.
7. North American glaciers shielded interior Alaska and the Yukon Territory from moisture flow. These physical barriers to moisture flow created a vast arid basin or protected 'inner court' spanning parts of three continents.^[7]

Biota

Climatic suitability for the woolly mammoths in the Late Pleistocene and Holocene. Increasing intensities of red represent increasing suitability of the climate and increasing intensities of green represent decreasing suitability. Black points are the records of mammoth presence for each of the periods. Black lines represent the northern limit of modern humans and black dotted lines indicate uncertainty in the limit of modern humans (D. Nogués-Bravo et al. 2008).^[19]

Animal biomass and plant productivity of the mammoth steppe were similar to today's African savannah.^[6] There is no comparison to it today.^[7][6]

Plants

The paleo-environment changed across time,^[20] a proposal that is supported from mammoth dung samples found in northern Yakutia.^[21] During Pleniglacial interstadials, alder, birch, and pine trees survived in northern Siberia, however during the Last Glacial Maximum only a treeless steppe vegetation existed. At the onset of the Late Glacial Interstadial (15,000–11,000 BP), global warming resulted in shrub and dwarf birch in northeastern Siberia, which was then colonized by open woodland with birch and spruce during the Younger Dryas (12,900–11,700 YBP). By the Holocene (10,000 YBP), patches of closed larch and pine forests developed.^[21] Past researchers had once assumed that the mammoth steppe was very unproductive because they had assumed that its soils had a very low carbon content; however, these soils (yedoma) were preserved in the permafrost of Siberia and Alaska and are the largest reservoir of organic carbon known. It was a highly productive environment.^[6][22] The vegetation was dominated by palatable high-productivity grasses, herbs and willow shrubs.^[3][6][8]

Animals

The mammoth steppe was dominated in biomass by bison, horse, and the woolly mammoth, and was the center for the evolution of the Pleistocene woolly fauna.^[7] On Wrangel Island, the remains of woolly mammoth, woolly rhinoceros, horse, bison and musk ox have been found. Reindeer and small animal remains do not preserve, but reindeer excrement has been found in sediment.^[6] In the most arid regions of the mammoth steppe that were to the south of Central Siberia and Mongolia, woolly rhinoceros were common^[23][6] but woolly mammoths were rare.^[24][6] Reindeer live in the far north of Mongolia today and historically their southern boundary passed through Germany and along the steppes of eastern Europe,^[25][6] indicating they once covered much of the mammoth steppe.^[6] Mammoths survived on the Taimyr Peninsula until the Holocene.^[8][6] A small population of mammoth survived on St. Paul Island, Alaska, up until 3750 BC,^[26][27] and the small^[28] mammoths of Wrangel Island survived until 1650 BC.^[29][30] Bison in Alaska and the Yukon, and horses and muskox in northern Siberia, have survived the loss of the mammoth steppe.^[6] One study has proposed that a change of suitable climate caused a significant drop in the mammoth population size, which made them vulnerable to hunting from expanding human populations. The coincidence of both of these impacts in the Holocene most likely set the place and time for the extinction of the woolly mammoth.^[19]

Decline of the mammoth steppe

The mammoth steppe had a cold, dry climate.^[7][6] During the past interglacial warmings, forests of trees and shrubs expanded northwards into the mammoth steppe, when northern Siberia, Alaska and the Yukon (Beringia) would have formed a mammoth steppe refugium. When the planet grew colder again, the mammoth steppe expanded.^[6] This ecosystem covered wide areas of the northern part of the globe, thrived for approximately 100,000 years without major changes, and then suddenly became extinct about 12,000 years ago.^[7]

There are two theories about the decline of the mammoth steppe.

