5. InVEST model details

The InVEST model suite is thoroughly documented in its user guide (Sharp et al. 2020). This source identifies how each of the 24 ecosystem service models are calculated, including how to obtain input data. However, the models officially included in InVEST do not always work at the global scale. Thus, we use modified versions of them that have been rewritten to run in parallel at the global scale. These modified versions of the models were first documented in Kim et al. (2018) and more fully in Chaplin-Kramer et al. (2019). In this section, we summarize the modifications made to enable global coverage.

For the pollination model, the global version assumed pollinators are fully abundant on any natural land covers (specifically classes 50 to 180 in our underlying ESACCI LULC database) and that all pollinators had the same relative efficacy and distance decay parameters for their pollination activity. Region-specific applications of InVEST often calibrate the model based on which species of pollinators are present and what their pollination efficiency is (which we did not do). We then calculated the proportional area of natural land covers around every plot of agricultural land (classes 10-20). In brief, the model estimates pollinator sufficiency based on the abundance of pollinator species given the two limiting resources on the landscape: pollinator nesting habitat and pollinator nectar sources (provided here by pollination-dependent crops). We calculated this globally following Chaplin-Kramer et al. (2019), which provided a global map of pollination sufficiency. This was an input to the algorithm described in SI Section 6 that connects InVEST biophysical outputs to GTAP inputs.

We perform the carbon storage calculations by applying a custom version of the InVEST carbon storage model. This version uses a globally-extended lookup table for IPCC Tier-1 (Ruesch and Gibbs 2008) values of carbon content defined for regions breaking out each continent, ecofloristic region and frontier forest status. The default InVEST model takes as an input a biophysical table with one of these regions.