Wednesday, June 13, 2012

The Current Mass Extinction


“Once there were brook trout in the streams in the mountains. You could see them standing in the amber current where the white edges of their fins wimpled softly in the flow. They smelled of moss in your hand. Polished and muscular and torsional. On their backs were vermiculate patterns that were maps of the world in its becoming. Maps and mazes. Of a thing which could not be put back. Not be made right again. In the deep glens where they lived all things were older than man and they hummed of mystery.”
(Cormack McCarthy, The Road)

I have described in an earlier post a rapid (in geologic terms) loss of species and a deteriorating environment, but the possibility that we, the human race, a "weedy" species, like dandelions in our lawns, may survive. And after many generations, our progeny may have no memory, no notion, of how much is missing from the impoverished world we have bequeathed them.

But there is another possibility. One in which things happen too fast for us to adapt, and along with the vast majority of other life on earth, we follow the Passenger Pigeon into extinction.

Climate scientists today are concerned about the so-called "tipping point," the moment at which a dynamical system, such as the earth, that has been changing slowly and predictably will suddenly "flip" to a state inimical to life as we know it. With respect to the climate, this can happen as a result of certain changes inducing other changes, which in turn, induce others and reinforce the original forcing function. This is a case of positive feedback not being a good thing.

Consider sea ice, for example, an implacable force of nature that covers an area on earth about two and one half times the size of Canada. Sea ice has a very significant impact on climate change. The ice has a bright surface that reflects sunlight back into space, so areas covered by sea ice don't absorb much solar energy, and temperatures in the polar regions remain relatively cool.
As warming temperatures melt sea ice, as they are doing now, fewer bright surfaces are available to reflect sunlight back into space, more solar energy is absorbed at the surface, and temperatures rise. As sea ice melts further, more solar energy is absorbed, and more sea ice melts.This chain of events starts a cycle of warming and melting, leading to greater and greater warming and continued loss of sea ice, with predictable results; the dynamics of sea ice freezing and melting reaches a tipping point where freezing can’t keep up with melting and the sea ice disappears, removing a vital component in the earth’s homeostasis -- its ability to maintain an equilibrium.

There’s another type of “melting” that’s taking place as a result of rising global temperatures, and that’s the thawing of the permafrost covering the earth’s tundra. Tundra is located at the top of the northern hemisphere in Europe, Asia and North America. It covers 20% of the earth's surface just below the polar cap. Permafrost trapped carbon buried since the Pleistocene era. When permafrost melts, that carbon comes bubbling to the surface of lakes, and dissipating into the atmosphere as methane, a greenhouse gas 23 times more potent than carbon dioxide. And the permafrost is melting -- at five times the rate previously thought.

The rapid release of methane will accelerate the greenhouse gas trapping effect that's currently warming the earth, and that will in turn, increase the rate at which sea ice is disappearing. And that takes us back to the role of sea ice in reflecting solar energy back into the atmosphere, instead of absorbing it in the ocean. You get the drift.

Another type of tipping point occurs when a particular ecosystem sustains so much damage that it can no longer sustain itself. This is what's happening in the Amazon Rainforest.

The dense forests of the Amazon soak up more than one-quarter of the world's atmospheric carbon, making it a critically important buffer against global warming. But a warming climate combined with unchecked slash and burn clearing is bringing the rainforest to the brink of disaster.
Billions of trees died in the record drought that struck the Amazon in 2010, and agriculture, and urban development along with the road building that accompanies it are destroy billions of additional trees and the essential and fragile ground cover that makes the rainforest possible.

The Amazon is but one of ten threatened forests on the earth. If forests lose their ability to act effectively as carbon sinks, additional green house gases will contribute to accelerating global warming, which will subject the earth to further extreme droughts, loss of additional trees, and runaway climate change.
Biologists who believe the earth is experiencing its sixth mass extinction identify five primary direct drivers in addition to climate change, all are the result of human behavior: habitat loss, invasive species, pollution, over-exploitation of resources, and the factor that magnifies all the others—human overpopulation.

According to studies, at least half of all plant and animal species are likely to disappear in the wild within the next 30-40 years, including many of the most familiar and beloved large mammals: elephants, polar bears, chimpanzees, gorillas and all the great apes, all the big cats, and many, many others.

Bird species are similarly imperiled, songbird populations have declined by 50% in the last 40 years. One out of every eight species of plant life worldwide and almost one third of the plant species within the United States already face extinction.

Populations of large ocean fish have declined by 90% since the 1950s. All around the world, birds, reptiles, mammals, amphibians, fish, and invertebrates, as well as trees, flowering plants, and other flora, are all in steep decline.

As disturbing as this rapid decline of species and its attendant support for a sixth extinction event is, there's an even more disturbing, even terrifying prospect -- sudden destabilization of the earth system with imminent death and destruction across all species, including most especially, human. Is this even remotely possible? You're damn right it is.

 I'll discuss this in a future post.

1 comment:

Richard Badalamente said...

It gets worse: “...droughts, heat waves and storms weaken the buffer effect exerted by terrestrial ecosystems on the climate system.” http://www.mpg.de/7501454/weather-extreme_carbon-cycle_cimate-change