Hydrologic regimes may change, although both an increase in groundwater recharge as well as decreases in ground water levels are possible. In general, shallow groundwater aquifers are expected to change more than deep aquifers. If groundwater levels and associated discharge and upwelling remain steady, sites with intact hydrology may be more resistant to change. Increased nutrient enrichment of groundwater is likely and could fuel an expansion of invasive species. Increased human demand for groundwater resources will also likely be an issue in some regions. High species diversity provides the ability for some species to expand if others decline, although most species appear to be more sensitive to hydrology and water chemistry than temperature. However, many sites are small and isolated with minimal opportunities for species to shift or migrate, giving fens high inherent vulnerability.