Natural Agents of Change
  • Flooding
  • Drought
  • Fire
  • Windstorms
  • Erosion/sediment deposition
  • Climate change
  • Glacial movement
  • Tectonic activity

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What impacts on watersheds also affect birds?

Human and natural factors can cause watershed change. Some change in watersheds is natural and is driven by natural disturbances such as floods and fire. However, human activities may cause impacts more severe in frequency and magnitude than natural agents of change alone. The beneficial natural functions of watersheds may be impaired or destroyed by a variety of human-made agents of change. Review the Watershed Academy Web module, Agents of Watershed Change, for more complete background on this topic.

Several types of human-caused impacts are most likely to affect birds. Probably the greatest impact to birds is from habitat loss due to land use changes, which includes the conversion of natural ecosystems--rivers, wetlands, grasslands, and forest--to mining areas, timber harvest zones, agricultural lands, and urban uses. These impacts can cause chemical, physical, and biological changes. For example, some agricultural activities can reduce natural habitats, increase sedimentation to rivers, increase nutrient runoff, and add chemical pollutants to upland, wetland and aquatic systems. Urbanization often eliminates habitats, increases sediment, heavy metal and nutrient loads to waters, and changes the rate and amount of runoff reaching rivers.

Such impacts to watershed habitats are recorded in decreased numbers of waterfowl due to loss of wetlands, fewer migratory songbirds as a result of forest fragmentation, or losses of bird species dependent on rare or limited habitats.

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Section 4 of 17