Vulnerability of riparian obligate species to the interactive effect of fire, climate and hydrological change

Climate change is expected to have multiple direct and indirect impacts on ecosystems in the interior western U.S. (Christensen et al., 2007; IPCC 2013). Global climate predictions for the Southwest include higher temperatures, more variable rainfall, and more drought periods, which will likely exacerbate the ongoing issues relating to wildfire and water allocation in the region (Christensen et al., 2007). Of particular concern to managers are the effects of climate and related changes on riparian habitats, which support a disproportionate amount of the biodiversity in the region. The Rio Grande Basin contains important water sources and habitats for municipalities, agriculture, recreation and wildlife in Colorado, New Mexico and Texas (Figure 1). The Rio Grande Basin also contains critical habitat for a number of riparian dependent species including the endangered southwestern willow flycatcher and the Rio Grande silvery minnow (BOR 2011). Climate change is expected to alter river flows through modified precipitation regimes and higher temperatures that increase evapotranspiration rates (Hansen 1991). Mean annual runoff is projected to decrease from 7.3 to 14.4% by 2050 (BOR 2011). Increased fire potential, though not well defined for riparian habitats, is also an issue where it may favor the establishment of exotic species like Tamarisk and accelerate the degradation of riparian forests (Ellis 2001). In addition, human populations in the region are expected to grow considerably, putting more pressure on natural systems competing for resources. Because competing land and water use leaves the riparian habitats of rivers like the Rio Grande are highly vulnerable to degradation, resource managers need information and tools to identify future conditions under various climate and fire scenarios. By assessing and understanding the impacts of climate and related disturbance change on these important habitats, managers will be able to better focus limited resources on the most critical needs as well as identify opportunities for promoting natural regeneration of riparian woodland and wetland habitats.