Wednesday, February 19, 2020

Emergency Recovery Plan could halt catastrophic collapse in world's freshwater biodiversity

by WWF

With biodiversity vanishing from rivers, lakes and wetlands at alarming speed, a new scientific paper outlines an Emergency Recovery Plan to reverse the rapid decline in the world's freshwater species and habitats—and safeguard our life support systems.

Published today in BioScience, the Emergency Recovery Plan calls for the world to take urgent steps to tackle the threats that have led to an 83% collapse in freshwater species populations and the loss of 30% of freshwater ecosystems since 1970—ecosystems that provide us with water, food, livelihoods, and protection from floods, droughts and storms.

Developed by a global team of scientists from WWF, International Union for Conservation of Nature (IUCN), Conservation International, Cardiff University and other eminent organizations and academic institutions, this is the first comprehensive plan to protect and restore freshwater habitats, which host more species per square kilometer than land or oceans—and are losing this extraordinary biodiversity two or three times faster.

The six-point plan prioritizes solutions that are rooted in cutting edge science and have already proven successful in certain locations: letting rivers flow more naturally, reducing pollution, protecting critical wetland habitats, ending overfishing and unsustainable sand mining in rivers and lakes, controlling invasive species, and safeguarding and restoring river connectivity through better planning of dams and other infrastructure.

Critically, with governments meeting in November to agree on a new global deal to conserve and restore biodiversity at a landmark conference of the Convention on Biological Diversity, the authors recommend some new targets, including on restoring water flows, controlling illegal and unregulated sand mining in rivers, and improving management of freshwater fisheries that feed hundreds of millions of people.

"Nowhere is the biodiversity crisis more acute than in the world's rivers, lakes and wetlands—with over a quarter of freshwater species now heading for extinction. The Emergency Recovery Plan can halt this decades-long decline and restore life to our dying freshwater ecosystems, which underpin all of our societies and economies," said Dave Tickner, WWF-UK Chief Freshwater Advisor and lead author on the paper.

Covering approximately 1% of the Earth's surface, rivers, lakes and freshwater wetlands are home to 10% of all species and more described fish species than in all the world's oceans. But they are rapidly disappearing with populations of freshwater megafauna—such as river dolphins, sturgeon, beavers, crocodiles and giant turtles—crashing by 88% in the past half century.

"The causes of the global collapse in freshwater biodiversity are no secret, yet the world has consistently failed to act, turning a blind eye to the worsening crisis even though healthy freshwater ecosystems are central to our survival. The Emergency Recovery Plan provides an ambitious roadmap to safeguarding freshwater biodiversity—and all the benefits it provides to people across the world," said co-author, Professor Steven Cooke of Carleton University in Canada.

The Emergency Recovery Plan highlights a variety of measures that together will transform the management and health of rivers, lakes and wetlands, such as treating more than 20% of sewage before it is flushed into nature, avoiding dams on the world's remaining free flowing rivers, and expanding and strengthening protected areas in partnership with local communities.

"All the solutions in the Emergency Recovery Plan have been tried and tested somewhere in the world: they are realistic, pragmatic and they work. We are calling on governments, investors, companies and communities to prioritize freshwater biodiversity—often neglected by the conservation and water management worlds. Now is the time to implement these solutions, before it is too late," said James Dalton, Director of IUCN's Global Water Programme.

"We have the last opportunity to create a world with rivers and lakes that once again teem with wildlife, and with wetlands that are healthy enough to sustain our communities and cities, but only if we stop treating them like sewers and wastelands," said Tickner. "This decade will be critical for freshwater biodiversity: countries must seize the chance to keep our life support systems running by ensuring freshwater conservation and restoration are central to a New Deal for Nature and People."

An 88 percent decline in large freshwater animals

More information: David Tickner et al. Bending the Curve of Global Freshwater Biodiversity Loss: An Emergency Recovery Plan, BioScience (2020). DOI: 10.1093/biosci/biaa002

Uganda army fights voracious desert locusts

by Michael O'hagan

Locusts swarms are threatening food supplies in East Africa, where 12 million are already going hungry

Under a warm morning sun scores of weary soldiers stare as millions of yellow locusts rise into the northern Ugandan sky, despite hours spent spraying vegetation with chemicals in an attempt to kill them.

