Climate Departure, Climate Exposure & Geoclimatic Stability

In this dataset we calculate three variables for HUC5 watersheds (split by ecoregion) within the Pacific Northwest (PNW): geoclimatic stability, climate departure, and climate resilience.

Geoclimatic Stability, as defined here, is a measure of a natural system's capacity to remain stable as the climate changes over time. This is based on two factors:

Climate Departure: a measure of how different the future climate is projected to be from the historical climate.

Climate Resilience: a measure of how resilient an area is expected to be to changes in climate (based on topoclimate diversity and landscape permeability).

A watershed with lower levels of climate departure and higher levels of climate resilience is more likely to sustain current levels of native biodiversity into the future (high geoclimatic stability).

Climate Departure is based on the difference between the projected future climate (2016-2045) and the historical climate (1971-2000) within each polygon. The higher the climate departure, the greater the difference the projected climate is from what the area experienced in the past. HadGEM2-ES is the climate model that the climate departure data was calculated from.

Climate departure is based on the departure of three climate variables: Minimum Temperature, Maximum Temperature, and Precipitation. For each variable, the standardized anomaly is calculated using the following formula:

d = (Xf- Xh)/σXh

where d is the difference, xf is the mean of the variable in the future period, xh is the mean of the variable in the historical period, and σxh is standard deviation of the variable in the historical period.

We then take the absolute value of these three differences and then take the mean of these three absolute values in order to capture the average climate departure among the three climate variables.As a final step, we take the natural log of the mean climate departure in order to reduce the influence of outliers.

Climate Resilience represents the mean climate resilience within each polygon, and is calculated from the Nature Conservancy's Terrestrial Climate Resilience Density (%) dataset generated as part of the Conserving Nature's Stage (CNS) project. It is based on two factors: topoclimate diversity and landscape permeability. For more information about this dataset and the CNS project visit the following url: https://www.conservationgateway.org/ConservationByGeography/NorthAmerica/UnitedStates/oregon /science/Pages/Resilient-Landscapes.aspx

Geoclimatic Stability is a integer value ranging from 1-4 (1=Low Stability, 2-3=Moderate Stability, 4=High Stability) that is calculated based on the climate departure value of each watershed relative to the range of climate departure values calculated for each watershed within an ecoregion and the climate resilience value calculated for that watershed. The logic used to calculate the geoclimatic stability score is as follows:

if resilience > 50%:

if departure > ecoregion_mid_departure:

geoclimatic stability = 3 (moderate)

else:

geoclimatic stability = 4 (high)

elif resilience if departure > ecoregion_mid_departure:

geoclimatic stability = 1 (low)

else:

geoclimatic stability = 2 (moderate)

The Geoclimatic Stability scores above can be interpreted as follows:

1 (low): A watershed with higher levels of climate departure and lower levels of climate resilience is less likely to sustain current levels of native biodiversity into the future and is therefore considered to have a lower geoclimatic stability level.

2 (moderate): A watershed with lower levels of climate departure and lower levels of climate resilience is considered to have moderate geoclimatic stability.

3 (moderate): A watershed with higher levels of climate departure and higher levels of climate resilience is considered to have moderate geoclimatic stability.

4 (high): A watershed with lower levels of climate departure and higher levels of climate resilience is more likely to sustain current levels of native biodiversity into the future and is considered to have a higher geoclimatic stability level.