Category Archives: Home and shelter

Kudzu Weeds Beaten, No Chemicals Needed

By John Upton

As Adam Macon led documentarians through a battered North Carolina wetland, vast criss-crosses of lamentably familiar vines marked the spot where cypress trees had been clearcut years before.

Among the weeds thriving where cypresses once grew were great drapes of kudzu. The invasive vine was introduced in the late 19th century to the U.S., where it became a popular — if regrettable — weapon in the fight against erosion.

Kudzu. Credit: Mike Ball.

Growing as fast as a foot a day, kudzu smothers utility poles, roadside forests and abandoned buildings throughout the U.S. South. Routinely headlining ‘worst invasive species‘ lists, the East Asian invader even has a sprawling nickname: ‘The vine that ate the south.’

“We came from this beautiful cypress forest, where we were knee-deep in water, and there was wildlife chirping all around, to this thicket of exotic invasives,” said Macon, a conservationist who campaigns against the wood-based industries that anchor the economies of some Southern towns, such as paper and wood pellet producers. He described kudzu as a “huge problem” for the region — one that’s “being promoted by increasing urbanization and industrial logging.”

Kudzu is treated using expensive cocktails of powerful herbicides. The cost and effort is so great that it’s often left untreated. Now, though, federal scientists say they have discovered a potent new strategy that appears to work just as well: a combination of mowing, spraying spores of a fungus disease that attacks the weed, and planting native grasses.

Despite its impressive performance as a weed, kudzu cannot establish itself where plants already thrive. That may be its greatest weakness, and it’s one that agricultural scientists are learning to exploit. But if kudzu sets seed in freshly bulldozed land, its vines can burst forth, beating out native plants to dominate fresh territory. It’s the seemingly indelible botanical mark of humanity’s heavy hand.

Illustrated by Perry Shirley.
Illustrated by Perry Shirley.

“Once it gets that foothold,” said Mark Weaver, a U.S. Department of Agriculture plant pathologist based in rural Mississippi, “it’s really aggressive.”

It isn’t enough to kill most of the marauding kudzu. It must be eradicated, or it will spring right back. Given high treatment costs, and low land values in the rural South, property owners have surrendered vast tracts to the weed. Millions of acres have been lost to kudzu throughout the country.

America wants its land back, but it will only do so on the cheap.

The kudzu-infected acres have “low economic value,” Weaver said. “They could have great ecological value, and that value is taken away when you have this monoculture of an exotic invasive weed. But who’s going to come up with the resources to tackle that problem?”

(American kudzu thickets have begun fostering swarms of kudzu bugs, which reached the country only recently. Initial research suggests the bugs could help reduce kudzu populations. The bugs are also attacking nearby crops, increasing the use of insecticides.)

Mark Weaver. Credit: Carol Morris.

For six years, Weaver led American government scientists in their war against kudzu. In experiments involving 99 plots at two kudzu-infested sites a few hours drive apart in Mississippi, Weaver and his USDA colleagues recently reported in Biocontrol Science and Technology paper that their new organic approach worked just as well as traditional chemical onslaughts.

“I think the reason kudzu has been so persistent is that, historically, people battling kudzu with older products ran out of money, ran out of energy and ran out of will,” Weaver said.

Not all of the treatments at the experiment sites were organic. Razed earth alternatives were labeled “Herbicide 3X,” plots sprayed with full doses of three types of more potent herbicides three times one year, and then one more time in the second year. Some plots were treated using newer herbicides that can legally be purchased and used by anybody — no license required. Some sites were mowed; others were not.

(Cartoonishly excessive though Herbicide 3X might sound, the scientists say it could be preferable to more traditional approaches using lower annual doses. That’s because those approaches may require annual spraying for a decade before the weed is eradicated.)

After two years, when the effectiveness of the chemical treatments were compared with the organic alternative, there were no statistically significant differences. The long-term success of the new approach may become clearer in the coming years, since underground kudzu reserves might be lurking beneath the newly planted switchgrass, ready to reemerge as choking vines.

