Appalachian Hemlock Northern Hardwood Near Future HCCVI

NatureServe’s framework for measuring climate change vulnerability of habitats and ecosystems (HCCVI) provides a practical approach to organize criteria and indicators for this purpose (Comer et al. 2012). This framework provides a scorecard for reporting on the relative climate change vulnerability of a given habitat or ecosystem type within hexagonal spatial analysis units that are >100km2 in size. These hexagon results were then clipped to the 90m current distribution of the ecological system, as represented in the national map of ecological systems.

The layer represents the scorecard of multiple indicator values of climate change exposure and ecological resilience. All component layers include index values standardized to a 0.0-1.0 range, with 1.0 indicating highest ecological condition, and 0.0 indicating lowest ecological condition.Therefore, the lowest quartile of index scores indicate Very High vulnerability to climate change effects within the assessment timeframe.

Climate change exposure is measured in two different ways and then combined to produce an overall exposure layer that is used as input into the HCCVI. The first metric measures change in temperature and precipitation relative to baseline climatic variability across time (year-to-year variability) producing a layer of how typical current climate values at a given location compared to baseline climate values across the distribution of the type. The second metric uses bioclimatic niche modeling to determine if climate change is likely to negatively or positively impact the vegetation type.

Resilience scores reflect the summary of subscores for ecological sensitivity and adaptive capacity. Measures for sensitivity of vegetation types include landscape condition (based on land use intensity), invasive annual grass risk (a single score representing the risk posed by invasives was applied across the distribution of the type), and vegetation departure. Vegetation Departure (VDEP) indicates how different current vegetation on a landscape is from estimated historical conditions. This measure is mapped by the national Landfire program, based on changes to species composition, structural stage, and canopy closure at regional scales.

Adaptive capacity addresses natural characteristics of the ecosystem type that lend a degree of capacity to cope with climate change stress. Adaptive capacity has two components: a biotic measure of estimates of diversity within functional species groups, and an abiotic measure of landscape diversity developed by The Nature Conservancy.