The ecological economics of land degradation: impacts on ecosystem service values.
We use two datasets to characterize impacts on ecosystem services. The first is a spatially explicit measure of the impact of human consumption or 'demand' on ecosystem services as measured by the human appropriation of net primary productivity (HANPP) derived from population distributions and aggregate national statistics. The second is an actual measure of loss of productivity or a proxy measure of 'supply' of ecosystem services derived from biophysical models, agricultural census data, and other empirical measures. This proxy measure of land degradation is the ratio of actual NPP to potential NPP. The HANPP dataset suggests that current 'demand' for NPP exceeds 'supply' at a corresponding ecosystem service value of $10.5 trillion per year. The land degradation measure suggests that we have lost $6.3 trillion per year of ecosystem service value to impaired ecosystem function. Agriculture amounts to 2.8% of global GDP. With global GDP standing at $63 trillion in 2010, all of agriculture represents $1.7 Trillion of the world's GDP. Our estimate of lost ecosystem services represent a significantly larger fraction ~10% of global GDP. This is one reason the economics of land degradation is about a lot more than the market value of agricultural products alone.