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Human-Made Changes

Change through anthropogenic factors is often closely tied to, and interactive with, natural change. A common form of human influence on watershed change is that the same type of change may occur, but at a very different magnitude or frequency. You will note in the following discussion of human-induced changes that many of the same effects on the ecosystem are evident, but at magnitudes or frequencies that watershed ecosystems have not become adapted to over time. As mentioned, when these intensified changes exceed certain thresholds, recovery is no longer certain and significant loss of natural resources, goods and services can result, to the detriment of human and ecological communities alike.

Given that some change is natural, could human-induced changes really be that harmful, or would ecosystems simply adapt to our modifications? The capacity of the human race to adversely influence the natural environment is best illustrated by our influence on the rate of biological species extinctions. In 1999, a working group of the world's leading evolutionary biologists ranked the brief period of human presence on earth as among the top 4 sources of mass biological extinctions in the planet's history. Recovery from the previous mass extinction period did take place, but it required 10 million years to occur.

Human-induced changes include those major agents of change listed at left, plus a large number of minor and indirect effects too numerous to include in this discussion. While many management measures to avoid, minimize or otherwise remediate human-made changes have been developed, these management remedies are covered in other Watershed Academy Web modules rather than here, due to module length.