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3.1.1: Ecosystem Diversity - Biology

3.1.1: Ecosystem Diversity - Biology


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Measuring biodiversity on a large scale involves measuring ecosystem diversity, the number of different ecosystems on Earth or in a geographical area as well as their relative abundances (figure (PageIndex{a})). The loss of an ecosystem means the loss of the interactions between species and the loss of biological productivity that an ecosystem is able to create. An example of a largely extinct ecosystem in North America is the prairie ecosystem (figure (PageIndex{a})). Prairies once spanned central North America from the boreal forest in northern Canada down into Mexico. They are now all but gone, replaced by crop fields, pasture lands, and suburban sprawl. Many of the species survive, but the hugely productive ecosystem that was responsible for creating our most productive agricultural soils is now gone. As a consequence, their soils are now being depleted unless they are maintained artificially at great expense.

Figure (PageIndex{a}): The variety of ecosystems on Earth—from the coral reef (top) to prairie (bottom)—enables a great diversity of species to exist. Top image by Wise Hok Wai Lum (CC-BY-SA). Bottom image modified from Jim Minnerath, USFWS.

The soil productivity described above is an example of an ecosystem service. These are the products and processes associated with biological systems and are directly or indirectly of immense value to the well-being of people. Some ecosystem services are processes such as the regulation of climate, flooding, and disease. Nutrient cycling, pollination, and regulation of crop pests are ecosystem services important to food production (see the Food Production and Ecosystem Services box below). The water cycle provides fresh water, and photosynthesis adds oxygen to our air. Other ecosystem services are human provisions including food, fuel, and fiber (such as cotton for clothing or timber). Medicines are another important provision (see Importance of Species Diversity). Furthermore, healthy ecosystems allow for recreational activities, such as hiking, kayaking, and camping, and educational opportunities, such as field trips. Nature is also the basis for a significant part of aesthetic and spiritual values held by many cultures.

In 1997, Robert Costanza and his colleagues estimated to annual value of ecosystem services to be $33 trillion dollars ($53 trillion in 2019 dollars), and many consider this to be an underestimation. For comparison the gross domestic product of the United States in 2020 was $21 trillion. Valuing ecosystem services can be difficult, particular for those services that are processes rather than provisions. One strategy is to calculate replacement cost. For example, how much would it cost to control a pest population if it was not regulated by natural processes? Figure (PageIndex{b}) illustrates the value of a few ecosystem services.

Figure (PageIndex{b}): The value of three ecosystem services. Greenhouse gas mitigation (which limits climate change) provided by forests is valued at $3.7 trillion. Unsustainable fisheries have compromised fish availability, costing $50 billion. Coral reef services, such as tourism, are valued at $30 million. Values are in 2010 dollars. Data from The Economics of Ecosystems and Biodiversity Synthesis Report. Image by Future Challenges (CC-BY-SA).

Food Production and Ecosystem Services

Food production relies on several interacting ecosystem services. Most soils contain a huge diversity of organisms that maintain nutrient cycles, breaking down organic matter into nutrient compounds that crops need for growth. These organisms also maintain soil texture that affects water and oxygen dynamics in the soil that are necessary for plant growth. Replacing the work of these organisms in forming arable (farmable) soil is not practically possible. They occur within ecosystems, such as soil ecosystems, as a result of the diverse metabolic activities of the organisms living there, but they provide benefits to human food production, drinking water availability, and breathable air.

Other key ecosystem services related to food production are plant pollination and crop pest control. It is estimated that honeybee pollination within the United States brings in $1.6 billion per year; other pollinators contribute up to $6.7 billion. Over 150 crops in the United States require pollination to produce. Many honeybee populations are managed by beekeepers who rent out their hives’ services to farmers. Honeybee populations in North America have been suffering large losses caused by a syndrome known as colony collapse disorder, a phenomenon with complex and interacting causes.

Other pollinators include a diverse array of other bee species and various insects and birds. Loss of these species would make growing crops requiring pollination impossible, increasing dependence on other crops. A 2002 study by Claire Kremen and colleagues found that native pollinators in Central California (those that historically occurred there; figure (PageIndex{c}) and d) provided full pollination to watermelon crops. This was only true on organic farms that were located near the natural habitat for these pollinators, highlighting the importance of sustainable farming practices and habitat conservation in preserving ecosystem services. Essentially, in a healthy ecosystem, native pollinators eliminated the need for rented honeybee hives. Note that while honeybees are valuable in an agricultural setting, they are not native to North America and can disrupt ecosystems by competing with native bees.

