The Free Press, Mankato, MN

April 17, 2009

Biodiversity decline a threat

By Don Gordon

Earth Day is April 22 and each year since 1976 I have written a special column to draw attention to this event. These columns are painful to write because the overall health of planet Earth is declining, but I am naive enough to think that discussion of the problems just might spur some of us to help with the recovery process.

Today, I am going to focus just on biodiversity, explain why it is essential, and discuss some ways we as individuals can help preserve it.

In a new book “How Human Health Depends on Biodiversity,” the authors drive home the point that humans need biodiversity. We need biodiversity for food, fiber, shelter, medicines, recycling of waste and a whole host of invaluable goods and services. In short, biodiversity makes the Earth habitable.

Yet, diversity is declining in practically every taxonomic category that has been analyzed. David Mindell writing in Science recently reported those threatened include 12 percent of all bird species, 20 percent of all mammals, a third of our fellow primates, 25 percent of the conifers and 52 percent of the cycads. Others have reported that one-third of the amphibian, fish and reptile species are threatened. Here in the U.S., The New York Times recently reported that a third of bird species are declining. In Hawaii, most of the bird species are threatened.

The environmental organization Garden Organic reports that 95 percent of the vegetables we eat come from just 20 species of plants, but 98 percent of vegetable varieties have disappeared during the last 100 years. Similar horror stories exist for fruit varieties.

Harvard biologist E. O. Wilson has argued that “every scrap of biological diversity is priceless, to be learned and cherished, never to be surrendered without a struggle.” Wilson attributes the loss of biodiversity to five forces summarized in the acronym HIPPO – habitat loss, invasive species, pollution, population growth and overexploitation of species for consumption.

The United Nations Millennium Ecosystem Assessment concluded: “Human actions are fundamentally, and to a significant extent, irreversibly changing the diversity of life on Earth, and most of these changes represent a loss of biodiversity.”

University of Minnesota Ecologist David Tilman has pointed out that there is not a square mile on this planet that has not been appropriated by man. We use 45 percent of the Earth’s water and productivity. We have degraded or pushed beyond their limits 15 of the earth’s 24 ecosystems. In short, our demand exceeds sustainability by 25 percent.

Haiti serves as a painful reminder of what can happen when declining diversity reaches a tipping point. The country has a population of 9.6 million and was once largely covered with forests. Now, less than four percent remains. It was once a tropical paradise, but with diminished diversity it cannot feed itself and is caught in a downward economic and ecological spiral. It is a failed state whose existence depends on the generosity of others. In some parts of China, biodiversity decline has forced farmers to pollinate fruit and vegetable crops by hand.

How can we help preserve diversity? There are no easy answers because diversity quite often takes a back seat to development or other problems which are deemed more important. For example, Colombia is the second most diverse country in the world, yet more than 2.6 million acres have been sprayed with herbicides in the war on drugs, and the toll on biodiversity has been enormous.

For individuals, simple diversity preserving actions might include using pesticides wisely and reducing pesticide use. For example, use corn gluten meal on the lawn in place of synthetic pesticides and never use toxic pesticides in the garden when bees are present. Buying organic shade grown coffee and keeping cats indoors or on a leash might save many bird species. Landscaping with native plants provides not only habitat, but a food source for several species.

References: State of the World 2008 and 2009

Don Gordon is professor emeritus of botany at Minnesota State University. Send questions concerning horticulture or the environment with a stamped, self-addressed long envelope to 52794 Deerwood Trail, Mankato, MN, 56003, or e-mail questions to