“Never before has a single species driven such profound changes to the habitats, composition and climate of the planet.”
A special issue of the Philosophical Transactions of the Royal Society B (Biological Science) — “Biological diversity in a changing world” — paints a bleak picture of what Homo ‘sapiens’ sapiens is doing to the other species on the planet.
Prior to this year, I wrote about extinction only occasionally — since the direct impact of unrestricted greenhouse gas emissions on humanity seemed to me more than reason enough to act. But the mass extinctions we are causing will directly harm our children and grandchildren as much as sea level rise. In particular, I believe scientists have not been talking enough about the devastation we are causing to marine life (see “Geological Society: Acidifying oceans spell marine biological meltdown “by end of century”).
In 2007, the IPCC warned that “as global average temperature increase exceeds about 3.5°C [relative to 1980 to 1999], model projections suggest significant extinctions (40-70% of species assessed) around the globe.” That is a temperature rise over pre-industrial levels of a bit more than 4.0°C. So the 5°C rise we are facing on our current emissions path would likely put extinctions beyond the high end of that range.
Given the irreversibility of mass extinction, and the multiple unintended consequences it engenders, it must be considered one of the most serious of the many catastrophic impacts we face if we don’t act soon.