Environment

What could be more 2020 than an ongoing invasion of jumping worms?
These earthworms are wriggling their way across the United States, voraciously devouring protective forest leaf litter and leaving behind bare, denuded soil. They displace other earthworms, centipedes, salamanders and ground-nesting birds, and disrupt forest food chains. They can invade more than five hectares in a single year, changing soil chemistry and microbial communities as they go, new research shows. And they don’t even need mates to reproduce.
Endemic to Japan and the Korean Peninsula, three invasive species of these worms — Amynthas agrestis, A. tokioensis and Metaphire hilgendorfi — have been in the United States for over a century. But just in the past 15 years, they’ve begun to spread widely (SNS: 10/7/16). Collectively known as Asian jumping worms, crazy worms, snake worms or Alabama jumpers, they’ve become well established across the South and Mid-Atlantic and have reached parts of the Northeast, Upper Midwest and West.
Jumping worms are often sold as compost worms or fishing bait. And that, says soil ecologist Nick Henshue of the University at Buffalo in New York, is partially how they’re spreading (SN: 11/5/17). Fishers like them because the worms wriggle and thrash like angry snakes, which lures fish, says Henshue. They’re also marketed as compost worms because they gobble up food scraps far faster than other earthworms, such as nightcrawlers and other Lumbricus species.

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But when it comes to ecology, the worms have more worrisome traits. Their egg cases, or cocoons, are so small that they can easily hitch a ride on a hiker’s or gardener’s shoe, or can be transported in mulch, compost or shared plants. Hundreds can exist within a square meter of ground.  
Compared with Lumbricus worms, jumping worms grow faster and reproduce faster — and without a mate, so one worm can create a whole invasion. Jumping worms also consume more nutrients than other earthworms, turning soil into dry granular pellets that resemble coffee grounds or ground beef — Henshue calls it “taco meat.” This can make the soil inhospitable to native plants and tree seedlings and far more likely to erode.
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Asian jumping worm species thrash furiously, unlike the more placid movements of other earthworm species. The jumping worms can also slime and shed their tails as defense mechanisms.
To date, scientists have worried most about the worms’ effects on ground cover. Prior to a jumping worm invasion, the soft layer of decomposing leaves, bark and sticks covering the forest floor might be more than a dozen centimeters thick. What’s left afterward is bare soil with a different structure and mineral content, says Sam Chan, an invasive species specialist with Oregon Sea Grant at Oregon State University in Corvallis. Worms can reduce leaf litter by 95 percent in a single season, he says.
That in turn can reduce or remove the forest understory, providing less nutrients or protection for the creatures that live there or for seedlings to grow. Eventually, different plants come in, usually invasive, nonnative species, says Bradley Herrick, an ecologist and research program manager at the University of Wisconsin–Madison Arboretum. And now, new research shows the worms are also changing the soil chemistry and the fungi, bacteria and microbes that live in the soils.
Invasive jumping worms can clear a forest of leaf litter in just a couple of months, as these pictures taken in Jacobsburg State Park near Nazareth, Pa., in June 2016 (left) and August 2016 (right) show.Nick Henshue
In a study in the October Soil Biology and Biochemistry, Herrick, soil scientist Gabriel Price-Christenson and colleagues tested samples from soils impacted by jumping worms. They were looking for changes in carbon and nitrogen levels and in soils’ release of carbon dioxide, which is produced by the metabolism of microbes and animals living in the soil. Results showed that the longer the worms had lived in the soils, the more the soils’ basal metabolic rate increased — meaning soils invaded by jumping worms could release more carbon dioxide into the atmosphere, says Price-Christenson, who is at the University of Illinois at Urbana-Champaign.
Relative amounts of carbon and nitrogen in soils with jumping worms also shifted, the team found. That can affect plant communities, Herrick says. For example, although nitrogen is a necessary nutrient, if there’s too much, or it’s available at the wrong time of year, plants or other soil organisms won’t be able to use it. 
