Biodiversity, a combination of the words biological and diversity, refers to variability of forms of life in a specific area. Ecologists define three levels of biodiversity: genetic biodiversity, species biodiversity, and ecosystem biodiversity. Genetic biodiversity refers to variability in the gene pool of a community. Species biodiversity, which is the form of biodiversity most often discussed, refers to the number of species living in an area. Ecosystem biodiversity refers to the number of ecosystems in a certain area. Ecosystems are all of the animals, plants, bacteria, and fungi as well as the physical components of the area. An ecosystem can be as large as an entire forest or as small as a clump of moss that provides a habitat for plants, microscopic invertebrates, and bacteria.
Biodiversity is important to humans for a number of reasons. It represents a significant resource of chemical and biological products including food, fibers, and medicine. It produces in clean air, clean water, and fertile soils. Ecologically, biodiversity contributes to ecosystem stability, which allows ecosystems to effectively withstand environmental perturbations.
Historical Background and Scientific Foundations
The variation among organisms on Earth is called biological diversity, or biodiversity. Biodiversity most oftenrefers to the number of species in a certain area, or the species diversity. Individuals that belong to the same species are able to mate and produce offspring that are fertile. Increased species biodiversity is also known as species richness. An ecosystem that has greater species biodiversity contains more ecological niches. An ecological niche is the collection of biological and physical requirements necessary for an organism to grow and reproduce. A coral reef with its many nooks and caves for hiding and influx of light from above contains many ecological niches and the species biodiversity is extremely high. On the other hand, the deep ocean, with its relatively homogeneous topography and lack of light, has low species biodiversity.
A second form of biodiversity is genetic biodiversity, which refers to the variability in the genetic material of the individuals in a certain population or community. Genetic biodiversity influences how well a species can adapt to environmental pressures. For example, suppose a population is impacted by a severe environmental stress, such as a drought or a fire. If the population has high genetic biodiversity, some of the individuals are likely to have adaptations that allow them to survive the impact. On the other hand, if genetic diversity is low, it is possible that the entire population will be adapted to a narrow range of ecological conditions; a more specialized ecological niche. If environmental conditions become extreme, the entire population will be threatened. The idea of genetic biodiversity extends beyond populations to communities. A community with more species will have a more genetic variation than one with fewer species. The genetic biodiversity of a community with more species is larger and there are likely to be populations within that community that can withstand environmental perturbations, should they occur.
An ecosystem is the community of living organisms as well as the physical components of an environment such as water, soil, and climate. Another level of biodiversity refers to ecosystem biodiversity. Ecosystem biodiversity has two related meanings and these two meanings also relate to species and genetic biodiversity. The first definition of ecosystem biodiversity refers to the number of ecosystems found in a certain area. Therefore, California, which includes temperate forests, prairies, deserts, temperate lakes, chaparral, kelp forests, beach
WORDS TO KNOW
BIODIVERSITY: Literally, “life diversity”: the wide range of plants and animals that exist within any given geographical region.
COMMUNITY: All of the populations of species living in a certain environment.
GENETIC: Having to do with the genetic material, or DNA, in an organism.
SPECIES: A biological classification group ranked below genus, consisting of related organisms capable of interbreeding.
ecosystems, estuaries, alpine forests, and rocky shorelines has greater ecosystem diversity than does Kansas, which primarily consists of prairies, rivers, and lake ecosystems. In general, places with more varied terrain tend to have more ecosystems than places where topography is more homogeneous. Because California has numerous types of landforms and climates (mountains, flat areas, ocean coasts, and lakes), it has more ecosystem biodiversity than Kansas, which is for the most part, a plain.
A second definition of ecosystem biodiversity refers to the number of ecological interactions among organisms in a certain area. For example, a coral reef ecosystem, composed of coral, sea stars, worms, sea slugs, snails, kelp, sea grass, fish, crabs, sharks, seals, whales, and plankton has much greater ecosystem diversity than the open ocean near Antarctica, which has an ecosystem composed primarily of phytoplankton, krill, fish, and whales. This form of ecosystem biodiversity is a measure of the complexity of an ecosystem. A more diverse ecosystem has more ecological niches, more feeding relationships among organisms, more organisms that capture energy, and more species that recycle organic nutrients into inorganic forms.