Figure (PageIndex{c}): The California bumble bee (Bombus californicus) is one of several native insects that provided watermelon pollination in Kremen and colleagues' study. Image by Rhododendrites (CC-BY-SA).

Figure (PageIndex{d}): Mason bees are efficient pollinators, and many are native to North America. Image by Robert Engelhardt (CC-BY-SA).

Finally, humans compete for their food with crop pests, most of which are insects. Pesticides control these competitors, but these are costly and lose their effectiveness over time as pest populations adapt. They also lead to collateral damage by killing non-pest species as well as beneficial insects like honeybees, and risking the health of agricultural workers and consumers. Moreover, these pesticides may migrate from the fields where they are applied and do damage to other ecosystems like streams, lakes, and even the ocean (see Industrial Agriculture and Environmental Toxicology). Ecologists believe that the bulk of the work in removing pests is actually done by predators and parasites of those pests, but the impact has not been well studied. A review found that in 74 percent of studies that looked for an effect of landscape complexity (forests and fallow fields near to crop fields) on natural enemies of pests, the greater the complexity, the greater the effect of pest-suppressing organisms. Another experimental study found that introducing multiple enemies of pea aphids (an important alfalfa pest) increased the yield of alfalfa significantly. This study shows that a diversity of pests is more effective at control than one single pest. Loss of diversity in pest enemies will inevitably make it more difficult and costly to grow food. The world’s growing human population faces significant challenges in the increasing costs and other difficulties associated with producing food.

References

Costanza, R., d'Arge, R., de Groot, R. et al. The value of the world's ecosystem services and natural capital. Nature 387, 253–260 (1997). DOI

Kremen, C., Williams, N. M., and Thorp, R. W. Crop pollination from native bees at risk from agricultural intensification. PNAS 99, 6812-16816 (2002). DOI


Definitions for ecosystem diversity ecosys·tem di·ver·si·ty

Ecosystem diversity deals with the variations in ecosystems within a geographical location and its overall impact on human existence and the environment. Ecological diversity is a type of biodiversity. It is the variation in the ecosystems found in a region or the variation in ecosystems over the whole planet. Biodiversity is important because it clears out our water, changes out climate, and provides us with food. Ecological diversity includes the variation in both terrestrial and aquatic ecosystems. Ecological diversity can also take into account the variation in the complexity of a biological community, including the number of different niches, the number of trophic levels and other ecological processes. An example of ecological diversity on a global scale would be the variation in ecosystems, such as deserts, forests, grasslands, wetlands and oceans. Ecological diversity is the largest scale of biodiversity, and within each ecosystem, there is a great deal of both species and genetic diversity.

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Ecosystem diversity refers to the diversity of a place at the level of ecosystems. The term differs from biodiversity, which refers to variation in species rather than ecosystems. Ecosystem diversity can also refer to the variety of ecosystems present in a biosphere, the variety of species and ecological processes that occur in different physical settings.


Conserving Biological Diversity through Ecosystem Resilience

CSIRO, Division of Wildlife and Ecology, P.O. Box 84, Lyneham, A.C.T. 2602, Australia, email [email protected]

CSIRO, Division of Wildlife and Ecology, P.O. Box 84, Lyneham, A.C.T. 2602, Australia, email [email protected]

Abstract

Confusion over the term ecological redundancy (Walker 1992) requires that the concept be clarified in order to advance the developing theory that maintaining ecosystem function conserves biological diversity. The species approach to conserving biological diversity assumes that the species in trouble are already identified. The ecosystem approach attempts to deal with the problem of conserving all the species in an ecosystem, including those not yet known. This is best achieved by ensuring that the ecosystem continues to function approximately as it has by maintaining its essential structure. Ecosystem stability (the probability of all species persisting) is enhanced if each important functional group of organisms (important for maintaining function and structure) comprises several ecologically equivalent species, each with different responses to environmental factors. In this sense ecological redundancy is good because it enhances ecosystem resilience, but functionally important groups (guilds, functional types) that have only one or very few species deserve priority conservation attention because their functions could be quickly lost with species extinctions.