The team also extracted DNA from worm poop and guts to examine differences in microbes among the jumping worm species, and tested the soils for bacterial and fungal changes. Each jumping worm species harbors a different collection of microbes in its gut, the results showed. That’s “a really important find,” Herrick says, “because for a long time, we were talking about jumping worms as a large group … but now we’re learning that [these different species] have different impacts on the soil, which will likely cascade down to having different effects on other worms, soil biota, pH and chemistry.”  
The finding suggests each species might have a unique niche in the environment, with gut microbes breaking down particular food sources. This allows multiple species to invade and thrive together, Herrick says. This makes sense, given findings of multiple species together, but it’s still a surprise that such similar worms would have different niches, he says.    
Scientists have been working hard to get a good handle on the biology of these worms, Henshue says. So the newly discovered soil chemistry and microbiology changes are “thoughtful” and important lines of research. But there’s still a lot that’s unknown, making it hard to predict how much farther the worms might spread and into what kinds of environments. One important question is how weather conditions affect the worms. For example, a prolonged drought this year in Wisconsin seems to have killed off many of the worms, Herrick says. Soils teeming with wriggling worms just a few weeks ago now hold far fewer.
Perhaps that’s a hopeful sign that even these hardy worms have their limits, but in the meantime, the onslaught of worms continues its march — with help from the humans who spread them. More

Acrid smoke continues to pollute skies in the western United States. On some recent days, the air quality in Portland, Seattle, San Francisco and Los Angeles has been so hazardous, it’s ranked among the worst in the world. 
It’s hard to predict when the smoke will fully clear. And with some parts of the West  having faced a week or more of extremely polluted air, the unusual, sustained nature of the assault is increasing worries about people’s health.
There’s plenty of evidence that air pollution — a broad category that includes soot, smog, and other pollutants from sources such as traffic, industry and fires — can harm health. The list of medical ailments associated with exposure to dirty air includes respiratory diseases, cardiovascular disease and diabetes (SN: 9/19/17).
Most of what’s known about the hazards of wildfire smoke has to do with particulate matter, the tiny bits of solids and liquids in polluted air. Wildfires are especially good at producing particles in a size range that can be dangerous to health. It isn’t clear yet if what fuels wildfire smoke — be it vegetation, a mix of trees and structures, or other human-made sources — affects the toxicity of particulate matter.
A growing body of evidence points to a range of risks to health during or soon after wildfires, such as increased trips to the emergency room for chronic lung conditions. But there are many more questions than answers about the long-term risks for people struggling to cope with day upon day of polluted air, and facing longer and fiercer fire seasons each year due to climate change (SN: 8/27/20).
Science News spoke with scientists about what’s in the air, the health risks and what more we need to learn.
What’s in wildfire smoke?
Wildfire smoke is a complex mixture of gases and particles that is similar to cigarette smoke but without the nicotine, says physician John Balmes of the University of California, San Francisco, who studies the effects of air pollution on health. “It has the same kind of mixture of nasty small particles and irritant gases.”
The precise chemical makeup of the smoke varies by fire. It depends on “the type of fuel burned — including structures, intensity of the fire, atmospheric mixing, and distance or age of smoke,” says Tania Busch Isaksen, who studies public health effects of wildfire smoke at the University of Washington in Seattle.
“Generally speaking, it’s a mixture of carbon dioxide, carbon monoxide, nitrogen oxides, particle matter — fine to coarse — hydrocarbons and other organic compounds,” she says. “Fine particulate matter, PM2.5, is what we are primarily concerned about when we consider impacts on health” (SN: 7/30/20).
Those particles are 2.5 micrometers across or smaller, or about one-thirtieth the width of a human hair (SN: 8/22/18). Common in air pollution produced not only by wildfires, but also by power plants and cars, these particles are so tiny that they can be inhaled deeply into the lungs. There, they can trigger inflammation and possibly seep into the bloodstream.
Can you see how much PM2.5 is in the air?
