"Many of our native bumblebee species are rapidly declining across North America"................I daresay that since living in Los Angeles(circa 1999), there has been a noticable decline of bumblebees of all kinds in my native plant garden that circles my home..........."They are important pollinators needed to grow North America's crops including apples, tomatoes, blueberries and legumes, as well as countless types of trees, shrubs, and wildflowers"..........'In particular, the American Bumblebee is at risk of extinction and it’s currently not protected in any way despite the drastic decline"............."The researchers found that the American Bumblebee’s area of occurrence has decreased by about 70 percent and its relative abundance fell by 89 percent from 2007-2016 compared to 1907-2006".................In addition to habitat alteration, during the 1990s, farmers began releasing captive bred Common Eastern Bumble Bees into greenhouses to increase crop production, especially for indoor-grown crops like tomatoes"................"Some colonies may have been infected with pathogens and parasites, which they then spread to wild bees in the same areas"..............."Honey bees, introduced to North America in the eighteenth century, may spread RNA viruses and other pathogens to wild bees through shared use of flowers".................."Another culprit is likely common pesticides, including neonicotinoids"..............."Neonicotinoid pesticides are particularly dangerous to bees because plants absorb them through the roots, rendering all plant parts toxic to insects".......... "This includes pollen and nectar, essential components of the bee diet"

http://feedproxy.google.com/~r/scienceblogrssfeed/~3/GxP3-gbWAkc/?utm_source=feedburner&utm_medium=email

Disappearing Bumblebee Species Under Threat Of Extinction

The American Bumblebee – a species once more commonly seen buzzing around Southern Ontario – is critically endangered, according to a new study led by York University.

The American Bumblebee

The finding, published in Journal of Insect Conservation, found the native North American species, Bombus pensylvanicus, is facing imminent extinction from Canada, considered the highest and most at-risk classification before extinction. Many bumblebee species are rapidly declining across North America, but are important pollinators needed to grow Canada’s crops including apples, tomatoes, blueberries and legumes, as well as countless types of trees, shrubs, and wildflowers.

The researchers assessed the extinction risk of the American Bumblebee, ranking the risk much higher than a federal advisory committee’s most recent assessment which classifies the species’ extinction risk at special concern.

“This species is at risk of extinction and it’s currently not protected in any way despite the drastic decline,” said Assistant Professor Sheila Colla, an expert in bees and endangered species in the Faculty of Environmental Studies.

 Range Map of the American Bumblebee(dotted line is
historical habitat,,,,,,,,,,,,green is current reduced range)

“Now that we have assessed the extent of the decline and located where the remainingpopulations are, we can look more closely at threats and habitat requirements to design an effective conservation management plan so that this species does not disappear from Canada forever,” said Colla, who co-authored and helped design the study.

Colla has been studying bumblebees in Southern Ontario since the mid-2000s. This study relies on the annual data that she and her fellow researchers have collected.

The study’s research team – led by Victoria MacPhail, Colla’s doctoral student, and including a scientist from the University of Vermont – used data from three sources. They analyzed Southern Ontario data from the citizen science program, Bumble Bee Watch, a collaboration of volunteers who submit bumblebee photos through a website or phone app for experts to identify. The researchers used the Bumble Bees of North America database to obtain records of bumblebee species in Ontario and Quebec dating back to the late-1800s. They also used their own field survey work which allowed them to evaluate the status of the species within its Canadian range, using the globally-recognized International Union for the Conservation of Nature (IUCN) Red List assessment criteria.

The American Bumblebee

The researchers found that the American Bumblebee’s area of occurrence has decreased by about 70 percent and its relative abundance fell by 89 percent from 2007-2016 compared to 1907-2006.

“This bumblebee species now has a reduced overall range,” explained MacPhail. “It used to stretch from Windsor to Toronto, and all the way to Ottawa and into the Quebec area, but it is now only found in some core areas and has experienced a 37 percent decrease in overall range.”