“Having witnessed the ability of kudzu to regenerate from root reserves, I question the long-term outcome of the treatments,” said Cornell University pest management scientist Matthew Frye, who has studied the weed.

Kudzu. Credit: Katie Ashdown.

The fungus sprayed was Myrothecium verrucaria. The pathogen is not yet commercially available. Weaver hopes that will soon change. The disease preys on broadleaf species, such as deciduous trees, meaning it could also attack and kill other plants.

The switchgrass helps prevent erosion, serving the same purpose for which the kudzu was originally planted. It grows quickly. It can withstand some herbicides that kill kudzu. And — perhaps most importantly — it’s not vulnerable to the fungus disease.

“We think the switchgrass may provide a competitive effect,” Weaver said. “If there’s remaining kudzu thats trying to reemerge, we have this canopy now that’s shading it out.”

After switchgrass has cemented its position on the land, other native species can follow it, suggesting that the new organic solution for kudzu infestations may also be the most durable.

Surviving Fires, Global Warming — With Naps

The unprecedented Black Saturday bushfires in the countryside surrounding Melbourne in 2009 left 1 million acres of Australian landscape charred. Squeaked mousey marsupial after losing its insect hunting grounds: “Yawn.”

Wildfire-adapted wildlife has to cope with more inferno-related threats than just the flames.

The scorched earth left behind by wildfire can be bereft of the plants and insects that are used for food by many small animals. As they move through the black landscape, these animals can lose their camouflage and succumb to predators.

To survive these tough times, some antechinuses — marsupial mice in Australia and New Guinea — amplify their siesta-style torpor, taking longer power naps every day.

That reduces their daily energy needs, allowing them to get by on less while the forest recovers around them.

“There’s a perception that bushfire affects animals through the direct effects of fire killing individuals,” said Australian National University researcher Sam Banks.

Illustrated by Perry Shirley.
Illustrated by Perry Shirley.

“Certainly, this happens,” Banks said. “But it seems to be the availability of crucial resources in the post-fire environment that determines whether animal populations persist.”

In 2009, Banks led a group of scientists that aimed to use the aftermath of the fires as a laboratory to investigate how two species of small marsupials survive and recolonize after bushfire.

The team found that agile antechinuses were more than twice as likely, compared with bush rats, to continue inhabiting a scorched habitat after a fire.

The antechinuses — which eat insects and, despite their outward resemblance, are not rodents — were 30 percent as likely to inhabit a burned patch of land compared with an unburned one. The bush rats (they are native rodents) were 12 percent as likely.

“It always seemed to me slightly unusual that such a small mammal with high energetic requirements would persist in burnt habitat with — presumably — reduced food availability,” Banks said.

An agile antechinus. Photo by Michael Sale/Flickr
An agile antechinus. Photo by Michael Sale/Flickr

New research suggests that the use of torpor could explain the antechinuses’ reluctance to flee post-fire landscapes.

“It’s interesting to see that they might have some physiological responses that would enable them to cope with tough periods,” Banks said, after reading the new paper, which was published in the journal OIKOS by a team of scientists from Australia’s University of New England.

“For antechinus, they shelter in hollow trees, all but the most decayed of which remain standing after fire,” Banks said. “I guess the torpor response helps them deal with the lack of food.”

The University of New England paper tracked brown antechinuses, which closely resemble agile antechinuses, in and near a 1,000-acre prescribed fire in a national park in southeastern Australia. The researchers focused on females, in which torpor is more pronounced.

One of the five females being studied in the burned area took shelter from the fire beneath rocks, where it was killed by the flames.

The other four took shelter in trees, where they survived. Before the fire, they had spent about half their time in states of torpor, in which metabolism slows down and energy is conserved. The same was also true for a control population studied.

After the fire, the four female survivors spent most of their time in torpor. The average power nap rose in length to an average of three to five hours — up from between one and three hours.

One female clocked up more than ten hours of nonstop torpor after the fire. That doubled the group’s pre-fire torpor record.

These marsupials are pulling a trick known as heterothermy.

