The map shows human impact; the percentage of human influence relative to the maximum influence recorded for each biome. I got it from Resilience Science, which got it from Science magazine (where, I confess, I missed it). It deals with reshaping ecological processes on domesticated land. Anyway, rather than write my own version of the paper by Peter Karieva and his collaborators (which is behind a paywall), I point you straight to Resilience Science, noting in passing that I am certain I would not have done as good a job.