These are all extinct birds. A great number of species have vanished from the Earth over the past few thousand years, and especially over the past century or two, as a direct result of human activities. Changing climates, introduction of invasive species, and habitat destruction are just a few of the causes. We know these things are happening, we can see the species going extinct, but an important question for science is how much damage we’re really doing.
Species went extinct before human activities started. Competition between species and environmental changes all were things that occur without us, so researchers have spent decades trying to understand how the current extinction rates compare to those prior to human involvement.
Decades ago, these estimates could be based on the fossil record and they weren’t bad. A scientist examining fossils could come up with reasonable numbers for extinction rates in the ocean, but many species don’t leave strong fossil records. For example, plants and animals that don’t have hard body parts don’t fossilize well in most cases.
The genetics revolution over the last 20 years has allowed for much better estimates of the die-off rate in these species as the rates of extinction can be compared to our new genetic understanding of how rapidly species diversity.
Using a combination of these techniques, scientists led by Brown University’s Jurriaan de Vos just published an updated estimate of how the current extinction rate compares to that prior to human involvement. Their best numbers can’t give incredible precision, but they calculate that current extinction rates are 1000 times what they were before human involvement, and even worse, those rates are increasing rapidly.
The kinds of extinction rates humans are causing around the world are enough that it remains safe to say humans are in the process of causing a mass extinction, where a large fraction of the species on Earth vanish over a short time period. Geologists refer to 5 mass extinctions from the fossil record, and studies like these suggest that we’re right in the middle of witnessing a 6th.
Image credits: Wikimedia