Appalachian Hemlock Northern Hardwood Forest Observed Climate Change Exposure

Climate exposure measures the degree of climate change a species, landscape, or vegetation type has already experienced, or is projected to experience. We analyzed climate change exposure for several vegetation types occurring within the National Capital Region for two time periods: the observed recent past (1981-2014) and the near-term future (2011-2040) To do this we measure change in temperature and precipitation relative to baseline (1948-1980) climatic variability across time (i.e. year-to-year variability) and across space (i.e. variation across geography). This group contains data for those two facets of exposure for a single vegetation type for the observed (1981-2014) period. More specifically, these include:


1) Climate Typicality: This analysis quantifies change relative to variability across time for a fixed location in geographic space This results in a map depicting departure from historical climate norms across the distribution of the type. Each pixel provides a measure of how “typical” current climate values at that location are when compared to baseline climate values. The scale ranges from 1, which indicates that the climate falls within the range of values observed during the baseline, to 0, which indicates the climate of the period is completely “novel”, or fully outside the range of conditions that occurred in the baseline.


2) Change in Climate Suitability: This analysis quantifies change relative to variability across geographic space. We use bioclimatic niche modeling to quantify change relative to the variability of climate across the vegetation type’s historical geographic distribution. This results in a map of where predicted climate suitability may be declining or improving. Values range from -1 (declining climate suitability) to 1 (improving climate suitability).


Both exposure metrics are combined to produce an overall exposure layer that is used as input into the Habitat Climate Change Vulnerability Index (HCCVI). See layer descriptions for more detailed explanation of methods for each exposure layer.