Chapter 4 Habitats
contributes to rising water temperatures, especially where water depths are shallow enough that the entire water column is subject to solar heating.
Climate Variability . Research conducted by Eaton and Sheller (1996) and Mohseni et al. (2003) assessed the effects of climate warming on 57 species of fishes in streams across the United States. Depending on minimum temperature tolerance assumptions, species requiring coolwater habitats could experience a 12–15% decrease in available habitat (DeWan et al. 2010) . When the connectivity between streams and rivers within drainage basins provides adequate dispersal corridors, species at the southern extent of their geographical distribution may shift their distributions northward into cooler habitats ( Allan et al. 2005 ). Where adequate dispersal corridors are limited or restricted, access to or availability of cooler water habitats may limit the range of those species subject to narrow temperature tolerance ( DeWan et al. 2010 ). Increased air temperatures may lead to increased water temperatures and potentially lower DO levels; however, increased air temperature may have varying effects on coolwater systems due to factors such as the degree of groundwater influence, amount of shading by riparian vegetation, and watershed aspect. Hot spells can have the same effect as overall increased air temperatures but on a much more acute scale. Problems such as increased evaporation and therefore, lower amounts of flowing water will vary depending on factors such as groundwater influence. Chronically warmer water temperatures and lower dissolved oxygen levels may increase stress on organisms. The increased water temperature alone can cause a decline in dissolved oxygen and if significant, can lead to fish kills, whether as a direct result of increased water temperature or as a secondary effect of algal blooms. Thermal stratification will likely not be an issue when aquatic systems are relatively shallow; however, the large river systems of the Piedmont and Coastal Plain ecoregions and deep-water reservoirs could experience stratification, algal blooms, and potential fish kills related to higher than normal water temperatures (DeWan et al. 2010; Band and Salvesen 2009) . Drought . Severe and prolonged droughts may decrease stream flow, decrease groundwater recharge, and increase evaporation. Lower water levels during dry times will increase stress to the system. Connectivity to contributing waters within the system will be restricted or eliminated by low and no-flow conditions. Changes in flow regime will likely result in changes in the overall stream morphology and transport of sediment that leads to altered habitat composition. The balance between surface flow and groundwater recharge may be altered. Decreases in overall summer precipitation may cause reduced water flows, which can further contribute to warmer water temperatures and water quality stressors (DeWan et al. 2010; Karl et al. 2009; Band and Salvesen 2009; US EPA 2010) . Pollution. Decreased stream flows can allow an accumulation of sediment and chemical inputs from stormwater runoff and effluent discharge because there is less frequent flushing in the system. Recent studies have shown that endocrine-disrupting chemicals (EDCs) in treated
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2025 NC Wildlife Action Plan
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