Category Archives: Forests

Fairy wasps unleashed to protect Eucalypts

By John Upton

Eucalyptus trees are the scraggly kings of Australian landscapes, growing hard and fast, resilient to fire and sundry other stresses. After their crowned heads were plucked from native wildlands and thrust into monoculture plantations in continents far afield, though, pests began sucking the antipodean puissance out of the botanical emperors.

Cue scientific tinkling and hopes for a tiny-winged salvation.

A healthy Eucalyptus plantation in Hawaii. Photo by Forest and Kim Starr.
A healthy Eucalyptus plantation in Hawaii. Photo by Forest and Kim Starr.

Natural forests and other ecosystems are being cleared the world over to make space for Eucalyptus plantations. They sprawl over millions of acres, from the American Southeast to Africa to New Zealand.

The trees are largely being grown to be pulped for paper and, more recently, to be burned to produce energy. Sometimes they’re just planted along paths and roads and as forests because they’re easy to grow, and they look nice.

Amid this upheaval, a biological chink has been gouged from the trees’ armors of hitherto resilience. Across the globe, Eucalypts in plantations and neighborhoods alike are being attacked by tiny sap-sucking bugs.

The culprits are called bronze bugs — because their victims’ hues change from green to bronze as their leaves dry out. As the sap is sucked from the trees, their growth is crippled. The heaviest of attacks can leave the trees dead.

Bronze bugs
Bronze bugs on a Eucalyptus leaf. Photo by Simon Lawson.

To protect hulking gum tree plantations from bronze bugs, scientists are starting to release even tinier critters. Their newest weapon is a species so small that it lays its eggs inside the eggs of the marauding pests, which hatch to feast on the meat of an egg that was laid for another, killing the unborn.

Eucalyptus trees, the bronze bugs that steal their sap, and the fairy wasps that hijack the bronze bugs’ eggs are all Australian natives. But until the turn of the century, few people had given the bronze bugs any thought. That’s when they started attacking trees in Sydney — possibly infesting tree species that had been transplanted outside their native ranges.

“There were very few records of it until it started outbreaking in Sydney in the early 2000s,” said Simon Lawson, a University of the Sunshine Coast entomologist who studies Eucalyptus pests.

From Sydney, the bronze bugs spread, hitchhiking with world trade to South America and South Africa, where the invasive populations made themselves at home amid their native prey. More recently, they’ve have been spreading through Europe and the Middle East. They’re also in New Zealand.

A fairy fly
A fairy fly. Illustrated by Perry Shirley.

The bronze bug outbreaks have coincided with a substantial rise since the 1990s in the spread of exotic pests in general — and, more recently, with a rise in the spread of Eucalyptus pests.

“Just in the last ten to 15 years or so, there’s been a real increase in the number of Australian-origin Eucalyptus insects that have been moving around the world into Eucalyptus plantations,” Lawson said.

To try to relieve the problem, Lawson and other researchers across the planet are turning to the pests’ natural predators. The main predator tested in laboratories and dispatched in the wild so far has been Cleruchoides noackae. C. noackae are from a family of wasp and ant relatives called fairyflies — or fairy wasps. As the name suggests, the family includes some of the tiniest insects ever discovered.

C. noackae
C. noackae. Photo by Samantha Bush, University of Pretoria.

Fairy wasps are often used as biological controls — as sentient insecticides.  They’re all parasitoids. That’s similar to a parasite, but dialed to a different equilibrium: parasites generally let their hosts live; parasitoids do not.

Following quarantine and tests that convinced them C. noackae was safe for native bugs, Brazilian agriculture officials released swarms of  them in the state of Minas Gerais in 2011. Two years later, field research found that about half the bronze bug eggs in local Eucalyptus plantations had been parasitized by the fairy wasps.

The results, which will be detailed in an upcoming scientific paper that’s still being finalized by Brazilian agriculture officials, are “quite a bit better than what we’ve seen in the native populations in Sydney that they’re derived from,” Lawson said.

Similar releases are planned or already underway in other South American countries and in South Africa.

Cracking the bronze bug problem, which was set off when Eucalypts were introduced to exotic environments, might mean doubling down on the number of species that are introduced to patch the problem over.

Ongoing research to identify alternative biological control agents, such as other species of fairy wasps, will also be critical for controlling the pests, Lawson said. “You’re better off having more than one agent.”

Bronze bug eggs on an infested leaf. Photo by Simon Lawson.
Bronze bug eggs on an infested leaf. Photo by Simon Lawson.

Why fish need wood

By John Upton

Trees don’t just provide habitat for arboreal and terrestrial creatures — dead trees that have toppled over in shallow waters are critical for aquatic wildlife. Woody habitat in lake littoral zones provides shelter for fish. It also supports the growth of algae and the like, which are eaten by herbivorous fish and other critters.

