Industrial humans are depopulating the globe of wildlife, driving populations and entire species extinct at the fastest rate in millions of years. It’s impossible to definitively quantify the extent of the losses we’re inflicting, because of three big unknowns:
Number of global species: We’ve catalogued about 1.5 million species, but know we haven’t catalogued everyone who’s out there. Estimates of total number of species with whom we share the planet range wildly from two million to ten million to two hundred million to one trillion.
Background extinction rate: Reconstructing species losses from fossil and molecular data is imprecise, with estimates from .1 to 2 extinctions per million species per year (E/MSY).
Current extinction rate: We can’t monitor all the species we’ve identified, and research is limited even for those we do track. It’s difficult to know whether a rare species is actually extinct, or just hasn’t been spotted for a while. The studies above differ in estimates of how much more quickly species are going extinct than the background rate—50 times or 1000 times faster. They do converge on an ongoing 100 E/MSY, but the source of that number is unclear.
Absolute numbers for extinctions per year are based on best guesses of the current extinction rate times estimates of the number of global species. Applying the above 100 E/MSY to the range of 2 to 200 million global species gives 200 to 20,000 extinctions per year, or .5 to 55 species per day.
Wildlife in decline
Extinction statistics underestimate biodiversity loss, since 95% or more of a species might die off without showing up in the numbers. Anywhere you look, ecological communities have been decimated or worse, as thousands of studies and millions of eyewitness accounts reveal. Two shocking global overviews:
The Living Plant Index measures a 58% decrease from 1970 to 2012 in populations of vertebrates—mammals, birds, reptiles, amphibians, and fish. Keep in mind that the 1970 biodiversity baseline was already tragically impoverished compared to a few hundred years ago.
A 2017 paper examining biological annihilation amongst vertebrates finds one third of vertebrate species are declining significantly. It concludes “Population extinctions today are orders of magnitude more frequent than species extinctions. Population extinctions, however, are a prelude to species extinctions, so Earth’s sixth mass extinction episode has proceeded further than most assume.”