Climate change

The Climatic Hypothesis assumes that the vast mammoth ecosystem could have only existed within a certain range of climatic parameters. At the beginning of the Holocene 10,000 years ago, mossy forests, tundra, lakes and wetlands displaced mammoth steppe. It has been assumed that in contrast to other previous interglacials the cold dry climate switched to a warmer wetter climate that, in turn, caused the disappearance of the grasslands and their dependent megafauna.^[3]

The extinct steppe bison (Bison priscus) survived across the northern region of central eastern Siberia until 8000 years ago. A study of the frozen mummy of a steppe bison found in northern Yakutia, Russia indicated that it was a pasture grazer in a habitat that was becoming dominated by shrub and tundra vegetation. Higher temperature and rainfall led to a decrease in its previous habitat during the early Holocene, and this led to population fragmentation followed by extinction.^[31]

In 2017 a study looked at the environmental conditions across Europe, Siberia and the Americas from 25,000–10,000 YBP. The study found that prolonged warming events leading to deglaciation and maximum rainfall occurred just prior to the transformation of the rangelands that supported megaherbivores into widespread wetlands that supported herbivore-resistant plants. The study proposes that moisture-driven environmental change led to the megafaunal extinctions, and that Africa's trans-equatorial position allowed rangeland to continue to exist between the deserts and the central forests; therefore fewer megafauna species became extinct there.^[32]

Human predation

The Ecosystem Hypothesis assumes that the vast mammoth ecosystem extended over a range of many regional climates and was not affected by climate fluctuations. Its highly productive grasslands were maintained by animals trampling any mosses and shrubs, and actively transpiring grasses and herbs dominated. At the beginning of the Holocene the rise in precipitation was accompanied by increased temperature, and so its climatic aridity did not change substantially. As a result of human hunting, the decreasing density of the animals was not enough to maintain the grasslands, leading to an increase in forests, shrubs and mosses with further animal reduction due to loss of feed. The mammoth continued to exist on isolated Wrangel Island until a few thousand years ago, and some of the other megafauna from that time still exist today, which indicates that something other than climate change was responsible for megafaunal extinctions.^[6]

Remains of mammoth that had been hunted by humans 45,000 YBP have been found at Yenisei Bay in the central Siberian Arctic.^[33] Two other sites in the Maksunuokha River valley to the south of the Shirokostan Peninsula, northeast Siberia, dated between 14,900 and 13,600 years ago showed the remains of mammoth hunting and the production of micro-blades similar to those found in northwest North America, suggesting a cultural connection.^[34]

Last remnants

Ubsunur Hollow Biosphere Reserve located on the border of Mongolia and the Republic of Tuva is one of the last remnants of the mammoth steppe^[1]

During the Holocene, the arid-adapted species became extinct or were reduced to minor habitats.^[7] Cold and dry conditions similar to the last glacial period are found today in the eastern Altai-Sayan mountains of Central Eurasia,^[35][1] with no significant changes occurring between the cold phase of the Pleistocene and the Holocene.^[36][1] Recent paleo-biome reconstruction^[37][38][1] and pollen analysis^{[39][40][41][1]} suggest that some present-day Altai-Sayan areas could be considered the closest analogy to the mammoth steppe environment.^[1] The environment of this region is considered to have been stable for the past 40,000 years. The Eastern part of the Altai-Sayan region forms a Last Glacial refugium. In both the Last Glacial and modern times, the eastern Altai-Sayan region has supported large herbivore and predator species adapted to the steppe, desert and alpine biomes where these biomes have not been separated by forest belts. None of the surviving Pleistocene mammals live in temperate forest, taiga, or tundra biomes. The areas of Ukok-Sailiugem in the southern Altai Republic, and Khar Us Nuur and Uvs Nuur (Ubsunur Hollow) in western Mongolia, have supported reindeer and saiga antelope since the glacial period.^[1]

Image gallery

The paleo-environment changed across time.^[20] Below is a gallery of mammoth steppe plants, the location where they have been identified as widespread, the time period and supporting citations.

