Category Archives: Climate and weather

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.

Stopping starfish virus ‘almost impossible’

By John Upton

Nearly 18 months into the worst marine epizootic that humanity has ever seen, scientists appear to have found the cause of death. A virus is being blamed for the mass die-off of starfish along North America’s western coastline. Sickened sea stars grow lethargic and their limbs start to curl. Next comes lesions and the shedding of limbs. The body deflates, then melts into puddles of slime and bone-like ossicles. More than a million starfish, coming from at least 20 species, have succumbed. Some local populations of the keystone predators, whose hunting prowess keep populations of plant grazers in check, have been decimated.

Hopes that the new diagnosis will usher forward a cure, however, are about as low as the deep-sea habitat of a brisingida.

Research described Sunday in Proceedings of the National Academy of Sciences blames the heretofore mysterious deaths on a densovirus — a type of virus that typically plagues crabs, shrimp and other invertebrates. The scientists gave the pathogen the name ‘sea star-associated densovirus,’ or SSaDV.

Illustrated by Perry Shirley.
Illustrated by Perry Shirley.

The scientists discovered that loads of the densovirus were higher in sick starfish collected from the wild than in asymptomatic specimens. They also found that exposing lab starfish to the germ “consistently” induced the hallmark symptoms of sea-star wasting disease, while exposing specimens to heat-killed viruses remained healthy.

When the scientists turned their attention to ethanol-preserved sea stars collected as early as 1923, they discovered that the disease has been infecting starfish since at least 1942.

So why would it suddenly turn into such an ecosystem-rattling problem?

That’s just how viruses roll.

“This is the case for many viruses, including HIV and Ebola, which were present in populations since at least the 1930s but only became epidemics in the 1970s and 80s,” said Ian Hewson, an associate professor in Cornell University’s microbiology department, the leader of the recent research.

Perhaps the virus chanced upon a powerful genetic mutation. An improvement to the way it builds capsids, which are shells that protect viruses during their extracellular ventures, might explain its virulence boost.

Perhaps the manifest changes underway in the ocean, where pollution, carbon dioxide and heat are piling up, has weakened the victims’ natural defenses.

The scientists can’t say, yet, which of these factors is to blame. But they do note that large populations of starfish jammed into small habitats appear to be more vulnerable to outbreaks.

They point to a booming sunflower seastar population prior to the first large outbreak.

“We speculate that the current disease event has been exacerbated by an overpopulation of adult sea stars in the Salish Sea immediately prior to the current disease event,” Hewson said. “The Salish Sea was indeed the first population in which the disease was seen; it was noted in June 2013 on the Olympic coast. The first mass mortality occurred in the Vancouver region shortly thereafter.”

That suggests that preventing sea star populations from booming might help protect against future outbreaks. Given that it’s not clear why the Salish Sea population boomed, that’s a daunting task.

Assuming the scientists have accurately identified the cause of the wasting disease, how else could the discovery be used to squelch the current outbreak?

The answer to that question will not fill you with joy.

Infected mottled stars from Washington. Photo by Ian Hewson.
Infected mottled stars from Washington. Photo by Ian Hewson.

“Protecting sea stars in nature from an established pathogen, like the virus seen here, is almost impossible,” Hewson said.

Because the virus is so geographically widespread, Hewson said it would be unfeasible and impractical to remove and protect healthy sea stars. “Likewise, inoculating stars against the virus to build resistance would also not be feasible on a large scale,” he said.

Still, the benefits of finally finding the cause of the disease shouldn’t be understated. “The identification of the causative agent of sea star wasting disease enables accurate diagnosis and more effective management,” said University of Washington professor Carolyn Friedman, one of the new study’s coauthors.

For cheerier sea star times, let’s all tune out of reality for just a moment, and tune into the uninfected antics of Patrick — SpongeBob SquarePants’s friend .

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.”

Ocean reserves help with acidification

By John Upton

Our power plants and cars have pumped so much carbon dioxide into the atmosphere that the oceans are becoming more acidic. Something like a quarter of our carbon dioxide pollution dissolves into the seas, where it reacts with water:

CO2 (aq) + H2\leftrightarrow H2CO3 \leftrightarrow HCO3 + H+ \leftrightarrow CO32− + 2 H+

Those leftover hydrogen ions at the right of the equation add up. The hydrogen ion concentration at the surface of the world’s oceans has increased by 26 percent since pre-industrial times, leading to a pH decline of 0.1. That might not sound like much, but it has been enough to kill off billions of farmed shellfish and punch holes in the shells of wild sea snails.

Illustrated by Perry Shirley
Illustrated by Perry Shirley

Shellfish and corals are especially vulnerable to ocean acidification because they rely on calcium carbonate to make their shells and skeletons. Ocean acidification increases concentrations of bicarbonate ions while decreasing concentrations of carbonate ions — and these animals need calcium carbonate to produce their protective body parts.

Fish, meanwhile, are thought to be suffering neurological effects of acidifying oceans, while vast mats of algae are expected to flourish.

The good news is that populations of animals naturally adapt to changes in their environments — and evolutionary changes to help some species cope with ocean acidification are already underway. The bad news is that changes in oceanic pH levels might be happening too quickly for animals to adapt, threatening scores of marine species with extinction.

I asked Ryan Kelly, an assistant professor at the University of Washington’s School of Marine and Environmental Affairs, and a coauthor of a recent BioScience paper about acidification that I wrote about for Pacific Standard, whether we could do anything to help species accelerate the rate with which they evolve needed adaptations.

