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Habitat and Diversity

A habitat is the place where a microorganism, plant, or animal naturally lives and grows. Over time, species have adapted to various habitats. Habitats vary botanically and zoologically due to the interaction of their living components with environmental factors such as water availability (including surface and subsurface runoff), bedrock geology, surficial geology, acidity of soil, mineral composition of soil, and past disturbances both natural and unnatural.

Species, within a habitat, require nutrients, water, shelter, and space to survive, all of which comprise their niche. An idealized niche is defined as the limits, for all of the important environmental features, within which individuals of a species can survive, grow, and reproduce, but is often reduced to a realized niche by competition between species. Over time some species' niches become more specialized as these species evolve reproductive advantages through more efficient and unique energy cycling. As habitats naturally develop, less energy in the system is left dormant and energy cycling is intensified.

Specialization enables a wide diversity of life forms to live with a limited supply of nutrients and energy. Older, more diverse ecosystems have the greatest species specialization. Without disturbance and given enough time, species richness and complexity peak. Conversely, natural or unnatural disturbances cause an ecosystem to revert to an earlier successional state. The ecosystem will then begin a series of seres (successional stages), the number of which depends on the disturbance and climate. The seres naturally mature towards increased complexity and energy conservation.

In the natural laboratory of Central and South American tropical wet forests, one can experience the most elegant example of energy utilization, as the forest literally hums like a massive power plant of life. In addition to climatic advantages of equatorial development, the endemic species of these forest communities escaped relatively unscathed from the glaciations that ended 9,000 years ago. Species seeking refuge from the massive ice sheets only increased the biological diversity. Now, these forests represent one of the oldest living experiments on earth and demonstrate the complexity ecosystems can obtain if left undisturbed for thousands of years.

As species become increasingly specialized, they become increasingly bound to more specific niches. A specialist's niche may only be found in rare habitats or habitats that are naturally far apart. Some species are mobile enough to reach suitable habitats if a disturbance leaves its present space uninhabitable, but some species do not possess such mobility or have no habitat corridors in which to travel. This is a reason that large, intact preserves contain many more species than smaller, fragmented preserves. This is also the concept behind ecologists and land conservationists' drive to connect all preserves, thus increasing their overall effectiveness.

In an intact ecosystem, specialists have an advantage, keeping the number of generalists in check. In a disturbed ecosystem, generalists have the advantage and their increased population size may slow or arrest specialists from re-inhabiting a community. Under constant disturbance, generalists start replacing specialists on regional scales.

Let's depart from the theoretical and briefly describe what has occurred in the eastern United States after the human persecution of the red wolf, Canis rufus. This southern wolf's distribution extended as far north as southern Pennsylvania and south to the Gulf of Mexico before colonial times. Its preferred habitats included dense, large tracts of upland forests, swamp forests, and coastal marshes. Its numbers declined steadily due to a combination of factors, including killing by man, habitat alterations, parasites, diseases, and competition from coyotes, Canis latrans. Coyotes not only competed for space and resource in what was left of the red wolves' niche, but coyotes also hybridized with red wolves. It is doubtful that a genetically pure red wolf exists in the wild today.

Coyotes are historically carnivores of the western plains and prefer open grasslands, brushy edges, and patchworks of fields interwoven with woodlands. As eastern forests were cleared, this opportunistic animal began to move east with the help of human introductions. The open cuts of interstate highways provided further corridors of suitable habitat. Red wolves, with their more specialized niche, could not compete with this generalist. Now, instead of having a carnivore specially adapted for the southeastern landscape, we have a carnivore with much more general habitat requirements living throughout the continental United States.

In this example, one species, due to human disturbance, replaced another. In many cases this scenario is played out with one species effectively eliminating many other species and is a major reason we are witnessing the sixth mass extinction on earth. The difference between this mass extinction and the first five is that a natural disaster is not the cause-at least not from our point of view. Instead, humans are the culprits.

An ecosystem dominated by generalists can comprise many individuals, but has few species using the limited resources. As more diverse habitats continually become disturbed, the probability that specialists will become extinct increases. The more chaotic or diverse a system, the more stable or the closer a system is to equilibrium. Everyone should remember from high school science experiments that the more data one obtained, the more accurate one's results. This concept of complexity equating to greater balance pervades everything in nature, within which we are only a trace element. Continually fragmenting our landscape will only lead to less diversity and decreased stability.

Based on the simple assumption that complexity in living systems increases with time, we should prioritize and conserve all of the earth's oldest communities that are still intact. To learn the most about how living systems work, it seems self-evident that one needs to study the most complex systems. Our existence is geologically minute. Once a diverse ecosystem is destroyed it is lost, in human terms, forever.