The term “biodiversity,” which biologist and author E.O. Wilson coined as a contraction of “biological diversity,” has come to be a sort of mantra for environmentalists. It is tossed about freely whenever there appears a threat on someone's environmental horizon, often without concern for its real meaning or importance. Like using garlic to ward off vampires, using “biodiversity” to ward off developers is the tactic of choice these days.

This tactic is unfortunate, because it desensitizes both the public and the policy-makers to how critical biodiversity is to our society and, indeed, to our planet itself. The discussion here presents a very brief overview of biodiversity, with emphasis on its relevance to the US Southwest, and how it dovetails with other topics discussed on these pages. A useful reference for this discussion is Biodiversity: Connecting with the Tapestry of Life, a joint publication of the Smithsonian Institution and the President’s Committee of Advisors on Science and Technology. (See the Smithsonian web site, on which page there is a link to a PDF of the full document.)

Biodiversity in its most comprehensive sense describes simply the wide variety of life on Earth. Scientists always work hard to develop precision, however, and so this comprehensive definition has been refined by breaking it into three levels. While these levels are tightly interlinked, they provide a clearer context for the discussion.

Ecosystem biodiversity refers to the variety of ecosystems on our planet. Although the precise definition of “ecosystem” is not entirely clear, it is obvious that tropical rain forests differ from deserts; that coral reefs differ from the arctic tundra. Each of these ecosystems—and it is equally important to emphasize that there is variety in an individual category, e.g., not all deserts are alike—includes its own unique variety of plant and animal species and interactions among them.

Species biodiversity, then, is the next level of diversity, because it occurs within an ecosystem. (Animals or plants are said to belong to the same species if they can reproduce with each other.) The interactions among the various species in an ecosystem, combined with the climatological and geological characteristics of the geographic area, determine the characteristics of that ecosystem.

Finally, within species, there is genetic biodiversity. Of course, this exists across species as well, which is the reason for species diversity. But the genetic diversity within an individual species is critical to the long-term health of that species. This is well-known to zoo-keepers concerned with the long-term survival of endangered species such as the snow leopard.

Each level of biodiversity plays a critical role in the next level up. Within species, genetic diversity is critical to the long-term health of that species. Within ecosystems, species diversity is critical to the viability of that ecosystem, especially as its climatological and geological conditions evolve. And, for our planet, the diversity of ecosystems fills every niche that offers nutrients for life to exist, from the hot ocean-floor vents to the arctic sea-ice and from the bottom of Death Valley to the rocks atop the Himalaya Mountains.

Here in the Four Corners region, biodiversity is every bit as important as it is anywhere else, if more subtle. Desert ecosystems, because of their harsh conditions and relatively low availability of nutrients, support fewer species than do, say, tropical rainforests. But each species within a desert ecosystem has an important role to play in its overall maintenance. For example, butterflies and moths are critical to pollinating the cacti, and the cacti provide food for these (and other) insects as well as shelter for birds. The birds eat the insects, keeping their numbers in check so they don’t decimate the plants.

As discussed in the section on wildfire, biodiversity is an important component of the overall health of forest ecosystems. In historical times, before fire suppression, the occasional low-intensity ground fire in pondersa forests would clear underbrush, resulting is a forest consisting of large, widely spaced trees with grasses and fast-growing woody shrubs in between. The variety of food sources supported a variety of animal species. In contrast, the pine forests of today are almost monocultures consisting of far too many closely spaced small trees that shade the ground and prevent any significant growth of grasses or other ground plants. This eliminates the food source for insects and mice, etc., that would otherwise live there, creating a monoculture of stunted pines with very little animal life.

Professor E.O Wilson called biodiversity “the very stuff of life.” To the extent that life is important, biodiversity is fundamental to its existence. Why is life important? Well, I, for one, like to eat, and rocks just don't do it for me. We need lichens to break the rocks down into dirt, microbes and fungi to process the dirt, plants to grow in it, and animals to eat the plants. Then we can think about dinner. And it is the diversity of life—biodiversity—that makes dinner interesting and healthful. Just think, if all we had to eat were parsnips...

Back to Environment index