“It’s now a rare sighting in Toronto,” said MacPhail. “In terms of relative abundance, compared to other bees, you’d have to catch 1,000 bumblebees to find four of this species, and that compares to finding 37 bees in the past. You could walk out the door and win the lottery and find it, or you could be searching for years and not find any.”

The American Bumblebee

This study echoes Colla’s previous findings with the critically endangered Rusty-patched Bumblebee, once found in Southern Ontario. The species has not been seen in Canada for about ten years and drastically declined towards extinction without receiving protection or conservation management.

“The American bumblebee is still found in areas throughout its Canadian range and immediate action may save it from the same fate as the Rusty-patched Bumblebee,” said Colla.

--------------------------------------------

https://phys.org/news/2018-12-reveals-decline-vermont-bumble-bees.html

DECEMBER 13, 2018

Study reveals striking decline of Vermont's bumble bees

by University of Vermont

A new study examining 100 years of bumble bee records reveals that almost half of Vermont's species, which are vital pollinators, have either vanished or are in serious decline.

After conducting the state's most extensive search for bumble bees, and combing through historical records from museum collections, the team has concluded that four of Vermont's 17 bumble bee species appear to have gone extinct.

The American Bumblebee

The study, led by University of Vermont (UVM) and Vermont Center for Ecostudies (VCE) researchers, was published in the Journal of Insect Conservation.

"We're losing bumble bees even before we fully understand their benefits to our economy and well-being, or how they fit into ecosystems," said Kent McFarland, conservation biologist at VCE.

Acquiring the data to understand the conservation status of Vermont's bumble bees was no small feat. From 2012 to 2014, study authors and a corps of over 50 trained citizen scientists searched the entire state, amassing a database exceeding 10,000 individual encounters with bumble bees from all of Vermont's counties and biophysical regions, and in 81% of the state's 255 municipalities.

To compare current bumble bee diversity and distribution in Vermont to historic records, the team assembled a database of nearly 2,000 bumble bee records, some from as early as 1915, from 13 public and private insect collections. The largest repository of specimens is held at the University of Vermont's Zadock Thompson Natural History Collection.

While the researchers cannot pinpoint what may have caused these sudden bumble bee population declines, habitat loss, parasites, pesticides, and climate change have all been implicated by recent bee studies in North America.

Now, conservationists here in Vermont and across the continent are sounding alarms.

Wild bees pollinate wildflowers and most crops in Vermont, including blueberries, tomatoes, squash, and one of the state's essential commodities: apples.

"Wild bees perform the majority of all pollination on Vermont farms, whether or not managed honey bees are present," said Leif Richardson, an ecologist with UVM's Gund Institute for Environment and Rubenstein School of Environment and Natural Resources. "As an ecosystem service, pollination is worth millions annually. But we don't know how the loss of native bee species will affect our food supply or overall environmental health."

Trouble for some bumble bees may come from a hitchhiker. In the 1990s, farmers began releasing captive bred Common Eastern Bumble Bees (Bombus impatiens) into greenhouses to increase crop production, especially for indoor-grown crops like tomatoes. Some colonies may have been infected with pathogens and parasites, which they then spread to wild bees in the same areas.

Honey bees, introduced to North America in the eighteenth century, may spread RNA viruses and other pathogens to wild bees through shared use of flowers, as recently found in Vermont.

Another culprit is likely common pesticides, including neonicotinoids. "Neonicotinoid pesticides are particularly dangerous to bees because plants absorb them through the roots, rendering all plant parts toxic to insects," said Richardson. "This includes pollen and nectar, essential components of the bee diet."

And it's not only neonicotinoids that may threaten bumble bees: recent research shows that such insecticides can have negative effects on bees when combined with commonly used fungicides.

Warming, drought, and other effects of climate change are impacting bumble bees in North America and Europe by causing both latitudinal and elevation changes in species distributions, with the majority of species experiencing consequent range contractions, according to a study published in 2015 in Science.

