4.7.2009: America's 4 July bonfires served a dual purpose yesterday. They burned the wood of trees destroyed by a trio of bugs that are devastating parts of the nation's forests.
With 750 million acres of forests in the United States, the scale of the problem is massive. Since 1999, the country has lost, on average, 1 per cent of its tree cover per year. This means these small insects have killed about 10 per cent of all US forests in 10 years.
Two of the bugs, says the government, have the potential to destroy $700bn (£429bn) worth of forests.
Already, one beetle – the emerald ash borer – has invaded 13 US states and two Canadian provinces. In those places, all movements of firewood are illegal and contractors who have moved logs have been fined by the courts and banned from working in the quarantined areas.
Last month, the emerald ash borer (or EAB) was identified in New York State, home to 700 million ash trees which sustain a profitable furniture industry and even provide the raw material for baseball bats. Ironically, the trees were replacements for elms killed off by Dutch elm disease. America's chestnut trees have also suffered catastrophic damage from blight.
The borer, which comes from China, first entered America in the wood of crates shipped to Detroit in the early 1990s, but it was 2002 before it was formally identified. The tiny, creamy-white larvae bore through the bark and adults start emerging in mid-June. The larvae damage causes general yellowing and thinning of the foliage, followed by crown dieback and the eventual death of the tree. The borer has killed around 50 million trees in Michigan and tens of millions in 12 surrounding states and in Canada's Ontario and Quebec.
Therese Poland, of the US Forest Service, said that in a bid to attract, trap, identify and monitor the insect, the service has researched the odours, or kairomones, produced by the ash; these allow the insects to identify the trees. Ms Poland said the service is hoping to find the "ultimate attractant", and it is hoped this will prove more successful than the sticky traps hoisted in tens of thousands of ash trees across the Midwest. Another theory – not Ms Poland's – is that purple attracts the male insect because it replicates the colour of a female's backside.
Ms Poland added that one of the problems is that the borer is difficult to find because the eggs are very small and are laid in bark cracks. The larvae can live under the bark for two years before they emerge from the wood in which they have been feeding, which means a harmless-looking piece of firewood can turn into a beetle-bomb.
"You stack the firewood up at your cabin and if it doesn't get burned right away, then a whole bunch of beetles might come out of it next year," Ms Poland said, adding that one piece of firewood could produce up to 50 beetles.
As the populations take hold and multiply, their range can increase exponentially. "The worst-case scenario is it could, in theory, wipe out ash trees in North America," Ms Poland said. "It could be as bad or worse than Dutch elm or chestnut blight."
Rick Hoebeke, an entomologist from Cornell University, said: "I would say the outlook for ash, if it [EAB] becomes widespread, is pretty bleak."
The economic impact could also be sizeable. The government says the eastern US produces nearly 114 million feet of ash board, valued at $25.1m. Mr Hoebeke added: "To lose a major species of hardwood like that would be devastating for a lot of industries, not to mention the impact on the ecosystem."
One of the hardest-hit towns is Worcester, Massachusetts, right in the heart of maple country, which has suffered a major onslaught of the Asian long-horn beetle (ALB). This beetle also came from China, and has been costing New York City and Long Island up to $40m a year since it arrived in 1996.
Meanwhile, the mountain pine beetle is rampant in the states of Colorado, Wyoming and Montana, among others. This insect, which, unlike the other two, is a North American native, has killed more than half the lodge pole pine over 14.5 million hectares in British Columbia and is now spreading into neighbouring Alberta.
It's a desperate situation for the Canadian forestry industry, which was already reeling from the collapse of the US housing market and has had to be bailed out by the Canadian government.
Foresters say that in recent years the numbers of the pine beetle have reached plague proportions, due in part to warmer winters which didn't deliver the below-40-degree cold snaps that used to kill off its larvae. So huge were the populations that, according to Staffan Lindgren, a professor of entomology, there were stories of what people called "beetle rain". He explained: "Under a perfectly blue sky, farmers would start hearing what sounded like rain on their tin roofs. It turned out it was beetles coming out and falling on the roofs, literally billions and billions of beetles."
