Category Archives: Ecology blog

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-photo
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.)

weaver
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-hillside
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.

Wine-delivering wasps

By John Upton

Yeast is a salubrious if invisible vintner, and scientists have discovered an important role that wasps have played in its spread and evolution in vineyards around the world.

Species of the single-celled fungal genus Saccharomyces feast on grape sugar and break it down to create alcohol molecules.

(That’s not all, of course. By shearing carbon and oxygen atoms away from carbohydrates in decomposing barley, the yeast produces booze while shaking loose pockets of carbon dioxide that manifest as bubbles in a freshly cracked beer. When the yeast produces those bubbles inside dough, the result is bread’s delightfully airy texture. Other genera of yeast fashion hard liquor, chocolate, soy sauce and scores of life’s other routine gastronomic indulgences from otherwise questionably-edible ingredients.)

Most modern wine, beer and bread makers purchase Saccharomyces and pour the yeast directly into their concoctions. But wine, beer and bread emerged as staples long before anybody understood their microbiotic secrets — in various continents and countless cultures over at least the last 9,000 years. Many of these early vintners, brewers and bakers relied on nature to deposit the mystical ingredient into their potions.

Where did this yeast come from, if not from a packet? How could nature be so dependably relied upon to provide this ingredient, apparently from thin air?

Illustrated by Perry Shirley
Illustrated by Perry Shirley

The answer rests in fungi’s remarkable ability to flood the environment with its own microscopic spores and then to lay low, requiring little to no sustenance, until it settles on food that allows it to quickly flourish.

A team of French and Italian scientists reported in 2012 in Proceedings of the National Academy of Sciences that vineyard-visiting social wasps in Italy were found to be both vectors and natural reservoirs of S. cerevisiae. The group, which expects to publish follow-up research in the same journal shortly, concluded that the wasps served as a “key environmental niche for the evolution” of a yeast used for winemaking — a yeast that cannot spread through the air unaided.

The group found the yeast inside the guts and nests of wasps, suggesting that the insects inadvertently gather the yeast while foraging in vineyards for food. Hibernating queens provide the yeast with a warm and safe winter home, and then the progenies of the queens help deposit the fungus back onto grapes as the fruit comes into season.

“Our work suggests that wasps could move wine strains and maintain diversity, favoring crosses between strains involved in wine making and wild strains,” Duccio Cavalieri, a microbiology professor at the  University of Florence who was involved with the research.

(A version of this post originally appeared on Wonk on the Wildlife in 2012.)

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.

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.

When Hybrids Go Wild

By John Upton

Q: How do you make a hybrid trout go wild?

A: You wait.

From a survival-of-the-fittest perspective, a domesticated animal is a poor facsimile of its wild relative. That’s why a salmon or a trout reared in a hatchery is less likely to survive in the ocean and return safely to its home river come spawning time.

When domesticated creatures are mixed with a population of wild ones, such as through fish-stocking programs, their domesticated genes, many of which are ill-suited to the idiosyncrasies of the new environment, can be passed on to the next wild-dwelling generation. The genetic contamination lingers so long in the newly hybridized population that wildlife management policies generally consider it to be permanent.

The good news for a hybrid-wearied world is that recent research suggests that a wild trout population’s newly-hybridized traits could be shed quickly — even if some of the hybrid DNA sticks around.

Illustrated by Perry Shirley.
Illustrated by Perry Shirley.

Ontario and Concordia University researchers reared brook trout from two hybridized populations and from one wild population in Ontario’s Algonquin Park. They also obtained trout from a nearby hatchery. The four populations were mixed equally in holding tanks, then released into three small, hitherto trout-free lakes in the North Shore region of Lake Huron.

The researchers sampled from the three lakes five months later, testing how well each of the strains had survived the rigors of the new environment. By then, most of the fish had died, which is normal after brook trout are planted

in Ontario waters. Mortality in one of the lakes was 96 percent. In the other two lakes: 80 percent. The scientists found that members of the hybrid and wild populations had similar chances of survival — and that they all fared better than their hatchery cousins.