From the tops of shea trees, fields of pea plants and tall grass savanna, the insects rise in a hypnotic murmuration, disappearing quickly to wreak devastation elsewhere.

The soldiers and agricultural officers will now have to hunt the elusive fast-moving swarms—a sign of the challenge facing nine east African countries now battling huge swarms of hungry desert locusts.

They arrived in conflict-torn South Sudan this week, with concerns already high of a humanitarian crisis in a region where 12 million are going hungry, according to the UN's Food and Agriculture Organization (FAO).

"One swarm of 40 to 80 million can consume food" for over 35,000 people in a day, Priya Gujadhur, a senior FAO official in Uganda, told AFP.

In Atira—a remote village of grass-thatched huts in northern Uganda—some 160 soldiers wearing protective plastic overalls, masks and goggles sprayed trees and plants with pesticide from before dawn in a bid to kill the resting insects.

But even after hours of work they were mostly able to reach only lower parts of the vegetation.

Large swarms of locusts can in a single day consume enough vegetation to feed 35,000 people

Major General Kavuma sits in the shade of a Neem Tree alongside civilian officials as locusts sprayed with pesticide earlier that morning fall around them, convulsing as they die.

An intense chemical smell hangs in the air.

'They surrounded me'

Zakaria Sagal, a 73-year-old subsistence farmer was weeding his field in Lopei village some 120 kilometres (75 miles) away, preparing to plant maize and sorghum, when without warning a swarm of locusts descended around him.

"From this side and this side and this side, they surrounded me," Sagal said, waving his arms in every direction.

"We have not yet planted our crops but if they return at harvest time they will destroy everything. We are not at all prepared."

East Africa's regional expert group, the Climate Prediction and Applications Centre (ICPAC), warned Tuesday that eggs laid across the migratory path will hatch in the next two months, and will continue breeding as the rainy season arrives in the region.

This will coincide with the main cropping season and could cause "significant crop losses... and could potentially worsen the food security situation", ICPAC said in a statement.

Soldiers have been deployed in Uganda to spray trees and savannas in a bid to beat back the infestation

'Panic mode'

Since 2018 a long period of dry weather followed by a series of cyclones that dumped water on the region created "excessively ideal conditions" for locusts to breed, says Gujadhur.

Nevertheless, governments in East Africa have been caught off guard and are currently in "panic mode" Gujadhur said.

The locusts arrived in South Sudan this week after hitting Ethiopia, Somalia, Kenya, Djibouti, Eritrea, Tanzania, Sudan and Uganda.

Desert locusts take over on a dizzying scale.

One swarm in Kenya reached around 2,400 square kilometres (about 930 square miles)—an area almost the size of Moscow—meaning it could contain up to 200 billion locusts.

"A swarm that size can consume food for 85 million people per day," said Gujadhur.

Ugandan authorities are aware that subsequent waves of locusts may pose problems in the weeks to come, but in the meantime they are attempting to control the current generation.

Locust eggs laid across the migratory path will hatch in the next two months, allowing the insects to continue to wreak havoc

Gujadhur is quick to praise the "quite strong and very quick" response from the Ugandan government but is concerned that while the army can provide valuable personnel, a military-led response may not be as effective as is necessary.

"It needs to be the scientists and (agriculture officials) who take the lead about where the control operations need to be and how and when and what time," she said.

'They eat anything green'

The soldiers have been working non-stop for two days, criss-crossing the plains on the few navigable roads, trying to keep up with the unpredictable swarms.

Major General Kavuma recognises that the biggest threat is from the eggs which are yet to hatch but is confident the army will be able to control this enemy.

"We have the chemicals to spray them, all we need is to map the places they have been landing and sleeping," he said.

"In two weeks time we will come back and by that time they will have hatched and that will be the time to destroy them by spraying."

