It's the rate of change in CO2 levels that is unprecedented in human history and for a long time in earths history. The effects of that change include ocean aci

It's the rate of change in CO2 levels that is unprecedented in human history and for a long time in earths history. The effects of that change include ocean acidification and habitat loss for many species. It stands to reason that atmospheric change on a timescale much smaller than what natural selection and species adaptation normally occur at could be very damaging to all sorts of ecosystems.