Ecology

History of Ecological Thought

The history of ecological thought, like that of the field of conservation biology, traces back several centuries. The earliest formal practice of ecological research on the relationship between organisms and their environment dates to the botanist Alexander von Humboldt, who in the early 19th century, described the relationship between plant distributions and regional climates. His work was followed by the publication of Charles Darwin's The Origin of Species in the mid 1800s, postulating an evolutionary, mechanistic perspective for ecology that departed from its earlier, descriptive focus. As developments in ecology continued over the next several decades, advances were made in the understanding of global bio-geochemical cycles (e.g., the nitrogen cycle); and the term biosphere came to be coined in 1875 by geologist Eduard Suess, to refer to that global sphere where the biota interacts with the lithosphere, atmosphere and hydrosphere. Such dynamic interactions were the focus of ecologists such as Henry Cowles and Frederic Clements toward the dawn of the 20th century, who established a tradition known as “dynamic ecology.” In the coastal dunes of the Great Lakes and the western prairies of the United States, respectively, Cowles and Clement examined the process of ecological succession, the sequence of ecological changes following a disturbance. Succession is the process by which an ecological community progresses over time from an initial, simple state to a latter, complex state as the system approached a stable equilibrium (sometimes called homeostasis). The change in the overall ecological community over time reflects, among other things, the loss and gain of individual species. A disturbance; such as wind damage, opening up of a forest gap by treefall, plowing of a field, creation of a patch by waves in an inter-tidal zone, or a rainfall event that creates an ephemeral pool, creates new localized habitats for different species to colonize and exploit. According to successional theory, early colonizers or invaders tend to be those that are best adapted to reproduce rapidly and quickly colonize the new habitat, and typically have high reproductive rates and small life spans. Such species are often referred to as r–strategists. During later stages in the successional sequence, r–strategists are gradually replaced by species that are slower to exploit the initial post-disturbance conditions, but are better adapted to continuing a viable population in the long term at or near the system's carrying capacity. Such slow-growing species are often referred to as K–strategists. According to strict Clementsian interpretation, most successional patches (seres) in a given locality will tend eventually toward a particular assemblage of “climax” species (i.e., a “monoclimax”) at the conclusion of the successional sequence, even when those seres reflect different stages in the successional series. The role of humans in ecological processes was viewed in a negative light, as interfering with the processes of natural succession.

...