5.8: Ecosystem Diversity - Biology

An ecosystem is a community plus the physical environment that it occupies at a given time. An ecosystem can exist at any scale, for example, from the size of a small tide pool up to the size of the entire biosphere. However, lakes, marshes, and forest stands represent more typical examples of the areas that are compared in discussions of ecosystem diversity.

Broadly speaking, the diversity of an ecosystem is dependent on the physical characteristics of the environment, the diversity of species present, and the interactions that the species have with each other and with the environment. Therefore, the functional complexity of an ecosystem can be expected to increase with the number and taxonomic diversity of the species present, and the vertical and horizontal complexity of the physical environment. However, one should note that some ecosystems (such as submarine black smokers, or hot springs) that do not appear to be physically complex, and that are not especially rich in species, may be considered to be functionally complex. This is because they include species that have remarkable biochemical specializations for surviving in the harsh environment and obtaining their energy from inorganic chemical sources (e.g., see discussions of Rothschild and Mancinelli, 2001).

The physical characteristics of an environment that affect ecosystem diversity are themselves quite complex (as previously noted for community diversity). These characteristics include, for example, the temperature, precipitation, and topography of the ecosystem. Therefore, there is a general trend for warm tropical ecosystems to be richer in species than cold temperate ecosystems (see "Spatial gradients in biodiversity"). Also, the energy flux in the environment can significantly affect the ecosystem. An exposed coastline with high wave energy will have a considerably different type of ecosystem than a low-energy environment such as a sheltered salt marsh. Similarly, an exposed hilltop or mountainside is likely to have stunted vegetation and low species diversity compared to more prolific vegetation and high species diversity in sheltered valleys (see Walter, 1985, and Smith, 1990 for general discussions on factors affecting ecosystems, and comparative ecosystem ecology).

Environmental disturbance on a variety of temporal and spatial scales can affect the species richness and, consequently, the diversity of an ecosystem. For example, river systems in the North Island of New Zealand have been affected by volcanic disturbance several times over the last 25,000 years. Ash-laden floods running down the rivers would have extirpated most of the fish fauna in the rivers, and recolonization has been possible only by a limited number of diadromous species (i.e., species, like eels and salmons, that migrate between freshwater and seawater at fixed times during their life cycle). Once the disturbed rivers had recovered, the diadromous species would have been able to recolonize the rivers by dispersal through the sea from other unaffected rivers (McDowall, 1996).

Nevertheless, moderate levels of occasional disturbance can also increase the species richness of an ecosystem by creating spatial heterogeneity in the ecosystem, and also by preventing certain species from dominating the ecosystem. (See the module on Organizing Principles of the Natural World for further discussion).

Ecosystems may be classified according to the dominant type of environment, or dominant type of species present; for example, a salt marsh ecosystem, a rocky shore intertidal ecosystem, a mangrove swamp ecosystem. Because temperature is an important aspect in shaping ecosystem diversity, it is also used in ecosystem classification (e.g., cold winter deserts, versus warm deserts) (Udvardy, 1975).

While the physical characteristics of an area will significantly influence the diversity of the species within a community, the organisms can also modify the physical characteristics of the ecosystem. For example, stony corals (Scleractinia) are responsible for building the extensive calcareous structures that are the basis for coral reef ecosystems that can extend thousands of kilometers (e.g. Great Barrier Reef). There are less extensive ways in which organisms can modify their ecosystems. For example, trees can modify the microclimate and the structure and chemical composition of the soil around them. For discussion of the geomorphic influences of various invertebrates and vertebrates see (Butler, 1995) and, for further discussion of ecosystem diversity see the module on Processes and functions of ecological systems .


a community plus the physical environment that it occupies at a given time

The Importance of the Variety of the Species of Life on Earth

Biological diversity is the variety of species of living organisms of an ecosystem. In ecosystems that are more biodiverse, such as tropical forests, a large variety of plants, microorganisms and animals live in ecosystems that are less biodiverse, such as deserts, there is less variety of living organisms.

