Stretching 17,000 km, the Great Lakes shoreline is the longest freshwater coast in the world. Healthy coastal ecosystems, including nearshore waters and their adjacent islands, wetlands, and beaches offer diverse habitats for a variety of plant, fish, and wildlife species. Coastal areas also provide many benefits for human populations, including access to recreational opportunities, filtration of pollutants from stormwater, access to water for consumption, power generation, and manufacturing, and outlets for wastewater discharge.
Human activities in the coastal zone often cause degradation to nearshore waters and disrupt coastal processes. Coastal development may be defined as “human use of the land connected with industrial, residential, agricultural, or transportation activities that substantially alters the natural landscape or affects the ecosystem.”1 Some impacts associated with shoreline development include:
- Fragmentation and destruction of terrestrial and aquatic habitat
- Loss of native plant and animal communities
- Altered flow regimes (caused by water withdrawals, diversions, channelization, and/or redirection of waste and stormwater flows)
- Increased run-off and reduced groundwater recharge due to increased impervious surface
- Increased pollutant discharges from many sources
- Altered thermal regimes
Mapping coastal development as a Great Lakes stressor
- We defined the coastal zone as land within 5 km of the Great Lakes shoreline. Development in this area impacts coastal and nearshore processes.
The extent of developed land, including "settlement and developed land" in Canada and "developed" land in the U.S. was estimated by determining the percentage of developed land within a 5-km radius of each shoreline pixel.
- Canadian data were derived from the Ontario Provincial Land Cover data base.
- U.S. data were derived from the National Land Cover database.
Percentage of developed land within 5 km of the Great Lakes.
- We assumed that the influence of developed land did not extend more than 1 km into the lakes, so the value of each shoreline pixel (a percentage 0-100) was assigned to the adjacent water pixel.
Distribution of coastal development as a stressor in the Laurentian Great Lakes (Inset: Western Lake Erie).