Abstract

La confusión existente sobre el término redundancia ecológica (ver Walker 1992) hace necesario que el concepto sea clarificado a efecto de avanzar en la teoría actualmente en desarrollo sobre el mantenimiento de la función ecosistémica que conserva la diversidad biológica. La estrategia en términos de especie para conservar la diversidad biológica asume que la especie en problemas ya ha sido identificada. La estrategia ecosistémica intenta abordar el problema de conservar todas las especies dentro de un ecosistema, incluyendo aquellas que todavía no son conocidas. La mejor forma de alcanzar esta meta es asegurando que el ecositema continúe funcionando aproximadamente de la misma forma en que lo ha hecho y manteniendo su estructura escencial. La estabilidad ecosistémica (la probabilidad de que todas las especies persistan) es aumentada si cada grupo funcional importante de organismos (importantes para el mantenimiento de la función y estructura), comprende varias especies ecológicamente equivalentes, cada una con repuestas diferentes a los factores ambientales. En este sentido, la redundancia ecológica es buena porque aumenta la resiliencia ecositémica, pero los grupos funcionales importantes (gremios, tipos funcionales) que tienen sólo unas pocas o una sóla especie merecen atención con respecto a la conservación prioritaria, porque sus funciones podrían ser rapidamente perdidas con las extinciones de especies.


Why is biodiversity important?

When most people think of biodiversity, they think of verdant Amazonian rainforests or vibrant coral reefs in tropical seas. But even a typical house in the suburbs teems with an amazing diversity of life. Spiders, insects and other arthropods crawl in nooks and crannies. Molds, algae and fungi bloom on our foods and in our showers. Grasses and weeds grow in the front yard. And birds and mammals camp out in our attics, eaves and chimneys.

In the home, however, many of us consider that diversity a bad thing and combat it with insecticides, household cleaners, weed killers and exterminators. On a global scale, however, biological diversity -- or biodiversity -- is vitally important to the health of our planet and humanity.

To understand why biodiversity is important, we have to think like biologists. Unlike nonscientists, biologists don't think of biodiversity strictly in terms of the number of species found on Earth. In fact, the variety of living things found across the planet -- also known as species diversity or species richness -- is just one part of biodiversity. Genetic diversity, which refers to genetic variation within and between populations, has a big role, too. For example, think about bald eagles in North America. Most bald eagles live in Alaska and British Columbia. Another large population lives in the Gulf States, from Texas and Baja California across to South Carolina and Florida. The number of genes -- discrete units of hereditary information consisting of unique DNA code -- found within all North American bald eagles represents their total genetic diversity.

Our eagle example also demonstrates another aspect of diversity. The Pacific Northwest represents a unique ecosystem. The Gulf Coast of Florida is another unique ecosystem with different characteristics. Having a rich variety of ecosystems, what biologists call ecosystem diversity, constitutes another important level of biodiversity.

Preserving biodiversity at any level may not seem like a big deal -- at first. After all, scientists have described and named nearly 2 million species of organisms. They think 10 million species or more exist on Earth, but haven't been discovered [source: Campbell]. What's the loss of a few species here and there? Well, according to evolutionary biologist E. O. Wilson, species loss may go against biophilia, or the tendency of humans to focus on life and lifelike processes. If this is true, then contributing to the destruction of living things goes against what it means to be human. It also reinforces the notion that we shouldn't deprive future generations of the same diversity of life we enjoy today.

That's the moral argument. We'll tackle the practical side of biodiversity next.


Biodiversity and Ecosystem Functioning

Species diversity is a major determinant of ecosystem productivity, stability, invasibility, and nutrient dynamics. Hundreds of studies spanning terrestrial, aquatic, and marine ecosystems show that high-diversity mixtures are approximately twice as productive as monocultures of the same species and that this difference increases through time. These impacts of higher diversity have multiple causes, including interspecific complementarity, greater use of limiting resources, decreased herbivory and disease, and nutrient-cycling feedbacks that increase nutrient stores and supply rates over the long term. These experimentally observed effects of diversity are consistent with predictions based on a variety of theories that share a common feature: All have trade-off-based mechanisms that allow long-term coexistence of many different competing species. Diversity loss has an effect as great as, or greater than, the effects of herbivory, fire, drought, nitrogen addition, elevated CO2, and other drivers of environmental change. The preservation, conservation, and restoration of biodiversity should be a high global priority.


