Niches and Biodiversity

    One of the major themes of ecology and environmental science is biodiversity- the nature and importance of the diversity of life to the earth, and to mankind. The concept begins with the observation that the earth's biota is abundant in number and variety, and is organized into complex systems we call food webs. Within these complex webs are food chains in which each level depends on the previous one in a trophic structure. [See Trophic]

    A grazer chain is a food chain which begins with an autotrophic producer and from there the energy passes through various levels of consumers. Humans belong to a grazer chain as either a primary or a secondary consumer usually.  Because we belong to a grazer chain, and because its members are usually quite visible components of the wildlife community, man seems much more aware of  the grazer cycle. The detritus chain begins with organic matter from detritus. This detritus can be from animal waste and decaying bodies, or it can be from plant waste.  Scavengers and decomposers feed on this organic matter and in turn become food for a succession of consumers. These may be some of the same consumers as those in the grazer chain, but they tend to be much more likely to be ignore, or disdained even, by man. But the fact is that the detritus chain is absolutely essential to the continued existence of earth's ecosystems. The planet could do without grazers entirely, including man, (although it would be much less interesting) but in order for plant life to continue producing organic material and oxygen, the detritus cycle is fundamental.

   Nature's biota occurs in such diverse variety that one must assume that this diversity is important to the normal functioning of ecosystems and the biosphere [See The Work of Nature by Yvonne Baskin]. Each species in the biosphere is said to have a niche. The niche is the role, function, or lifestyle of the species. Niches include the species' position in the trophic structure, the type of habitat it frequents, feeding and other habits - really each and every characteristic and condition which describes the species and its place in the biosphere. Man, in his narrow view, cannot always see the value of species. Through his narrow lens man only appreciates that which directly benefits him or gives him pleasure. Yet it is often the insignificant and invisible species which play large roles in the normal functioning of ecosystems.

    Yet man tends to simplify ecosystems. From our agricultural systems to the natural habitats we impact in various ways, the result of our presence is simplification and loss of diversity. In the case of the former, our agricultural systems, this simplification has a definite advantage - productivity. In nature there is not much left over from the existing food web for man to harvest.  At one time, early in our population's growth, we could sustain our population by hunting and gathering, but no more. Man's population is simply too dense to harvest enough from nature's bounty.

    About 9000 years ago [See "New Worlds", Living Planet video] man discovered he could cultivate and breed the plants and animals he liked and provide a stable food supply. That led to the expansion of his population and the alteration of natural habitats to facilitate agriculture. The result is that most of the globe has been impacted by man's activities including major alterations to most ecosystems by introductions and extinctions. The biota we've created is very fragile, its characteristics are very specialized and not adaptable to the stresses and changes. The nature of a web is that it has many links and interconnections which provide stability. If any one link is eliminated, the web survives. Weaker perhaps, but not destroyed. The presence of great diversity provides many pathways for food and energy. But a simple food chain is only as strong as the weakest link. If one link is lost, the chain collapses. So it is with the instability and fragility of our food supply.

    So we've developed the monoculture, a system of production based on simplification and hybridization of plants and animals to produce the food we need.  This system, while it has the definite advantage of productivity sacrifices the advantages of nature's diversity.  In nature stresses such as fire, flood, drought and the like are parts of the natural cycle and communities have inherent adaptations to them. No one needs to fertilize and water natural communities, no one needs to replant. Natural systems are self-sustaining. But man's systems are extremely fragile. They need to be managed, protected from pests (there are no pests in nature, only in man's systems), protected from winter, protected from drought, fertilized, watered, etc. Are there compromises we can make that take advantage of nature's diversity while producing the food that we need?

The Nature of Biodiversity

Biodiversity takes three important forms:

1) Genetic Diversity - This is the gene pool of characteristics representing successful adaptations to all of the changes encountered by earth's biota. It is the product of the millions, even billions, of years of evolution of earth's biota. As genetic characteristics are lost, fewer genetic characteristics are available to adapt to continued changes, some of them quite rapid, such as global warming and the like.

2) Species Diversity - Genes do not adapt and evolve by themselves. Species are the medium for the perpetuation of the gene pool, and the gene pool is the basis for success of species. For the gene pool to be protected, species diversity must be preserved.

3) Habitat Diversity - Habitat is the ultimate necessity for preservation of species. You can keep species in zoos and seed banks. They may be valuable for repopulating the wild, and zoos are certainly important for education of humans about species. But they are nearly useless for the perpetuation of successful and adaptive genetic characteristics. The reason - the characteristics which will be selected in a zoo are totally at odds with those important in nature. Docility, living well in captivity, these are not characteristics which will provide success in the wild.

    So it is important to provide the habitat which will provide the living space for species to adapt and evolve and perpetuate the gene pool necessary for continued success of earth's biota. The alternative, at best, is for our planet to become (per David Quammen) the "Planet of the Weeds", and at worst for the demise of  much of earth's life, including man.