Thousands of years ago, Native Americans burned forests to remove underbrush to make hunting or farming easier. Later, early European settlers built dams and mills on creeks. People cleared land for farms or to make use of the timber. Sometimes streams were redirected into canals. As the population grew, more and more land was cleared for agriculture, houses, roads, stores, offices, and schools. In cities, particularly large old cities, combined sewage and stormwater pipes may have overflowed (and may continue to overflow) into local streams during rainstorms. Streams in many cities are have been channelized or buried in pipes.

These water and land uses affect natural communities in many ways. Here are just a few examples:

• Cleared land no longer provides the same habitat for plants or animals.
• Forests that regrow on land that was cleared may be a different composition than the natural community that originally lived there.
• An increase in the amount of land covered by paved roads, parking lots, and buildings increases stormwater runoff into streams, leading to erosion, pollution, and altered patterns of flooding and sedimentation.
• Landscaping may introduce non-native invasive plants that can spread to nearby natural communities.
• Dams prevent fish from swimming upstream to spawn.

Some of the effects on natural communities may last for decades, hundreds of years, or be essentially permanent.

To learn more about the specific history of water and land use in a park or natural area, find that park under Parks and Places, and explore its Stewardship and Ecological Threats page.

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