The Sixth Mass Extinction

Did you know that you're in the midst of the sixth great mass extinction in Earth's history? Over four billion years, and only six extinctions. It's rather remarkable that it's happening in your time, don't you think? Or should we not be surprised?

The greatest irony is undoubtedly that you even have something to do with it. Oh, I don't want to blame you, necessarily: just by living the way you do, the way you've been brought up, the way you've been shown, you've been contributing to the extinction of millions of species. And millions more are destined for life's trash heap soon.

Perhaps you'd like to know more about how this is happening, and what you can do to minimize its effects. I want to tell a sad tale about the Monteverde Cloud Forest, in Costa Rica.

Let's start with the Intergovernmental Panel on Climate Change's most recent predictions (from 2007): "Climate change is likely to lead to some irreversible impacts. There is medium confidence that approximately 20 to 30% of species assessed so far are likely to be at increased risk of extinction if increases in global average warming exceed 1.5 to 2.5oC (relative to 1980-1999). As global average temperature increase exceeds about 3.5oC, model projections suggest significant extinctions (40 to 70% of species assessed) around the globe." From the IPCC Synthesis Report 2007.

"Astonishing," I thought, when I first heard it. "Can it really be possible that we stand by and watch as we eliminate half of Earth's species by our ridiculous reliance on fossil fuels?" The more I see, the more I believe that the answer is "Yes!"

So let's see how this might come about in a couple of cases: one I know of personally; the other comes from the other side of the globe, in Australia.

I went to Costa Rica in the summer of 2011, as part of a class studying the tropical rainforest and cloudforests there. The cloudforests are particularly interesting: they're at high elevation, literally "up in the clouds" (as the name suggests), and feature really interesting biology (such as stunted rainforest trees -- you feel like you're a giant in a rainforest, because your head is up in the canopy!).

My aunt Nelle is a great one for bird-watching, and she'd told me to keep my eye out for a Resplendent Quetzal, which was once commonly found in the Monteverde Cloud Forest. However, warming climate has meant that the toucan is moving up, threatening the quetzal. I'll let another friend of the quetzal tell her story:
Toucans [are] a relative newcomers to the Monteverde area and people who have been here a long time didn't used to see them. The toucans preferred lower altitudes. But as the temperatures have increased they moved further up the mountain. Now they are quite common in Bajo del Tigre. The trouble is that toucans like to eat eggs and some of the birds up here that are already threatened, like the three-wattled bellbird and the quetzal make their nests in tree hollows. They haven't learnt how to protect their eggs from toucans because they never used to have them around their nests. Toucans love quetzal and bellbird eggs.

Last year as part of the canopy campaign for the local school some of us spent many hours on the bridge in the cloud forest reserve watching a pair of quetzals tending their nest. Two weeks later the tree hollow was torn open and the nest and the young were gone. No one saw what got the nest but it must have been pretty strong to tear open even a rotten tree. The last thing bellbirds and quetzals need is more tragedies like that.

Rowan Eisner Published as a blog on January 17, 2012, Friends of the Rainforest. For a more scientific reference, try The effects of climate change on tropical birds, Review Article, Biological Conservation, Volume 148, Issue 1, April 2012, Pages 1-18 Cagan H. Sekercioglu, et al.: "In Monteverde, Costa Rica, climate change has already enabled keel-billed toucans (Ramphastos sulfuratus), cavity-nesting nest predators, to expand their range into the highlands, where they now compete with the montane forest specialist resplendent quetzals (Pharomachrus mocinno) for nest holes, as well as preying on quetzal nests (Pounds et al., 1999)." I met Alan Pounds in Monteverde when I was there.

Sad to say I didn't see any quetzals while I was in Costa Rica. I did see leaf cutter ants, however, and this surprised our guide. "We're not used to seeing leaf cutter ants up here," he said. Another recent arrival, and another threat to endemic species.

Australia's Golden Bowerbird is another climate-change study, on the other side of the world: The World Wildlife Fund produced a rather depressing report entitled "Bird Species and Climate Change", which included this summary of research on Australia's golden bowerbird: "The golden bowerbird, along with many other birds in the Wet Tropics of Australia's northeast, is highly vulnerable to climate change. Its suitable habitat would decrease 63 per cent with less than 1oC of future warming, up to 98 per cent with 2-3oC of warming, and completely disappear with between 3 and 4oC of warming, illustrating why this zone's climate scenario has been termed 'an impending environmental catastrophe.'"

It cites the primary research of Hilbert et al., in "Golden bowerbird (Prionodura newtonia) habitat in past, present and future climates: predicted extinction of a vertebrate in tropical highlands due to global warming"
(as well as the 2003 paper Climate change in Australian tropical rainforests: an impending environmental catastrophe -- and that's a title to give anyone pause). The graphic at right is from that publication, and shows the complete extinction of all 65 endemic vertibrates studied by 7 degrees C of warming.

The World Bank is operating under the assumption of 4 degrees C of warming by the end of the century, which would lead to the predicted extinction of about two-thirds of the species studied.

It's sometimes hard to be cheery in the face of the climate change news. The only good news is perhaps the fact that we're aware of the problem. The biggest question of all is this, from the human perspective: how many species (and which) can slip away before we, too, become "committed to extinction"?

I often think of Kubler-Ross's "Five Stages of Grief", which she formulated to summarize typical responses to those learning of a terminal disease. Her responses ("DABDA") were

Why not extend this to our response to climate change? Dr. Steve Running has done just that. In 2007 he took Kubler-Ross's stages, and framed them in terms of climate. Here's the short-hand version: As Dr. Running says, however, "[a]n obvious flaw in this analogy is that many people are simply ignoring the global warming issue, a detachment they cannot achieve when they are personally facing cancer." But doesn't this simply suggest that people are still stuck in the denial phase? While not as personally threatening as terminal cancer, we're facing a potentially civilization-terminating crisis (back to nuts and berries), if not worse -- a species-terminating crisis (back to cockroaches eating the nuts and berries):

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