A basic principle of ecology is succession theory or ecological succession (Clements 1916). Nature is assumed to have an ideal state or “climax community”. A community such as a forest evolves through a series of orderly stages. At its mature, final stage, a community is said to be in equilibrium with a stable composition of specific species. Although equilibrium can be thrown out of balance by natural phenomena (windstorms, landslides, and wildfires), the community is assumed to recover and return to its optimal state. Much of traditional ecology, environmental science, and conservation are based on the notion that equilibrium and stability are good for nature. The mature, age old rainforests of Amazonia are rich with biodiversity and are considered prime examples of undisturbed, mature wilderness or a climax community.
In recent decades, new ecologists have questioned the assumptions of succession theory (Botkin 1990; Connell 1978) and criticize traditional conservation based on succession theory’s idea that nature should be protected from disturbance, change, and people. In contrast to succession theory, the new ecology considers natural disturbances not only common, but, integral to ecosystem health and biodiversity. The instability, non-equilibrium, and at times chaos created by disturbance encourage environmental heterogeneity through the creation of patches, mosaics, and edges of distinct habitats where diverse species can compete and thrive (Botkin 1990; Zimmerer and Young 1998).
Borrowing insights from the new ecology, historical ecologists focus on human activities as a major source of disturbance (Balee and Erickson 2006a; Stahl 2000, 2006; Zimmerer and Young 1998). In contrast to natural disturbances, human or anthropogenic disturbances are highly patterned in timing, frequency, intensity, scale, context, complexity, and diversity (Blumler 1998; Erickson 2006; Pyne 1998). Common examples of human disturbance are burning, erosion, settlement, roads, farming, and deforestation, but can also include subtle activities such as weeding, transplanting, cultivation, fertilizing, and seeding which encourages certain species over others and which may increase overall biodiversity and biomass. Despite the negativity implied, disturbance by humans usually involves intentionality and planning, although the long term effects may be unknown and unintended when they occur.
Building on the findings of new ecologists that intermediate levels of disturbance are optimal for species diversity, Blumler (1998) suggests that a variety of disturbances and
Timing or disturbance heterogeneity are as important as intensity. Human disturbances keep the environment in a form of arrested succession and disequilibrium. Secondary rather than primary forest is encouraged, which may increase biodiversity, biomass, and ecosystem heterogeneity, especially of wild and domesticated species exploited by humans that thrive in such contexts.
World History