No. These particles are so tiny and difficult to see that “even if the air seems clear, PM2.5 could be at levels that are dangerous,” says Perry Hystad, an environmental epidemiologist at Oregon State University in Corvallis. In the United States, the most reliable gauge of PM2.5 is the Air Quality Index, or AQI, which is based on data from air quality monitoring stations that measure the concentrations of pollutants in the air.
The U.S. Environmental Protection Agency developed the index to grade levels of common air pollutants, such as ozone, PM2.5  and carbon monoxide. On a scale from 0 to 500, higher numbers indicate dirtier air. The EPA assigns AQI scores to different types of pollution based on studies of each contaminant’s health effects.
The EPA considers scores up to 100 — indicating an average 35.4 micrograms of particulate matter per cubic meter of air over 24 hours  — generally safe. Scores from 101 to 200 may pose particular risk to people in sensitive groups, such as children and those with heart or lung diseases. Those people are advised to limit or avoid prolonged or vigorous outdoor activity. Above 200, everyone should cut down on physical activity outside. At scores 300 or above, with at least 250.4 micrograms of PM2.5 per cubic meter of air, everyone should avoid going outside.
Smoke blanketing the western United States has created hazardous, and at times off-the-chart, levels of pollution in many places. For instance, on the morning of September 17, areas of Oregon near Portland showed PM2.5 AQI levels up to around a hazardous 380. In regions of central California northeast of Fresno, AQI levels reached a staggering 780.
“Especially under conditions that we’re experiencing here in the western United States, it would be wise to check the AQI on a daily basis,” says Kent Pinkerton, a biologist at University of California, Davis.

What happens when people breathe in wildfire smoke?
“Wildfires, through the combustion process, create lots and lots of particles” in the size range of PM2.5, says Colleen Reid, an environmental epidemiologist and health geographer at the University of Colorado Boulder. A breath of these microscopic particles can send them all the way to the alveoli, the tiny sacs where the lungs and the blood swap oxygen and carbon dioxide.
Research in lab dishes has found that the particles can lead to inflammation and oxidative stress, in which reactive molecules that contain oxygen build up and can damage cells. The smallest pollution particles may make their way into the bloodstream, possibly causing harm to the cardiovascular system.
The research linking PM2.5 with health generally does not consider what types of materials are burning, so “at this point we are concerned about all PM2.5 regardless of source,” says Anthony Wexler, who studies particulate pollutants at the University of California, Davis. “But the source is likely important.”
Historically, wildfires have burned mostly plant matter. But many of the recent devastating fires in the western U.S., such as the Camp Fire that destroyed the town of Paradise, Calif., in 2018, have devoured human-made structures (SN: 11/15/18). “Houses have paint and solvents and plastics and all this other terrible stuff going up in smoke, too, which may be increasing the toxicity of the material that’s being emitted,” says Wexler. He is currently preparing an experiment to compare the toxicity of the smoke from burnt household materials with that from woody materials.
The impact of extended exposures to wildfire smoke also needs more research. Wildfires put a lot of pollution into the air, more than what’s generally produced from industrial and traffic sources, Reid says. But it’s often for a short period of time. “What’s going on right now in Oregon and Washington and California, where they’ve had essentially a week of very unhealthy levels of air pollution, is less common,” she says.
Recent fires in the western United States have consumed not only trees but many buildings like this one, in Butte County, Calif., which went up in flames on September 9. Some researchers are concerned that plastics and other materials in homes may make smoke more toxic.Noah Berger/Associated Press
What are the immediate health risks from wildfire smoke?
Breathing in smoky air can irritate the respiratory tract, leading to coughing, sore throats and itchy, watery eyes. The foul air can also cause headaches and fatigue.
Hospital visits for lung care go up during wildfires compared to periods without them, according to studies of emergency department traffic. For instance, an increase in PM2.5 exposure related to wildfires in northern California in 2008 was associated with an increase in risk for emergency department visits and hospitalizations for asthma, Reid and colleagues reported in Environmental Research in 2016. The 2012 wildfires in Colorado were linked to a rise in emergency department visits for asthma and chronic obstructive pulmonary disease, according to a 2016 study in Environmental Health. There’s some evidence of increased trips to the hospital for cardiovascular health problems during wildfires as well.
