We're To Blame For The Sixth Mass Extinction Happening Now

by Monica Joshi

We are having a greater effect on the environment than ever before. This effect, in part, is caused by increasing use of fossil fuels, absurd mass culling of animals as well as rapid depletion of soil and water sources due to concentrated agriculture. One of those effects is a mass extinction event, the likes of which we have never seen before, or at least not for 65 million years. This is an alarming finding of a new published study in the journal Science Advances.

This latest research was conducted by an international team lead by Gerardo Ceballos of the National Autonomous University of Mexico. As measuring extinction rates is notoriously hard, it is mind-blowing that these studies have overcome some of the common issues and are producing profoundly worrying results.

The new research was designed to determine how human actions over the past 500 years have affected the extinction rates of vertebrates: mammals, fish, birds, reptiles and amphibians. It has found that there is a definite sign of elevated species loss which has markedly accelerated over the past couple of hundred years. This is so vast that life on Earth is embarking on its sixth greatest extinction event in its 3.5 billion year history.

There is always a risk that such work overestimates modern extinction rates, as it must make some assumptions given the very limited data available. Ceballos and his team wanted to put a floor on these numbers, to establish extinction rates for species that were very conservative, with the understanding that whatever the rate of species lost has actually been, it could not be any lower given the data available.

This makes their findings even more significant because even with such conservative estimates, they find extinction rates are much, much higher than the background rate of extinction – the rate of species loss in the absence of any human impacts.

A number of studies have attempted to estimate the background rate of extinction. These have produced upper values of about one out of every million species being lost each year.

Using recent work by co-author Anthony Barnosky, they effectively double this background rate and so assume that two out of every million species will disappear through natural causes each year. This, inevitably, should mean that differences between the background and human driven extinction rates will be smaller. But they find that the importance of more recent extinctions is so great as to override any natural processes.

The “very conservative estimate” of species loss uses the International Union of Conservation of Nature data. This contains documented examples of some species becoming extinct. They use the same data source to produce the “conservative estimate” which includes known extinct species and those species believed to be extinct or extinct in the wild.

The paper has been published in an open access journal, which includes the list of vertebrate species known to have disappeared since the year 1500. The Latin names for these species would be familiar only to specialists, but even the common names are exotic and strange: the Cuban coney, red-bellied gracile, broad-faced potoroo and southern gastric brooding frog. Bye bye, broad-faced potoroo, we hardly knew you to begin with.

Why should we care, however, when this is such a “natural” part of the extinction process? Even if it is actually amplified by our human-built industrialization?

One possible response to this is, well, we wouldn't be here given a drastic atmospheric change. We are just as reliant on the nature around us as it is on us. Whether it’s pollinating our crops, purifying our water, providing fish to eat or fibres to weave, we are dependent on biodiversity. Ecosystems can only continue to provide things for us if they continue to function in a similar way that they have been for centuries.

The relationship between species diversity and ecosystem function is very complex and not well understood. We don't yet understand the threshold after which we would still be able to survive on Earth without the system the way that it is now.

If we regard the Earth as nothing more than a source of resources and a sink for our pollution, if we value other species only in terms of what they can provide to us, then we will continue to do what we are doing now without sense of remorse. This will, inevitably, increase the risk that the Earth will cease to function in the ways that human species requires both now and in the future. This can only reduce the complexity and beauty of our home in the cosmos by eventually causing it great harm.

This latest research tells us what we already intuitively knew to be true. Humans have, in the space of a few centuries, caused a great havoc in the Earth’s biosphere. Liquidating biodiversity to produce products and services has an end point. To put it in simple terms: we all want to be rich, but this earth simply can't support all that we want when we are rich. Science is starting to sketch out what that end point could look like, but it simply cannot tell us why to stop before we reach it. It might be best to take sincere measures to slow down this change.

Edward O. Wilson claims that the biosphere is incredibly delicate, and without a change in behaviour, we will irreversibly destroy the biodiversity on the planet.