As the globe warms and as aquifers are sucked dry, lake levels in many parts of the world are falling. And as a lake’s water level drops, semi-submerged trees that ring the lake’s shallows can be left high-and-dry. That can decimate fish populations — harming birds and other species that feed on them.

“Reduced lake levels generally decrease littoral habitat, which is critical to aquatic food webs,” wrote University of Wisconsin researchers in a recent paper published by the Canadian Journal of Fisheries and Aquatic Sciences. “Fishes across all trophic levels are known to rely heavily on littoral food sources, with littoral zones supporting 65% of the consumption by lentic fish communities and 57% of their body carbon.”

Illustrated by Perry Shirley.
Illustrated by Perry Shirley.

The scientists sampled fish from 2000 until 2005 and again from 2007 to 2009 in Wisconsin’s Little Rock Lake, which is in the Great Lakes region. Declining water levels in the Great Lakes, which is Earth’s largest body of fresh surface water, are a major worry for scientists.

During the monitoring period, drought led to a decline in water levels of a little more than a meter. That left three quarters of the lake’s woody habitat stranded on land. The following graphs from the paper show the close relationship between water levels and woody habitat:

lake-level

The sampling results painted a picture of an ecosystem in steep decline — a decline that the scientists linked to the loss of soggy wood.

Things got so bad during the drought that the scientists’ minnow traps started to come up empty.

“The rapid decline of the perch population was associated with the loss of available CWH [coarse woody habitat],” the paper states. “Perch first failed to appear in a trapping event in 2005, after only a 10% loss of CWH. No perch were detected in 2008 or 2009 after 58% and 72% of the available CWH had been stranded from the littoral zone.”

The loss of the perch was blamed on the declining water levels, with changed temperature and oxygen levels potentially contributing. A loss of food was also stated as a potential factor. As was the loss of spawning habitat and loss of shelter from predators due to the disappearance of woody habitat.

“Previous research has suggested the potential for predator–prey encounter rates to increase with reduced CWH, which would result in intense bass predation on perch. … [T]he severe depletion of the perch population might have been exacerbated by the relatively high densities of bass in Little Rock South, which initially increased with reduced lake level.”

Eventually, though, the largemouth bass were found to grow more slowly as the lake’s water level fell.

The study’s lead author, Jereme Gaeta, tells Wonk on the Wildlife that the findings have implications for a warming planet.

“Future climate projections are uncertain, but we generally expect evaporation to outpace precipitation in many regions such as northern Wisconsin,” Gaeta said. “Our research shows that loss of littoral habitat can change not only the way fishes interact but also change fish community and food web structure.”

To help protect aquatic communities from the loss of littoral woody habitat, the paper recommends manually placing dead trees in lakes — something scientists call tree drops.

“Potential preventative measures when lake levels drop are limited. Our best options are to protect and restore natural shorelines to ensure future inputs of woody structure are possible and, when water levels begin to drop, add trees to deeper waters or steeper shorelines,” Gaeta said.

Little Rock Lake
This photograph from the paper shows wood stranded above Little Rock Lake’s shoreline as water levels declined.

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

Forests pump carbon into soil

By John Upton

Photosynthesis is easy enough to understand: Plants use the power of the sun to combine carbon dioxide and water into sugar. What’s perhaps less easy to understand is what happens to all of the carbon-rich sugar that it produces. New research shows that vast amounts of it are pumped down to fungi deep in the ground, keeping the carbon out of the atmosphere and keeping the climate cool.

Some of the energy-rich sugar is shipped around the plant to power cells, and then is often eaten by herbivorous animals or flutters to the ground with fallen leaves to be gobbled up by microscopic organisms. But some of the sugar is pumped down to the roots and traded with mycorrhizal fungi in exchange for nutrients.

The mycorrhizal fungi take the sugar from the plants, and in return they feed nutrients to the plants. Fungi send stretching tentacles, called mycelia, through the ground to forage for nitrogen, phosphorous and other nutrients that are valued by the plants. They use those nutrients as currency with which they buy sugar.

Illustrated by Perry Shirley.
Illustrated by Perry Shirley.

The sugar that’s passed from the plant to the fungi contains lots of carbon, which the plant originally sucked out of the air as carbon dioxide. Scientists have discovered that most of the carbon that’s stored in some forest floors is sequestered in the bodies of the dirt-dwelling fungi — not, as had been presumed, in the decomposing leaf litter.