• Gallery - plant, place and period
• 

  Artemisia, Taymyr lowlands 24,000–10,300 YBP,^[42] Yakutia 22,500 YBP,^[21] Alaska and the Yukon 15,000-11,500 YBP^[20][6]
  
• 

  Cyperaceae (sedges), Yakutia 22,500 YBP,^[21] Alaska and the Yukon 15,000-11,500 YBP^[20][6]
  
• 

  Gramineae (grasses), Taymyr lowlands 24,000–10,300 YBP,^[42] Yakutia 22,500 YBP,^[21] Alaska and the Yukon 15,000-11,500 YBP^[20][6]
  
• 

  Salix (willow), Taymyr lowlands 24,000–10,300 YBP,^[42] Yakutia 22,500 YBP,^[21] Alaska and the Yukon 15,000-11,500 YBP^[20][6]
  
• 

  Rubus chamaemorus (cloudberry) Yakutia 22,500 YBP^[21]
  
• 

  Potentilla (cinquefoil) Yakutia 22,500 YBP^[21]
  
• 

  Larch Taymyr lowlands 48,000–25,000 YBP, then later 9,400-2,900 YBP^[42]
  
• 

  Betula nana (dwarf birch) Taymyr lowlands 48,000–25,000 YBP^[42]
  

Discovery Advances Efforts to Prevent Spread of Cancer

News   Jun 25, 2018 | Original story from University of Alberta

Original link:  https://www.technologynetworks.com/tn/news/discovery-advances-efforts-to-prevent-spread-of-cancer-305326

 

Oregon Health and Science University, Knight Cancer
Institute. NCI Visuals

Newly identified gene targets could be key to preventing the spread of cancer, new University of Alberta research has shown.

In a study published last week in Nature Communications, a team of U of A researchers said that because they’ve identified the appropriate genes, there’s potential to create therapies that could almost completely block metastasis in a number of deadly cancers.

“It’s of potentially incredible significance,” said John Lewis, the Alberta Cancer Foundation Frank and Carla Sojonky Chair in Prostate Cancer Research at the U of A and a member of the Cancer Research Institute of Northern Alberta (CRINA). “Metastasis kills 90 per cent of all patients who have cancer, and with this study we have discovered 11 new ways to potentially end metastasis.”

In the study, the team used a unique platform it created—a shell-less avian embryo—to visualize the growth and spread of cancer cells in real time. The researchers used a molecular tool called a knockout library to insert short hairpin RNA (shRNA) vectors into cancer cells that bound to specific genes in the cells and stopped them from activating. They then inserted those cancer cells into the shell-less embryos and observed as they formed clusters of cancer, identifying which ones showed properties of being non-metastatic.

“When we found compact colonies [of cancer], that meant that the key steps of metastasis were blocked,” said Konstantin Stoletov, lead author of the study and a research associate in the Lewis lab. “After that we could pull them out, query what the gene is and then validate that the gene is actually responsible for metastasis.”

The approach allowed the team to detect and identify 11 genes that play essential roles in cancer cell metastasis. According to the researchers, the genes discovered are widely involved in the process of metastasis and not unique to any one cancer.

They now plan to test the metastasis-associated genes and gene-products as drug targets with an aim of stopping metastasis.

“We know that cancer, once it becomes metastatic, will keep spreading to other parts of the body and continue to get worse because of that,” said Lewis. “If we can stop metastasis at any step of progression in cancer patients, we’re going to have a significant effect on survival.”

The team is now hoping to progress its research to human trials over the next few years. The Lewis lab is also expanding efforts to explore for other types of genes called microRNAs that may present even stronger therapeutic targets for preventing metastasis.

The research was funded by the Canadian Cancer Society and the Alberta Cancer Foundation.

Lewis and Stoletov’s paper, “Quantitative in vivo whole genome motility screen reveals novel therapeutic targets to block cancer metastasis,” was published June 14 in Nature Communications.

This article has been republished from materials provided by University of Alberta. Note: material may have been edited for length and content. For further information, please contact the cited source.

Sustainability science

From Wikipedia, the free encyclopedia

 

Sustainability science emerged in the 21st century as a new academic discipline. This new field of science was officially introduced with a "Birth Statement" at the World Congress "Challenges of a Changing Earth 2001" in Amsterdam organized by the International Council for Science (ICSU), the International Geosphere-Biosphere Programme (IGBP), the International Human Dimensions Programme on Global Environmental Change and the World Climate Research Programme (WCRP). The field reflects a desire to give the generalities and broad-based approach of “sustainability” a stronger analytic and scientific underpinning as it "brings together scholarship and practice, global and local perspectives from north and south, and disciplines across the natural and social sciences, engineering, and medicine". Ecologist William C. Clark proposes that it can be usefully thought of as "neither 'basic' nor 'applied' research but as a field defined by the problems it addresses rather than by the disciplines it employs" and that it "serves the need for advancing both knowledge and action by creating a dynamic bridge between the two".

