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Reflecting on the Extinction Crisis

February 14, 2011

Regrettably, we are now living in the sixth great  extinction event in the history of our planet.  How do we know this?  Well, I’ll give you two numbers.


1. The Background Extinction Rate (BER). This is what we can consider the “normal” rate of species extinction in the history of life on earth.  If you remember, humanity’s short history makes it just a small feature in this story.  (If you don’t,Dawkins explains this well using a piano.)

The BER is typically given in units of “million species years”, the number of species that would go extinct in just 1 year if there were only 1 million of them.  The BER is not constant, but we can come up with a rough number for periods of time that correspond with non-extinction events.

Since the last great extinction event, the BER has been about 1 species per MSY. This translates to about 10-100 species a year given our present counts of all living organisms (from mammals to fungi).


2. The Current Extinction Rate. Meanwhile, since the 20th century, the extinction rate has jumped dramatically.  Though there are now a variety of estimates, they all agree that the extinction rate has skyrocketed.   In general, the extinction rate has grown by 2-3 orders of magnitude. For example, E.O. Wilson gave an estimate of 27,000 species lost per year in the early 90s, and it’s only grown since then.

The cause of the growth in the extinction rate is clear. Since leaving Africa 50,000 years ago (or earlier), humanity has tamed the land, eaten up entire species, and made the planet far less hospitable to other forms of life.  Extinctions, as a result, are largely correlated with the growth of human populations.

Here’s a good visual:

The present rate of species loss means that we will lose half of all species by 2100.  From the perspective of mother nature, human civilization has contributed about as much as cataclysmic volcanoesmeteors, and climate change.  This reality overwhelms me, but I do have several good reasons to hope.


First, we have the capacity to understand what we are doing, provided there is the right event to wake us up. On this, I think of the experience of J. Robert Oppenheimer following the first successful detonation of an atomic bomb in 1945.  Recalling the Bhagavad Gita, he thought “Now I am become death, the destroyer of worlds.”  Here he says those words:


Second, we also have the capacity to transcend our narrow existence and think of ourselves as part of a larger community of living organisms. The most frequent used example is that of the “blue marble effect”, which was the growth in environmental consciousness resulting from the first images of Earth from space.

Thankfully, these experiences do not usually require radical expansions in technology.  As a divemaster in Utila, Honduras, I saw firsthand how often scuba diving a reef or snorkeling with a whale shark could change people’s perspectives on conservation.  Here’s a a video of a freediving encounter with a whale shark:

And a great recording of one of my clients enthusiastically explaining how an encounter made them feel (hit play to listen with the video):



Third, there is an ever increasing body of evidence that our planet is not healthy. Some of it is anecdotal and can be quite gripping, such as this story of a polar bear swimming nine days to find land.  Though the mother bear survived, the cub did not.  And much more is clear and compelling research, like this excellent study by Dr. Villy Christensen.

(The visualization of this graphic is far cooler.)


And fourth, we are beginning to actually measure how much we depend on a healthy environment. The valuation of ecosystem services offers great potential for us to begin considering the environment in policy-making.  For example, a UNEP study has found that one hectare of coral reef can be worth anywhere from $130,000 to $1.2 million per year, as they provide such services as tourism, fishing, scientific study, and storm and erosion protections.  The World Bank is now reviewing how we might institute “green accounting” measures, as described here:

(Though, in some countries, green accounting may be too politically challenging. The NY Times reports that China’s “Green GDP” project gave results that were “so sobering — in some provinces the pollution-adjusted growth rates were reduced almost to zero — that the project was banished to China’s ivory tower this spring and stripped of official influence.”)

To close, we might consider the words of Julia Whitty in The Fragile Edge as she reflects on the loss of coral reefs (p. 278):

“[W]ith or without either our help or hindrances the earth’s reefs will go and then come again, as long as the sun delivers its rays and the waters flow.  Whatever role we might play in the next great extinction will surely have less effect on the tenacious reemergence of reef-builders than it will on us.  Reefs, we know, can survive without us.  The opposite may not be true.”

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