Karina Clemmensen, a researcher at the Swedish University of Agricultural Scientists, led research that investigated where carbon was being stored in two forested Swedish islands. The researchers discovered that 50 to 70 percent of stored carbon in the forests was locked up in the root layer, where the mycorrhizal fungi thrive.

The research took place in boreal forests, but Clemmensen said other ecosystems might also push much of their carbon down into the soil.

“In agricultural fields, arbuscular mycorrhizal fungi are normally the dominant mycorrhizal type,” Clemmensen said in an email. “Our result though – as stands here – is valid for the boreal forest only.”

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

Beetles ride global warming up rockies, into vulnerable pines

Illustrated by Perry Shirley.

By John Upton

The grand pine forests that dominate the Rocky Mountains in the American West morph with the montane altitudes. High peaks are home to whitebark pine, a slow growing species that produces energy-rich, pine cone-encased seeds that help grizzly bears grow plump enough to survive hibernation. At lower altitudes are the faster growing lodgepole pines.

The lodgepole pines have long been plagued by occasional infestations of native pine beetles. These dark beetles burrow into tree bark to lay their eggs, which hatch into larvae that feast on the phloem. (Phloem is a tender organ found just beneath the bark that ferries sugars produced by photosynthesizing leaves to other parts of the tree.)

A full blown infestation of phloem-munching beetle larvae is generally fatal. But lodgepole pines have developed a repertoire of defenses against the herbivorous creepy crawlies. They churn out sap and pour it over the invading beetles. They exhale chemicals that repel and kill the adults, prevent eggs from hatching and wreak general havoc with the beetles’ diminutive ecosystems.

Pine trees covered with snow near the top of Polar Peak lift at Fernie Alpine Resort in the Rocky Mountains, British Columbia / Flickr: DCZwick

Whitebark pines have not developed these defenses, at least not to the same extent as their lower-altitude cousins, because they haven’t needed them. The beetles can’t bear the bitter winters that have long swept over the Rocky Mountains’ higher peaks. But now, as climate change sweeps warmer weather over these towering peaks, the whitebarks are in newfound peril.

During occasional warm periods in the past, the beetles would march up the mountains and find a footing in whitebark forests. Then temperatures would return to normal and the pest populations would die off.

“However,” entomologists and ecologists report in the latest edition of Proceedings of the National Academy of Sciences, “recent continuously warm weather has allowed persistent reproduction in this keystone (beetle) species.”

The warming peaks have ushered in an era of beetle infestations that many of the trees have been unable to withstand. More than 100 million acres of mountain forest has been impacted during the past decade. Great forests that used to soak up carbon now lay dead and rotting, releasing their carbon back into the atmosphere, further accelerating the global warming that contributed to their demise.

The Rocky Mountains on Dec. 19, 2012 / Flickr: NASA Goddard Photo and Video

I asked the study’s lead researcher, Ken Raffa, an entomology professor at the University of Wisconsin, Madison, whether he thought the whitepines would be able to evolve defenses against the pine beetles quickly enough to protect themselves from being wiped out. He said he didn’t know: This is something he’s currently investigating, by studying how various tree genotypes are distributed across the mountain landscapes.

But of particular concern to Raffa is the fact that whitepines grow and reproduce very slowly, not producing viable seeds until they reach their 50s, while the beetles can reproduce every year or two, creating an evolutionary handicap.

In addition to marauding beetles, the whitepines also face tremendous threats from white pine blister rust, a ravaging fungus disease. “To be viable,” Raffa said, “whitebark pine would have to escape both.”

Cloud forest trees drink water down

By John Upton

One of the first things that every botany student learns is the simple process by which trees drink water. The water enters the roots from moisture in the soil and is sucked up the trunk through straw-like xylem to the leaves, where some evaporates. The combined effects of water tension and water cohesion inside the xylem and evaporation from the leaves keeps the water flowing against the force of gravity.

Researcher Greg Goldsmith simulates clouds in a laboratory to study foliar water uptake / Courtesy: Drew Fulton (Canopy in the Clouds)

A study of trees growing on Costa Rican mountains revealed that some high-altitude species can pull switcheroos on this widespread drinking system. When the soil is parched and their canopies are saturated by clouds, these trees use their leaves to suck water out of the air and then send the moisture back toward their trunks.

“Water is still moving along a gradient from areas with more water to areas with less water,” Greg Goldsmith, a tropical plant ecologist at the University of California, Berkeley and lead author of the study, which appeared this month in Ecology Letters, told me. “It’s just a different gradient.”

The clouds that nurture these cloud forests are evaporating as the planet warms, meaning the cloud-drinking strategy could doom those trees that rely upon it. That would be bad news for the birds and other wildlife that live in cloud forests, which are some of the world’s most striking and biodiverse ecosystems.