Locusts arrived in South Sudan this week after hitting Ethiopia, Somalia, Kenya, Djibouti, Eritrea, Tanzania, Sudan and Uganda

Back in Lopei village, Elizabeth Namoe, 40, a shopkeeper in nearby Moroto had been visiting family when the swarm arrived.

"When the locusts settle they eat anything green, the animals will die because they have nothing to feed on, then even the people (will suffer)," she said.

"The children will be affected by hunger and famine since all life comes from all that is green. I fear so much."

Locust swarms arrive in South Sudan, threatening more misery

Coronavirus outbreak slashes China carbon emissions: study

The coronavirus outbreak has hit the Chinese economy hard, but also lowered the country's carbon emissions as a result, researchers say

The coronavirus epidemic that has paralysed the Chinese economy may have a silver lining for the environment.

China's carbon emissions have dropped by least 100 million metric tonnes over the past two weeks, according to a study published on Wednesday by the Centre for Research on Energy and Clean Air (CREA) in Finland.

That is nearly six percent of global emissions during the same period last year.

The rapid spread of the novel coronavirus—which has killed over 2,000 and infected more than 74,000 people across China—has led to a drop in demand for coal and oil, resulting in the emissions slump, the study published on the British-based Carbon Brief website said.

Over the past two weeks, daily power generation at coal power plants was at a four-year low compared with the same period last year, while steel production has sunk to a five-year low, researchers found.

China is the world's biggest importer and consumer of oil, but production at refineries in Shandong province—the country's petroleum hub—fell to the lowest level since autumn 2015, the report said.

Economic activity in China usually picks up after the Lunar New Year holiday, which began on January 25.

But authorities extended the holidays this year—by a week in many parts of the country including Shanghai—in an effort to contain the epidemic by keeping people at home.

"Measures to contain coronavirus have resulted in reductions of 15 percent to 40 percent in output across key industrial sectors," the report said.

"This is likely to have wiped out a quarter or more of the country's CO2 (carbon dioxide) emissions over the past two weeks, the period when activity would normally have resumed after the Chinese New Year holiday."

But environmentalists have warned that the reduction is temporary, and that a government stimulus—if directed at ramping up production among heavy polluters—could reverse the environmental gains.

"After the coronavirus calms down, it is quite likely we will observe a round of so-called 'retaliatory pollutions' - factories maximising production to compensate for their losses during the shutdown period," said Li Shuo, a policy adviser for Greenpeace China.

"This is a tested and proven pattern."

Meanwhile, China's nitrogen dioxide emissions—a byproduct of fossil fuel combustion in vehicles and power plants—fell 36 percent in the week following the Lunar New Year holidays, compared with the same period a year earlier, according to another study by CREA that used satellite data.

New obstacles ahead in China's pollution fight: report

Image: International Space Station transits the moon

by European Space Agency

Say cheese.

Amateur astrophotographer Javier Manteca captured the International Space Station as flew in front of the moon on 5 February.

While most eyes were on the change of command ceremony taking place inside the Space Station ahead of ESA astronaut Luca Parmitano's return to Earth, Javier set up his gear to track the Station from the small town of Campo Real in Madrid, Spain.

Using a camera attached to a 150/750 telescope recording at 25 frames per second, Javier captured the 690 millisecond transit on video and composed this image made from 17 stacked frames.

For Javier, this was a moment two years in the making. He posted the image to his Twitter and Instagram, where you can find more of his work.

Luca returned to Earth the day after this photo, on 6 February, ending a record-breaking 201 days in space for his Beyond mission.

Highlights of his mission include four complex sorties that earned him the European record for most cumulative hours spent on spacewalks, remotely operating a rover in the Netherlands from space, and being the first Italian European commander of the Station.

Another European milestone was met this week. The Orion spacecraft that will fly around the moon on the Artemis-1 mission completed thermal-vacuum testing in the world's largest vacuum chamber at NASA's Plum Brook Station in Ohio, U.S..

ESA's contribution to the mission is the European Service Module that will power the vehicle as well as provide electricity, water, oxygen and nitrogen and keep the spacecraft at the right temperature and on course.