Abiotic Factors and Biodiversity

More Bite-Sized Q&As Below

2. How does biological diversity relate to the characteristics of the abiotic factors of an ecosystem?

The availability of abiotic factors such as light, moisture, mineral salts, heat and carbon dioxide, more or less conditions the biodiversity of an ecosystem. Photosynthesis depends on water and light, and plants also need mineral salts, carbon dioxide and adequate temperature for their cells to work. In environments where these factors are not restrictive, the synthesis of organic material (by photosynthesis) is at a maximum, plants and algae can reproduce easier, the population of these organisms increases, potential ecological niches multiply and new species emerge. The large mass of producers makes the appearance of a diversity of consumers of several orders possible. In environments with restrictive abiotic factors, such as deserts, producers exist in small numbers and have less diversity, a feature that is extended to consumers and causes fewer ecological niches to be explored.

Vegetal stratification and biodiversity

3. How does the vegetal stratification of an ecosystem influence its biological diversity?

The vegetal stratification of an ecosystem, such as the strata of the Amazon Rainforest, creates vertical layers with particular abiotic and biotic factors, dividing the ecosystem into several different environments. Therefore, in the upper layer near the canopies of large trees, the exposure to light, rain and wind is greater, whereas moisture is lower compared to the lower layers. As you go down the strata, the penetration of light diminishes and moisture increases. Regarding ਋iotic factors, communities of each stratum present different compositions and features, food habits, reproduction strategies, etc. Such variations in abiotic and biotic factors put selective pressure on living organisms, causing them to be diversified as result, there are more ecological niches to be explored and more varied organisms emerge during the evolutionary process.

4. Despite having a large amount of biodiversity, why is the Amazon Rainforest facing the risk of desertification?

The natural soil of the Amazon Rainforest is not very fertile but it is enriched by the vegetal covering made of leaves and branches that fall from the trees. Deforestation reduces this enrichment. In deforestation zones, the rain falls directly on the ground causing erosion, “washing” away large areas (leaching) and contributing to making the soil even less fertile. In addition to that, deforestation prevents the recycling of essential nutrients for plants, such as nitrogen. In this manner, those regions and their neighboring regions undergo desertification.

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Measures of biodiversity are useful in assessing the overall productivity and integrity of interconnected biotic and abiotic components of ecosystems.

Fermilab fully supports the efforts to increase biodiversity across all habitats and community types. Pictured is a high-quality, wet-mesic prairie restoration on site. Photo credit: R. Campbell

Biodiversity is the diversity of life in a given area and a general indicator of overall ecological health. Biodiversity includes genetic, species, community and ecosystem diversity. The various methods of expressing the level of diversity — information measures such as the Shannon-Weaver or Simpson’s indices or species richness or evenness measures — generally get at the same thing. Measures of biodiversity are useful in assessing the overall productivity and integrity of interconnected biotic and abiotic components of ecosystems.

On the North American prairie in the 19th century, as pioneers broke through the prairie sod and replaced the highly diverse tallgrass community with row crops, the drop in biodiversity was devastating. As the number of plant species declined, the number of insects, birds and other consumers that depended on them declined as well. However, not all disturbance is detrimental. Intermediate levels of disturbance appear to provide the right balance for tolerant and intolerant species to coexist, maximizing biological diversity. Managing for that balance across habitat types and through time is a primary goal in ecological land management.

Considering only species diversity is not adequate. At least two additional kinds of diversity have implications for ecosystems. Genetic diversity within species is important to provide flexibility of species to adapt to particular habitats over long spans of time. Structural diversity, that is, heterogeneity of the plant community, provides other plants and animals with the diverse specialized habitats and microhabitats they need to thrive.

During the last half of the 20th century up to the present time, conservation organizations have undertaken reconstruction and restoration of functioning and highly diverse ecosystems. Ecological land management strategies consist of a matrix of prescribed treatments used across space and time to accomplish desired objectives. A mix of traditional and novel techniques may be used. Performing the same management technique on the same parcel of land selects for species that can tolerate that disturbance at the expense of others, which may not produce desired outcomes. Habitats thrive, and landscape-level diversity increases when managers provide a range of disturbance types and regimes, creating a mosaic of vegetation structure and successional stages across communities.

