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Humanity's Fundamental Environmental Limits -- model input files
These data constitute the spatially explicit input to our model of Earth's biophysical human carrying capacity (Binder et al 2020). They include average daily estimates of photosynthetically active radiation (PAR), light interception efficiency (EI) of crop canopy, and precipitation net of evapotranspiration (WATERFLUX); as well as land areas of each grid cell and the fractions currently farmed and irrigated. The data are made available here in a .mat (Matlab) file.
WATERFLUX is calculated as PRECIPITATION - PET, with negative values retained for purposes of the model.
PET is calculated with the Hargreaves (1985) equation using data for temperature and PAR (re-scaled by 1/0.487 to capture the full light spectrum).
Daily PAR for terrestrial areas are calculated from the high-frequency, instantaneous PAR values of the GLASS PAR product, using a generalized integration method developed by Holdahl (2019). For more detail, see: https://ethanholdahl.shinyapps.io/PAR_App/
Baseline daily interception efficiencies are calculated in two steps. First, growing periods are determined based on temperature data. All days with temperature minima in excess of 0 deg C (terrestrial) or with temperature means in excess of 10 deg C (ocean) are initially designated as eligible growing days. All eligible days that are part of a sequence of 30 or more consecutive eligible days (minimum season length) retain final designation as part of a growing period; other days are excluded. In the second step, light interception efficiencies of the crop canopy are calculated according to a quadratic equation fit to data reported in Dohleman and Long (2009).
AREA is calculated using the 'areaquad' function of Matlab's Mapping Toolbox.
FARMED is the percent of each grid cell dedicated to crop or pasture, based on data from Ramankutty et al (2008).
IRRIGATED is the percent of farmed land equipped for irrigation in each grid cell, based the Ramankutty data referenced above in conjunction with irrigation data from FAO's Aquastat (Siebert et al 2013). In the 1.7% of cases in which estimates of irrigated land exceed estimates of cultivated land, irrigation fractions are capped at 1.
PAR: MJ m-2 day-1
WATERFLUX: mm m-2 day-1
IRRIGATION, FARMED and EI are dimensionless.
All data have been resampled and aligned to a common 1-by-1 degree grid using Matlab's Mapping Toolbox. The upper left cell of each matrix (1, 1) corresponds to -179.5 deg E and 89.5 deg N.
For further information regarding the use and sources of these data, please consult our article, "Humanity's Fundamental Environmental Limits", in Human Ecology, available at: