4.2 Aquatic Communities
4.2.6.3 Problems Affecting Habitats One of the most important issues concerning groundwater systems is the increasing demand for water supplies due to growth and urbanization (Land et al. 2004) . Groundwater extraction to meet this demand is often at unsustainable rates (Fleury 2009) and results in declining water levels, saltwater encroachment (in Coastal Plain systems), dewatering, and land subsidence (e.g., sink holes) (Land et al. 2004; Fleury 2009) . Groundwater pressure can drop when there is rapid and excessive drawdown of an aquifer and the pore space holding the groundwater shrinks. Tis leads to compaction of the aquifer at depth (Fleury 2009) . Voids can form in the soils and porous rock that once held water, which causes subsidence and col- lapse of the land surface (Patton and DeHan 1998; Fleury 2009) . According to the USGS, groundwater withdrawals from the Castle Hayne aquifer have caused land subsidence measuring as large as 7 inches, and has been documented (during the 33-year period from 1935–68) in the central Coastal Plain of North Carolina. Overall water-level declines are estimated to be as much as 20 feet near pumping centers (McSwain et al. 2014; USGS 2014b) . Mining operations can remove notable features from the landscape and alter the hydrau- lic gradients that contribute to groundwater systems. Quarrying often reduces spring discharge, causing drawdown of the water table, sinkholes, and the destruction of caves. Tailing ponds associated with mining operations may leak or collapse, and can become a source of toxic chemicals in local water supplies. Because of their permeable rock structure and presence of sink holes, karst systems are especially vulnerable to pollution, water withdrawals, and changes in land use (Bakalowicz 2005; Calo and Parise 2009; Brinkmann and Parise 2012) . Agricultural activities can degrade the qual- ity of groundwater quality through the usage of fertilizers and pesticides and storage or disposal of livestock or poultry wastes on land (Freeze and Cherry 1979 ). Contamination from nitrate-based fertilizers used on agricultural lands can wash into groundwater that is a source of residential drinking-water wells (Fleury 2009) . Dripwater fows are critical both to cave biota and to the microclimates of the caves them- selves, and if those fows carry surface-level contaminants, the entire cave environment can be afected (Fleury 2009) . Human use of caves can alter the physical structure of the caves themselves, change the water chemistry or hydrology within the cave, or destroy cave structures and cave-dwelling organisms (Fleury 2009) . Another concern is the advance of the saltwater front from coastal waters into freshwater systems, commonly referred to as saltwater encroachment. For example, New Bern’s fresh- water wells have experienced saltwater encroachment since the late 1960s. A Cove City drinking-water well feld was about 5 miles west of where the front was previously located
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2015 NC Wildlife Action Plan
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