Roads to Reconciliation: Conflict and Dialogue in the Twenty-First Century by Benson Brown Amy;Poremski Karen M.;

Author:Benson Brown, Amy;Poremski, Karen M.;
Language: eng
Format: epub
ISBN: 1900016
Publisher: Taylor & Francis Group

What Is Biodiversity? How Much of It Is There?

Let me review some of the basic facts concerning biological diversity, or biodiversity for short. First of all, I define biodiversity as simply the expression for all the forms of life examined at the different levels of biological organization. How much biodiversity is there? If you just consider the Australian ecosystem, from rain forests to mangroves, to shallow marine areas and all the species that occupy it, there are somewhere between 1.5 and 1.8 million species. And this includes only species we know well enough to have given scientific names and for which we have determined at least a rudimentary anatomical diagnosis. This number is not exact because a full census has not been attempted, and we can only note generalities in the kinds of organisms that make up the bulk of biodiversity, especially insects. The main photosynthetic organisms in diversity are, as you would expect, the flowering plants. But we should note that this is due in large part to the intricate and complex coevolution within those groups that has occurred since the end of the Mesozoic era, about 70–90 million years ago in geologic time.

Another way to begin to grasp biodiversity is to consider the size of organisms relative to their population in the world. And so the beetle, representing insects, looms like a Goodyear blimp above the tiny elephant, which represents our 5,000 known mammal species. The elephant hides beneath a tree-sized fungus, which is even an understatement: 60,000 species of known fungi are really only a small fraction of the estimated 1.6 million species of fungi that exist. The point of this is that we do not know, to the nearest order of magnitude, the number of species, of organisms that live on earth. This might be as low as 5 or 6 million, but that is highly unlikely; it might be as high as 100 million, or even higher as we get to know microbial biodiversity even better.4 Some say that a good figure to settle on is 10 million, but no biologist knows with any degree of confidence if that is a good number.

Another exercise in perspective helps here: If you were to take out the four strands of DNA of a typical body cell and put them in real space, you would have a single molecule about a meter long, which you could not see because it would be 2 billionths of a meter across. If you magically magnified that DNA from a human cell until it was the width of a piece of string, it would extend approximately 1,800 miles, the distance from New York to Dallas. As you walk along, you would be reading off the genetic letters, the nucleotide pairs, at about 100 per inch. That is the information in an organism; it is something to bear in mind when we allow a species to go extinct.

Thanks to breakthroughs in genomics and exponentially increasing technical power, we can now perform a full gene inventory of species.

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