From 26 December until 9 February, the spacecraft was subjected to environmental temperatures varying from –175°C to 75°C to give it its first taste of space.

NO BUTTER, NO LEMON, NO WHITE WINE

Half a million mussels cooked to death at a New Zealand beach

Business Insider•February 15, 2020

New Zealand resident Brandon Ferguson discovered over 500,000 dead mussels and shells when he went walking along the shores of the Maunganui Bluff Beach in the country's North Island.

Ferguson told Business Insider that he had witnessed this type of event on the same beach in the past, with different types of shellfish washing up dead along the shores.

One expert said the mussels had essentially cooked to death due to hot weather and mid-day low tides.

Ferguson shared a video of the experience in the hopes that the global community would take notice of the effects of climate change happening right outside his doorstep.

steamed mussels

Shutterstock/135pixels

Hundreds of thousands of mussels cooked to death in New Zealand due to rising temperatures in New Zealand's oceans.

New Zealand resident Brandon Ferguson posted a video on Facebook from Maunganui Bluff Beach, located on the country's North Island, showing hundreds-of-thousands of dead mussels that had washed up on the shore.

Ferguson told Business Insider that he happened upon the sight while out with friends and family last week.

"I'm local to the area so I'm always out on 'the coast' gathering food for the family," he said. "That day I was out with friends and family while they were fishing. We waited for the tide to turn so we could gather mussels."

But instead, Ferguson saw hundreds of thousands of green-lipped mussels that had turned up dead.

"It smelled like dead rotting seafood," Ferguson said. "Some of the mussels were empty, some of them were dead ... Some were just floating around in the tide."

"There were well over 500,000 mussels and shells littering the coastline."

Mussels that washed up on the Maunganui Bluff Beach in Aranga, New Zealand.

Brandon Ferguson

Ferguson said that he had witnessed this type of event on the same beach in the past, with different types of shellfish washing up dead along the shores. He blamed rising temperatures and warming sea waters for the phenomena.

"It has happened in the past due to warm water temperatures, low mid-day tides, and high pressures," he said.

A 2019 report from the New Zealand government supports Ferguson's theory — climate change has been warming sea temperatures, devastating the country's native marine plants, animals and habitats.

According to the report, between 1981 and 2018, overall sea-surface temperatures across New Zealand's four oceanic regions, including Chatham Rise, the Tasman Sea, subtropical, and subantarctic increased between 0.1 and 0.2 degrees Celsius per decade.

"New Zealand's oceans act like a giant sponge against the effects of climate change," New Zealand's Secretary for the Environment Vicky Robertson wrote in the report. "It's likely our seas take up more carbon dioxide than our forests, but there is only so much they and the life in them can take – and the limits aren't yet known."

Robertson explained that the warmer the water gets, the less able it is to absorb greenhouse gases like carbon dioxide, which have been increasingly released into the atmosphere and have a strong impact on climate change.

"The growth of species in the oceans is affected, and coastal communities and habitats are at risk from flooding and sea-level rise," Robertson said.

In December, a 386,000-square-mile chunk of the Pacific Ocean east of New Zealand rose about 10 degrees Fahrenheit warmer than average, threatening the survival of fish and coral in the region.

Andrew Jeffs, a marine scientist at the University of Auckland, told the New Zealand Herald that the mussels in Ferguson's video likely died from "heat stress" brought on by hot weather and mid-day low tides.

"The mussels die of heat stress. You imagine lying in the midday sun every day for four hours for the best part of a week. You'd be pretty sunburnt at the end of that," he told The Herald.

Jeffs added the stark prediction that soon the mollusks may disappear entirely from New Zealand as temperatures continue to rise.

"In many other countries, we are seeing poleward movement of the distribution of the species as they adjust to temperature increases associated with climate change," he told the Herald. "I expect we may see the same in New Zealand."

Ferguson said he shared his video in the hopes that the global community would take notice of the effects of climate change happening right outside his doorstep.

