Resource: Biodiversity in the Dzangha-Sangha Rain Forest

Biodiversity refers to the richness, or variety, of life on our planet. The total number of different plants, animals, and microorganisms today—estimated to be at least 10 million—is the product of more than three billion years of evolutionary history. Groups of species that perform similar roles in a given ecosystem are known as functional types. Species may be organized into functional types based on factors such as what they consume or their place in the food web as producers, consumers, or decomposers.

Certain species, called keystone species, have a disproportionate impact on the ecosystems they live in. Consequently, the loss of keystone species creates a more significant impact through an ecosystem than does the loss of its other inhabitants. This does not mean that other inhabitants are insignificant. At first glance, some species appear to have trivial niches. However, often these inhabitants have important functions that involve other species. For example, when a plant disappears from an ecosystem, it can take with it up to 30 other species, including other plants, insects, and even higher animals.

Healthy ecosystems perform many functions that benefit all its inhabitants. They purify the air, filter harmful substances from water, convert decaying matter to nutrients, and moderate erosion and flooding. Research indicates that declining biodiversity can lead to an overall decline in ecosystem functioning. By contrast, an ecosystem with more species is likely to be more stable than one that has fewer species. For example, grassland plots with a greater number of plant species are better able to withstand drought than those with less species diversity.

Through statistical analysis of extinction and diversification in the fossil record, we know that biodiversity is slow to recover after an extinction event. One possible explanation for this is that extinction does not just eliminate species or groups of species, it also removes the roles that those species play within ecosystems. Recovery becomes more complicated because specialized roles—such as the way some parasites live on just one species, or the fact that certain animals consume just one kind of food—do not evolve until their hosts are already well established.

Ultimately, we humans derive most of our food, shelter, and clothing, as well as medicines and industrial products, from biological sources—and these biological sources contribute to the proper functioning of the ecosystems we inhabit. This brings up an important question: How should we act knowing that numerous life forms are vanishing—or in danger of vanishing—from our planet?

To learn more about how many of Earth's materials, processes, and organisms are inextricably linked to many others, check out An Everglades Visit.

To learn more about the different feeding relationships that characterize a food web, check out Antarctic Food Web Game.

To learn more about how animals both compete and cooperate for survival, check out Coral Reef Connections.

To learn more about extinctions and diversification over the history of life on Earth, check Invalid resource code: outtdc02.sci.ess.earthsys.deeptime.

• List some different ways that humans living in the Central African Republic use plants and animals.
• List some ways that animals use plants.
• List some ways that animals use other animals.
• What changes do you think might occur in the forest/bai/river habitats if people no longer lived there?
• Choose a habitat near where you live and draw a picture showing the web of interactions among the people, plants, and animals there.