To a large extent, the various definitions of biodiversity overlap. An area that contains numerous ecosystems will contain a high diversity of interactions among organisms. A region with numerous interactions among organisms likely has a large number of species and high species biodiversity. If a region has high species biodiversity, it has a lot of genetic variability in the organisms that make up the ecosystem.
Numerous factors influence ecological biodiversity. Ecological biodiversity is greater in places where ecological resources are abundant. Where the topography is more varied, there are more places for shelter and more places to escape predation. In places where rainfall and sunlight are abundant, photosynthesis is greater and plants grow rapidly, providing a source of food for other organisms. In places where the climate is more stable, more species can adapt to the more reliable conditions. Places where extreme weather occurs often tend to have less ecological biodiversity. As a result, the tropics have more ecological biodiversity than the poles; rain forests and temperate forests have more ecological biodiversity than deserts; coral reefs have more ecological biodiversity than does the open ocean.
Finally, the history of a location influences the ecological diversity. For example, Greenland was covered by glaciers until about 10,000 years ago. The diversity on Greenland is low because there has been little time for species to immigrate and adapt to the environment and complex ecological interactions have not had a lot of time to develop.
Impacts and Issues
Biodiversity in all of its forms—ecological, species, and genetic—is important for numerous reasons. Humans rely on ecosystems for many functions. Ecosystems produce the food humans eat and the fiber that humans used for clothing and shelter. The diversity of plants in the many ecosystems is the source for medicines that humans use to treat disease. Coastal ecosystems, in particular, play a major role in scrubbing water of pollutants and producing clean water that can be used for drinking and washing. All of the oxygen on the planet results from photosynthesis from plants in forests and phytoplankton in the oceans.
When ecosystems are more diverse, they are better able to withstand environmental perturbations. When a more ecologically complex ecosystem is impacted by human activities and environmental pressures, there are likely to be organisms and interactions among organisms that can continue to exist despite the impact. For example, before word processing programs had automatic back up features, the only way to save a document was for the user to provide the save command to the program. More modern programs have automatic save features and computers themselves have back up features. If something happens to one of the save processes, the document will still likely be saved using a different process. In the same way, an ecosystem with more diversity will likely be able to continue functioning even if something happens to a portion of it because of an environmental perturbation.
As human activity impacts the environmental conditions on the planet, by changing the climate, removing natural habitat for development, and through pollution, the diversity of ecosystems are negatively impacted in numerous ways. More organisms are currently undergoing extinction than at any other time in Earth’ss history because of habitat loss to human development, pollution, and climate change. This has immediate impacts on the species biodiversity of an ecosystem. If a top predator is removed from an ecosystem, the entire ecosystem
is impacted. Ecologist R T. Paine showed that the removal of starfish, the top predator in rocky intertidal ecosystems, decreased diversity throughout the entire area causing a collapse of the ecosystem.
Pollution is a serous threat to ecosystem diversity. Toxic pesticides and fertilizers are spread on agricultural crops and their impact is rarely confined to agricultural pests. For example, the European red mite became a significant pest in orchards because pesticides likely removed its competitors. Climate change threatens the biodiversity of many ecosystems. Currently, corals are dying at a rapid rate throughout the world. One probable reason for this is the warming of ocean temperatures as a result of global climate change. Coral reefs are one of the most diverse ecosystems on the planet, not only home to countless species, but a place of enormous forms of interactions among species. When the corals die, the many ecosystems that occur in the reefs diminish in biodiversity.
See Also Biodiversity; Climate Change; Coastal Ecosystems; Coral Reefs and Corals; Ecosystems; Endangered Species; Estuaries; Extinction and Extirpation; Freshwater and Freshwater Ecosystems; Genetic Diversity; Marine Ecosystems; Reef Ecosystems
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Australian Museum. “Australia’s Biodiversity.” 2005. http://www.amonline.net.au/biodiversity/index.htm (accessed February 18, 2008).
National Geographic. “Intraspecies Diversity Helps Ecosystems, Study Says.” August 21, 2002. http://news.nationalgeographic.com/news/2002/08/0821_020821_diversity.html (accessed February 18, 2008).
United Nations Environmental Programme. “World Atlas of Biodiversity.” 2007. http://stort.unep-wcmc.org/imaps/gb2002/book/viewer.htm (accessed February 18, 2008)