A heterothermic mammal or bird can display the characteristics of a warm-blooded endotherm, churning through energy as it ferrets about for food and mates. But when it needs to slow its demand for energy, it can hibernate, or enter a briefer form of daily hibernation known as torpor, displaying characteristics of a cold-blooded ectotherm — such as a snake.

The list of heterotrophs is long — check out this table from a Current Biology article by University of New England professor Fritz Geiser. Geiser also led the antechinus torpor study published in OIKOS.

Current Biology
Current Biology

Some scientists have argued that heterothermy helped some mammals survive the mass extinction that killed the dinosaurs.

As earth’s biosphere plunders into the anthropocene, and as greenhouse gas pollution drives longer and harsher wildfire seasons, these marsupials’ heterothermy may give them a fire-resistant evolutionary upper hand.

It is “likely,” Geiser wrote in his 2013 Current Biology essay, that “opportunistic heterotherms may be better equipped” than other species to cope with “anthropogenic influences such as habitat destruction, introduced species, novel pathogens and specifically global warming.”

That, he wrote, is because these animals have “highly flexible” energy needs, can limit foraging and avoid predators.

Wolverine wipeout

By John Upton

A warming world means a melting cryosphere, which is bad news for species that have evolved to thrive on ice and in snow. Polar bears made depressing history in 2008 when they became the first species to be listed under the U.S. Endangered Species Act solely because of threats from climate change. These sea ice-dwelling carnivores had appeared poised, until Tuesday, to be joined in their global warming-induced regulatory infamy by snow-burrowing wolverines.

Wolverines resemble small bears with bushy tails. They are also known as mountain devils, gluttons, caracajou, and skunk bears. They are the largest member of Mustelidae — a carniverous family of mammals that includes otters, badgers, weasels, and ferrets.

Illustrated by Perry Shirley.
Illustrated by Perry Shirley.

While polar bears are a highly visible species, wolverines are enchantingly difficult to spot. This is despite their inhabitation of a broad swath of the Arctic that includes northern portions of Europe, Asia, and North America.  In North America, most the populations inhabit Canada and Alaska, although several hundred individuals are estimated to live in the contiguous U.S., mostly in the northern Rocky Mountains. These populations have recently been growing, yet fears over the future of snow in the Lower 48 had federal officials considering adding wolverines to the list of threatened species. On Tuesday, the U.S. Fish & Wildlife Service ruled against the proposed wolverine listing.

Wolverines breed more slowly than most mammals, making them especially vulnerable to breeding disruptions. Once a female reaches the age of three, she normally becomes pregnant every year — but most pregnancies are strategically aborted. That’s because it can take two years or more for the wolverine to forage enough carrion, fruits, and berries, and to hunt enough small animals and insects, to build up the energy reserves needed to raise a litter.

Once she is ready to rear a litter, the female adopts a very specific denning strategy — one that will make it difficult for the species to survive in the parts of its territories where snow becomes history. The wolverines dig their dens in deep snow, forming living spaces around logs and rocks that include tunnels, runways, and bedsites. There has never been a record of a wolverine denning in anything other than excavated snow. And whenever such a cave starts to melt, the wolverine mother abandons it.

“We have determined that habitat loss due to increasing temperatures and reduced late spring snowpack due to climate change is likely to have a significant negative population-level impact on wolverine populations in the contiguous United States,” U.S. Fish & Wildlife Service officials wrote in the proposal to list those populations as threatened.

“In the future, wolverine habitat is likely to be reduced to the point that the wolverine in the contiguous United States is in danger of extinction.”

At least one senior FWS official had been pushing the agency to reject the proposal, arguing that it relies too much on “speculation” about the future effects of climate change. The agency announced on Tuesday that scientists know “too little about the ecology of the wolverine” to list it as threatened or endangered at this time. The ruling “does not close door on this issue,” one official said.

It was this focus on uncertainties that was already making scientists who served on a panel that advised the government on the proposal hot under the collar.

“Myself and the other climate scientists on the panel are disappointed that they’re focusing on the uncertainty, and appear to be ignoring the aspects of science that are much more certain,” said Tim Link, a hydrology professor at the University of Idaho.