Habitat loss and urbanization are also taking their toll on pollinator populations of all kinds, bees included. The study found that diversity and abundance of bumble bee fauna in Vermont were strongly influenced by land use and land cover. For example, grassland cover was one of the strongest drivers of species diversity and predictors of individual species occurrence. In Vermont, most grasslands are located in agricultural landscapes, where pesticide application is more frequent, and periodic mowing can destroy bee nests and forage.

The association between bumble bees and hayfields and other grasslands is cause for concern, because the state lost nearly 2% of its grassland cover between 1996 and 2010, an average of nearly 1,000 acres annually. Land cover change may interact with other issues, such as climate change, to drive bumble bee declines.

Vanishing bees

Despite examining more than 10,000 bumble bees since the turn of the century, the scientists did not encounter a single Rusty-patched Bumble Bee (Bombus affinis), which was fairly common in Vermont until the 1990s. The last known record for Vermont was a drone collected on August 31, 1999 in the Intervale in Burlington. Information from this study helped the Vermont Agency of Natural Resources list this species as Endangered in the state in 2015, followed two years later by the U.S. Fish and Wildlife Service listing it as federally Endangered.

"This investigation confirms our fear that the Rusty-patched Bumble Bee is almost certainly extinct in Vermont and may never be back," said McFarland. "We hardly knew it – and now it's gone."

The Vermont Bumble Bee Atlas, a project of VCE's Vermont Atlas of Life, revealed that at least three other bumble bee species warranted listing in Vermont:

• Ashton Cuckoo Bumble Bee (Bombus ashtoni) infiltrates colonies of Rusty-patched and Yellow-banded Bumble Bees, enslaves the workers and uses them to feed its young. With the Yellow-banded Bumble Bee severely depleted and the Rusty-patched Bumble Bees now gone, so goes the invader. It was last seen in 1999 and is listed as Endangered in Vermont.
• Yellow-banded Bumble Bee (Bombus terricola) had been feared to be on the brink of extinction in Vermont, but new encounters with this bumble bee during the VCE survey suggest it might be surviving some threats. It was listed as Threatened in Vermont.
• American Bumble Bee (Bombus pensylvanicus), once a common bumble bee in the Champlain Valley, it has not been found since a University of Vermont student's unwitting discovery in 2000. A detailed report is being written to consider it for listing status in the state.

But not all bumble bees have fared poorly. The biologists found that the five species that increased the most belonged to the dominant subgenus in North America called Pyrobombus, which is relatively stable or increasing in other areas of the continent as well. The Common Eastern Bumble Bee appears to be expanding its range, possibly in part due to transport of managed colonies for crop pollination.

"I've been amazed to see how this study, and other recent pollinator news, has increased the public's awareness of bumble bees in Vermont," says Spencer Hardy, a field biologist for VCE during the study. "It seems a lot more people are paying attention to bumble bees and are conversant in their ecology and diversity."

"Our next step is to move from investigation toward solutions," said McFarland. "But those solutions will take hard work and partnerships among federal and state agencies, conservation research groups like ours, and the public."

"These collections are priceless," said VCE biologist Sara Zahendra of the historic bee collections used in the study. "Decades ago, students and biologists likely had no idea that some of the species they were collecting would completely disappear. Without these collections, we wouldn't know how our bee populations have changed."

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More information: Leif L. Richardson et al. Bumble bee (Bombus) distribution and diversity in Vermont, USA: a century of change, Journal of Insect Conservation (2018). DOI: 10.1007/s10841-018-0113-5

J. T. Kerr et al. Climate change impacts on bumblebees converge across continents, Science(2015). DOI: 10.1126/science.aaa7031