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  • Biodiversity is being lost at an alarming rate which poses a risk to the provision of ecosystem services.
  • The Convention of Biological Diversity provides a global legal framework for action on biodiversity It is a key instrument to promote sustainable development and tackle the global loss of biodiversity.
  • Biodiversity can be measured through the use of quantitative indicators, although no single unified approach exists.
  • Biodiversity also underpins ecosystem function and the provision of ecosystem services.

The term biodiversity encompasses variety of biological life at more than one scale. It is not only the variety of species (both plant and animal) but also the variety of genes within those species and the variety of ecosystems in which the species reside. 

Author information


Department of Biology, Institute of Microbiology and Swiss Institute of Bioinformatics, ETH Zürich, Zürich, Switzerland

Shinichi Sunagawa & Shinichi Sunagawa

Department of Marine Biology and Oceanography, Institute of Marine Sciences–CSIC, Barcelona, Spain

Silvia G. Acinas & Silvia G. Acinas

Structural and Computational Biology, European Molecular Biology Laboratory, Heidelberg, Germany

Peer Bork, Peer Bork & Stefanie Kandels

Max Delbrück Center for Molecular Medicine, Berlin, Germany

Department of Bioinformatics, Biocenter, University of Würzburg, Würzburg, Germany

Institut de Biologie de l’ENS, Département de Biologie, École Normale Supérieure, CNRS, INSERM, Université PSL, Paris, France

Chris Bowler, Chris Bowler, Eric Karsenti & Eric Karsenti

Research Federation for the Study of Global Ocean Systems Ecology and Evolution, FR2022/Tara GOSEE, Paris, France

Chris Bowler, Marcel Babin, Chris Bowler, Colomban de Vargas, Gabriel Gorsky, Nigel Grimsley, Lionel Guidi, Pascal Hingamp, Olivier Jaillon, Stefanie Kandels, Eric Karsenti, Magali Lescot, Christian Sardet, Lars Stemmann, Patrick Wincker, Damien Eveillard, Gabriel Gorsky, Lionel Guidi, Eric Karsenti, Fabien Lombard, Patrick Wincker & Colomban de Vargas

Université de Nantes, CNRS, UMR6004, LS2N, Nantes, France

Sorbonne Université, CNRS, Laboratoire d’Océanographie de Villefranche, Villefranche-sur-Mer, France

Gabriel Gorsky, Lionel Guidi, Christian Sardet, Lars Stemmann, Gabriel Gorsky, Lionel Guidi & Fabien Lombard

Stazione Zoologica Anton Dohrn, Naples, Italy

Daniele Iudicone & Daniele Iudicone

Directors’ Research, European Molecular Biology Laboratory, Heidelberg, Germany

Eric Karsenti & Eric Karsenti

Institute for Chemical Research, Kyoto University, Kyoto, Japan

Hiroyuki Ogata & Hiroyuki Ogata

PANGAEA, University of Bremen, Bremen, Germany

Stéphane Pesant & Stephane Pesant

MARUM, Center for Marine Environmental Sciences, University of Bremen, Bremen, Germany

Stéphane Pesant & Stephane Pesant

Department of Microbiology, The Ohio State University, Columbus, OH, USA

Matthew B. Sullivan & Matthew B. Sullivan

Department of Civil, Environmental and Geodetic Engineering, The Ohio State University, Columbus, OH, USA

Matthew B. Sullivan & Matthew B. Sullivan

Center for RNA Biology, The Ohio State University, Columbus, OH, USA

Matthew B. Sullivan & Matthew B. Sullivan

Génomique Métabolique, Genoscope, Institut de Biologie Francois Jacob, Commissariat à l’Énergie Atomique, CNRS, Université Evry, Université Paris-Saclay, Evry, France

Olivier Jaillon, Patrick Wincker & Patrick Wincker

Sorbonne Université and CNRS, UMR 7144 (AD2M), ECOMAP, Station Biologique de Roscoff, Roscoff, France

Colomban de Vargas, Fabrice Not & Colomban de Vargas

Département de Biologie, Québec Océan and Takuvik Joint International Laboratory (UMI 3376), Université Laval (Canada)–CNRS (France), Université Laval, Quebec, QC, Canada

