Tuesday, March 31, 2015
“Trees Can’t Run… Trees Can’t Hide”
If you believe in neither global climate change nor evolution, today’s blog is definitely not for you. But let’s just say, the future of the rich, thick forests that cover much of Canada and the Western United States (and, of course other vast regions of North America) is very much in doubt. It seems that as trees experience drier, warmer climate, perhaps reflecting the reaction of other other species, many lose their ability to resist disease and insect infestation, becoming increasingly vulnerable to a rather clear death. Most prominent among these assaults is the rather dramatic rise in bark beetle attacks of these forests (the dry, brown trees among the green above).
“These tiny winged beetles have long been culling sickly trees in North American forests. But in recent years, they've been working overtime. Prolonged droughts and shorter winters have spurred bark beetles to kill billions of trees in what's likely the largest forest insect outbreak ever recorded, about 10 times the size of past eruptions. ‘A doubling would have been remarkable,’ [Entomologist Diana] Six says. ‘Ten times screams that something is really going wrong.’…
“Mountain pine, spruce, piñon ips, and other kinds of bark beetles have chomped 46 million of the country's 850 million acres of forested land, from the Yukon down the spine of the Rocky Mountains all the way to Mexico. Yellowstone's grizzly bears have run out of pinecones to eat because of the beetles. Skiers and backpackers have watched their brushy green playgrounds fade as trees fall down, sometimes at a rate of 100,000 trunks a day. Real estate agents have seen home prices plummet from "viewshed contamination" in areas ransacked by the bugs. And the devastation isn't likely to let up anytime soon. As climate change warms the North American woods, we can expect these bugs to continue to proliferate and thrive in higher elevations—meaning more beetles in the coming century, preying on bigger chunks of the country.”
“A healthy tree can usually beat back invading beetles by deploying chemical defenses and flooding them out with sticky resin. But just as dehydration makes humans weaker, heat and drought impede a tree's ability to fight back—less water means less resin. In some areas of the Rocky Mountain West, the mid-2000s was the driest, hottest stretch in 800 years. From 2000 to 2012, bark beetles killed enough trees to cover the entire state of Colorado. ‘Insects reflect their environment,’ explains renowned entomologist Ken Raffa—they serve as a barometer of vast changes taking place in an ecosystem.” MotherJones.com, March 19th.
Responses to bark beetle attacks have ranged from cutting down swathes of trees to stop or slow the encroachment of the winged beetles (but they can fly) or to open massive new logging operations to allow harvesting before what many believe is an inevitable and massive loss of timber. There is one little, tiny problems with that approach. It seems that trees are evolving a natural resistance to both drought and the beetle, and there appear to be new varieties of several species of trees that repeatedly withstand their environmental attacks, related diseases and, surprisingly, bark beetles. So when these massive harvesting or preventive measures are applied indiscriminately, the number of “evolved” trees, ready to spread their seeds, are culled along with the more vulnerable members of their species.
“…Six believes that the blitz on the bugs could backfire in a big way. For starters, she says, cutting trees "quite often removes more trees than the beetles would"—effectively outbeetling the beetles. But more importantly, intriguing evidence suggests that the bugs might be on the forest's side. Six and other scientists are beginning to wonder: What if the insects that have wrought this devastation actually know more than we do about adapting to a changing climate?...
“But Six has a different way of looking at the trees' plight: as a battle for survival, with the army of beetles as a helper. She found compelling evidence of this after stumbling across the work of Forest Service researcher Constance Millar, with whom she had crossed paths at beetle conferences.
“Millar was comparing tree core measurements of limber pines, a slight species found in the eastern Sierras of California that can live to be 1,000 years old. After mountain pine beetles ravaged one of her study sites in the late 1980s, certain trees survived. They were all around the same size and age as the surrounding trees that the beetles tore through, so Millar looked closer at tree ring records and began to suspect that, though they looked identical on the outside, the stand in fact had contained two genetically distinct groups of trees. One group had fared well during the 1800s, when the globe was still in the Little Ice Age and average temperatures were cooler. But this group weakened during the warmer 1900s, and grew more slowly as a result. Meanwhile, the second group seemed better suited for the warmer climate, and started to grow faster.
“When beetle populations exploded in the 1980s, this second group mounted a much more successful battle against the bugs. After surviving the epidemic, this group of trees ‘ratcheted forward rapidly,’ Millar explains. When an outbreak flared up in the mid-2000s, the bugs failed to infiltrate any of the survivor trees in the stand. The beetles had helped pare down the trees that had adapted to the Little Ice Age, leaving behind the ones better suited to hotter weather. Millar found similar patterns in whitebark pines and thinks it's possible that this type of beetle-assisted natural selection is going on in different types of trees all over the country.
“When Six read Millar's studies, she was floored. Was it possible, she wondered, that we've been going about beetle management all wrong? ‘It just hit me,’ she says. ‘There is something amazing happening here.’” MotherJones.com. So as amateurs elect to mess with Mother Nature, she has an uncanny ability to punish the perpetrators. As legislatures think they are fighting infestation by increasing the acreage in public lands available for timber harvesting, they actually many be dooming masses more forestland to extinction.
I’m Peter Dekom, point out those ”little stories” that just might change your life in a big way in the not-too-distant future.