"It's getting worse and worse every year," he told Business Insider. "At times like this we should wake up and start respecting these places and pay attention to what is happening before we lose our 'taonga' [a Māori word meaning 'treasure'] for good."

He says he is "heartbroken" to see the native sea life in his hometown disappear, and says he fears for the extinction of the species in the country.

"I fear that our next generation is going to miss out," he said. "Thats what hurts me the most."

Mussels 'cooked alive' in balmy New Zealand ocean

Mussels are sensitive to pollution and temperature change

Up to half a million mussels were effectively cooked in the wild in unusually balmy waters on the New Zealand coast in a massive "die-off" that marine experts have linked to climate change.

The dead molluscs were found by Auckland man Brandon Ferguson earlier this month at Maunganui Bluff Beach, near the northern tip of the North Island.

Footage posted to social media shows a stunned Ferguson wading through rockpools choked almost knee-deep with mussel shells remarking "they're all dead... there's nothing left".

Professor Chris Battershill, a marine ecologist at Waikato University, said there had been similar die-off in recent years involving tuatua cockles and clams.

"The common denominators seem to be really hot conditions with lots of sunlight and unusually calm waters for an extended period," he told AFP.

"This leads to a combination of heat stress and the animals running out of oxygen because the water's so still. They eventually succumb... they're effectively cooked alive."

Battershill the extreme conditions were unusual.

"Is it related to climate change, I think it is," he said.

"Mussels are hardy little animals—you think about when they're harvested they survive in the supermarket with just a little water on them.

"So it's taken extreme conditions to kill them. And when you have a number of die-offs in recent years involving a number of species then you really need to sit up and take notice."

University of Auckland marine scientist Andrew Jeffs said more mass die-offs were likely to occur as a result of climate change.

He said mussel populations would eventually move to cooler waters as temperatures rose.

"I am expecting that it is likely to ultimately result in the displacement of mussel beds from shores in northern parts of the country with them continuing to be found further south," he told AFP.

Australia's got mussels (but it could be a problem)

Researchers uncover the genetics of how corn can adapt faster to new climates

by University of Delaware

Maize is a staple food all over the world. In the United States, where it's better known as corn, nearly 90 million acres were planted in 2018, earning $47.2 billion in crop cash receipts.

But, under the effects of climate change, this signature crop may not fare so well. As the world tries to feed a population skyrocketing to nine billion by 2050, that has major implications. So, what can we do about it? The answer might be exotic.

A multi-institutional team led by University of Delaware plant geneticist Randy Wisser decoded the genetic map for how maize from tropical environments can be adapted to the temperate U.S. summer growing season. Wisser sees these exotic varieties, which are rarely used in breeding, as key to creating next-era varieties of corn.

The research team included scientists from UD, North Carolina State University, University of Wisconsin, University of Missouri, Iowa State University, Texas A&M University and the U.S. Department of Agriculture-Agricultural Research Service. The resulting study, highlighted by the editorial board of Genetics, provides a new lens into the future viability of one of the world's most important grains.

"If we can expand the genetic base by using exotic varieties, perhaps we can counter stresses such as emerging diseases and drought associated with growing corn in a changing climate," said Wisser, associate professor in UD's Department of Plant and Soil Sciences. "That is critical to ensuring ample production for the billions of people who depend on it for food and other products."

Modern maize strains were created from only a small fraction of the global maize population. This limited infusion of diversity raises concerns about the vulnerability of American corn in a shifting climate. The U.S. Department of Agriculture (USDA) seed bank includes tens of thousands of varieties, but many are just not being used.

"We know that the tropical maize varieties represent our greatest reservoir of genetic diversity," said study co-author Jim Holland, a plant geneticist with the USDA Agricultural Research Service at North Carolina State. "This study improved our understanding of those genetics, so we can use this information to guide future breeding efforts to safeguard the corn crop."

Certain exotic strains of maize better handle drought or waterlogging or low-nitrogen soil, for example. But because these strains have evolved outside the U.S., they are not immediately suited to states like Delaware. So, exotics first need to be pre-adapted.

