By Gail Gallessich

Accelerating rates of species extinction pose major problems for humanity, according to a comprehensive study headed by a biologist at UC Santa Barbara and published recently in the journal Nature.

The groundbreaking statistical analysis demonstrates that the preservation of biodiversity—both the number and type of species—is needed to maintain ecological balance and “services” to the ecosystem.

“By combining the results of more than a hundred studies performed over two decades, we were able to conclusively show that the extinction of species from our planet will change the way pests and diseases are controlled, organic wastes are broken down and recycled, food is produced by ecosystems, and water is purified,” said Bradley J. Cardinale, first author and UCSB associate professor of ecology, evolution and marine biology.

“Until recently, scientists knew a lot about the causes of extinctions, but surprisingly little about their consequences,” said Diane S. Srivastava, second author and professor in the Department of Zoology at the University of British Columbia.

Cardinale explained that one-third to one-half of all the species on the planet are expected to be lost in the next 100 years, and that currently species are going extinct thousands of times faster than they have historically. The losses are due to the cutting down of rainforests, development, pollution, and the introduction of exotic species that take over indigenous species’ niches.

He pointed out that setting aside a variety of protected areas—marine areas, national parks, and ecological reserves—can help to preserve biodiversity. Additionally it is important to consider biological “hot spots” where biodiversity is high. “We could save a lot of species with only small areas, by putting aside hot spots,” Cardinale said.

To illustrate, one of the studies included in the analysis focuses on the role of species diversity in controlling agricultural pests on Wisconsin alfalfa crops. The evidence shows that together a specific group of predators (the ladybug, the damsel bug, and the parasitic wasp) can reduce the density of aphids to a greater extent than that predicted for each natural enemy alone.

Cardinale explained that controlling the aphids is worth millions of dollars to Wisconsin farmers alone. An added benefit is the fact that when the three key predators abound, farmers do not have to spray their alfalfa crops.