School of Marine Sciences, University of Maine, Orono, ME, USA

Emmanuel Boss & Lee Karp-Boss

European Molecular Biology Laboratory, European Bioinformatics Institute, Welcome Trust Genome Campus, Hinxton, Cambridge, UK

Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA

CNRS UMR 7232, Biologie Intégrative des Organismes Marins, Banyuls-sur-Mer, France

Sorbonne Universités Paris 06, OOB UPMC, Banyuls-sur-Mer, France

Aix Marseille Universit/e, Université de Toulon, CNRS, IRD, MIO UM 110, Marseille, France

Pascal Hingamp & Magali Lescot

Bigelow Laboratory for Ocean Sciences, East Boothbay, ME, USA

Nicole Poulton & Mike Sieracki

Department of Microbiology and Immunology, Rega Institute, KU Leuven, Leuven, Belgium

Center for the Biology of Disease, VIB KU Leuven, Leuven, Belgium

Department of Applied Biological Sciences, Vrije Universiteit Brussel, Brussels, Belgium

Department of Geosciences, Laboratoire de Météorologie Dynamique, École Normale Supérieure, Paris, France

Ocean Physics Laboratory, University of Western Brittany, Brest, France

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Tara Oceans Coordinators

  • Silvia G. Acinas
  • , Marcel Babin
  • , Peer Bork
  • , Emmanuel Boss
  • , Chris Bowler
  • , Guy Cochrane
  • , Colomban de Vargas
  • , Michael Follows
  • , Gabriel Gorsky
  • , Nigel Grimsley
  • , Lionel Guidi
  • , Pascal Hingamp
  • , Daniele Iudicone
  • , Olivier Jaillon
  • , Stefanie Kandels
  • , Lee Karp-Boss
  • , Eric Karsenti
  • , Magali Lescot
  • , Fabrice Not
  • , Hiroyuki Ogata
  • , Stéphane Pesant
  • , Nicole Poulton
  • , Jeroen Raes
  • , Christian Sardet
  • , Mike Sieracki
  • , Sabrina Speich
  • , Lars Stemmann
  • , Matthew B. Sullivan
  • , Shinichi Sunagawa
  • & Patrick Wincker


S. Sunagawa and C.d.V. are the lead authors of the article and all other authors contributed to discussion of the content, writing and editing of the article.

Corresponding authors


Distinguishing a putative invader from a previously overlooked cryptic species can be a challenging task. Our results highlight the importance of extensive sampling to differentiate between native and introduced ranges in widespread marine invertebrates and illustrate the difficulty of correctly identifying non-indigenous species in marine invertebrates with poorly resolved taxonomy.

When attempting to match a population that is suspected of having been recently introduced to a source population, samples meant to represent a particular region usually originate from only a small portion of a species' local range, e.g. [28,34,87]. As there may be considerable variation in habitat quality along the range of widely distributed coastal species [88], such a sampling design can result in incorrect conclusions being drawn on whether populations are exotic or native when multiple genetic lineages are present within regions. In our case, some of the species identified have a preference for sheltered conditions (Pyura herdmani, P. dalbyi and Pyura sp.), whereas others can also be found at exposed sites on the open coast (P. stolonifera and P. praeputialis) [67]. Even more importantly, the fact that co-distributed coastal invertebrates in Australia, South Africa and North America tend to have congruent phylogeographic patterns that are often linked to well-documented marine biogeographic disjunctions, e.g. [84-86,89,90], indicates that it is crucial to collect samples in all biogeographic provinces in which a widespread species is represented (e.g. P. herdmani). To achieve good sampling cover, it is thus necessary to collect samples at as many sites as possible rather than obtaining large numbers of samples from a small number of sites. The latter approach is commonly used in population genetic studies in order to accurately estimate genetic diversity at each site, but such information is of little value when the aim of a study is to identify the source population of a putative invader.

Failure to identify and control a non-indigenous species could lead to habitat monopolisation at the expense of native species (e.g. in our study the populations in Chile, New Zealand and Western Australia), while the removal of an organism mistakenly identified as being invasive would constitute habitat destruction and may even result in the extinction of a native species (e.g. Pyura herdmani in Morocco). An inadequate sampling design, in which large numbers of sequences are generated but not all of the evolutionary lineages present in a particular region are recovered, can give researchers a false sense of confidence about the alien or indigenous status of poorly known marine organisms. This may obstruct management efforts aimed at controlling an introduced species during the critical early stages of an invasion.