“‘Accelerating’ species’ evolutionary adaptations to acidification would mean either tweaking the heritability of traits — and it’s unclear whether this is desirable, or how to do it; or increasing the strength of selection — which would mean making the selective impacts of acidification worse than they already are,” Kelly said. “So I’m thinking that, in an evolutionary sense, you don’t want to accelerate adaptation.”

Is there anything that we can do?

“What you do want to do, in order to protect marine ecosystems as we know them, is to preserve the adaptive capacity of the species that make up those ecosystems. That means preserving the genetic diversity that exists within those species, so that when the selective pressures of acidification happen, there will be some variability in those species’ responses. When there’s no genetic diversity, you get no variability in response to selective pressure, and natural selection and evolution doesn’t really work.”

Which means that we need to expand and improve the globe’s network of marine reserves, banning fishing in some places, and giving species the best possible shot of surviving the storm of acidity that’s building around them.

“From a conservation perspective, measures that preserve existing genetic diversity safeguard the adaptive capacity of species and ecosystems. This means working to maintain large population sizes and not fragmenting habitats, which are common conservation measures.”

As U.S. Secretary of State John Kerry led workshops last month dealing with ocean acidification and other ocean health issues, President Barack Obama’s administration proposed sweeping expansions of marine reserves surrounding remote Pacific Ocean atolls. The move would limit fishing for tuna and other species, helping to protect top predators that are critical for ecosystem health, while also protecting smaller species that are killed as bycatch.

“This is an important step in trying to maintain the health of this region and, as a result, the surrounding areas in the Pacific,” said Lance Morgan, president of Marine Conservation Institute. “It will give us more resilience into the future. We’ll have to replicate this and do more work in other areas as well, but it is an important step.”

Meanwhile, the National Oceanic and Atmospheric Administration is planning to expand the boundaries of Gulf of the Farallones National Marine Sanctuary and Cordell Bank National Marine Sanctuary, both of which lie off the West Coast, where strong upwelling leads to especially severe rates of ocean acidification. Meanwhile, Kiribati recently announced that it would close an area the size of California to fishing to help wildlife recover.

Ocean acidification is not a major consideration in the creation of marine reserves, but it’s a growing threat against which the reserves can help populations of wildlife evolve natural defenses.

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.

Global warming is changing how caterpillars eat

By John Upton

Animals can evolve to survive global warming by changing their behavior and by changing their bodies. Butterflies are particularly sensitive to climate change, and changes in their behavior have been well documented — most notably in their migration patterns and ranges. North American Butterfly Association president Jeffrey Glassberg recently told the Maryland Independent that climate change is affecting Rhopalocera on a vast scale. “There’s a whole suite of butterflies whose ranges are retreating,” he said. (Such changes are the subject of Flight Behavior, a novel by Barbara Kingsolver dealing with climate change.)

And now comes the first evidence that butterfly larvae are changing the internal workings of their bodies to help them cope with warming temperatures.

Illustrated by Perry Shirley.
Illustrated by Perry Shirley.

University of North Carolina scientists studied the optimal feeding temperatures of Colias spp. caterpillars from California’s Sacramento Valley and Colorado’s Montrose Valley. The frequency of very hot days and nights at both sample sites have increased since the 1970s, when a similar study with the same caterpillar populations was conducted. Caterpillars feed best within specific temperature ranges, and the researchers discovered that the caterpillars have evolved to feed at higher temperatures. The results of the study were published in the journal Functional Ecology:

This study is among the first to show population changes in physiological performance in response to recent climate change, although previous theoretical work has predicted such changes. While previous work has highlighted adaptation to seasonal timing, specifically photoperiodic cues, our work suggests that rapid adaptation to changing thermal regimes may also be an essential mechanism.

I asked lead researcher Jessica Higgins whether she thinks that butterflies are among the first organisms to adapt their physiologies to warming conditions — or whether she thinks this was just the first time that such changes have been detected by scientists.

“I do think that other organisms may be adapting, but we can’t detect it because of the lack of good historical data,” Higgins said. “What made my experiment so unique was that I had this snapshot of caterpillar physiology back in the 1970s. I was able to compare my results with what they previously found and then correlate it with temperature. I think my study highlights that there can be adaption to physiological traits — not just changes in seasonality, which has been the main focus of previous adaptation-to-climate studies. “

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.”

California’s water hightails east

Illustration by Perry Shirley

By John Upton

California’s Central Valley is one of the world’s most productive crop-growing regions. But growing crops in the vast rich soils requires a lot of water. Some of that water comes from melting Sierra mountain range snow, with a pinch of rainfall mixed into the rivers that are tapped for irrigation. But farmers also pump a lot of their water out of the ground.

Since the early 1960s, about 60 million acre-feet more water has been pumped out of the valley’s aquifers than has seeped back into them. That’s enough water to supply every resident of California for eight years.

Where has that water gone?

A lot of water that is pumped out of the ground evaporates. In some places, that contributes to rising seas, with water being shifted from the land into the oceans.

But in California, scientists have discovered that evaporating Central Valley water turns into clouds that deposit their consignments east of the Sierra, fueling the monsoons of the Southwestern United States and increasing flows in the Colorado River by more than one quarter. The findings were published online Tuesday in Geophysical Research Letters.

California ends up getting some of the water back. Some Colorado River water is diverted and sent west through what the study’s lead researcher, Jay Famiglietti of the University of California at Irvine, dubs an “anthropogenic loop.”

Famiglietti told me that the study illustrates that large-scale water management practices, such as irrigation, can have “profound regional, and even global” impacts.

“We need to understand, much better, what those impacts are,” Famiglietti said.

Valley Grapes
Grape vines growing in California’s Central Valley / Flickr: AquaMaven

 

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.”