The Siren Call of Biodiversity

We are well aware of the struggles that systematists experienced for decades, often receiving disdain as members of a dying profession. Unrecognized by many were the challenges and excitement of evolutionary and biogeographical insights that can be gained by understanding the diversity of biota in relation to past and present biogeochemical constraints. The melding of morphological, developmental, and molecular differentiation of species into reinforcing criteria for determining evolutionary pathways, separations, and convergences is truly exciting. Our understanding of the natural relationships is improving at a rate impossible just a few years ago. Importantly, renewed federal and philanthropic support of this discipline has stimulated study and encouraged young workers to participate. A true renaissance of evolutionary biosystematics is occurring.

The impetus for much of the renaissance to determine the diversity of our biosphere emanated from perceptive insights and concerns of individuals, such as E. O. Wilson (1985, 1988, 1992), who brought the problems of diminishing global biodiversity into overdue prominence. Biodiversity loss rates vary because of differences in intensities of disturbance to habitats as well as the number of species originally inhabiting particular areas. Because of the great biodiversity in many tropical forested areas that are very vulnerable to catastrophic alterations by human activities, much attention has been correctly given to these critical ecosystems. Biodiversity of most microbial, plant, and animal groups of inland stream, lake, and wetland ecosystems, however, is poorly known. Temperate and tropical freshwater ecosystems likely have similar high biodiversity.

Maximum biodiversity of freshwater ecosystems occurs where the extremely high heterogeneity of wetland and littoral areas interfaces with pelagic regions of lakes or rivers. Maximum functional stability of aquatic ecosystems occurs in those aquatic ecosystems where the terrestrial-wetland-littoral interface regions are strongly coupled to the open water of lakes and river channels (Wetzel, 1999, 2001). Part of that stability is afforded by the chemical characteristics of detrital particulate and dissolved organic matter derived from higher plant tissues. As a result, a direct concordance of biodiversity and relative ecosystem stability occurs.

Great attention and effort is presently directed toward determining what biodiversity exists in the biosphere. As important as such documentation is to appreciate existing community complexity, species differentiation and separation, it alone is not enough. Biodiversity surveys without coupled action to preserve ecosystem functions can be misleading and negatively affect biodiversity simply because of the false promise that some remedial action is being taken while the constant loss of species continues unabated (Moss, 2000). The functional integrity of freshwater ecosystems is often simply not maintained by uses to which lakes and rivers are commonly being put. For example, even though riverine and lacustrine wetlands are of some 160 times greater economic value to society than an equal area of cropland (Costanza, et al., 1997), wetlands are still being continually destroyed for agricultural purposes. Replacement or restored wetlands are rarely hydrologically or functionally equivalent to those destroyed, and a great deal of the original biodiversity is lost as a result.

It is essential that we as limnologists provide compelling arguments to the public and policy makers that all parts of aquatic ecosystems are integrated functionally, particularly in flood plains and at other land-water interface regions. Some of the human modifications of aquatic ecosystems not only catastrophically degrade biodiversity but also are economically foolish. Both advocates of exploitation and conservation need to compromise. Many of the fragmented, piecemeal conservation measures can be futile because they do not maintain functional integrity of the ecosystems. Our responsibility to understand and advocate the reality of long-term biodiversity requirements has never been greater.

Robert G. Wetzel >>>
General Secretary and Treasurer

References Cited

Costanza, R, and others. 1997. The value of the world’s ecosystem services and natural capital. Nature 387:253-260.

Moss, B. 2000. Biodiversity in fresh waters – an issue of species preservation or system functioning? Environ. Conserv. 27:1-4.

Wetzel, R. G. 1999. Biodiversity and shifting energetic stability within freshwater ecosystems. Arch. Hydrobiol. Spec. Issues Advanc. Limnol. 5419-32.

Wetzel, R. G. 2001. Limnology: Lake and River Ecosystems. Academic Press, San Diego. 1012 pp.

Wilson, E. O. 1985. The biological diversity crisis. BioScience 35:700-706.

Wilson, E. O. 1988. Biodiversity. National Academy Press, Washington, DC. 521 pp.

Wilson, E. O. 1992. The Diversity of Life. Harvard University. Press, Cambridge, MA. 424 pp.