One of the hybrid populations studied had last been contaminated with hatchery fish some five generations earlier. The other had been hybridized for 11 generations.  The results, the scientists wrote in a paper published recently in Evolutionary Applications, “suggest that within five to eleven generations, selection can remove introduced foreign genes from wild populations.”

The findings are a reminder of the fast pace at which evolution is capable of working.

“Allowing natural selection to act for relatively few generations can produce hybridized populations that closely resemble nearby non-hybridized populations — both physically and ecologically,” said Concordia University’s Andrew Harbicht, one of the researchers behind the study.

“Certain genetic vestiges will persist into the future over the long term. But, generally, the hybrids will behave ecologically similarly to their wild predecessors after a fairly short time period,” Harbicht said.

When Comets Are Fertilizer

By John Upton

One of the main ingredients needed for life might have arrived here after an ancient meteor grabbed a cold one for Mother Earth out of an equally ancient chemical ice chest.

On Earth, nitrogen is wildly abundant, making up the vast majority of the air that we breathe. Conveniently, nitrogen is also critical for life as we know it. Every strand of DNA and every piece of protein that its genetic code describes contains nitrogen. When you drive a car, you’re spraying fertilizer out of your tailpipe, often helping weeds outgrow native species. That’s because fossil fuels harbor the nitrogen that was in the algae and other life forms that fossilized and provided you with your fuel.

Weirdly, though, the  types of nitrogen isotopes found here on Earth are different than those found through much of the solar system. That suggests that the nitrogen we breathe today was not floating freely in the clouds of space dust that clumped together to form the planets. At least some of it arrived here, as German researchers wrote in a letter published Monday in Nature Geoscience, from a “primordial cosmochemical source.”

The part of a meteor that survives its incendiary passage through Earth’s atmosphere is called a meteorite,  and some meteorites contain the mineral carlsbergite. After chemically analyzing carlsbergite and putting it under a powerful microscope, the researchers concluded that its nitrogen isotopes more closely resembled the nitrogen in Earth’s atmosphere than that found in regular cometary ice. The finding adds to speculation that these carlsbergite-wielding meteorites fertilized our planet with its nitrogen, making life as we know it possible here.

Illustrated by Perry Shirley.
Illustrated by Perry Shirley.

“Some nitrogen might have come from other sources, but we don’t know what they are,” one of the researchers, Dennis Harries, of the Friedrich-Schiller-Universität, told us. “We don’t know how much ammonia came directly to Earth, but it is quite certain that ammonia reacted in the meteorite’s parent body to form nitrogen-bearing organic molecules like amino acids. These molecules might have brought nitrogen to Earth and might have helped life to emerge.”

So where did these planet fertilizing comets come from?

Perhaps, the scientists say, vast regions of icy ammonia that pocked the early solar system were broken up by powerful shock waves that sent their chunks spinning away as meteors. Such shock waves might have been produced back when Jupiter’s sunward trajectory was bumped into a new direction by the effects of Saturn’s gravity.

“Jupiter being involved is just an idea — our research is primarily about the existence of the ammonia in this ice,” Harries said. “The icy bodies could have been brought to Earth by Jupiter’s change in tack.”

Natural History of Sex

By John Upton

If you could exchange the orgasmic gift of mammal-style intercourse for the messy ritual of dribbling fluids together, would you?

If you were the lineage of the world’s fish, then the latest evidence suggests that the answer to that unlikely conundrum would be, ‘Yes,’ to the great surprise of scientists documenting backbone-baring animals’ earliest known instances of internal fertilization.

We’re not talking about pudgy, panting penetration following happy hour pitchers. We’re talking rock-hard prehistoric fish, dermal claspers and paired dermal plates — locked, hundreds of millions of years ago, in ocean-floor embraces.

Bow guppy bow wow.

antiarchs
Illustrated by Perry Shirley.

