The Beetle and the Feedback
The valleys of the Interior of British Columbia are like slashes in the earth’s skin — deep, steep, dramatic, falling precipitously into dark, narrow lakes. The landscape looks like frozen violence, the product of a time when tectonic plates collided, their edges crumpling and folding under the unimaginable force of crustal jockeying.
But the violence is not frozen, and the jockeying is not over. The plates are still moving. Their sudden shifts are earthquakes, and their vents are volcanoes. These mountains and valleys are part of a stupendous “Ring of Fire” that surrounds the entire Pacific Ocean.
We think of geology as finished, complete, the world having been made ready for its masters. But geology is never finished. Nature is always a work in progress. On our recent trip, Marjorie and I enjoyed the hot springs of Ainsworth and Nakusp. What heats that water? The hell-fires in the basement of the mountains.
The slopes of these valleys should be a uniform swath of green: spruce and fir, pine and cedar. In 2010, however, great rusty smudges on the mountainsides mark the corpses of vast numbers of dead trees. British Columbia is suffering from a massive mountain pine beetle infestation, and more than a billion of its trees have died. The infestation stretches south to Colorado and east to Alberta.
The villainous beetle is a little black bug about the size of a grain of rice. It lays its eggs under the bark of pine trees, and when the eggs hatch, the larvae eat the white phloem layer under the bark, cutting off the tree’s supply of water and nutrients. The beetle does have predators — woodpeckers, for instance — but the predators have been overwhelmed by the sheer size of the infestation.
The factor that normally controls the beetle population is cold weather. For the last decade, however, even the normally-cold Interior has had mild winters, while the summers have been sizzling. Marjorie and I spent 21 broiling days in BC last month, and the alleged rainforest gave us only one day of rain. This is thoroughly novel. BC’s summers used to be warm but moist.
This is climate change in action. And here’s the kicker: BC’s forests have normally been a huge sink for carbon, sucking carbon dioxide out of the air and sequestering its carbon within the trees. When trees die, however, they slowly but inexorably release all that stored CO2.
The shocking result is that BC’s forests have not only stopped absorbing carbon, they’re now emitting it — and on a huge scale. Last year, the carbon emissions from the dying forests were larger than all the human emissions in BC, and roughly double the size of the emissions from the Alberta tar sands.
This is a positive feedback loop — an outcome that amplifies the original cause. Emissions change the climate, and the changed climate creates even more emissions. The result is a self-feeding, intensifying spiral. There’s a feedback loop in the Arctic, where ice cover has normally reflected the sun’s heat back into space. As the ice shrinks, the dark water absorbs heat, and the remaining ice shrinks ever faster.
Another feedback loop is the ice-and-gas crystals known as “clathrates,” which exist at the bottom of the sea and form the permafrost in some parts of the Arctic. Clathrates sequester methane gas, which is more than 20 times as potent a climate-warming agent as carbon dioxide. As temperatures rise, however, clathrates disintegrate and the methane escapes into the atmosphere, driving up the temperatures.
The eventual result of such feedback loops, scientists hypothesize, could be runaway global warming, where feedback loops keep reinforcing one another and the process becomes self-fuelling and irreversible, speeding up like a snowball rolling down a hill.
If it can’t be stopped, it would be smarter not to start it. The emissions caused by the pine beetle were a shock to scientists — but who knows what other high-risk feedback loops we may be creating? Human civilization evolved over the past 10,000 years, nurtured by a period of uncharacteristically stable and temperate climate. For us, this hospitable climate is utterly indispensable. We should treat it with reverential care.
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