Wolverines and polar bears certainly aren’t the only species that will feel the heat as global temperatures rise. Dozens of species of coral might be added to the endangered species list because of the combined effects of disease, warming ocean temperatures, and ocean acidification. Like global warming, ocean acidification is caused by carbon dioxide pollution, which is produced by fossil fuel burning and by deforestation.

“From the history of the Endangered Species Act, if you look at the 1,500-plus species that have been listed, the overwhelming majority have not been listed because of climate change,” said Mike Senator, an attorney with the Defenders of Wildlife, which had been pressuring the government to list wolverines under the Act.

“It’s been the loss of habitat and other threats — but that’s not entirely surprising, given that climate change has been recognized as a relatively recent issue. We certainly expect that we’ll see more species listed, at least in part, because of climate change.”

Black-backed woodpeckers would face extinction without wildfires

By John Upton

Illustrated by Perry Shirley.
Illustrated by Perry Shirley.

This summer has been a tinder-dry scorcher in the American West, where climate change is being blamed for a horror fire season. Mountain snow is melting earlier nowadays and summers are getting hotter — and that perilous partnership is fueling a steady surge in the frequency and size of the region’s wildfires.

The infernos kill firefighters, destroy homes and damage public infrastructure.

But it’s worth remembering that fires are healthy and regenerative phenomena in many ecosystems — including those in the West.

Blazes clear out water-hogging undergrowth and provide blank slates upon which timberlands can grow anew, boosting forest biodiversity. Rugged pods that encase the seeds of some specialized plants open after fire, sowing the genesis of the next generation in fertile fields wiped clean of competitors.

It’s not just plants that have evolved to rely on fire. Woodpeckers, for example, can flourish in its wake. The black-backed woodpecker has a particularly specialized diet that leaves it dependent upon the charred aftermath of wildfires. The species feasts on the wood-boring beetles that proliferate in burned trees following blazes in Western American mountain-ranges.

Rim Fire
The aftermath of the Rim Fire, the fourth-largest wildfire in Californian history, photographed near Yosemite National Park in early September by San Francisco journalist Chris Roberts.

But us humans are not as fond of fire as are the beetles or the woodpeckers that hunt them. Public policy dictates that fires should be avoided and, if that fails, confronted without compromise. The practice of preemptively thinning out forests to reduce fire impacts, and the logging of forests after they burn, have both taken heavy tolls on the black-backed woodpeckers.

Populations of these birds have been harmed so severely by public policies of wildfire suppression that the federal government is reviewing whether genetically distinct populations in two regions should be added to its list of endangered species.

“This is the first time in the history of the Endangered Species Act that the government has initiated steps to protect a wildlife species that depends upon stands of fire-killed trees,” Chad Hanson, an ecologist with Earth Island Institute, said when the U.S. Fish & Wildlife Service announced the review in June.

A clean-up following the Rim Fire, making it more difficult for black-backed woodpeckers to inhabit this area. Photo by Mike McMillan of the U.S. Forest Service.
A clean-up following the Rim Fire, making it more difficult for black-backed woodpeckers to inhabit this area. Photo by Mike McMillan of the U.S. Forest Service.

Hanson coauthored research published in May in The Open Forest Science Journal that showed just how severely one of those two populations of woodpeckers, which lives in the Sierra Nevada and southern Cascade ranges of California and Oregon, has been affected by humanity’s wont to battle fire. Hanson and his colleague, Dennis Odion, obtained data from the government and from their own observations which they used to model the effects of typical wildfire suppression policies in the Sierra on the species’ habitat.

“A scenario based on thinning 20 percent of mature forests over a 20-year period, and post-fire logging in 33 percent of potential habitat created by fire, reduced the amount of primary habitat after 27 years to 30 percent of the amount that would occur without these treatments,” the scientists wrote in the paper.

“Our results indicate that conserving the distinct population of black-backed woodpeckers in the southern Cascades and Sierra Nevada and the biodiversity for which they are an indicator will require that more unthinned area be burned by wildfires and protected after fire as critical habitat.”

