by Whit Gibbons

February 24, 2002

Last week I said I would answer one of the most basic environmental questions: why should we try to preserve natural biodiversity?

Conflicts related to species preservation and protection of biodiversity continue to arise among different groups and individuals throughout the world. The ubiquity and the abundance of such clashes suggest that no universally accepted statement exists about the importance of preserving biodiversity, in part because issues outside the realm of ecology are involved. Economics and personal agendas, plus different interpretations of the same environmental information, guarantee that such disputes will never disappear.

Nonetheless, those who appreciate the natural world should continue to maintain the need for protecting natural biodiversity. Some answers given by environmentalists two decades ago are still worth educating people about. For example, science has limited knowledge of the biochemical and genetic traits of most known organisms and knows nothing of species still undiscovered. Therefore, environmental destruction could eliminate a species possessing a medical marvel, food product, or other valuable human resource.

For those needing evidence, consider the rosy periwinkle of Madagascar, a tiny plant discovered to produce a chemical used to combat childhood leukemia. Or, the chemicals produced on the skin of tropical poison dart frogs, which offer promise as a painkiller many times more powerful than morphine.

Various other reasons have been advanced for conserving other species. Ethical, aesthetic, and religious grounds are difficult to argue against because they are personal positions that individuals take on the issue. On the other hand, convincing someone who does not have a similar ethical code or the same appreciation of diverse habitats or a sense of stewardship may be difficult or impossible. Arguments based on these issues often end in a stalemate, with the environment and biodiversity being winners or losers depending on who has the most clout economically, politically, or with the general public.

Scientific justifications for maintaining natural biodiversity include environmental stability and productivity. A study published in Nature by University of Maryland scientists B. J. Cardinale, M. A. Palmer, and S. L. Collins lends experimental support to this argument. Unraveling all plant and animal interactions in an ecosystem is too complex and difficult for any study, so the investigators examined how a single group of insects, caddisflies, were affected by a loss in biodiversity.

Caddisflies are flying insects whose larvae live in streams, attaching to a rock underwater. The caddisfly larva's feeding mechanism is to build a little net to capture tiny particles of organic matter. In a sense, they lasso their food as it passes by them in the water. The details of the study are complex, but the conclusion seems irrefutable--as the number of different caddisfly species present in a stream increased, the more productive and efficient each species became. Extending this finding to the broader issue of overall biodiversity, reducing the number of species in a system reduces the effectiveness of the remaining species.

After reading a recent article in Science, anyone might wonder why debate continues about whether environmental health can be diminished by a loss of biodiversity. According to A. Hector of Imperial College in England and R. Hooper of the National Institute of Environmental Studies in Japan, the first ecological experiment, conducted by botanists in the early 1800s, was designed to test the effects on cultivation of mixing different species of grasses. Charles Darwin referred to the early study in "The Origin of Species," stating that "it has been experimentally proved [that] a greater weight of dry herbage" can be harvested when several species of grasses are grown together than when one species is grown alone. In essence, Darwin came to the same conclusions as those reported after the recent caddisfly experiment.

Although various reasons can be given for why we should try to preserve natural biodiversity, none is a clincher that will stop environmental destruction and the continued loss of species and their populations. Perhaps the best answer is another question: what right does someone have to eliminate native species and destroy natural habitats when someone else wants them to endure?

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