The field is focused on examining the interactions between human, environmental, and engineered systems to understand and contribute to solutions for complex challenges that threaten the future of humanity and the integrity of the life support systems of the planet, such as climate change, biodiversity loss, pollution and land and water degradation.

Sustainability science, like sustainability itself, derives some impetus from the concepts of sustainable development and environmental science.^[6] Sustainability science provides a critical framework for sustainability^[7] while sustainability measurement provides the evidence-based quantitative data needed to guide sustainability governance.^[8]

Definition

Consensual definition of sustainability science is as elusive as the definition of "sustainability" or "sustainable development". In an overview presented on its website in 2008 the Sustainability Science Program at Harvard University described the field in the following way, stressing its interdisciplinarity:

'Sustainability science' is problem-driven, interdisciplinary scholarship that seeks to facilitate the design, implementation, and evaluation of effective interventions that foster shared prosperity and reduced poverty while protecting the environment. It is defined by the problems it addresses rather than the disciplines it employs. It thus draws as needed from multiple disciplines of the natural, social, medical and engineering sciences, from the professions, and from the knowledge of practice.^[9]

Susan W. Kieffer and colleagues, in 2003, suggested, more specifically, that sustainability science is:

... the cultivation, integration, and application of knowledge about Earth systems gained especially from the holistic and historical sciences (such as geology, ecology, climatology, oceanography) coordinated with knowledge about human interrelationships gained from the social sciences and humanities, in order to evaluate, mitigate, and minimize the consequences, regionally and worldwide, of human impacts on planetary systems and on societies across the globe and into the future – that is, in order that humans can be knowledgeable Earth stewards.^[10]

It has been noted that the new paradigm

... must encompass different magnitudes of scales (of time, space, and function), multiple balances (dynamics), multiple actors (interests) and multiple failures (systemic faults).^[11]

Others take a much broader view of sustainability science, emphasizing the need to analyze the root causes of the fundamental unsustainability of the prevailing economic system, such as the emphasis on growth as key to solving political and social problems and advancing society's well-being. In a 2012 article entitled "Sustainability Science Needs to Include Sustainable Consumption," published in Environment: Science and Policy for Sustainable Development, Halina Brown argues that sustainability science must include the study of the sociology of material consumption and the structure of consumerist society, the role of technology in aggravating the unsustainable social practices, as well as in solving the problems they create, the macroeconomic theories that presuppose economic growth as a necessary condition for advancing societal well-being, and others.^[12]

Broad objectives

The case for making research and development an important component of sustainable development strategies was embraced by many international scientific organizations in the mid-1980s, promoted by the Brundtland Commission's report Our Common Future in 1987, and noted in the Agenda 21 plan that emerged from the United Nations Conference on Environment and Development in 1992 and further developed at the World Summit on Sustainable Development, held in Johannesburg in 2002.

The topics of the following sub-headings indicate recurring themes that are addressed in the literature of sustainability science.^[13] In 2010 a compendium of basic papers in this new discipline was published as Readings in Sustainability Science and Technology, edited by Robert Kates, with a preface by William Clark.^[14] The 2012 Commentary by Halina Brown extensively expands the scope of that seminal publication.^[12] This is work in progress. The 2012 Encyclopedia of Sustainability Science and Technology was created as a collaboration of over 1000 scientists to provide peer-reviewed entries covering sustainability research and policy evaluations of technology.^[15]

Knowledge structuring of issues

Knowledge structuring has been identified as an essential first step in the effort to acquire a comprehensive view of sustainability issues which are both complex and interconnected. This is needed as a response to the requirements of academia, industry and government.

Coordination of data

The key research and data for sustainability are sourced from many scientific disciplines, topics and organisations. A major part of knowledge structuring will entail building up the tools that provide an “overview” of what is known. Sustainability science can construct and coordinate a framework within which the vast amount of data can be easily accessed.

