4.2 Aquatic Communities
T ABLE 4.10 Comparison of climate change with other threats to medium river communities
Rank Order Comments
Threat
Development
1 Residential development, particularly in steep slope areas, is of partic- ular concern because of increased erosion. Most coolwater streams are larger streams and rivers and many have wider valleys where land use is more susceptible to being developed than on steeper sloped headwater streams. Row crops, agricultural grazing, and urban/suburban develop- ment are common. Increased impervious surfaces due to roads, parking lots, homes, and businesses increase the amount and speed of runof being delivered into aquatic systems. 1 Stormwater runof will amplify the loading of nutrients, sediment, and contaminants into streams, rivers, and reservoirs, which may alter overall channel design, have a negative efect on biota due to habitat changes, increased turbidity, and chemical exposure, and afect drink- ing water quality (Band and Salvesen 2009) . 1 Runof from urban areas often contains higher concentrations of nutri- ents (such as nitrogen and phosphorus), sediment, metals, hydrocar- bons, and microbes. An increase in frequency and intensity of storms due to climate change will have a similar impact on stream systems by increasing pollutant loading. Point and nonpoint sources—runof and EDCs—are also threats. 1 Livestock access to streams contributes heavily to bank erosion, sedi- mentation, and nutrient input. 1 Riparian vegetation serves as nutrient input to the stream community and helps regulate stream temperature by providing shade. Lack of riparian vegetation or inadequate width of forested bufer can cause streambank erosion and sedimentation. 2 Loss of forest cover can cause increased erosion and sedimentation and negatively impact aquatic systems. Poorly constructed and maintained timber roads are another source of erosion. 2 Irrigation and water supply withdrawals pose a threat to fow regime. Water withdrawals can be problematic, particularly in streams with already low 7Q10 fows, because they may reduce available habitat for aquatic species. Decreased groundwater recharge between storms due to impervious surfaces leads to a decrease in stream basefow. 2 Many rivers that were once free-fowing are now fooded by reservoirs, severely fragmenting habitat and often isolating populations of species above and below the impoundment. Floodplains and wetlands are nat- ural features designed for food control through attenuation and dissi- pation of foodwaters. Development and other impacts can reduce this service. 3 Climate change is predicted to decrease rainfall and therefore limit water supply. Efects will likely compound with other threats to increase the severity of several threats to aquatic systems. 4 Invasive plants in the riparian area can have negative impacts on stream systems by creating a monoculture (such as Japanese Knotweed) with poor nutrient inputs, reducing bank stability, and allowing too much sunlight and therefore warmer stream temperatures. Invasive aquatic species, like the Asian Clam or Rusty Crayfsh, may have negative efects on native species, such as competition for space and resources.
Sediment and Erosion
Pollution
Cattle in Streams
Lack of Riparian Vegetation
Conversion to Agriculture/ Silviculture
Water Withdrawals
Flood Regime Alteration
Climate Change
Invasive Species
270
2015 NC Wildlife Action Plan
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