Journal information: Science 

Off of yesterday's POST regarding how Beetle infested forests impact browsers and carnivores, wanted to explore how these western North American native insects impact forest succession(tree composition)...........What tree species will step forth and "frontier" the dead pines and spruces?...........The USDA, U.S. Forest Service and Colorado Parks & Wildlife say the following---"Mountain pine beetles are likely to create multi-aged forest stands by removing large-diameter trees, reducing stand densities, and providing growing space for other canopy trees and below the main canopy"................."As an example, in the Yellowstone Area after a beetle outbreak in the ‘60 & ‘70s, about 40-70% of the overstory trees died, with surviving trees increasing in growth by 2-3 fold for two decades"........."Pine recruitment(% of forest cover) has been at least equal to previous decades"..........."Pine beetle killed stands recover to pre-MPB stand structure in a century with Logger uncut & partial cut stands dominated by fir and clear Logger cut stands similar in composition to pre-MPB stands dominated by pine"..........."While that has been the path in Yellowstone post beetle outbreak, it is recognized tha regenerating forests can take many different paths, depending on various factors including local climate and the presence of other trees such as aspen, spruce, and fir"..............."Some beetle-killed forests may grow back with more natural diversity than exists today, and others may regenerate back to pure single-aged lodgepole pine".........."Future dominance of species will vary from site to site depending on factors such as site quality, established regeneration, moisture, elevation, and cardinal direction of stands".............

https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/stelprdb5359293.pdf

https://www.motherjones.com/environment/2015/03/bark-pine-beetles-climate-change-diana-six/

Bark Beetles Are Decimating Our Forests. That Might Actually Be a Good Thing.

They gobble up trees and send politicians into a frenzy. But do the bugs know more about climate change than we do?

Maddie Oatman/May/June 2015

There is an eerie feel to this grove of lodgepole pines that I can’t quite put my finger on as entomologist Diana Six tromps ahead of me, hatchet in hand, scanning the southwestern Montana woods for her target. But as she digs the blade into a towering trunk, it finally hits me: the smell. There’s no scent of pine needles, no sharp, minty note wafting through the brisk fall air.

Six hacks away hunks of bark until she reveals an inner layer riddled with wormy passageways. “Hey, looky!” she exclaims, poking at a small black form. “Are you dead? Yeah, you’re dead.” She extends her hand, holding a tiny oval, maybe a quarter of an inch long. Scientists often compare this insect to a grain of rice, but Six prefers mouse dropping: “Beetle in one hand, mouse turd in another. You can’t tell them apart.” She turns to the next few trees in search of more traces. Pill-size holes pock their ashen trunks—a sign, along with the missing pine scent, of a forest reeling from an invasion.

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,” 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.

BEETLEMANIA

From 2000 to 2014, bark beetles destroyed large swaths of forests in the American West—and they’re not done yet.

In hopes of staving off complete catastrophe, the United States Forest Service, which oversees 80 percent of the country’s woodlands, has launched a beetle offensive, chopping down trees to prevent future infestations. The USFS believes this strategy reduces trees’ competition for resources, allowing the few that remain to better resist invading bugs. This theory just so happens to also benefit loggers, who are more than willing to help thin the forests. Politicians, too, have jumped on board, often on behalf of the timber industry: More than 50 bills introduced since 2001 in Congress proposed increasing timber harvests in part to help deal with beetle outbreaks.

But 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?

A BUG’S LIFE

An adult mountain pine beetle lays her eggs under the bark. On her way, she disperses fungi that turn the trees’ tissue into food for her babies, eventually killing the tree.

Though they’re often described as pesky invaders, bark beetles have been a key part of conifer ecosystems for ages, ensuring that groves don’t get overcrowded. When a female mountain pine beetle locates a frail tree, she emits a chemical signal to her friends, who swarm to her by the hundreds. Together they chew through the bark until they reach the phloem, a cushy resinous layer between the outer bark and the sapwood that carries sugars through the tree. There, they lay their eggs in tunnels, and eventually a new generation of beetles hatches, grows up, and flies away. But before they do, the mature beetles also spread a special fungus in the center of the trunk. And that’s where things get really interesting.