Interdisciplinary approaches

The attempt, by sustainability science, to understand the integrated “whole” of planetary and human systems requires cooperation between scientific, social and economic disciplines, public and private sectors, academia and government. In short it requires a massive global cooperative effort and one major task of sustainability science is to assist integrated cross-disciplinary coordination.

Journals

• Consilience: The Journal of Sustainable Development, seminannual journal published since 2009, now "in partnership with Columbia University Libraries".^[16]
• International Journal of Sustainable Development & World Ecology, journal with six issues per year, published since 1994 by Taylor & Francis.^[17]
• Surveys and Perspectives Integrating Environment & Society (S.A.P.I.EN.S.), semiannual journal published by Veolia Environment from 2008-2015.^[18] A notable essay on sustainability indicators by Paul-Marie Boulanger appeared in the first issue.^[19]
• Sustainability Science, journal launched by Springer in June 2006.^[20]
• Sustainability: Science, Practice, Policy, an open-access journal for sustainable solutions launched in March 2005. Now published by Taylor & Francis.^[21]
• Sustainability: The Journal of Record, bimonthly journal published by Mary Ann Liebert, Inc. beginning in December 2007.^[22]
• A section dedicated to sustainability science in the multidisciplinary journal Proceedings of the National Academy of Sciences was launched in 2006.^[23]
• GAIA: Ecological Perspectives for Science and Society / GAIA: Ökologische Perspektiven für Wissenschaft und Gesellschaft, a quarterly inter- and transdisciplinary journal for scientists and other interested parties concerned with the causes and analyses of environmental and sustainability problems and their solutions. Launched in 1992 and published by oekom verlag on behalf of GAIA Society – Konstanz, St. Gallen, Zurich.^[24]

List of sustainability science programs

In recent years, more and more university degree programs have developed formal curricula which address issues of sustainability science and global change:

Bachelor's

• B.A. or B.S. Sustainability at Arizona State University, USA
• B.S. Sustainability Studies at Florida Institute of Technology, USA
• B.S. or B.S./M.S. combined - Sustainability Science at Montclair State University, NJ, USA
• B.Sc. Environmental Sciences at Leuphana University Lueneburg, Germany
• B.Sc. Environmental and Sustainability Studies at Leuphana University Lueneburg, Germany
• B.Sc. Sustainability Science at Solent University, UK

Master's

• M.S. Sustainability: Science and Society at Brock University, ON, Canada
• M.Sc. Sustainability Science and Solutions, Lappeenranta University of Technology, Finland
• M.Sc. Sustainability Science at Montclair State University, NJ, USA
• M.Sc. Sustainability Science at Leuphana University Lueneburg, Germany
• MBA Sustainability Management at Leuphana University Lueneburg, Germany
• Master's degree at the IATEUR - Urban, Regional Planning and Sustainability Science Institute, Reims University, France
• M.Sc. "Sustainability Science and Policy" at Maastricht University - ICIS, The Netherlands
• MS/MBA Erb Institute for Sustainable Enterprise (multiple sub specialties) at the University of Michigan, USA
• M.Sc. "Sustainable Resource Management" at the Technical University of Munich, Germany
• M.Sc. "Global Change Ecology" at the University of Bayreuth, Germany
• M.Sc. "Global Change Management" at the University of Applied Sciences Eberswalde, Germany
• M.Sc. "Environmental Change and Global Sustainability" at the University of Helsinki, Finland
• M.Sc. "Environmental Studies and Sustainability Science" at the University of Lund, Sweden
• "Master of Development Practice Degree Program" at the University of Minnesota, USA
• "Lund University's International Master's Programme in Environmental Studies and Sustainability Science" at Lund University, Sweden.
• "Master`s Degree in Creative Sustainability" at Aalto University, Finland
• M.Sc. Strategic Leadership towards Sustainability at Blekinge Institute of Technology, Karlskrona, Sweden
• Master's in Sustainable Product-Service System Innovation at Blekinge Institute of Technology, Karlskrona, Sweden
• MSc Environmental Technology at Imperial College London, UK, offers eight specialist streams in: water, pollution, business, global environmental change & policy, economics & policy, ecological management, environmental analysis & assessment, energy policy.
• MPhil in Engineering for Sustainable Development, University of Cambridge, UK
• M.Sc. Sustainability Science, University of Massachusetts Amherst, USA
• MSEM (Professional Masters in Sustainability and Environmental Management), at the University of Saskatchewan, School of Environment and Sustainability, Saskatoon, SK, Canada
• M.S. Sustainability Management, Columbia University, USA

