A new study suggests that plants won’t save us from global warming
News and notes about science
The last time the atmosphere contained as much carbon dioxide as now, dinosaurs roamed what was a verdant landscape. The Earth’s lushness was at least partly caused by the abundance of CO2, which plants use for photosynthesis. That has led to the idea that more CO2 in the atmosphere could create a literally greener planet.
Today, plants and soil around the world absorb roughly a quarter of the greenhouse gases that humans release into the atmosphere, helping the Earth avoid some of the worst effects of climate change. In an ideal situation, as levels of carbon dioxide increased, plants would soak up more of these emissions, helping to fuel their growth.
But in a recent study published in the journal Nature, researchers found that under a warming climate, rather than absorbing more greenhouse gas emissions, plants and soil may start absorbing less, accelerating the rate of change.
“We have this image of the planet getting very, very green as we move into the future,” said Pierre Gentine, an environmental engineering professor at Columbia University and an author of the study. “But it may be the opposite.”
Researchers know that atmospheric concentrations of carbon dioxide increase in dry years, a sign the Earth is absorbing fewer emissions.
When the soil is dry, plants are stressed and cannot absorb as much CO2 to perform photosynthesis. At the same time, because dry conditions are often accompanied by warm temperatures, microorganisms in the soil, which are more productive when it’s warm, release more CO2.
As the climate changes, there will be more years of extreme weather. That means extreme droughts, followed by years of heavier than normal rainfall, will become more likely. The researchers wondered if those conditions would balance out.
To check, they ran four different climate simulations and used satellite observations. The goal was to see the effect that soil moisture had on Earth’s ability to absorb greenhouse gas emissions.
Though plants and soil could absorb more CO2 in the wetter years, it did not make up for their reduced ability to absorb CO2 when soil was dry.
Even when a drought year is followed by a year as wet as the previous one was dry, it is not enough to compensate for the dry year. — Kendra Pierre-louis
From morning persons and night owls, an arsenal of DNA
Early to bed and early to rise is a maxim that’s easy to follow for some people and devilishly hard for others.
Now, in a study published recently in Nature Communications, researchers curious about the genetic underpinnings of chronotype — whether you are a morning person, a night owl or somewhere in between — looked at about 700,000 people’s genomes. They identified 351 variations that may be connected to when people go to bed. The study goes on to suggest tantalizing links between chronotype and mental health.
The researchers drew on data from 23andme, the genetic testing company, and the UK Biobank, which tracks hundreds of thousands of volunteer subjects in Britain, about 85,000 of whom wear activity monitors that record their movements.
Those data were key, said Michael Weedon, a bioinformaticist at University of Exeter in England and an author of the new paper; earlier studies had relied only on people’s subjective opinions of whether they were morning people. Using the activity monitors, however, the team was able to confirm that self-reported morning people did go to sleep earlier — and people with the most morning-linked gene variants went to bed 25 minutes earlier than people with the fewest.
The genes flagged in the study play a wide variety of roles in the body.
Many seem to play a role in brain tissues, and others are already known to be central to the body’s circadian rhythm. A few were active mainly in the retina, and the people who possessed an uncommon version of one of these genes had an increased chance of being night owls, said Samuel Jones, a researcher at the University of Exeter and the study’s lead author. That could imply a potential a connection between how the eye responds to sunlight and when a person sleeps.
Another gene was involved in the body’s processing of caffeine and nicotine. Continued study of these and the other genes could provide leads for future work on the biology of sleep timing.
When the researchers crunched the numbers on chronotype’s connection to mental health, they also found that self-identified morning people reported a higher level of general well-being. People in this group also were less likely to report having depression or schizophrenia, in line with epidemiological studies suggesting that evening people struggle with mentalhealth. — Veronique Greenwood
Obesity’s risk at a younger age
The risk of developing obesity-related cancer is increasing in successive generations, along with increasing rates of obesity.
Researchers studied the incidence of 30 of the most common cancers, including 12 that are obesity related, from 1995 to 2014 in people ages 25 to 84 — more than 14.6 million cases. The study is in Lancet Public Health
Using five-year age cohorts, they found that for six of the 12 obesity-related cancers (multiple myeloma, colorectal, uterine, gallbladder, kidney and pancreatic) the risk for disease increased in adults 25 to 49, with the magnitude of the increases steeper with younger age.
For example, compared with people born in 1950, those born in 1985 had a risk of multiple myeloma 59 percent higher, and a risk of pancreatic cancer more than twice as high at comparable ages.
At the same time, incidence decreased for smoking-related and infection-related cancers. The senior author, Ahmedin Jemal, a scientist with the American Cancer Society, said that diet and exercise are of course essential in reducing obesity rates, but that interventions by health care professionals are also needed.
“Primary care physicians should regularly assess body weight,” he said. “Only a third of obese patients actually get a diagnosis of and counseling for obesity.”
— Nicholas Bakalar
Flying squirrels that glow pink in the dark
One spring night in Wisconsin, John Martin, a biologist, was in his backyard with an ultraviolet flashlight. Suddenly, a hot-pink squirrel flew by.
It was a southern flying squirrel, a small, furry creature most active at dawn and dusk. Under most circumstances, it has a warm brown color. But in the beam of Martin’s flashlight, it sported a gaudy DayGlo hue closer to something you might see in a nightclub or a Jazzercise class circa 1988.
“He told his colleagues at Northland College, but of course, everyone was pretty skeptical,” said Allison Kohler, a graduate student at Texas A&M University.
Martin asked Kohler, then a student at Northland, to look into it. After examining more than 100 specimens of flying squirrels across two museum collections and spotting five more squirrels under UV light in the wild, the researchers and their colleagues reported surprising results last week in the Journal of Mammalogy: The pink is real.
Three different species of flying squirrel — including Humboldt’s flying squirrel — turned that color under ultraviolet illumination.
What the flying squirrels get out of it is still a mystery.
Confirming that the squirrels are even capable of seeing in ultraviolet wavelengths will require additional study, Kohler said.
The researchers have some hypotheses concerning what’s behind the squirrels’ Day-glo displays. Ultraviolet rays are abundant during the dawn and dusk periods when the squirrels are moving around. So it is reasonable to expect that the fluorescence is visible to other organisms even when there are no biologists with UV flashlights in the vicinity.
The vivid pink color might have evolved to confuse the owls who prey on the squirrels. Those birds of prey fluoresce in precisely the same hue themselves; a flying squirrel may look, superficially at least, like a flying owl.
Or, if it’s confirmed that the squirrels see UV, the color might have something to do with mating or signaling to other flying squirrels. — Veronique Greenwood
High blood pressure affects the brain
Elevated blood pressure in people under 40 is associated with reduced brain volume, a new study has found. The effect was apparent even in people with blood pressure readings in the range generally considered normal.
The analysis, published in Neurology, included 423 adults between 19 and 40 who had their blood pressure measured and underwent MRI examinations of the brain. Researchers divided the blood pressure findings into categories increasing in four steps from under 120/80 to greater than 140/90.
They found that higher blood pressure readings were directly correlated with lower gray matter volume in several parts of the brain. Even in the groups with pressure within a range widely considered normal — between 120 and 140 systolic (the top number) — brain volumes were smaller compared with those with readings under 120.
Some have assumed that changes in brain volume emerge only in older people and after many years of hypertension, but these results suggest that the changes can begin even in people in their early 20s.
“This is a gradual change that probably happens throughout life, and ends where people have a stroke or cognitive decline,” said the lead author, H. Lina Schaare, a doctoral candidate at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig, Germany. “A blood pressure around 130 in young people is not necessarily benign.” — Nicholas Bakalar