Pine Beetles

Six focuses on the “evolutionary marriage” of beetle and fungi at her four-person lab at the University of Montana, where she is the chair of the department of ecosystems and conservation sciences. Structures in bark beetles’ mouths have evolved to carry certain types of fungi that convert the tree’s tissue into nutrientsfor the bug. The fungi have “figured out how to hail the beetle that will get them to the center of the tree,” Six says. “It’s like getting a taxi.” The fungi leave blue-gray streaks in the trees they kill; “blue-stain pine” has become a specialty product, used to make everything from cabins to coffins to iPod cases.

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 watermeans 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.

Spruce Beetle

Typically, beetle swells subside when they either run out of trees or when long, cold winters freeze them off (though some larvae typically survive, since they produce antifreeze that can keep them safe down to 30 below). But in warm weather the bugs thrive. In 2008, a team of biologists at the University of Colorado observed pine beetles flying and attacking trees in June, a month earlier than previously recorded. With warmer springs, the beetle flight season had doubled, meaning they could mature and lay eggs—and then their babies could mature and lay eggs—all within one summer.

That’s not the only big change. Even as the mountain pine beetles run out of lodgepole pines to devour in the United States, in 2011 the insects made their first jump into a new species of tree, the jack pine, in Alberta. “Those trees don’t have evolved defenses,” Six says, “and they’re not fighting back.” The ability to invade a new species means the insects could begin a trek east across Canada’s boreal forest, then head south into the jack, red, and white pines of Minnesota and the Great Lakes region, and on to the woods of the East Coast. Similarly, last year, the reddish-black spruce beetle infested five times as many acres in Colorado as it did in 2009. And in the last decade, scientists spotted the southern pine beetle north of the Mason-Dixon Line for the first time on record, in New Jersey and later on Long Island. As investigative journalist Andrew Nikiforuk put it in his 2011 book on the outbreaks, we now belong to the “empire of the beetle.”

In a weird way, all of this is exciting news for Six: She is not only one of the world’s foremost experts in beetle-fungi symbiosis, but proud to be “one of the few people in Montana that thinks bark beetles are cute.” (She’s even brewed her own beer from beetle fungi.) As a child, she filled her bedroom in Upland, California, with jars of insects and her fungus collection. But as a teenager, she got into drugs, quit high school, and started living on the streets. Nine years later, she attended night school, where teachers urged her to become the first in her family to go to college. And when she finally did, she couldn’t get enough: classes in microbiology and integrated pest management led to a master’s degree in veterinary entomology, then a Ph.D. in entomology and mycology and a postdoc in chemical ecology, focused on insect pheromones.

"Spruce beetle and mountain pine beetle outbreaks have impacted millions of acres of conifer forest from Alaska to northern Mexico"..........."These species are native to North America, and periodic outbreaks have shaped the structure and composition of conifer forests for millennia"................ "To characterize the response of a suite of mammalian species to beetle‐induced changes in vegetation in the southern Rocky Mountains, Colorado Parks and Wildlife(WPS) deployed cameras at 300 randomly selected sites during summer 2013–2014"............. . "Ungulates(deer, elk, moose) generally exhibited a positive association with bark beetle outbreaks"............ "Elk were positively associated with severity, but not a decade after outbreak.........."Mule deer exhibited the opposite relationship"............."Moose used forest stands adjacent to preferred willow habitat, peaking3–7 yr after an outbreak commenced, but only in high severity locales"............"Black bears, American marten, snowshoe hares, and porcupines did not appear to be substantially influenced by beetle activity"............"Red fox use was positively associated with beetle stands after a decade, but overall use declined as severity increased"............."Red squirrel use declined in severely impacted stands, likely as a response to diminished cone crops".................."Golden‐mantled ground squirrels and chipmunks exhibited a shallow negative relationship after a decade passed as did coyotes"

https://www.google.com/url?rct=j&sa=t&url=https://www.craigdailypress.com/news/cpw-study-investigates-wildlife-response-to-forest-conditions-from-bark-beetle-outbreaks-in-colorado/&ct=ga&cd=CAEYASoUMTEyMDc2MjQ4ODEyNDM0MzE2NDYyGmFjZjNlMjE0YjlhZmI5MzM6Y29tOmVuOlVT&usg=AFQjCNH5q0r_bxRzU4_ADQcsaaPrLrngYA

click on the title of this paper(underscored) to read full article:
“Ecosphere”: Mammalian responses to changed forest conditions resulting from bark beetle outbreaks in the southern Rocky Mountains.