The following table was lifted from the paper. It compares the amount of black-backed woodpecker habitat available within a study area following 27 years of simulated fire suppression policies:

woodpeckers and fire

And this photograph of an acorn placed in the trunk of a Rim Fire-charred pine is an endearing reminder that wildlife perseveres following fire. Wild Equity Institute founder Brent Plater tells me it might have been put there by a squirrel or a scrub jay — but that it was most likely the handiwork of an acorn woodpecker. “Caching acorns in tree cavities is what they do for a living,” he said.

Photo by Chris Roberts
Photo by Chris Roberts

Research: Bat-killing fungus arrived from afar

By John Upton

A ripple of bat deaths has grown since 2006 to become millions of Chiroptera deep, stretching out from its New York epicenter into five Canadian provinces and west at least as far as Missouri. The latest state to be affected was Minnesota, where infected bats were discovered in two parks.

The dead bats were all members of species that hibernate — and they succumbed to white nose syndrome. The disease is caused by a fungus that eats away at their wings and faces.

Little brown bats are among the worst affected. These adorably tiny bats were common throughout Eastern America as little as a decade ago, sucking down mosquitoes and other pests during their nocturnal maunders. Now the species appears to be on the verge of being listed as federally endangered.

Illustrated by Perry Shirley.
Illustrated by Perry Shirley.

Mammals appear to have developed high body temperatures to help stave off infections of fungi. But hibernating bats have a chink in that armor: When they hibernate, their body temperatures plummet. And when most bats hibernate, they huddle together, which helps the fungal infection spread through the slumbering colony.

What caused this fast-moving fungus to suddenly begin attacking bats? Did it go rogue, evolving from a soil eater into a devourer of bat flesh? Or is it an invasive species that arrived from some far-flung place?

A pair of Wisconsin-based U.S. Forest Service scientists studied the DNA of the disease along with that of more than a dozen species of other fungi found growing in bat caves in the eastern U.S. What they found, first and foremost, was that the pathogen was not quite what everybody thought it was.

Scientists have called the disease Geomycetes destructans since it was identified in 2009. But the recent research, described in the journal Fungal Biology, indicates that the fungus is actually a member of the genus Pseudogymnoascus. Hence, it has been reclassified P. destructans.

Of the other species of Pseudogymnoascus fungi sampled in the studied hibernacula, the scientists reported that none were closely related to P. destructans. That’s significant, because it suggests that white-nose syndrome arrived in New York from some other part of the world, perhaps on the shoes of a traveler or shipped in as a few spores with freight.

Researcher Andrew Minnis said the study is part of a wider effort to find a way to protect bats from the fungus. “Once key elements of this [fungus] species’ biology, including mechanisms of pathogenicity, are identified, it will be possible to target them,” he said.

Once it was realized that many related fungi were present in bat caves, but weren’t killing bats, “thoughts arose that these species could be used for comparative purposes — to understand why P. destructans is different,” he said. Following the findings from this study, “further and more informed comparative work can now be performed.”

Confirmed and suspected white-nose syndrome cases. Map updated August, 2013 by the U.S. government.
Confirmed and suspected white-nose syndrome cases. Map updated August, 2013 by the U.S. government.

How do plants cope with shade?

By John Upton

Plants can tell when they have germinated in the shade of their competitors. Neighboring leaves absorb most of the red and blue wavelengths from the sun but reflect the far-red wavelengths. A preponderance of waves of light at the far-red end of the spectrum, compared with the intensity of light that’s more readily visible to humans, warns a plant that it’s going to need to fight to survive.

Plants growing in the shade can fight to survive by adopting one of two strategies: They can try to avoid the shade, or they can adapt to it.

Shade avoidance is the more common strategy, especially in grasslands and in other habitats where most of the plants grow to roughly the same height. To escape the shade, a plant using this strategy will prioritize the growth of its stem over its roots and over its leaves, most of which will be grown high along the stem, in a bid to stretch itself into the sun’s nourishing rays.

