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Adding Climate Variables

adding_climate_variables.Rmd

Adding Climate Variables

Range shifts are hypothesized to be driven, in part, by changes in climate variables that affect species’ ability to survive, expand to new areas, or contract from their existing ranges. It is therefore logical that changes in climate variables contribute to the range changes documented in the BioShifts database.

The BioShifts team has standardized calculations for changes in temperature and precipitation within the geographical regions that range shifts were recorded (hereafter, study areas), and, when available, within the study areas cropped to the range of the individual species (hereafter, species-specific study areas). within each study area and species-specific study area, we provide baseline temperature and precipitation over individual study durations, average trends (change/year) in temperature and precipitation, and the spatial velocity of climate change (km/year??) across latitudinal or elevational gradients (matching the gradient of each associated range shift).

All climate data can be supplemented to selected range shifts with the add_baselines(), add_trends(), and add_cv() functions, but raw climate data can also be accessed with data(climate_variables).

Understanding Resolutions

Climate data were collected and caculated with [[satelite??]] data at four different resolutions: 1km, 25km, 50km and 110km. Summary statistics calculated between the four different resolutions may vary in several ways, so we allow users the option to access data from whichever resolution they feel is appropriate.

These four resolutions offer different trade-offs, because they affect both the variability of climate variables between grid cells (small resolutions will vary more, especially in heterogenous environments), but they will also affect velocities, since climate velocity is calculated as change in trends / spatial gradient of environmental values. Larger grid cells will generally result in flatter (smaller) spatial variability in temperature values, decreasing the denominators of climate velocity, and therefore resulting in larger velocity values, compared to climate velocity calculated between small grid cells.