The Effect of Human Population on Biodiversity (cont'd).
by Edward J. Otten, MD

"Although some species may be now increasing, more or less rapidly, in numbers, all cannot do so, for the world would not hold them."

Charles Darwin On the Origin of Species

The technology that enabled our species to control and eliminate other species is only obtained at a price. The price is in the form of pollution. The burning of fossil fuels and use of petrochemicals and heavy metals have led to the increase of "greenhouse gases" and the contamination of the water, the key to life on earth. Increase in carbon dioxide, nitrogen oxides and destruction of the ozone layer can all lead to global warming and an increase of the sea level, glacial melting and perhaps increasing in hurricane intensity and the El Nino phenomena. While there have always been periods of global warming throughout geological history, it is not the absolute temperature that is important , but rather the rate at which the temperature increases. Many species are able to respond to changing climate by moving to more suitable environments. This is a slow process, especially for plant species. A rapid increase over a few thousand years combined with human barriers to movement such as roads, cities, and agricultural areas will not allow species to move before destruction occurs. An example is coral reefs which make up a small areas of the oceans but contain 25% of fish species. An increase of 1º C. in water temperature will destroy an entire reef and the fish therein. An increase in population will certainly increase the demands on the earth’s resources of land, water, minerals, plants, animals, and air.

Habitat fragmentation is another major threat to biodiversity. Humans have recognized that native species can help support human endeavors, such as agriculture and medical research, and have attempted to preserve small "islands" of native habitat within oceans of human habitat. While noble in intent, this isolation of species has in many cases led to their demise. Usually the"island" is too small to sustain the species within it and many species, unable to migrate or renew their fragmented gene pool, become extinct. For example, some bird species in the tropics cannot find adequate food or nesting materials in the small "preserves" and are unable to leave because of surrounding agricultural land. Similarly, a number of migratory songbirds, such as the Townsend's Warbler, have been pushed to the brink of extinction because their traditional migratory routes are so altered by human activity that they can no longer pass safely from one "island" of forest to the next.

The most destructive of all human activities, with regard to biodiversity loss, is outright habitat destruction, such as deforestation, wetland drainage, and the conversion of diverse grassland prairies to endless seas of monocropping agriculture. Thousand of plant species are destroyed for agriculture, firewood and building materials. Habitat destruction affects all species found within that ecosystem. While destruction of a forest may only take months, regeneration, even if it were possible, might take thousands of years. The inhabitants of Easter Island had a civilization advanced enough to erect monoliths, but in less than one hundred years had depleted the trees on the island until they were unable to build house or canoes, nor catch fish for food, and ended by murdering each other for the few resources available.

All five of these processes are happening at a rapid pace; over harvesting, alien species introduction, habitat fragmentation, pollution and habit destruction. Half of all species will be extinct in the next 100 years... unless we act now to intervene and correct our course. The human species will certainly be harmed by this biotic impoverishment, even if we have adequate nutritional needs. No scientist can predict what the impact of this amount of species loss over such a short time will be, but it cannot be for the better.