Illustrated by Perry Shirley
Illustrated by Perry Shirley

That’s according to Dutch researchers, writing in the February issue of Trends in Plant Science. But the scientists point out that precious little is known about how plants pursue the alternative strategy of shade adaptation. They argue that specific additional research is needed to help explain how some plants, such as shrubs that grow in forests, have adapted to shady environments. There are indications that these specialized plants tolerate shade by regulating levels of certain proteins and hormones, and by suppressing the plant kingdom’s normal instinct to spend lots of energy to grow out of the shade.

“Analysis on pairs of shade and non-shade species could provide information,” the scientists, led by Charlotte Gommers and Ronald Pierik of Utrecht University, wrote in their paper. “To investigate shade tolerance fully, we will need to venture outside our genetic models.”

Better understanding shade tolerance wouldn’t just fuel cocktail party chatter among ecophysiologists — it could help to increase the amount of food available around the world. If scientists could train crops to develop shade adaptation strategies, then those crops would be expected to invest more energy into growing harvestable yields, such as juicy cobs of corn, instead of unnecessarily wiry stalks.

“This might lead towards crop varieties which, when grown in high density, do not invest in undesirable shoot elongation, but do adapt their shaded, lower strata of the vegetation for more efficient photosynthesis.”

Yosemite National Park
Shade avoidance is common in meadows, grasslands and in other habitats where most plants grow to the same height; Shrubs growing in forests often adopt shade tolerance strategies / John Upton

New island, same old ecological succession theory

Norderoogsand / Illustration by Perry Shirley

By John Upton

It’s easy to think of the earth’s lands as static. But shorelines are constantly shifting as sea levels and land masses rise and fall. New islands can appear, and old ones can be engulfed by the tides.

Sandbanks appear frequently in the  Wadden Sea National Park, off the coast of Germany, as tides and waves push particles of sand around. These are normally ephemeral features that wax and wane like an erratic moon.

But during the past decade, scientists have watched with interest as one particular sandbank has weathered the storms and grown into a full blown island.

Norderoogsand, as it is named, is sheltered by nearby islands and has benefited from rare occurrences of high storm surges during its short life. As reported by The Telegraph, some of the dunes on  the 34 acre island have reached four meters.

Norderoogsand is already home to grasses and seabirds. These are among the wildlife that typically first occupy a new island. According to ecological succession theory, pioneer species such as these are the first to colonize a new or recently scorched land mass. Pioneer species travel easily and they are generally hardy.

Once pioneer species have been established, the environment becomes more accommodating for other species, such as mammals and slow-growing trees.

“Birds are usually first to arrive naturally, and they can often bring in plant seeds or other species in their feathers or droppings,” Dan Grout, a scientist at the nonprofit Island Conservation, told me. “The rate of colonization will depend on the few usual factors such as distances to other land masses, likely migration routes and, not insignificantly, whether human visitation will assist in any directed or inadvertent release of organisms.”

Scientists are looking forward to watching as ecological succession plays itself out on the young island, where gulls, geese, plovers, terns and peregrine falcons have been spotted. “It is to be hoped that the rare sandwich tern will also discover these dunes as a breeding place,” a conservationist told Die Welt newspaper.

But the ecological extravaganza could be fleeting, the experts warn. The entire island could yet be wiped out by a strong tide surge.

Fate of world’s ‘ugliest’ fish unknown, presumed miserable

By John Upton

The blobfish routinely ranks high in publishers’ “ugliest animals” lists. But its maligned existence is as mysterious as the creature is aesthetically challenged.

The fish live along the floor of the ocean off Southeastern Australia,  leading generally lethargic lives and grabbing at passing sea urchins and mollusks. These deep-sea creatures share similar habitats with lobsters and crabs. They are often plucked from the ocean as by-catch by fishermen targeting the nearby crustaceans with their trawlers.

Illustrated by Perry Shirley.
Illustrated by Perry Shirley.

A flurry of news articles appeared a few years ago warning that the destructive trawling practices had left the blobfish in danger of extinction. Problem is, the fish is so rarely encountered by humans and it has been studied so little by scientists that nobody really knows how it’s faring.