“The phenomenon of water from clouds entering leaves — foliar water uptake — indicates a much tighter relationship between clouds and cloud forest plants than previously known,” Goldsmith said.

Tropical mountain cloud forests are renowned for their high biodiversity but are threatened by climate change / Courtesy: Drew Fulton (Canopy in the Clouds)

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.

Mushrooms make it rain in the Amazon

By John Upton

It’s not enough for mushrooms to simply produce spores. A little more than one-third of the world’s known fungal species, including mushrooms, puffballs and rusts, use a neat canon-ball trick that sends those spores sailing through the air toward newfound territory.

Clouds forming over the Napo River, Peru / Flickr: Photographer 23

This trick relies on the detonation of a fluid-filled sac to send so-called ballistospores airborne. It turns out that this neat trick not only helps fungus spread: Scientists recently discovered that these explosions may help keep the rain falling over the Amazon rainforest.

Water cannot condense into a rain drop unless it has something solid, a “seed,” to grow around, such as a speck of dust or a grain of pollen. Lawrence Berkeley National Laboratory researchers searching for the seeds that help clouds form in the Amazon think they have found what they were looking for.

They reported in Science late last month that potassium salts coalesced with organic material to form the seeds that create the Amazon’s clouds. Based in part on an abundance of ballistospores in the atmospheres, the researchers think the salts are squirted out when these spores are ejected from fungus during the night.

“The source of potassium could only have been natural forest organisms,” researcher Mary Gilles said in a press release published by the Lab on Monday.

Fungi are already known to play a critical role in breaking down old wood and leaves on the forest floor, recycling the nutrients and making them available for plants and animals; and now it appears that they also help to keep the Amazon wet and rainforesty. A pretty neat trick.

Mushrooms form ballistospores in their gills / Flickr: jo-h

Fungus-infected forests heat the planet

By John Upton

Forests suck carbon dioxide out of the air. They use solar energy to combine the carbon dioxide with water droplets to form sugars that fuel plant growth. During that chemical reaction, known as photosynthesis, waste oxygen is released back into the air.

So the effects of widespread deforestation by lumberjacks and bulldozers are relatively easy to understand. Less forests means more carbon dioxide, which heats the planet, and less oxygen for us to breathe.

New research has revealed that deforestation can take an even more sinister turn when it’s performed by a fungus. Fungal pathogens and fungus-like diseases are stealthily felling forests across the world. Forests at Big Sur disappeared in less than a decade after sudden oak death moved onto their turf. Cypress canker, native to California, is destroying trees across Europe. Dutch elm disease has forever changed the landscape on the East Coast.

Trees in Yale Myers Forest, CT, may look healthy, but many are rotting from the inside. Heart rot fungus breaks down the wood into substances that are consumed by bacteria, which further break the material down into methane. / Flickr: morrowlong

These symptoms of a sick planet do more than merely strip the earth of some of its greatest carbon sponges. Scientists have discovered that fungus disease can cause some of the wood in infected trees to break down not into carbon dioxide (CO2), but to break down anaerobically with the assistance of bacteria into methane (CH4), which is a far more potent and damaging greenhouse gas.

The university researchers measured methane levels in Connecticut woodlands infected by heart rot, a fungus disease, and reported in the journal Geophysical Research Letters that concentrations were so high in some places that it was flammable. Methane concentration in the air is normally less than 2 parts per million, but the researchers discovered levels in some trees that reached more than 160,000 parts per million. The average methane concentration in the forest was 15,000 parts per million.

The ailing forest was releasing enough methane to counteract the climate-cooling benefits of nearly one-fifth of the carbon dioxide it was absorbing, researchers calculated.

The researchers point out that their study covered just one forest, and one type of fungus disease. This particular disease is unique in that the trees often appear outwardly healthy while they rot away from the inside. But they warn that other fungal diseases that are laying waste to woodlands around the world could have similar effects.

“I think it’s fair to say that wood-rotting fungi in general could lead to this effect,” lead researcher Kristofer Covey, a Ph.D. candidate at Yale University’s School of Forestry, told me. “It’s hard to say if more aggressive fungal pathogens could lead to further emissions or not.”

Now is a terrible time to be losing forests. They are needed to help soak up all the carbon we’re pumping into the atmosphere when we burn fossil fuels. So this discovery comes as a double-whammy: Not only are we losing carbon-storing forests to fungus, but the fungi are taking carbon that had been stored in the trees and helping to turn it into a particularly potent greenhouse gas that further accelerates the rate of climate change.

The discovery offers one more reason to protect our forests from fungus diseases. Unfortunately, the problem has become so rampant that there is very little that we can do about it.