How to calculate Simpson's Diversity Index (AP Biology)

Simpson's Diversity Index (SDI) is one approach to quantifying biodiversity. There are a number of other options that may be used (such as species richness and Shannon's Diversity Index), but the AP Biology Equation and Formula Sheet includes Simpson's, so AP Biology students should be prepared to use it for the AP Biology exam. SDI takes both the number of species and the population size of each species into account. The resulting value is between 0 and 1, with 0 representing no diversity (all individuals in an area are the same species) and 1 representing maximum diversity.

This post uses the version of SDI found on the AP Biology formula sheet. Another version of the equation is used for small communities. The two versions are sometimes called finite (small samples) and infinite (large samples). AP Biology uses the infinite version of the equation. The specific formula that appears on the AP exam will be used here, even though the simulations used for these examples produce small sample sizes. The Resources page (and Google drive) includes worksheets for both versions of SDI as well as species richness options.

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Quick ecology vocab review before getting into the equation a community is a group of different species in a given area and a population is a group of individuals of the same species in an area.

Two variables are needed for this formula. First is the total number of individuals in the community. Second is the population size for each species. In a real study, scientists use various sampling techniques to estimate population sizes. For the purposes of practice, we will use a simulation to collect data.

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There are two simulations on Biology Simulations that lend themselves well to practicing diversity calculations. For our first example, we'll use the Biodiversity simulation. In this simulation, each time the "Produce Community" button is clicked, an animal community is produced in the forest ecosystem. Random components include the total number of individuals and the number of species represented. Pictured below is a sample run of the simulation, with each species circled in a different color. Identifying each species by name isn't important to completing the calculation, you just need to keep track of how many individuals are in each population.

Classification and scale

An ecosystem is the smallest unit of a living system which is functionally independent. There is no fixed size of an ecosystem. It can exist at any scale and could, for example, be a complex collection of organisms within the gut of a termite, a grain of soil, a forest or an entire ocean 6 . Some even consider the earth to be a single ecosystem 6 . The fluidity in the concept of what constitutes an ecosystem has caused considerable scientific debate in theoretical ecology. It is argued that, until it is possible to classify an ecosystem as a precise definable unit, it will not be possible to accurately study the resilience or fragility of these systems 7 .

Led by IUCN, a process now exists to develop a methodology to assess the state of ecosystems and to produce a list of “threatened ecosystems” 2 , 8 which is currently being tested in country-level studies. This complements the ongoing work to assess the state of species which, at the global scale, is presented through the IUCN Red List of Species 9 . The aim of a list of threatened ecosystems is to focus conservation action on a higher structural level than the species level, in order to benefit several species at the same time. This process is challenged by the lack of an agreed method for classifying ecosystems and the lack of an agreed global list of ecosystem types to classify.

Sustainable Actions


  • Examples of treaties to protect species include: The Convention on Wetlands of International Importance (1971), The Convention of International Trade in Endangered Species (CITES) (1973), and the Convention on Biological Diversity (CBD) (1992). 28
  • The Endangered Species Act (ESA) (1973), administered by the Interior Department’s Fish and Wildlife Service and the Commerce Department’s National Marine Fisheries Service, aims to protect and recover imperiled species and the ecosystems they depend on. 29
  • 191 countries have National Biodiversity Strategic Action Plans for the conservation and sustainable use of biological diversity. 30
  • Over 238,000 protected areas (such as national parks and reserves) have been established, covering nearly 15% of the land and 7.3% of the sea. The size of the protected areas is now more than 18 times larger than it was in 1962. 31

