Mapping the Transgression of the Planetary Boundary for Functional Biosphere Integrity

Abstract

Two new control variables have been suggested for quantitatively assessing the core planetary boundary for functional biosphere integrity: 1) Human appropriation of net primary production (HANPP) and 2) a metric for ecological disruption (EcoRisk). HANPP is a measure of the pressure exerted on the biosphere by removing energy otherwise available to ecosystem processes. EcoRisk indicates ecological disequilibrium through changes in vegetation structure and biogeochemical state variables as a measure of more general ecological disruption.We use simulations with the Dynamic Global Vegetation Model LPJmL to map the status of these variables at a spatial resolution of 0.5◦x0.5◦ and quantify their temporal evolution since the year 1600. We additionally quantify local boundary thresholds using a newly developed methodology at grid-cell scale by comparing with independent indicators for biosphere integrity. We find that EcoRisk and BioCol are good predictors of degradation for a variety of ecological empiricaldatasets.We finally combine both indicators into a meta-metric, and aggregate results globally to a planetary boundary status based on the land area showing a transgression of the local thresholds relative to the preindustrial state. We find that the local boundary is currently transgressed on 66% of the global ice-free land surface, with 47% already at high risk of degradation.

Keywords: planetary boundaries, biosphere integrity, HANPP, Earth system, ecosystem change, vegetation shift