Colorado Parks & Wildlife(CPW) study investigates wildlife response to forest conditions from bark beetle outbreaks in Colorado

| April 20, 2019; CPW

Deer and other animals were studied on their response to beetle outbreaks.

Colorado Parks and Wildlife

DENVER — As Colorado’s private and public forests recover from insect and disease outbreaks and other disturbances, humans and wildlife are adjusting to significant environmental changes. Spruce beetle and mountain pine beetle outbreaks may have changed the way you recreate, but have you thought about how wildlife are responding?

That’s precisely the question research scientists from Colorado Parks and Wildlife and the U.S. Forest Service attempted to answer in a recently published paper in the journal “Ecosphere”: Mammalian responses to changed forest conditions resulting from bark beetle outbreaks in the southern Rocky Mountains.

Randomly selected sampling sites (gray circles) where passive infrared game cameras were deployed in spruce‐fir (green) and lodgepole pine (yellow) forests in Colorado, USA, 2013–2014. Brown and orange are the approximate extents of spruce beetle and mountain pine beetle impacts in spruce‐fir and lodgepole pine forests, respectively, as of 2014.

“It’s such a far-reaching event, both in terms of the amount of the state impacted and how far into the future this impact will ripple,” said author Jake Ivan, a senior scientist in the Mammals Research Section of Colorado Parks and Wildlife. “As a first cut, we wanted to try to get a handle on how various species altered their use of these impacted areas, and we focused on lodgepole pine and spruce-fir systems as those two types of subalpine forest were hardest hit (by mountain pine beetle and spruce beetle, respectively).”

Wildlife Technician Kat Bernier with Colorado Parks and Wildlife with one of the game cameras she installed in a recent study.
Colorado Parks and Wildlife

To do this, the researchers hired a team of technicians to deploy game cameras at 300 randomly located sites in subalpine forests across the state. The sites represented a gradient of beetle activity from green forests with no beetles to forests that had been impacted more than a decade prior to sampling. The cameras were mounted low to the ground and pointed at a “lure tree” where a piece of wool, soaked in that most universal of all wildlife lures — peanut butter — was tied. This setup allowed researchers to obtain photos of the various mammalian species living in the vicinity, from chipmunks to moose.

The effort returned over 300,000 photos of 26 species.

“As is often the case with big changes to a landscape, the response varied widely by species,” Ivan said. “There were species that responded positively and used these impacted areas more intensely, some species that responded negatively, and others that didn’t seem to care at all.”

Ungulates were among the big winners in this changed system, although their response varied. Elk, for example, tended to increase their use of impacted areas in the decade after a beetle outbreak, responding most strongly in areas where the beetle impact was most severe with more dead trees.

Mammalian species that exhibited a positive association between use of forested stands and beetle activity (either years since the outbreak occurred, severity, or both). Curves and 95% confidence intervals represent model‐averaged responses across all fitted curves described in Fig. 2. From left to right, panels indicate predicted model‐averaged responses for cases where 10%, 50%, and 90% of the overstory in a stand is killed by beetle activity. From top to bottom, panels show predicted responses for elk, mule deer, and moose. Probability of use was estimated to vary little between the spruce‐fir and lodgepole pine stands, so responses were pooled across habitat types.

Use of beetle-impacted areas by moose, however, increased immediately after trees died, peaked three to seven years after the outbreak, then declined. Mule deer showed increasing use of beetle-impacted areas with each year after an outbreak, but unlike elk, their use was not strongly related to severity. Researchers attribute increased use to increased forage and hiding cover available as understory and shrub cover increases once the forest canopy opens up.