Biodiversity increases and decreases ecosystem stability

Losses and gains in species diversity affect ecological stability 1-7 and the sustainability of ecosystem functions and services 8-13 . Experiments and models have revealed positive, negative and no effects of diversity on individual components of stability, such as temporal variability, resistance and resilience 2,3,6,11,12,14 . How these stability components covary remains poorly understood 15 . Similarly, the effects of diversity on overall ecosystem stability 16 , which is conceptually akin to ecosystem multifunctionality 17,18 , remain unknown. Here we studied communities of aquatic ciliates to understand how temporal variability, resistance and overall ecosystem stability responded to diversity (that is, species richness) in a large experiment involving 690 micro-ecosystems sampled 19 times over 40 days, resulting in 12,939 samplings. Species richness increased temporal stability but decreased resistance to warming. Thus, two stability components covaried negatively along the diversity gradient. Previous biodiversity manipulation studies rarely reported such negative covariation despite general predictions of the negative effects of diversity on individual stability components 3 . Integrating our findings with the ecosystem multifunctionality concept revealed hump- and U-shaped effects of diversity on overall ecosystem stability. That is, biodiversity can increase overall ecosystem stability when biodiversity is low, and decrease it when biodiversity is high, or the opposite with a U-shaped relationship. The effects of diversity on ecosystem multifunctionality would also be hump- or U-shaped if diversity had positive effects on some functions and negative effects on others. Linking the ecosystem multifunctionality concept and ecosystem stability can transform the perceived effects of diversity on ecological stability and may help to translate this science into policy-relevant information.


Biodiversity is usually explored at three levels - genetic diversity, species diversity and ecosystem diversity. These three levels work together to create the complexity of life on Earth.

Genetic diversity

Genetic diversity is the variety of genes within a species. Each species is made up of individuals that have their own particular genetic composition. This means a species may have different populations, each having different genetic compositions. To conserve genetic diversity, different populations of a species must be conserved.

Genes are the basic units of all life on Earth. They are responsible for both the similarities and the differences between organisms.

Not all groups of animals have the same degree of genetic diversity. Kangaroos, for example, come from recent evolutionary lines and are genetically very similar. Carnivorous marsupials, called dasyurids, come from more ancient lines and are genetically far more diverse. Some scientists believe that we should concentrate on saving more genetically diverse groups, such as dasyurids, which include the Tasmanian Devil, the Numbat and quolls.

If we lose one species of dasyurid, we lose a substantial genetic resource. Several species of dasyurids are endangered and at least one, the Tasmanian Tiger, has disappeared forever since Europeans arrived in Australia.


Acknowledgements

We thank Alison Feldmann-Iles and Amrei Binzer for comments on the manuscript. F.D.S. has received funding by Deutsche Bundesstiftung Umwelt (20008/995). C.G. is supported by the Leopoldina Fellowship Programme under contract number LPDS 2012-07. B.C.R. and U.B. gratefully acknowledge the support of the German Centre for integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig funded by the German Research Foundation (FZT 118). This is ISEM publication 2016-161.


ECONOMIC COSTS

The federal livestock grazing program is heavily subsidized, getting more than $100 million annually in direct subsidies — and possibly three times that in indirect subsidies. The western livestock industry would evaporate as suddenly as fur trapping if it had to pay market rates for services it gets from the federal government.

In 2015 the Center commissioned resource economists to study the economic costs of livestock grazing on public lands. We found that the federal lands grazing program generated $125 million less than what the federal government spent on the program in 2014. Further, we found that federal grazing fees are 93 percent less than fees charged for non-irrigated western private grazing land, or just $1.69 per animal per month for each cow and calf that grazes the public land. (It costs more to feed a house cat.)

Despite the extreme damage done by grazing, western federal rangelands account for less than 3 percent of all forage fed to livestock in the United States. In fact, beef prices wouldn’t be affected if all livestock were removed from public lands in the West.


3.1.1: Ecosystem Diversity - Biology

Three Levels of Biodiversity

Researchers generally accept three levels of biodiversity: genetic, species, and ecosystem. These levels are all interrelated yet distinct enough that they can be studied as three separate components. Some researchers believe that there are fewer or more levels than these, but the consensus is that three levels is a good number to work with. Most studies, either theoretical or experimental, focus on the species level, as it is the easiest to work on both conceptually and in practice. The following parts will cover all levels of diversity, though examples will generally use the species level.