Master's and doctoral

• M.Sc/M.A/Ph.D in Sustainability Science at School of Sustainability, Arizona State University, Tempe, USA
• M.Sc. in Sustainability Science and PhD in Environmental Management at Montclair State University, NJ, USA
• M.Sc./Ph.D. "Building Science and Sustainability" in the Department of Architecture at the University of California, Berkeley, USA
• M.Sc. Sustainability/PhD in Sustainability Science at the United Nations University Institute for the Advanced Study of Sustainability, Tokyo, Japan
• M.Sc./Ph.D. in Environment and Sustainability at the University of Saskatchewan, School of Environment and Sustainability, Saskatoon, SK, Canada
• "Graduate Program in Sustainability Science" at the University of Tokyo, Japan
• "Graduate Program in Sustainability Science" at Hosei University, Japan
• M.Sc/Ph.D. in Sustainability Science at the National Autonomous University of Mexico (UNAM), Mexico City, Mexico
• Ph.D. in Sustainable Development, Columbia University, USA

Other

• Course on the Science of Sustainability by the department of Earth and Environmental Sciences at Indian Institute of Science Education & Research, Bhopal.
• Environmental Science and Policy Program at Clark University, Worcester, MA, USA, offers a graduate seminar "Sustainable Consumption Production."
• "Global Change Ecology" at the University of California, Irvine, USA
• "Sustainability Specialization" at Michigan State University, USA
• Graduate Certificate in Sustainability at Michigan Technological University, USA [3]
• Undergraduate certificate in environment and sustainability at the University of Saskatchewan, School of Environment and Sustainability, Saskatoon, SK, Canada
• Minor in Global Environmental Sustainability and Sustainable Water Interdisciplinary Minor (SWIM) at the School of Global Environmental Sustainability at Colorado State University [4], USA

Recently, numbers of people doing a PhD gather under the title of sustainable sciences purposes. They come from different backgrounds and work around this topic. This sort of work enables the topic to be interdisciplinary and improve the work of PhDs. Here is an example of such gathering : BhIOSS Group (Birmingham Initiative on Sustainable Sciences)

Ecological yield

From Wikipedia, the free encyclopedia

Ecological yield is the harvestable population growth of an ecosystem. It is most commonly measured in forestry: sustainable forestry is defined as that which does not harvest more wood in a year than has grown in that year, within a given patch of forest.

However, the concept is also applicable to water, soil, and any other aspect of an ecosystem which can be both harvested and renewed—called renewable resources. The carrying capacity of an ecosystem is reduced over time if more than the amount which is "renewed" (refreshed or regrown or rebuilt) is consumed.

Ecosystem services analysis calculates the global yield of the Earth's biosphere to humans as a whole. This is said to be greater in size than the entire human economy. However, it is more than just yield, but also the natural processes that increase biodiversity and conserve habitat which result in the total value of these services. "Yield" of ecological commodities like wood or water, useful to humans, is only a part of it.

Very often an ecological yield in one place offsets an ecological load in another. Greenhouse gas released in one place, for instance, is fairly evenly distributed in the atmosphere, and so greenhouse gas control can be achieved by creating a carbon sink literally anywhere else.

History

Some of the earliest academic papers on the subject were researching methods of sustainable fishing. Work of Russel et al. in 1931 observed in particular that ”it appears that the ideal of a stabilised fishery yielding a constant maximum value is impractical.”^[1] This work was mostly theoretical. Practical work would begin later, performed by industry and government agencies.

Motivation

Ecological yield is a theoretical construct which aggregates information from several physically measurable quantities. It can be used to reason about other ecological indicators such as the footprint. It can also be used as a decision-making tool for governments and corporations.