Global Initiatives

  • The Strategic Plan for Biodiversity 2011-2020 is a framework of five strategic goals and twenty targets adopted by the Convention on Biological Diversity in 2010. 32 If current trends continue or worsen, these goals will not be achieved and other goals set forth in the Paris Agreement and the 2050 Vision for Biodiversity will be undermined. 20
  • The United Nations developed a list of Sustainable Development Goals (SDG’s) in 2015 that commit to preserving biodiversity of aquatic and terrestrial organisms, among other things. Fulfilling the SDG’s has the potential to greatly increase biodiversity and its associated benefits. 33
  1. United Nations (UN) Treaty Series (1993) Convention on Biological Diversity. Vol. 1760, I-30619.
  2. Millennium Ecosystem Assessment (2005) Ecosystems and Human Well-being: Biodiversity Synthesis. World Resources Institute, Washington, DC.
  3. Primack, R. (2010) Essentials of Conservation Biology. Sunderland, MA: Sinauer Associates, Inc.
  4. Stiling, P. (2015) Ecology: Global Insights & Investigations. New York, NY: McGraw-Hill Education.
  5. Mora, C., et al. (2011) How Many Species Are There on Earth and in the Ocean? PLoS Biol 9(8): e1001127.
  6. NatureServe (2020) NatureServe Explorer.
  7. NatureServe (2002) States of the Union: Ranking America’s Biodiversity.
  8. Strayer, D. and D. Dudgeon (2010) “Freshwater biodiversity conservation: recent progress and future challenges.” Journal of the North American Benthological Society, 29(1): 344-358.
  9. Daniel, R., et al. (2018) “An inverse latitudinal gradient in speciation rate for marine fishes.” Nature 559: 392–395.
  10. Daily, G. (1997) Nature’s Services: Societal Dependence on Natural Ecosystems. D.C.: Island Press.
  11. Cardinale, B., et al. (2012) “Biodiversity loss and its impact on humanity.” Nature 486:59-67.
  12. UN Environmental Programme (UNEP) (2019) Global Environment Outlook (GEO-6).
  13. UN Environmental Programme (UNEP) (2012) Global Environment Outlook (GEO-5).
  14. U.S. Fish and Wildlife Service (2020) Listed Species Summary (Boxscore).
  15. Stern, N. (2007) The Stern Review: The Economics of Climate Change. Cambridge Univ. Press.
  16. National Geographic (2019) “See how much of the Amazon is burning, how it compares to other years.”
  17. World Wildlife Fund (2020) Australia’s 2019-2020 Bushfires: The Wildlife Toll.
  18. International Sustainability Unit (2015) “Tropical Forests: A Review.”
  19. Pinsky, M. & S. Palumbi (2014). Meta-analysis reveals lower genetic diversity inoverfished populations. Molecular Ecology 23:29-39.
  20. Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) (2019) “Summary for policymakers of the global assessment report on biodiversity and ecosystem services”
  21. Food and Agriculture Organization of the United Nations (UN FAO) (2006) The Role of Biotechnology in Exploring and Protecting Agricultural Genetic Resources.
  22. UN FAO (2015) The Second Report on the State of the World’s Animal Genetic Resources for Food and Agriculture.
  23. UN FAO (1997) State of the World’s Plant Genetic Resources for Food and Agriculture.
  24. UN FAO (2004) Building on Gender, Agrobiodiversity and Local Knowledge.
  25. Khoury, C., et al. (2014) “Increasing homogeneity in global food supplies and the implications for food security.” Proceedings of the National Academy of Sciences, 111(11), 4001–4006.
  26. Barnosky, A., et al. (2011) “Has the Earth’s sixth mass extinction already arrived?” Nature 471:51–57.
  27. U.S. Fish & Wildlife Services (2020) “All Threatened & Endangered Animals & Plants.”
  28. Pierce, D. (2007) “Do we really care about biodiversity?” Environmental and Resource Economics, 7 (1): 313-333.
  29. U.S. Fish and Wildlife Service (2009) More than 20 Years of Conserving Endangered Species.
  30. UNEP (2020) “National Biodiversity Strategies and Action Plans.”
  31. UNEP (2018) “List of Protected Areas.”
  32. Secretariat of the Convention on Biological Diversity (2010) Strategic Plan for Biodiversity 2011-2020 and the Aichi Targets.
  33. United Nations (2019) “Sustainable Development Goals.”

CSS has developed a growing set of factsheets that cover topics including energy, water, food, waste, buildings, materials, and transportation systems.

Watch the video: Οικοσυστήματα (January 2022).