A new scientific study peers into the most intimate moments in the lives of fish of several closely related ancient fish genii — MicrobrachiusPterichthyodes and Bothriolepis. Each was an antiarch, which was a heavily-armored order of fish known as placoderms. Placoderms were early gnathostomes, an infraphylum also called boned vertebrates, which includes all the fish alive today.  Gnathostomes started the branch on our evolutionary family tree that blossomed into lizards, birds and apes.

These long-dead fish were caught in the act of possessing the organs needed for sexual penetration. In a question over which came first, be it fish intercourse or external spawning, the answer would seem to be the former.

(The word antiarch means “opposite anus,” by the by, because a scientist once mistook a fossil’s mouth for its ass. And, while we’re at it, one of the species studied was M. dicki. Because somebody couldn’t help themselves.)

We’ve included a sketch of this primal love making below. Just make sure there are no underaged fish fossils in the room.

Mating Microbrachius
Adapted from a figure in Nature showing Microbrachius mating.

Is there anything cuter than fish that lock arms like that at a time like that? In real life, the width of that embracing scene would have been an adorable inch and a half.

We’re not sure if those are expressions of ecstasy — or the shocked looks that are to be expected when scientific method walks through the doors of ancient history during the most intimate of hypothesized moments. But we did confirm with Flinders University paleontology professor John Long that those big holes are where the eyes and nostrils would be. Because we didn’t want to get anything ass-backwards.

By now you might be wondering such things as, What does this have to do with me? If I took the right medicine, could I lead a life like that? And, How can I not think about this next time I’m bonking my boyfriend, or rolling in the hay at that haystack that my wife and I both like; won’t somebody please come and scoop the vision of adorable ancient randiness from my braincase? Aarrrggghhhhh.

We don’t know the answers to all your implied imaginary questions. What we do know comes from a study published Sunday in Nature by a large team of scientists led by Long.

The scientists analyzed fossils of the three genii that we mentioned earlier, and found in the males what they believe to be evidence of dermal claspers. They also found what they take to be the paired dermal plates of their female counterparts. Place those together and you’ve got yourself some internal fertilization, Velcro style.

The researchers write that the claspers found in these fossils resemble those of ptyctodonts, an order of placoderms that came after the unfortunately-named antiarchs. Those similarities, they wrote, suggest that “all placoderm claspers are homologous,” and that “internal fertilization characterized all placoderms.”

And they say that implies that spawning, which is so popular with the gnathostomes of today, must be an evolutionary adaptation that began with internal fertilization, even though such a transformation had been regarded as implausible.

“The complex physiology of fish that internally fertilize precludes a reversion back to spawning in water,” Long told us. “Yet our analysis shows it was the most likely explanation.”

Conservation biology, meet the digital age

By John Upton

Strap a two-kilogram tracking device to a 40-gram wood thrush and watch where it flies. Absolutely nowhere. If researchers had tried to track the migratory patterns of Washington D.C.’s official bird in 1994 using Lotek Engineering’s then-state-of-the-art GPS_1000 animal tracker, that’s what would have happened.

Fast forward past 20 of the birds’ international migrations.

Newer iterations of the same company’s GPS tracking devices, each weighing 2 grams, were attached this summer to the backs of 125 wood thrushes. The birds are migrating to Central America, obliviously recording location data that scientists aim to retrieve and put to use in understanding why their populations are declining.

Illustrated by Perry Shirley
Illustrated by Perry Shirley

Technological marvels of the modern age, including miniaturized microchips and batteries, improved GPS devices, and Big Data are arming conservation biologists with powerful new tracking tools. The progress could barely have come at a more felicitous time, with modern life’s hazardous side effects thrusting countless wildlife populations into little-understood nosedives.

“We don’t know where most animals go,” said Peter Marra, head of the Smithsonian Migratory Bird Center, which is involved with the wood thrush tracking study. “There are an infinite number of questions that we can ask once we can start tracking these animals throughout the year.”