“The assertion that the blobfish is threatened is the overlap of its small geographic range and habitat with the areas hit hard by deep sea bottom trawling,” said University of York Professor Callum Roberts, a marine conservation biologist whose research focuses on human impacts on marine ecosystems, “and the fact that it seems to be rare.”

ExxonMobil blends toxic dispersants with oil spill, angering nigerian officials

By John Upton

Nigerian oil spill officials have accused an Exxon Mobil subsidiary of using harmful oil dispersants at the site of a large spill without their permission.

BP used similar dispersants after the Deepwater Horizon spill, sickening cleanup workers. The toxic chemicals help oil blend with water. That removes some slick from the surface; a public relations exercise that hides spilled oil and disguises the true size of a spill. But it plunges the spilled fuel deep into the water column, where it’s deadly to fish, dolphins, plankton and other marine life.

As Mobil Producing Nigeria seeks to contain its third oil spill in just three months at the Qua Iboe oil fields, along the Atlantic coastline, the company has angered National Oil Spills Detection and Response Agency officials through its use of dispersants.

“No approval was sought,” agency director Musa Idris told News Agency of Nigeria.

The company is telling the press that it received permission to use the dispersants from the Department of Petroleum Resources. Not only does Idris say that’s irrelevant – he insists that his agency is in charge of oil spill responses – but he appears to question the very honesty of Mobil’s claim.

“The DPR approval letter is questionable and we should see it,” Idris said.

Update: A December oil spill at the same site was Mobil Producing Nigeria’s fourth spill there in as many months.

Holey moly, tree cavities disappearing

A squirrel disappearing into a tree / Flick: ibm4381

By John Upton

Large, old trees sporting gaping holes in their trunks are like empty nesters who open their homes and hearts to foster kids, or to help raise grandchildren.

Tree cavities provide homes for all manner of life, including mushrooms, birds, bats and possums. They can provide respite from squalls and from scorching or freezing temperatures, sculpting microenvironments and boosting biodiversity.

But these holes are disappearing.

Tree holes normally arise over painstakingly long periods, sometimes with the assistance of woodpeckers, termites or fungus. They are most commonly found in the most senior members of a tree stand. Sometimes, cavity-pocked trees are dead trees that remain standing for decades.

Large mountain ashes and the holes that these grand Eucalypts harbor are disappearing from Victoria, scientists discovered during a 15-year study / Flickr: louisa_catlover

Scientists warn that climate change, logging and other human activities are prematurely felling the world’s oldest trees, taking their cavities down with them. Droughts and intense fires are taking heavy tolls.

“The loss is global,” warned a team of foresters and other scientists in a paper published Friday in the online journal PLOS ONE.

“Many ecosystems worldwide are increasingly characterized by the rapid loss of large trees with cavities, a failure to recruit new trees with cavities, or both,” the scientists wrote. “Many kinds of human disturbances cause this problem, including recurrent logging, altered fire regimes, grazing by domestic livestock, and the impacts of exotic plants.”

The scientists monitored populations of Eucalytpus trees in the southeastern Australian state of Victoria, some of which were growing in areas hit hard during unprecedented bushfires in 2009 that killed 173 people. They found an alarming decline in the number of cavity-bearing specimens.

Leadbeater’s possums are Victoria’s faunal emblem but they survive only in a few remaining pockets of old growth mountain ash forest. If the tree holes in which they nest disappear, the species could disappear with them. / Flickr: Greens MPs

In areas severely impacted by fires, the number of cavity-bearing trees declined from 138 in 2006 to 42 in 2012, greatly diminishing the number of holes available for use by Leadbeater’s possums and other creatures. But the losses were also staggering in areas unaffected by fire: The number of cavity-bearing trees in these areas fell from 414 in 1997 to 159 in 2011.

“There was a heat-induced, drought-induced mortality spike in the deaths of large trees,” lead researcher David Lindenmayer of the Australian National University told me in an email. “These kinds of findings are seen in many kinds of forests worldwide.”

Perhaps even more alarmingly, during this period of disappearing holes, not a single new tree cavity was formed in the study area during the entire 15 years of research. It’s as if hundreds of homes were razed but no new ones were built to replace them.