Medical visits for kids go up during wildfires too. During the 2017 Lilac Fire in San Diego county, visits for respiratory problems to a children’s hospital rose due to increased exposure to PM2.5, according to a 2020 study in the Annals of the American Thoracic Society.
Children, especially the very young and those with diseases like asthma, can be more vulnerable to health effects from wildfires. “They breathe more air per minute compared to adults” to meet their physiological needs, says Marissa Hauptman, a pediatrician at Boston Children’s Hospital. That can add up to more exposure. And developing lungs “are more susceptible to injury,” she says. 
A developing fetus may also be at risk from exposure to PM2.5. In a 2012 study in Environmental Health Perspectives, Reid and colleagues reported a slight decrease in birth weight for infants from pregnancies that occurred during the 2003 wildfires in Southern California. Mothers exposed to smoke from Colorado wildfires during the second trimester were more likely to give birth prematurely, according to a 2019 study in the International Journal of Environmental Research and Public Health. Infants born early or smaller than usual can face developmental delays.
What’s known about long-term health risks from wildfire smoke?
Not much. But a few studies provide some initial clues.
One examined how wildfires that scorched large areas of Indonesia in 1997 impacted health 10 years later. This population-wide study found that males and the elderly were worse off in 2007 for health measures such as lung function, the researchers reported in Economics & Human Biology in 2017.
In the United States, the wildfire smoke that plagued the Seeley Lake community in Montana in 2017 has parallels to the prolonged, hazardous exposures happening now in the West. The wildfires produced extremely high levels of PM2.5 from July 31 to September 18 that year; the daily average was 221 micrograms per cubic meter of air. Christopher Migliaccio, a respiratory immunology researcher at the University of Montana in Missoula, and his colleagues screened adults in the community right after the last day of increased smoke and two more times in each of the following two years.
Compared with members of a Montana community that hadn’t been exposed to the same levels of smoke, the participants from the Seeley Lake area had poorer lung function one and two years out, Migliaccio and his colleagues reported in Toxics in August. “I thought people might be worse right after,” he says, “but it’s a little bit of a delayed response.”
Migliaccio and colleagues had planned to screen the participants again this year, but COVID-19 got in the way. Eventually they hope to see whether, in participants that still have worse lung function, the condition is treatable or if it’s “the new normal.”
Can a mask protect you from wildfire smoke?
It depends on the type of mask. “Cloth masks, which are effective at preventing transmission of SARS-CoV-2 [the virus that causes COVID-19] … don’t do anything to protect the wearer from exposure to wildfire smoke,” Balmes says (SN: 6/26/20). Surgical masks provide some protection. But “an N95 is the best protection.” N95 masks are designed to filter out at least 95 percent of airborne particles.
But N95 masks are in short supply, and those masks have not been certified for use by children as they don’t fit properly. So the best protection is to avoid exposure. “People should stay indoors as much as possible with the windows closed,” Balmes says.

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How can people keep indoor air clean?
“If they have central ventilation, they should turn that to recirculation,” Balmes says. That can reduce the amount of smoke that enters the home. People can also use a High Efficiency Particulate Air, or HEPA purifier to smoke-proof a single room. And those who cannot afford a HEPA cleaner can put together a makeshift purifier using a MERV-13 furnace filter and a box fan, Balmes says. “They’re not as good as the proper devices, but they do provide some protection.”
People hunkered down indoors can also keep the air clear by not burning gas stoves or candles, or even vacuuming — which can stir up particles inside the home.
But some people don’t have a home to escape to. King County in Washington announced on September 11 the opening of a clean air shelter for people experiencing homelessness.
How else might wildfires be harming health?
