Earth’s “sixth mass extinction” is well underway: up to 50% of all individual animals have been lost in recent decades and almost half of land mammals have lost 80% of their range in the last century. Vertebrate populations have fallen by an average of 60% since the 1970s, and in some countries there has been an even faster decline of insects – vital, of course, for aerating the soil, pollinating blossoms, and controlling insect and plant pests. [...] Even more frighteningly, a 3.5 Celsius rise is considered by some to be ”the extinction point”, because: "the food chain collapses, oceanic plankton dies off, and terrestrial vegetation is severely limited. The grasslands we use for agriculture are threatened the most. The extinction of species will create chaos. For example, the disappearance of bees will create enormous problems with pollination. The acidification of the oceans depletes the oxygen in the waters. Temperatures higher than the extinction point are being predicted, not by crackpots, ideologues or sci-fi writers, but by serious scientists."

— Socialism or Extinction by Ted Reese (Page 5)