Are we raising the biological diversity of the planet? Is that what the Anthropocene is about?
Human development — dubbed the age of the Anthropocene — boosts biodiversity in other ways too. New anthropogenic habitats, such as farmland and cities, usually support fewer species than the original ones, but they contain some that were previously rare or absent. The ensemble of new and old habitats holds more species than the original vegetation — habitat diversity is one of the strongest predictors of ecological diversity. Climate change also tends to boost regional diversity, because diversity increases with temperature and precipitation, both of which are rising (on average, but not everywhere). Global-diversity gradients dictate that more warm-adapted species are available to colonize new areas than cold-adapted species retreat from those areas as the climate warms.
Writing in Nature, Phil Roberts goes on to suggest:
Rather than the catastrophic declines often portrayed, empirical evidence points to ecological increases in the number of terrestrial species in most of the world’s regions over recent decades and centuries, even though the total number of species on the planet is declining.