But all is not lost – at least according to Rob Mangold, director of forest health protection for the US Forest Service. In an exclusive interview he insisted that the forests could recover, but said they did need to be managed very differently.
"Forests are resilient. An area might be bare, but the trees will come again. But it is a big impact and we have a big mountain pine epidemic in the West, especially Montana, Wyoming and Colorado," he said.
Last year alone, the mountain pine beetle killed six million acres of forest, but still Mr Mangold has hope. He insisted: "We have to manage the forest better – making sure there is the right mix of ages and species – not just all one type, one age. And the social licence for managing forests is there now, the best for 15 years.
"Only 10 years ago, people were saying how 'you can't cut the trees down, we must preserve the forest'. Now they want us in to manage it."
As for the two exotic invaders – the EAB and the Asian long-horn beetle: "We don't want 'em, but we got 'em," said Mr Mangold. Already, the ALB has been eradicated from Chicago and big efforts to control it continue in New York.
But Worcester, Massachusetts, remains a problem; 22,000 trees have had to be cut down. Mr Mangold said: "The city is very forested, really close to the maple forests of Central New England. It's had a big impact on the city streets and we're going to do a lot of replanting there. The whole situation was also exacerbated by a huge ice storm that laid a lot of non-infested trees on the ground."
One solution being touted in the forest community is that they could bring in the EAB's Chinese predators, a form of wasp, but so far it's remained no more than an idea. Nationally, however, the big worry is climate change.
"The implications are a concern to us," Mr Mangold said. "It's getting drier and hotter and we want to plant what should be the right trees for the right place but that's getting more difficult to work out. To some extent we're on unknown ground. I'm not trying to minimise what's going on because there are certainly big impacts locally and the EAB could be in more states that we haven't caught up with yet. We got a big country and it's hard to find these things."
Meanwhile, the prospects for eradicating the emerald ash borer look dim. Mr Mangold admitted: "We're probably going to have to learn to live with this thing."
There could be a lot more bonfires to come...
Issued by: The Independent
Author: Graham Mol
Issue date: July 5, 2009
Link to Article: Origin of this text
MISSOULA, Mont. — When Ken Salazar — then a senator from Colorado, now secretary of the interior — called the attack on millions of acres of pine forests by the bark beetle the Katrina of the West, he was expressing the common view of the explosive growth of the beetles as an unmitigated disaster.
But not everybody sees it that way. Some environmentalists and scientists support the beetles. While they acknowledge the severity of the problems the beetles are causing, they argue that the insects, which kill only mature trees larger than five inches in diameter, are a natural phenomenon, like forest fires, and play a vital ecological role.
“It’s not the end of the forests, and they are not destroyed,” said Diana L. Six, a professor of forest entomology and pathology at the University of Montana here, who has studied the beetle for 16 years, as she walked in a beetle-infected forest near here recently .
“Lodge pole pine evolved to go out with a stand-replacing event, such as fire or beetles, then regenerate really quickly,” she said. “When they hit 80 or 90 years of age all of a sudden the beetles become a player — the trees are big enough for the beetles to attack. They reset the clock on the stand.”
Dr. Gregg DeNitto, a forest health specialist with the Forest Service here, said the beetles were not “an exotic like the emerald ash bore.”
“This is a native insect in a native host, and these are normal biological processes that have happened for millennia,” Dr. DeNitto said.
Nothing can or should be done to halt the spread of the beetle, experts say. After they kill the mature trees, the soil becomes more fertile as nitrogen levels increase, sometimes tripling. The growth rate of surviving trees increases when the infestation ends. After dead trees fall over or burn, grass grows and provides elk habitat, and slightly more diverse forests rise up.
Beetles help by breaking down fallen trees, as well. “They digest the wood and are valuable in terms of nutrient recycling,” said Dr. Ken Raffa, an entomologist at the University of Wisconsin who studies the beetles. “And they introduce micro-organisms that further break down the wood.”
Still, it is a grim time for people who work, play and live in the woods. Mountain pine beetles affect nearly 6.5 million acres, an expanse more than 50 percent greater in 2008 than in 2007. If all types of bark beetles are included, the figure is 8 million acres — a level of destruction not seen in 150 years — and the number is expected to grow this year.