To propel animal-tracking innovation, the Smithsonian Conservation Biology Institute and Smithsonian National Zoological Park are teaming up with Airbus, Intel, United Airlines, and other corporate behemoths under an initiative they’re calling Partners in the Sky. It aims to shrink tracking devices to less than 1 gram; to track tagged animals using satellites and by fitting commercial planes with receivers; and to harness burgeoning computer power to understand and predict the migrations of elephants, whales, salamanders, and other animals.

“Our ultimate goal is to track any animal, anywhere in the world, throughout its life,” Marra said.

Where did all the bugs go?

By John Upton

Ever noticed that your car’s windshield is smattered with fewer bugs after long country drives than used to be the case? That’s good news for gas-station squeegee duties — but it’s foul news for the planet.

The world’s bug populations are crashing faster than a swarm of mosquitoes into a backwater bug zapper. And that has reverberating yet little-understood consequences for the species and ecosystems that rely on insects for food, pollination, pest control, nutrient cycling, and decomposition.

A Science paper dealing with the planet’s sixth great extinction, underway since 1500, warns that invertebrate species are faring even worse than vertebrates. Two-thirds of monitored bug populations have declined by an average of 45 percent. Their habitat is being destroyed, and they are being drenched with agricultural insecticides.

The July 25 paper was penned by an international team of researchers led by Stanford University’s Rodolfo Dirzo following an exhaustive literature review. The following chart from the paper shows the  percentage of species of insects in the orders ColeopteraHymenopteraLepidoptera, and Odonata that have declined by as much as 40 percent (shown in dark red) during just the past four decades.

bugs-declines-bThe next chart also includes data on Orthoptera, which includes grasshoppers and crickets.

bugs-declines-aVertebrate populations, meanwhile, have fallen by an average of a quarter, the researchers found. The largest of these species are faring the worst.

vertebrate-declines“In the past 500 years, humans have triggered a wave of extinction, threat, and local population declines that may be comparable in both rate and magnitude with the five previous mass extinctions of Earth’s history,” the researchers wrote in the paper. “This recent pulse of animal loss, hereafter referred to as the Anthropocene defaunation, is not only a conspicuous consequence of human impacts on the planet but also a primary driver of global environmental change in its own right.”

The problem of creepy-crawly declines could be worse than anybody realizes. Unlike charismatic mammals, very few invertebrate species, including lowly centipedes, slugs, spiders, and worms, come under the trained eyes of scientists or conservationists. Fewer than 1 percent of the 1.4 million described species of invertebrates have been assessed for threats by the International Union for Conservation of Nature, which maintains the Red List of Threatened Species. Of those few species that have been assessed, 40 percent were found to be threatened.

Lepidoptera, which includes butterflies, moths, and of course their caterpillar larval stages, are the best studied and monitored order of insects, and evidence suggests that their abundance has fallen by 35 percent worldwide. Lepidopteran species richness is nearly 8 times greater in undisturbed sites than in developed areas, and abundance appears to be 60 percent higher on average in near-pristine environments than elsewhere.

As bad as that might be, it appears that these plant-munchers, which metamorphose into nectar-sucking plant pollinators, are faring far better than lesser-studied orders of insects.

bugs-decline-c

Snails and their shell-less terrestrial gastropod mollusk cousins, the slugs, by sticky contrast, are among the least-well studied. These species may seem like mere pests to many gardeners, but they help break down organic material and they provide food for larger animals. Grasping how slug and snail populations are coping with the defaunation of the Anthropocene relies right now on little more than educated guesswork.

“We mentioned slugs as a point of reference regarding the fact that many groups of invertebrates have been very poorly studied in rigorous, quantitative ways and over long, consistent periods,” Dirzo told us.

Illustrated by Perry Shirley

“Given the fact that at least some species of terrestrial mollusks seem to do well in disturbed areas, I suspect several of them might not be so severely impacted and might be thriving,” Dirzo said. Then again, he added, “given their strong dependence on moist, relatively mild-to-cool habitats, climate disruption might have a strong, negative impact on them.”

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.”