In prior work, Wisser and his colleagues showed how 10 years of repeated genetic selection was required to adapt a tropical strain of maize to the temperate U.S. Co-author Arnel Hallauer spent a decade adapting the population through selective breeding, so it could flourish in an environment like Delaware.

"What's so cool now is that we could go back to the original generations from Dr. Hallauer and grow them side by side in the same field," Wisser said of the first-of-its-kind experimental design. "This allows us to rule out the influence of the environment on each trait, directly exposing the genetic component of evolution. This has opened a 'back to the future' channel where we can redesign our approach to developing modern varieties."

While extremely impressive, a decade to adapt exotic maize to new environments is a lot of time when the climate change clock is ticking.

"Unfortunately, this process takes 10 years, which is not counting ongoing evaluations and integrating the exotic variations into more commonly used types of maize," Wisser said. "With the climate threats we face, that's a long time. So, gaining insights into this evolutionary process will help us devise ways to shorten the time span."

Accelerating adaptation

Wisser isn't wasting any time as he explores ways to bolster corn's ability to survive and thrive. He and Holland are working on a new project to cut that time span in half.

In cutting-edge research funded by the U.S. Department of Agriculture's National Institute of Food and Agriculture, the team is analyzing how corn genomes behave in a target environment as they aim to formulate a predictive model for fitness.

"What we're doing is sequencing the genomes and measuring traits like flowering time or disease for individuals in one generation. From this, we can generate a lookup table that allows us to foresee which individuals in the next generation have the best traits based on their genetic profiles alone," Wisser said. "And our lookup table can be tailored to predict how the individuals will behave in a particular environment or location like Delaware."

That means plant breeders could grow a second generation of corn anywhere outside of Delaware, but still predict which individuals would be the most fit for Delaware's environment.

"For instance, even if the plants are grown at a location where a disease is not present, our prediction model can still select the resistant plants and cross them to enrich the genes that underlie resistance," Wisser said.

With this approach, researchers don't have to wait out a Delaware winter, so they can continue to pre-adapt the population for at least one extra generation per year. That's how 10 years of selective breeding for pre-adaptation could become five, providing a quicker route to access exotic genes.

This new effort connects to the Genomes To Fields (G2F) Initiative, developed in 2013 for understanding and capitalizing on the link between genomes and crop performance for the benefit of growers, consumers and society.

If Wisser and Holland can develop a method to rapidly pre-adapt exotics, this opens a lane for G2F to test the impact of these unique genomes on crop performance.

"Our goal is to advance the science so breeders can draw on a wider array of the diversity that has accumulated across thousands of years of evolution," explained Wisser, who has been involved in the public-private initiative since its beginning. "In turn, they can produce improved varieties for producers and consumers facing the challenges of climate change."

Researcher seeks holistic understanding of disease resistance in maize

More information: Randall J. Wisser et al. The Genomic Basis for Short-Term Evolution of Environmental Adaptation in Maize, Genetics (2019). DOI: 10.1534/genetics.119.302780

Predicting 50,000 years of bird migrations

by Yale University

Neither wind, nor rain—nor massive sheets of ice—have kept Earth's birds from their appointed rounds of migrating to better climes, according to a new study.

That's the conclusion of a new study from the Max Planck-Yale Center for Biodiversity Movement and Global Change (MPYC), which simulated global bird migrations during scenarios of past climate conditions. The researchers said that, in the Americas in particular, migrating birds successfully maneuvered vastly changing landscapes in the past 50,000 years.

"Our simulations predict that bird migration worldwide has remained relatively constant over this period, suggesting an origin for this phenomenon that is older than the glacial cycles of recent Earth history," said first author Marius Somveille, a former MPYC researcher who is starting a postdoctoral position at Colorado State University.

Yet there has been regional variation in migrating birds' response to climate change, the researchers said. In the Americas, for example, there has been a larger increase in the distances that birds have migrated over the past 50,000 years, compared with other parts of the world.

"In the last ice age, up to about 18,000 years ago, North America had an ice sheet that covered a large part of the continent and prevented bird species from living there," said Yale's Walter Jetz, senior author of the study, professor of ecology and evolutionary biology, and co-director of MPYC.