The Forest Service’s chief forester, Rick Cables, who oversees the Rocky Mountain Region, told Congress in June that fire in vast acreages of downed timber could burn so hot in places it would bake the soil, causing extreme erosion and runoff, and pollute water supplies to millions of people in the Southwest.
“People in Phoenix and Las Vegas depend on the water, and I have to balance that with an ecosystem trying to reset itself,” Mr. Cables said. Prescribed fire or mechanical thinning of dead trees are being considered to reduce the risk of fire in beetle-killed stands in some watersheds.
There is virtually no research on fires in an outbreak this large. “We’ve never seen this many trees dead on the landscape,” said Dr. Barbara J. Bentz, a Forest Service entomologist. “We don’t know what the ramifications are.”
Both Dr. DeNitto and Dr. Six allow that the current outbreak is not entirely natural. Human intervention in the form of fire suppression and large-scale clear cuts mean that many forests are simultaneously vulnerable.
Under natural conditions a forest is a patchwork of different-age trees, which means the beetles also create a patchwork of dead trees. “If they come up against a young patch, they’ll quit,” Dr. Six said. “If it’s old, they keep on going. But we’ve lost that mosaic, so they keep on going.”
The major human-caused element of the current outbreak, though, is a warmer climate, which has opened new territory to the beetles. And this has caused some experts to view the beetle infestations as unnaturally severe. “The absolute minimum temperatures are 6 to 10 degrees higher now,” said Dr. Steve Running, an ecologist at the University of Montana who is a member of the Intergovernmental Panel on Climate Change and is studying the effect of warming on Western ecosystems.
In the 1950s, minimum temperatures were 42 to 47 degrees below zero. The last decade, the minimum was 35 below, with fewer days at minimum. The rise in minimums is important, Dr. Running said, “because at the lower temperatures it only took a couple of nights for the larvae to freeze to death.”
The growing season in the West has also grown longer by two weeks, Dr. Running said, while the precipitation has stayed the same, which translates to a drought. Trees stressed by drought cannot effectively fend off the beetles.
Dr. Six argues that this outbreak is so extreme in duration, intensity and scope that the beetles are behaving like an exotic species in some places and may damage a critical Western ecosystem based around the white bark pine.
High altitudes, where the insects’ life span was very limited, are warming, and the beetles there have gone from a two-year life cycle to one year. There are so many more beetles that in combination with a disease called blister rust, they will probably wipe out white bark pines in many areas.
Dr. Six says she remains amazed at the beetles’ adaptation. “It’s impressive something could evolve such a complicated and effective way of living in the woods,” she said. “It’s awesome.”
When the beetles hatch, they mass for an attack on the next tree by sending out a chemical signal that tells other beetles it is time for an assault. They need to have sufficient numbers to overwhelm the tree, and need to do it within three or four days, or the tree will win. If the beetles lay eggs and they hatch, they eat a nutrient-carrying membrane and kill the tree.
The tree is not that nutritious, though, so the beetles bring carry-out. “They carry fungus from tree to tree in pockets and inoculate the trees with it,” Dr. Six said.
There are so many insects now that some behaviors have changed. They often go after trees that are smaller and younger than trees they have attacked in the past, or after healthy trees. Beetles used to hatch during two weeks in July, Dr. Six said, and “now they hatch beginning in May and go until October.”
“The whole ecosystem is changing,” she said. “I’ve never seen anything like it.”
While more than 6 million acres in the United States have been affected by mountain pine beetles, the number is 34 million acres in British Columbia. “It’s a continental-scale phenomenon,” said Dan Tinker, a professor of forest and fire ecology at the University of Wyoming, referring to the total of the beetle kills. “We’re all taken aback right now.”
There is no forseeable end to the outbreak, Dr. Six said. “If it’s climate-driven,” she said, “we have to reverse climate change.”
Issued by: The New York Times
Issue date: July 5, 2009
Link to Article: Origin of this text
Climate change happens: beetles to destroy American forests