What is it?
Genetic diversity is the variety present at the level of genes. Genes, made of DNA (right), are the building blocks that determine how an organism will develop and what its traits and abilities will be. This level of diversity can differ by alleles (different variants of the same gene, such as blue or brown eyes), by entire genes (which determine traits, such as the ability to metabolize a particular substance), or by units larger than genes such as chromosomal structure.

Genetic diversity can be measured at many different levels, including population, species, community, and biome. Which level is used depends upon what is being examined and why, but genetic diversity is important at each of these levels.

Why is it important?
The amount of diversity at the genetic level is important because it represents the raw material for evolution and adaptation. More genetic diversity in a species or population means a greater ability for some of the individuals in it to adapt to changes in the environment. Less diversity leads to uniformity, which is a problem in the long term, as it is unlikely that any individual in the population would be able to adapt to changing conditions. As an example, modern agricultural practices use monocultures, which are large cultures of genetically identical plants. This is an advantage when is comes to growing and harvesting crops, but can be a problem when a disease or parasite attacks the field, as every plant in the field will be susceptible. Monocultures are also unable to deal well with changing conditions.

What is it related to?
Within species, genetic diversity often increases with environmental variability, which can be expected. If the environment often changes, different genes will have an advantage at different times or places. In this situation genetic diversity remains high because many genes are in the population at any given time. If the environment didn't change, then the small number of genes that had an advantage in that unchanging environment would spread at the cost of the others, causing a drop in genetic diversity.

In communities, it can increase with the diversity of species. How much it increases depends not only on the number of species, but also on how closely related the species are. Species that are closely related (e.g. two species of maple) have similar genetic structures and makeup and therefore do not contribute much additional genetic diversity. These closely-related species will contribute to genetic diversity in the community less than more remotely-related species (e.g. a maple and a pine) would.

An increase in species diversity can also affect the genetic diversity, and do so differently at different levels. If there are many species, the genetic diversity at that level will be larger than when there are fewer species. On the other hand, genetic diversity within each species can decrease. This can happen if the large number of species means so much competition that each species must be extremely specialized, such as only eating a single type of food. If they are so specialized, this specialization will lead to little genetic diversity within any of the species.

Biodiversity studies typically focus on species. They do so not because species diversity is more important than the other two types, but because species diversity is easier to work with. Species are relatively easy to identify by eye in the field, whereas genetic diversity (above) requires laboratories, time and resources to identify and ecosystem diversity (see below) needs many complex measurements to be taken over a long period of time. Species are also easier to conceptualize and have been the basis of much of the evolutionary and ecological research that biodiversity draws on.

Species are well known and are distinct units of diversity. Each species can be considered to have a particular "role" in the ecosystem, so the addition or loss of single species may have consequences for the system as a whole. Conservation efforts often begin with the recognition that a species is endangered in some way, and a change in the number of species in an ecosystem is a readily obtainable and easily comprehensible measure of how healthy the ecosystem is.

For more information on the species level of biodiversity, visit the Redpath Museum's Biodiversity of Quebec website (link will open in a new browser window).

Ecosystem-level theory deals with species distributions and community patterns, the role and function of key species, and combines species functions and interactions. The term "ecosystem" here represents all levels greater than species: associations, communities, ecosystems, and the like. Different names are used for this level and it is sometimes divided into several different levels, such as community and ecosystem levels all these levels are included in this overview. This is the least-understood level of the three described here due to the complexity of the interactions. Trying to understand all the species in an ecosystem and how they affect each other and their surroundings while at the same time being affected themselves, is extremely complex.

One of the difficulties in examining communities is that the transitions between them are usually not very sharp. A lake may have a very sharp boundary between it and the deciduous forest it is in, but the deciduous forest will shift much more gradually to grasslands or to a coniferous forest. This lack of sharp boundaries is known as "open communities" (as opposed to "closed communities," which would have sudden transitions) and makes studying ecosystems difficult, since even defining and delimiting them can be problematic.

Some researchers think of communities as simply the sum of their species and processes, and don't think that any of the properties found in communities are special to that level. Many others disagree, claiming that many of the characteristics of communities are unique and cannot be extrapolated from the species level. Examples of these characteristics include the levels of the food chain and the species at each of those levels, guilds (species in a community that are functionally similar), and other interactions.


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Comments:

  1. Fenrishura

    Dear blog administrator, where are you from?

  2. Kajin

    .Rarely. You can say this exception :) from the rules



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