"This ice sheet retreated and birds colonized the land—and those birds were likely highly migratory, as seasonality in this area was pronounced. Our simulations suggest that toward the present this part of the world has seen both migratory distances and migration activity significantly increase," he said.

The study appears in the journal Nature Communications.

Using existing data about the global distribution of migratory birds, the researchers created a model that predicted migrations based on energy efficiency: They positioned each species' breeding and non-breeding ranges in a way that accounted for the availability of food and how much energy birds would reasonably expend during migration.

To estimate migration activity far in the past, the researchers applied their model to reconstructions of past climate conditions.

Co-author and MPYC co-director Martin Wikelski of the Max Planck Institute of Animal Behavior said the findings may be of use to conservationists and policymakers because the simulations "have the potential to inform predictions of how future climate change will impact bird migrations."How will the winds of climate change affect migratory birds?

More information: Marius Somveille et al. Simulation-based reconstruction of global bird migration over the past 50,000 years, Nature Communications (2020). DOI: 10.1038/s41467-020-14589-2

Eating junk food found to impair the role of the hippocampus in regulating gorging

by Bob Yirka , Medical Xpress

A team of researchers from Australia, the U.S. and the U.K. has found that eating junk food can alter the ability of the hippocampus to constrain junk food intake. In their paper published in the journal Royal Society Open Science, the group describes experiments they conducted with volunteers and their eating habits, and what they learned from them.

Most of the western world has learned of the dangers of eating junk food—it leads to overeating, obesity and a host of health problems. But scientists are still trying to figure out why people have such a difficult time stopping themselves from eating junk food. In this new effort, the researchers enlisted 110 volunteers in their early 20s who had a history of healthy eating to learn what happens to the body after one week of junk food consumption.

Half of the volunteers ate as they normally did for a week; the other half ate junk food—specifically, meals high in fat, carbs and sugar. After the week was over, all of the volunteers were invited to eat breakfast together in a lab setting. Each of the volunteers was given a memory test before and after eating, along with a survey that queried them on how much they enjoyed eating the food they had been consuming over the course of the study week.

The memory tests revealed lower scores for the volunteers after eating junk food for a week. But more importantly, they also showed hippocampus impairment directly after eating a single junk food meal. Prior research has shown the hippocampus plays a role in regulating eating—but it was not able to do its job properly after a volunteer ate a plate of Belgian waffles. And because of that, the volunteers were not signaled to stop eating once they were full. Instead, they gorged. And after a week of gorging, the volunteers retained memories of the pleasures of gorging while forgetting those of less pleasurable foods. The result was difficulty in refraining from eating junk food.

How to get on track when weekend eating is your downfall

More information: Richard J. Stevenson et al. Hippocampal-dependent appetitive control is impaired by experimental exposure to a Western-style diet, Royal Society Open Science (2020). DOI: 10.1098/rsos.191338

Researchers discover new mechanism for the coexistence of species

by AMOLF

Researchers from the AMOLF institute in Amsterdam and Harvard have shown that the ability of organisms to move around plays a role in stabilizing ecosystems. In their paper published 19 February 2020 in Nature, they describe how the competition between 'movers' and 'growers' leads to a balance in which both types of bacteria can continue to exist alongside each other.

We are all too familiar with the threats to our planet's ecosystems: global warming, forest fires, nitrogen deposition, biodiversity decline, and even mass extinctions. But what actually makes ecosystems stable or fragile? What prevents one species from outcompeting all others, and hence driving them to extinction?

These questions have captivated biologists since Darwin. We have learned that food webs and cooperation between species are key pieces to this puzzle, because they help explain how species depend on one another to survive. Now, a group of biophysicists from the Netherlands and the U.S. have advanced a startling finding: The active movement of organisms can also drive ecosystem diversity and stability through a remarkably simple mechanism that does not require food webs or cooperation.

