06 Biodiversity
Menu  |  back

The term biodiversity refers to the diversity of plant and animal species, the diversity within species and the diversity of ecosystems. Just as the human body is dependant on the division of labour between a multiplicity of cells and organs, an ecosystem, too, is dependant on the division of labour through biodiversity. For this reason, the scenario of gradual evolution, which is supposed to have started with a single cell, is unrealistic. It is conceivable that the ecosystems in which we live today must have been put together in a very short time, possibly within a few days.

In recent years, there has been a great deal of discussion and research in the area of biodiversity. The focus, in general, has been on saving and preserving ecosystems. That led to a wholly new understanding of and new methods of protecting endangered species. Instead of attempting to save individual species, one protects the entire ecosystems in which they appear. Thereby, species that are not so seriously threatened are protected at the same time.
 
The collective ecological service performed by the different species working for each other ensures that our planet remains clean and capable of supporting life. Biologist Yvonne Baskin writes, “It is this lavish array of organisms that we call ‘biodiversity,’ an intricately linked web of living things whose activities work in concert to make the Earth a uniquely habitable planet” (1).

It is impossible to draw up a full list of all ecological relationships. The most obvious ones are the food chains and the balance between oxygen and carbon dioxide maintained by plants and animals. Many degrading organisms make the soil fertile. Other biodiversity services purify the water, detoxify poisonous substances, regulate the climate, and pollinate the flowers.

Various experiments have been carried out in the course of research on biodiversity. In the course of these, it was discovered that highly diversified communities are more stable, more productive and resistant to stress (2) (3) (4). They have greater soil fertility and are, generally, in better condition.

 
Redundant systems:

An interesting phenomenon of ecosystems is redundancy, which means multiple back up of individual services.  This means that a service performed by one species can also be undertaken by another. For this reason it was assumed that various redundancies make certain species superfluous (5). However, because all plants generally contribute both to soil fertility and to productivity, it is difficult to judge whether one can decide on the deficiency of one species on the basis of individual studies alone. What if this very species would also perform other services?  In recent years, ecologists have turned away from talking about superfluous species; in fact, they even have a tendency to no longer to use the word “redundant” (6).

With what we know today about biodiversity, it seems hardly possible that ecosystems or even life itself could exist without biodiversity and its eco-chemical and eco-physical services. The diverse services and the organisms that they offer must have existed side by side from the beginning because they form a complex system which cannot be reduced without penalty.


Co-evolution as an explanation for ecology:
 
As long as ecology appeared to be only a loose collection of organisms without connecting relationships, it was conceivable that it could have been built up by a gradual, directionless process. However, as more discoveries are made about the unbelievably complex network of biodiversity, the advocates of the theory of evolution see themselves as being in a similar dilemma as they were when the complex structure of cells was discovered. Because ecology is built upon such multi-layered, multi-species complexity, the explanation of its development, being a result of random events, represents a rather too painful challenge to our readiness to believe it.

 

In order to escape from this dilemma, the talk nowadays, when someone wishes to explain how ecology came about, is often of co-evolution. Co-evolution is defined as “the common evolution of two or more species,” which “cannot interbreed and which have a close ecological relationship" (7). Regarding this, however, it must be noted that the ecological relationship precedes co-evolution. For that reason, co-evolution cannot be the answer to the question of the emergence of ecology. On this topic, biologist Henry Zuill writes, “I have no problem with two species fine-tuning an existing ecological relationship; I do have a problem with using co-evolution to explain the origin of ecological services. That is an altogether different problem. Remember, we are talking about an essential multispecies integrated service system—an entire integrated system. There seems to be no adequate evolutionary way to explain this. How could multiple organisms have once lived independently of services they now require?” Zuill continues, “It appears that life on Earth actually makes other life on Earth possible. That is, life on Earth makes it possible for life on Earth to proceed. This is not saying that life made (past tense) life on Earth exist, of course. It is saying that the whole system had to be present for life to go on existing. If this is true, there is no room for gradually unfolding ecology” (8).


These 07  |  Menu
back

(1)  Yvonne Baskin, The Work of Nature: How the Diversity of Life Sustains Us, Island Press, Washington D.C., 1997.

(2)  J.J. Ewel et al., Tropical soil fertility changes under monoculture and successional communities of different structure, Ecological Applications 1(3), 1991, pages 289–302.

(3)  Shahid Naeem, Lindsey J. Thompson, Sharon P. Lawler, John H. Lawton und Richard M. Woodfin, Declining biodiversity can alter the performance of ecosystems, Nature 368, 21. April 1994, pages 734–737.

(4)  David Tilman, Biodiversity: Populations and Stability, Ecology, Vol. 77, 1996, pages 350–363.

(5)  B.H. Walker, Biodiversity and Ecological Redundancy, Conservation Biology, 1992 pages 8–23.

(6)  Ref. (1), page 20.

(7)  Robert Leo Smith, Elements of Ecology, 3. Auflage, Harper Collins, page G-3.

(8)  Henry Zuill wrote in „Akte Genesis“ by John F. Ashton, 1999, a contribution on the theme of biodiversity, which is the basis of this thesis.

Comment this Site!