Biodiversity sustains life because almost all species are dependent on other species to live. They depend on other species for food, soil quality (such as plants’ dependence on earthworms), shelter, and even for bodily processes like digestion. The loss of a single species can have drastic consequences for many species and begin a chain reaction of destruction as radiating lines of dependency are severed.
The Cascade Effect
The chain reaction where loss of one part of a system causes the entire system to collapse is called a cascade effect. Relationships between the species on Earth are like a giant web. Sometimes a thread of the web can be cut without destroying the threads around it, but more often cutting one thread will bring a whole portion of the web crashing down.
Umbrella Species
The species who form these crucial parts of the web are called umbrella species. They influence their environment so drastically that, without them, their habitat becomes unrecognizable. So many species depend on the changes they make that losing them causes a cascade of other extinctions. The tiny coral animals who build reefs are such a species.
On the opposite end of the size gradient are elephants, another umbrella species. With their tremendous size, a six-ton African elephant—a smaller species than the Asian elephant!—must eat 300 to 400 pounds, 135 to 150 kilograms, of food every day in order to stay alive. The changes they make by feeding and traveling provide shelter for other species of animals (felled brush, cleared areas, dugouts), and make way for different species of plants, which provide food for yet more animals.
Biodiversity and the Future
Biodiversity is important to the future of life on earth. Just as there are umbrella species, there are umbrella ecosystems. These are areas which only cover a small portion of the Earth but contain the largest number of species, or are the only places on Earth that some species can breed. The tropical and temperate rainforests are such regions, as are coral reefs, ocean fish hatcheries, and polar ice sheets and tundra. Even freshwater ecosystems--estimated to contain only .0093% of all the water on earth--contain 12% of all known species.
These habitats, especially wetlands and estuaries (the areas where fresh and saltwater systems meet) are also umbrella ecosystems. These ecosystems perform tremendous services for the planet, such as creation of earth’s breathable oxygen, regulation of climate, breeding habitat for fish, invertebrates, and water mammals, and filtration of fresh water.
Without maintaining our high biodiversity of plants, animals, fungi, and microorganisms, even the few species we are most familiar with will no longer be able to survive on Earth.
Sources:
Encyclopedia of Earth, http://www.eoearth.org/article/biodiversity
Conservation International: Biodiversity Hotspots
WWF, Biodiversity 911: Saving Life on Earth, http://www.biodiversity911.org/
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