Study Estimates the Magnitude of the 6th Extinction Crisis for the First Time – But it is Possible to Prevent it

For the first time ever, a scientific study has estimated the percentage of species that will go extinct if we disturb all the remaining tropical forests on Earth, and the results are higher than expected — around of 40% of species (although it varies by group) will be lost if humans continue to destroy or degrade the Earth’s remaining tropical forests. Although there has been a growing awareness among scientists and even among the mainstream media that we are now entering the Earth’s 6th Mass Extinction Event, until recently there has been little scientific analysis of how bad this extinction event is going to be or how close we are to implementing measures to avoid it. This study, performed by a scientist at Macquarie University in Sydney, used real-world data of species richness (i.e. # of species) at 875 locations around the world of 11 groups of organisms (i.e. trees and 10 groups of animals from different insect types to large and small mammals). He then plotted their species richness (i.e. total number of species) against the % of habitat disturbed (e.g. logged, burned or otherwise disrupted). He found that if all remaining habitat is disturbed, we are likely to lose 30% of tree species and 8 to 65% of the 10 animal groups. These results are even worse expected, since disturbed habitats do often still contain forest in a damaged state — which the author thought would harbor a higher abundance of life.


Above: A graph showing the last 5 Mass Extinction Events (large font) over the past 0.5 billion years from the perspective of marine biodiversity. Extinction intensity refers to the % of genera (each genus is a group of species) that were completely wiped out (i.e. not a single species made it through the extinction event). Image copyrighted under Creative Commons (CC By-SA 3.0 license).

The author also regards his estimates as conservative, because he did not take into account other factors beyond habitat destruction such as hunting and he added the possibility that a mass extinction event could have already happened and we don’t even know it:

“A mass extinction could have happened right under our noses because we just don’t know much about the many rare species that are most vulnerable to extinction,” Alroy said. “To figure out whether this is true, a lot more field work needs to be done in the tropics. The time to do it is now.”

The reality is we aren’t able to assess this possibility because we still don’t have a good grasp of the total biodiversity of tropical forests or planet Earth (to date, we have identified 1.75 million species out of an estimated 3 to 100 million species on Earth).

This is all the more reason to do everything in our power to avoid or greatly minimize the impending 6th mass extinction event, since there is still so much of this world’s biodiversity that is unexplored or which we know very little about — and should be protected both for the sake of maintaining a healthy ecosystem on Earth and for the future benefits it could bring mankind.

An increasing number of scientists and activists have been supporting a new plan that has been fashioned to directly deal with the threat of the 6th global extinction. The plan, which is “Half-Earth” or “Nature Needs Half,” involves protecting half the Earth’s habitat in order to save upward of 80% of all species and respecting the rights of indigenous and local communities to effectively manage large areas of natural habitat (which they are already doing, but often face opposition from governments that don’t respect their rights). Recent scientific analysis has also shown that for many parts of Earth’s surface this goal is still realistically within reach. Essentially the world’s governments and communities are currently adding protected areas (i.e. including community-managed reserves) at an increase of a 4% every decade, but we would have to double this to reach the 50% protection goal by 2050.

We are also gaining increasingly sophisticated technologies (e.g. Global Forest Watch) to monitor the world’s forest and oceans. However, achieving protection of the world’s habitats is going to require far more than just new technologies, new laws or new protected areas. It is going to require us to step outside of our comfort zones and change our way of thinking about conservation and how we relate to one another — most especially by supporting indigenous and local community management and ownership of natural areas, which is already successfully occurring in some parts of the world but hasn’t truly taken off yet. Ultimately, we need to start seeing humans as the solution and not just the cause of the 6th extinction crisis. We are an incredibly influential species but there are an incredibly large number of people around the world who are committed to protecting their local environment while making a sustainable livelihood. We need to recognize and support their right to do so—maybe acknowledging and supporting the other half of humanity will help us save half of nature too.

Cover Image: “Earth Day 2007 – Atlantic Reflection”  by Bruce Irving. Photo copyrighted under CC BY-NC-SA 2.0 license.


Alroy, J. (2017). Effects of habitat disturbance on tropical forest biodiversity. Proceedings of the National Academy of Sciences of the United States of America. doi:10.1073/pnas.1611855114

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