in Australia, Brazil, Canada, USA

What if forests started dying because of climate change? Oh wait… they already are

Little progress seems to have been made at the UN climate negotiations in Bonn over the past two weeks. Meanwhile, climate change is already having a serious impact on forests, through the increase in severity and frequency of droughts, fires and/or beetle attacks.

According to Dr Craig Allen, Forest Ecologist at the US Geological Survey, in North America, “We’re looking at tree mortality over a scale of tens of millions of hectares in the last decade alone.” The bad news is that this is typical of what’s happening around the world. In an interview recently on ABC Television, Allen explained that droughts and heat waves are triggering “mass waves of mortality”. He adds that, “No major forest type is immune.”

It’s not necessarily the drought that kills the tree. Allen explains that,

“There may be insects and fungal pests that emerge at that point in time but underlying it is the physiological stress on the trees that compromises their defences… So what we’re seeing in these forest die-off events around the world are trees passing the tipping point of stress – the thresholds of mortality. Unfortunately we don’t know very much about these thresholds at this point.”

The ABC programme can be viewed by clicking on the image below:

This programme focusses mainly on the impacts of climate change on trees and forests in Australia. Scientists have found that the numbers of insects attacking the trees is increasing. Dr George Matusick, a forest pathologist, says that,

“The numbers are scary. Where we might have seen one, maybe two per square metre, now we’re seeing fifty, sixty, seventy, eighty. We’ve seen even as high as one hundred.”

Scientists in the USA are seeing similar patterns. In March 2012, a study by scientists from the Department of Ecology and Evolutionary Biology, University of Colorado, was published in the American Naturalist. The study looks at the mountain pine beetles that have killed large areas of pine forest in North America.

They found that mountain pine beetles are breeding twice a year:

“Long thought to produce only one generation of tree-killing offspring annually, some populations of mountain pine beetles now produce two generations per year, dramatically increasing the potential for the bugs to kill lodgepole and ponderosa pine trees.”

This means that there “could be to 60 times as many beetles attacking trees in any given year,” the scientists found. They point out the seriousness in terms of the climate of the mountain pine beetle [MPB] infestation:

“The current MPB epidemic is the largest in history, extending from the Yukon Territory, Canada, to southern California and New Mexico…. To date, more than 13 million ha [hectares] of trees have been killed in British Columbia. The MPB-killed trees in British Columbia alone will release 990 million tons of CO2 into the atmosphere, an amount equal to five times the annual emissions from all forms of transportation in the country.”

The 2005 drought in the Amazon led to the release of 1.6 billion tonnes of carbon to the atmosphere. The 2010 drought was even worse, leading to as much as 2.2 billion tonnes of carbon being released.

As Joe Romm points out on Climate Progress, this is only the beginning of climate change feedbacks. In the USA,

“we’ve only warmed about a degree Fahrenheit in the last few decades. Imagine the unexpected nonlinear impacts and feedbacks we face when we warm 10 times that this century, as we are likely to do if we keep listening to the do nothing or do little crowd.”

The impacts of climate change on forests dramatically illustrate that doing something about climate change must mean reducing the amount of fossil fuel that is burned. There is no way of addressing climate change by trading the carbon stored in forests against continued emissions. Doing so will only accelerate the tipping point of the death of vast areas of the world’s forests.

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