"Movement is fundamental to essentially all organisms—even plants move by seed dispersal," says Sander Tans at the AMOLF institute in Amsterdam. "Bacteria are well known to move actively. Our experiments show how this movement can keep different bacterial species, typically called strains, together in a larger population. There is a rich literature on the possible roles of movement in such coexistence of species, but direct experiments that can exclude other explanations were lacking.

The coexistence paradox—what prevents extinctions in a competitive world?

To find bacterial species that might form a minimal stable ecosystem in the lab, the Ph.D. student Sebastian Gude took two species (also called strains) from the gut of the same animal. If both survived there, perhaps they would also do so in his experiments. To follow their competition, he colored one blue and the other red. However, all his first attempts failed in the beginning. One of the two strains always lost the competition when grown together, with these bacteria always producing fewer offspring than the other. This blue 'loser' strain would thus become outnumbered by the red 'winner' strain, and was ultimately driven to extinction.

Gude's luck took a dramatic upturn, however, when he changed the design of the experiment. He took the sugary liquid in which the bacteria normally grew, and turned it into a gel reminiscent of a jelly desert. When the blue 'loser' bacteria growing on the gel became outnumbered by the reds, they started to produce more offspring than the reds, and were thus winning. But in turn, the reds also became more competitive when rare. In this way, both strains escaped extinction, and hence coexisted together. These results underscore the fundamental paradox of the coexistence debate: What causes losers that are close to extinction to suddenly start winning?

Getting territorial

To resolve this conundrum, Gude followed the competition by making movies. "The results were quite striking," says Tom Shimizu. "We saw the populations migrating into the gel like a wave, where they multiplied using the sugars they encountered. Initially, red dominated the expansion and blue was barely seen. But then the red advance suddenly stopped just when the blues emerged, and were seen to overtake the reds' front, where they formed a thin layer. After that, the wave was blue only. The blue bacteria could thus proliferate alone in the deeper regions of the gel, freed from competition from the reds that could not reach that far. This also explained the coexistence: Whenever blue were rare, they could build up their population in the deeper regions of the gel."

Should I spread or should I grow?

But how did the blue bacteria organize themselves and efficiently confine the red? Did they signal to each other or secrete toxins, as is known for some bacteria? In trying to address these questions the team discovered a rather different mechanism. The blue bacteria were indeed worse at proliferating, as they lost in a direct competition. But they compensated by migrating faster. By reaching the farther regions first, they could finish the local sugars. Hence, they gave the red no chance there, and could thus block their advance, a bit like in a scorched earth strategy.

Tans: "Some bacteria apparently are good at proliferating, and others at migrating. But they cannot excel at both. This makes sense because both activities cost a lot of energy. Such specialization is often observed, though effects on coexistence are often difficult to prove. Here we could manipulate the capacity to migrate and proliferate by genetic engineering, and show it alone is enough for coexistence. Other mechanisms like exchanging toxins or dependencies like in food webs are thus not required per se."

Disturbance ecology

Of course, in the real world, bacteria cannot count on encountering bowls of Jello left out of the fridge. Luckily for them, they don't need to, as pristine pastures of fresh nutrients do arise more often than expected. Much like the vegetation that colonize cleared soil after forest fires, many bacteria grow on patches of resources, from fallen fruits to decomposing animals, or—for those microbes that inhabit your gut—the lunch you just had.

Shimizu says, "We demonstrated this migration-proliferation mechanism in motile bacteria. But what we found is for instance evocative of models of plant ecology where fast-growing plants compete with plants that invest more in spreading their seeds." He added that there is a lot to be learned about more complex scenarios. "There is a lot of interest in explaining the diversity of bacteria in the human gut, which we now know, thanks to modern DNA analysis, is intimately related to our health. Our findings suggest that looking at motility genes and their spatial distribution within the gut might help explain some of that diversity."

Genetic redundancy aids competition among bacteria in symbiosis with squid

More information: Bacterial coexistence driven by motility and spatial competition, Sebastian Gude, Erçağ Pinçe, Katja M. Taute, Anne-Bart Seinen, Thomas S. Shimizu, and Sander J. Tans, Nature 2020, DOI: 10.1038/s41586-020-2033-2

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