Ecological footprint

The idea of ecological footprints is to measure the cost of economic activity in terms of the amount of ecologically productive land required to sustain it. Doing this accurately requires estimating how productive the land is; in other words, it requires measuring ecological yield. Conversely, one can extract ecological yield estimates from ecological footprint estimates.

Avoiding overexploitation

Corporations take out loans to buy equipment and land use rights. In order to pay back these loans, they must extract and sell resources from the land. If the corporation is ignorant of the yield of the land in question, then the debt instruments may demand a yield greater than the ecological capacity to renew. Green economics links this process with ecocide and poses solutions through monetary reform.

Even well-meaning corporations may systematically overestimate the yield of an ecosystem. In the case of multiple corporations bidding for land rights, an economic phenomenon known as the winner's curse causes the winning party to systematically overestimate the economic value of the land. Typically the economic value comes mostly from the ecological yield, in which case the corporation will overestimate that as well.

Another form of overestimation may come from generalizing data from other ecosystems. For example, the same species of fish in two different systems may have significantly different diets. If its diet in one region consists mostly of algae but in another region consists largely of smaller fish, then it will be more expensive for the latter ecosystem to produce the fish. Yield will be correspondingly lower in the second region. This example illustrates the need for ecosystem-specific study and monitoring in order to reason about ecological yield.

Definition and properties

One may define yearly ecological yield for a fixed ecological product as follows: the yield is the amount of the product which may be removed from the ecosystem so that it is capable of recovering in one year. As a theoretical property of ecosystems, it cannot be measured directly but only estimated. Note that definition is sensitive to the time period which is allowed for recovery: the amount of product one can remove which regenerates over 3 years is not necessarily 3 times that which one can remove and regenerate over 1 year. The yearly ecological yield is most useful because of the cycle of seasons and the commercial notion of the fiscal year. The seasons affect growth through temperature, sunlight, and rain, especially at the lowest trophic level. The fiscal year affects decisions by corporations to harvest resources: they may choose to harvest at or above ideal levels based on their need for short-term cash flow.

Calculation techniques

Yield of the whole biosphere

In 1986, Vitousek et al.^[2] estimated that humans made use of 50 petagrams (50 billion tons) per year of biomass produced from photosynthesis. They also estimated that these 50 billion tons comprised between 20% and 40% of photosynthetic activity on earth. Separately, the Global Footprint Network estimates the total human footprint as 1.6 times the total biosphere. ^[3] This implies that ecosystems are overexploited by a factor of 1.6 on average.

Theoretical prediction

In most biomes, the only form of primary production is photosynthesis. In other words, all new biomass can be traced back to photosynthetic plants and algae by a chain of predation. Therefore, one can predict the yield of one organism in an ecosystem as a function of the yield of its primary producers. When the biomass from prey is converted into biomass in its predator, some losses occur due to biological and thermodynamic inefficiency. The conversion rate is typically about 10%. In other words, 100 kg of plant matter may be converted into 10 kg of herbivores, which then may be converted to 1 kg of carnivores who exclusively eat herbivores. One can compute the trophic level of an organism as the weighted average of length of the predation chain from the organism to a primary producer. This trophic level determines an exponential multiplier to convert from primary producer biomass to the organism's biomass.

Measurement techniques

Measuring forests

One can measure the amount of wood removed from a forest by asking the company who removed it; typically only one company has the logging rights to any given plot of land. In order to measure the regrowth of the forest in the coming year, typically one picks a representative subsample of the region and tracks every single tree in the subsample.

One such study measured growth in a section of the Tapajós National Forest for 13 years after logging activity.^[4] The loggers intended to harvest on a 30-year cycle. Logging in this region is restricted to mature trees measuring at least 45 cm DBH. Before logging, the region had somewhere between 150 m³ and 200 m³ of mature tree volume per hectare. Loggers removed about 75 m³ of tree per hectare, between 40% and 50% of the standing mass.

The authors show that growth rates in the region were elevated for up to 3 years after logging. After 13 years of growth, the basal area reached 75% of its original volume. They also show that logging makes substantial changes to the species composition and canopy structure of the forest. This introduces subjectivity into the notion of "recovery" for an ecosystem.