Friday, September 20, 2019

Disease and climate change result in bland autumn colors

“It’s seasonal so next year we might not see it at all. That’s the good news”

Do you recall the hot dry summer of 2002? You may not, but the aspen trees around Colorado remember and some of them are apparently paying the price for the drought conditions of six and seven years ago.



Many experts believe the recent cases of Sudden Aspen Decline (SAD) are a result of the drought conditions in Colorado between 2002 and 2005. The drought stressed out the aspen trees, and that’s not good news for Crested Butte and Gunnison.
Given Crested Butte’s proximity to one of the largest aspen forests in the world, SAD is a huge concern. Not only do aspens bring flocks of tourists in the fall to view the gold of changing leaves, sick aspen stands affect elk herds, other forest trees and the overall appearance of an area.
Most people would agree that this recent fall leaf-peeping season was somewhat disappointing around Crested Butte. But the good news is that SAD is probably not to blame for the 2009 conditions. Jim Worrall, a plant pathologist with the U.S. Forest Service in the Gunnison office, says this year’s conditions came about from the wet spring.
“The biggest thing this year was a Marssonina leaf blight,” Worrall says. “This year was the biggest statewide epidemic of that disease I’ve ever seen.”
Worrall says, “It came about from the very wet spring we had. The symptoms of the disease includes brown to black leaf spots and it gives a bronze or rust tinge to the canopy. The colors aren’t as bright. Another symptom is defoliation. Leaves could start falling off as early as late June or July and that’s what happened around here. Some of the thinning look we had this year was Marssonina instead of SAD. It’s seasonal, so next year we might not see it at all. That’s the good news.”
Crested Butte-Mt. Crested Butte Chamber of Commerce director Richard Bond agrees that is good news.
“The aspens bring in thousands of people to the area in the fall, whether they are looking for fall colors or hunting for elk,” he says. “I’ve had dozens of calls the last few weeks from people asking about the colors. In fact, I’d say some people with businesses in the area don’t view fall as an off-season anymore. Autumn activity is very important.”
Worrall says in the long term, this area is seeing the impact of SAD and that could eliminate some aspen groves, but overall, the Crested Butte and Gunnison area has been lucky.
He says the Kebler Pass region is fairly unaffected. “There are just a few patches on the western end of it,” he says. “If you had gone north from Paonia on Steven’s Gulch Road—that area does have some impressive damage and has kind of become famous as one of the areas to get a panorama of the SAD damage.”
According to U.S. Forest Service observations, “Since 2004, USFS Forest Health Management aerial surveys and local field studies have reported a rapid increase in crown dieback and stem mortality in Colorado’s aspens.” Statewide aerial surveys indicate that in 2006 approximately 5 percent of aspen forests were experiencing this type of rapid decline, a Forest Service assessment states. In 2007, the amount was about 13 percent. The 2008 survey showed that 17 percent of the forests were affected. Aspens at low elevations and those located on south to west aspects are very vulnerable to warm drought.
“We’re certainly seeing it in the Gunnison basin,” confirms Worrall. “There are significant amounts but it is not as severe as in other parts of the state.”
His 2009 statistics show that in the Gunnison National Forest, about 65,000 acres have been affected, or about 16 percent of the aspen forests. “That includes the Paonia and Gunnison ranger districts and I would bet that the Gunnison Forest is significantly less impacted than Paonia. I really can’t say for certain why that is,” says Worrall.
Worrall says a delayed reaction from the droughts earlier this decade is believed to be causing the SAD.
“The interesting thing about the drought is that this was a combination of hot and dry and that really stresses the trees,” he says. “It’s surprising it’s such a long-term stress. We’re still seeing the after effects of that drought. The insects and pathogens get in there while the trees are weak and they don’t back out, and the trees eventually die.”
Worrall says the hypothesis of drought causing the stress in aspen ties in with effects from climate change. “It’s not too big a stretch to suggest that Sudden Aspen Decline is the early effects of climate change,” he says.
High Country Citizens’ Alliance climate and clean energy coordinator Chris Menges agrees SAD is a problem but also agrees that there is some good news for this area. “Our aspens appear to be impacted but overall are in much better health than others throughout the state,” he says. “Predictions are that the most impacted aspen groves will be on south facing aspects and at lower elevations and Crested Butte is not at a lower elevation. Our aspen groves should remain more spectacular and intact than most of the state. That’s good news for tourists looking for fall colors and hunters looking for elk.”
What can be done? A couple of things might help, according to Worrall. “Aspen normally regenerates from sprouting from the roots. That occurs most prolifically when the aspen is disturbed abruptly from actions like fire or cutting,” he says. “The problem we are seeing is that the aspen is not regenerating after the gradual death of the trees through SAD. If it’s not regenerating, then we could lose some of our aspen stands and we’ll probably see sparse aspen stands or a conversion of those stands to other plants and trees.
“So, we think and hope that if we go into some of these stands early while they still have energetic, live roots and disturb them with fire or cutting, it gives them a chance to generate new sprouts,” Worrall continues. “We are looking at a couple of projects involving cutting or prescribed burns in the area. The strategy there is to try to regenerate even healthy stands. Stands that are less than 40 years old are generally unaffected by SAD.”
Menges hopes such forest management actions can help but he also hopes that area residents will become more aware that the Rocky Mountain West is beginning to see on-the ground impacts of climate change.
“On a global scale, the effects of climate change are alarming and accelerating faster than anticipated. Though not as visible to us, areas throughout Colorado and the west are seeing some very direct impacts,” says Menges. “The most noted impacts of climate change like the loss of the northern ice sheets or dramatic desertification are going on far away from here but the impacts touching our backyard should also be noted.”
Worrall agrees that climate change will probably continue to have a big effect on the local aspen groves. “Now, there is some indication that we may be peaking on this episode of SAD,” he says. “There don’t seem to be new areas popping up. In the long term, it is tied into climate change and if we see more episodes of a warm drought, SAD could reoccur and get worse.”
Menges says people can take individual action to help the overall situations as well. “From decreased snow packs to SAD in the forest, we’re seeing signs of climate change around here and the best science available projects things will become much worse if we don’t do all we can to reduce greenhouse gas emissions,” Menges says. “I’d encourage everyone to do what they can to lower their carbon footprint.”
Menges notes that making these changes can save money. “The best news is that the solution to the climate crisis is in fact the solution to the economic crisis,” he explains. Visit the Climate and Clean Energy page at for more information. In the meantime, look forward to some good autumn gold in the hills around Crested Butte and Gunnison next year.

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