The toll that the wildfires have on mental health could also be significant. The past month in the Pacific Northwest has brought images reminiscent of a science fiction novel: hazy, deep orange skies that sometimes completely obscured the sun, turning day to night.
Extreme wildfires, with the potential for long periods of time in which the air is a danger, can upend people’s lives and add to stress levels. One of the few respites to the COVID-19 pandemic — going out for a breath of fresh air — has been shut off for millions of people. And there are many that have no choice but to work or live outdoors, exposed to hazardous air. “There could be a psychological impact of that,” says Reid. “That needs to be explored.” More

Pollution can play havoc with pollinators’ favorite flower smells. But one kind of moth can learn how to take to an unfamiliar new scent like, well, a moth to a flame.
Floral aromas help pollinators locate their favorite plants. Scientists have established that air pollutants scramble those fragrances, throwing off the tracking abilities of such beneficial insects as honeybees (SN: 4/24/08). But new lab experiments demonstrate that one pollinator, the tobacco hawkmoth (Manduca sexta), can quickly learn that a pollution-altered scent comes from the jasmine tobacco flower (Nicotiana alata) that the insect likes.
That ability may imply that the moth can find food and pollinate plants, including crucial crops, despite some air pollution, researchers report September 2 in the Journal of Chemical Ecology. Scientists already knew that some pollinators can learn new smells, but this is the first study to demonstrate an insect overcoming pollution’s effects on odors.
Chemical ecologist Markus Knaden and colleagues focused on one pollutant — ozone, the main ingredient in smog. Ozone reacts with flower aroma molecules, changing their chemical structure and therefore their fragrance.

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In Knaden’s lab at the Max Planck Institute for Chemical Ecology in Jena, Germany, his team blew an ozone-altered N. alata scent from a tiny tube into a refrigerator-sized plexiglass tunnel, with a moth awaiting at the far end of the tunnel. Usually, when the moth smells the unaltered floral fragrance, it flies upwind and uses its long, skinny mouthparts to probe the tube the way that it would a blossom.
The researchers expected that the modified scent might throw the moth off a little. But the insect wasn’t attracted at all to a flower aroma exposed to levels of ozone that are typical on some hot, sunny days.
In addition to scent, tobacco hawkmoths track flowers visually, so Knaden’s team used that trait, along with a sweet snack, to train the moth to be attracted to a pollution-altered scent. The researchers wrapped a brightly-colored artificial flower around the tube to lure the moth back across the tunnel, despite the unfamiliar aroma. And the team added sugar water to the artificial flower. After a moth was given four minutes to taste the sweet stuff, it was attracted to the new smell when sent into the tunnel 15 minutes later, even when neither the sugar water nor the visual cue of the artificial flower was present. 
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In the lab, researchers showed that tobacco hawkmoths can learn to drink from a fake flower whose scent has been scrambled by pollution. To train the moths to accept the altered scent, a visual cue — dressing up a tube emitting a fouled bouquet as an artificial flower — attracts the moth, and a sugar-water reward teaches the insect that it’s worth a return trip.
Still, in an ozone-polluted environment in the wild, tobacco hawkmoths would have to be close enough to a tobacco flower to see it to learn its altered scent, and Knaden isn’t sure how often that will occur. The moths are difficult to observe in nature because they feed at twilight and are fast flyers.
“This study is a clarion call to other scientists” to examine whether and how different pollinators might also adapt to human-driven changes to their environment, says chemical ecologist Shannon Olsson of the Tata Institute of Fundamental Research in Bangalore, India, who wasn’t involved with the work.
Although the results suggest that some adaptation by insects to pollution is possible, Knaden is cautious about being too optimistic. “I don’t want the take-home message to be that pollution is not a problem,” he says. “Pollution is a problem.”
This study focused on only one moth species, but Knaden’s team is now working on planning experiments with other pollinators that are easier to follow than tobacco hawkmoths. While he suspects honeybees might also be as adaptable as the moth was, that won’t be true of every pollinator. “The situation can become very bad for insects that are not as clever or cannot see that well.” More

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