Red squirrels were among the few species to be negatively impacted.

Mammalian species that exhibited a negative association between use of forested stands and beetle activity (either years since the outbreak occurred, severity, or both). Curves and 95% confidence intervals represent model‐averaged responses across all fitted curves described in Fig. 2. From left to right, panels indicate predicted responses for cases where 10%, 50%, and 90% of the overstory in a stand is killed by beetle activity. From top to bottom, panels show predicted responses for red squirrel, golden‐mantled ground squirrel, chipmunk spp., and coyote. Red squirrel use was estimated to vary between the spruce‐fir (blue) and lodgepole pine (gray) stands. For other species, habitat stratum was less important and responses were pooled across habitat types.

“I imagine their decreased use is largely related to the loss of cone crops, which take a big hit when all of the mature trees in a stand die,” Ivan said. “That’s the main food source for squirrels in these systems, and storing those cones in middens so they can get at them later is what helps get them through the winter.”

Mammalian species that exhibited little association between use of forested stands and beetle activity (either years since the outbreak occurred, severity, or both). Curves and 95% confidence intervals represent model‐averaged responses across all fitted curves described in Fig. 2. From left to right, panels indicate predicted responses for cases where 10%, 50%, and 90% of the overstory in a stand is killed by beetle activity. From top to bottom, panels show predicted responses for American marten, black bear, snowshoe hare, and porcupine. For snowshoe hares and porcupine, use was estimated to vary between the spruce‐fir (blue) and lodgepole pine (gray) stands. For other species, habitat stratum was less important and responses were pooled across habitat types.

While the response of some species is easily explained, for others, an easy explanation doesn’t exist. Pine martens, for instance, commonly prey on red squirrels, yet use of beetle-impacted stands by pine martens did not follow the noticeable decline of red squirrels. Instead, marten use remained completely unchanged through time, regardless of severity of the outbreak.

“This project gave us a better understanding of what to expect in the coming years as beetles finish their march through the green forests in the state,” Ivan said. “It gives us a sense of issues that may arise both in the non-game world, and in the game world.”

For instance, results from this project suggest that snowshoe hares, the primary food source for threatened Canada lynx, may weather the bark beetle outbreaks largely unscathed. However, lynx may be at increased risk during years of low hare abundance when they would normally turn to red squirrels to get them through.

Mammalian species that exhibited mixed associations between use of forested stands and beetle activity (either positive association with years since the outbreak but negative association with severity, or vice versa). Curves and 95% confidence intervals represent model‐averaged responses across all fitted curves described in Fig. 2. From left to right, panels indicate predicted responses for cases where 10%, 50%, and 90% of the overstory in a stand is killed by beetle activity. From top to bottom, panels show predicted responses for red fox and yellow‐bellied marmot. Use was estimated to vary little between the spruce‐fir and lodgepole pine stands, so responses were pooled across habitat types for these species.

On the game side, scientists expect that in some areas, elk will focus their habitat use in severely impacted areas during early season hunts. However, access and travel in these patches is difficult for hunters due to down timber. So, in some places, it’s possible to end up with a mismatch between elk availability and hunter access.    

“On the one hand, it is a bit sad to see all of these dead trees on the landscape, but on the other, we’re witnessing a once-in-a-millennia event, and Colorado is ground zero,” Ivan said. “It’s quite a spectacle from an ecological perspective.”

Bark beetles are native to Colorado and have been around for eons. Their life cycle involves burrowing into the inner bark of mature trees as adults and laying eggs in galleries.

The eggs hatch into larvae, which then travel through the bark, eating and growing. Eventually the larvae pupate into adults, which exit the bark, fly to another tree and start the process anew. The loss of inner bark from adult and larval activity interrupts the flow of water and nutrients and kills the tree. Large expanses of mature forest across the west, coupled with climate changes such as drought that simultaneously stress trees while boosting insect productivity have created current epidemic conditions.