Why we need biodiversity

By Don Gordon
Mankato Free Press
Sunday, Jan. 10, 2010

The United Nations has designated 2010 as the International Year of Biodiversity. Calling attention to this topic can’t come soon enough. Geoffrey Lean, writing in the Telegraph, reports that extinction rates are 1,000 and 10,000 times the natural rate.

We have not had an extinction rate this high since the demise of the dinosaurs. Some experts estimate that 13 million forms of life will disappear by the end of this century. In short, we are literally destroying the riches of this plan et at the fastest rate ever witnessed by man.

One out of every eight species worldwide is threatened with extinction. The list includes 30 percent of the world’s birds, a quarter of the mammals and 47 percent of the plants. In the plant category, those endangered include 14 percent of the roses and cherries and 32 percent of the irises and lilies. Here in the United States, 29 percent of our 16,108 plant species are in imminent danger.

Destroying biodiversity can have disastrous consequences, and there is no better example than Haiti. This country was once 99 percent covered in forest, and it produced nearly 50 percent of the coffee and sugar used in Europe. Today, more than 99 per cent of the original forest is gone, and the country is regarded as the poorest in the Western Hemisphere.

There are scores of reason for pre serving biodiversity. For example, we need these organisms for food, to hold soil, decompose our waste, purify water and reduce air pollution.

Quite often, the principal reason given for preserving bio diversity centers on the actual or potential medicinal value of plants and animals to humans.

For example, save a forest or prairie because the species there might contain a cure for cancer or some other exotic disease.

Now, here is a new reason. Save a forest or prairie, and it might prevent you from getting an infectious disease. In “Biodiversity Loss Affects Global Disease Ecology,” published in the journal Bioscience, researchers at the University of Vermont demonstrate that the emergence or reemergence of many diseases is correlated with loss of biodiversity.

The authors believe that the spread of malaria in Peru can be correlated with deforestation. When the structural framework of the forest was eliminated, the density of malaria transmitting mosquitoes increased, as did the biting rate.

In Minnesota, as well as in other parts of the United States, Lyme disease is of major concern, but the research team believes this disease was probably historically rare.

Humans get this disease from ticks infected with a bacterium, Borrelia burgdorferi. The ticks obtain the bacterium by feeding on small mammals, such as white-footed mice, Peromyscus leucopus. Now, let’s go back a bit when we had more mammals and more forest cover. At that time, the ticks fed on many species, and only a limited number of ticks carried the disease to people.

As the population of humans increased, forested areas and mammals’ diversity declined. In contrast, white-footed mice, which thrive in species-poor places, increased significantly. Today, white-footed mice are the biggest reservoir of Lyme disease in the Northeastern United States.

Montira Pongsiri, one of the lead authors concludes, “The more white footed mice that are in the forest, the greater chance more ticks will be infected and the greater chance you have of getting bitten by an infected tick.” If you are worried about getting Lyme disease, you could just stay indoors or wear protective clothing, but Pongsiri believes protecting large forested areas in the vicinity of residential areas might be a better idea.

During the last three centuries we have destroyed 40 percent of the world’s forests and a great deal of the diversity they contained. Many scientists believe this has occurred because we have failed to put a price tag on the value of diversity. In 2010, the Year of Biodiversity, let’s hope we put a realistic value on a resource that is irreplaceable.

Don Gordon is professor emeritus of botany at Minnesota State University, Mankato.

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