Josh Fisher, Associate Professor of Environmental Science at Chapman’s Schmid College of Science and Technology said, “There is a lot of interest in climate mitigation by restoring those degraded lands with forests and other ecosystems. This study is exactly what is needed to put the idea of ecosystem restoration as a nature-based climate solution into actual practice.”

This study, led by scientists on four different continents, is an assessment of how much of those lands could be restored, the amount of carbon that could be captured from the atmosphere and put into those restored lands (to mitigate climate change), and how much water is required to support those ecosystems. The authors then compared those water requirements to actual and projected future water availability. The findings provide a nuanced understanding of the trade-offs and synergies between carbon sequestration goals and water security, offering an empirical framework to guide the sustainable implementation of ecosystem restoration strategies.

Key Findings

• Their analysis reveals that maximal carbon restoration on global land would lead to a 26% decline in global water availability per capita. In the current period 38 of the 175 countries would experience an over 100% decline, essentially depleting their water resources. Similarly, 20 countries currently without water scarcity would transition into conditions of water scarcity under maximal carbon restoration, especially Australia. Conversely, 58 countries would experience increased water availability per capita. Overall, our results suggest that carbon restoration could adversely impact water security in most countries, particularly in dry regions and densely populated areas.
• As countries delineate their net-zero strategies, the differential trade-offs between carbon storage and water resource management across different climatic, ecological, and societal contexts must be judiciously considered. This study serves as a foundation for more synergistic integration of carbon restoration and water security objectives, guiding policymakers, researchers, and practitioners alike.

This is according to a new study from the University of Michigan’s School for Environment and Sustainability.

“It’s a very worrying confluence that does keep me up,” said Joshua Newell, a professor with the school’s Center for Sustainable Systems and senior author of the study. “The communities that are most at risk of catastrophic flooding are the least prepared and the least likely to get prepared.”

He has termed this three-fold susceptibility “triple exposure.”

The first factor in this exposure is that the Federal Emergency Management Agency has underestimated the flooding risks in many counties across the country. Secondly, markers of social vulnerability, such as low income and mobility limitations, hamper the ability of individuals to take preventative measures, evacuate before floods and recover and rebuild after a flooding event.

Lastly, in certain communities, there’s a pervasive skepticism that climate change is happening at all.

“It’s not just the flooding, it’s not only that it’s affecting socially vulnerable populations, there is also an extra layer of vulnerability in that people are unprepared and unaware of the risk they are facing,” said Dimitrios Gounaridis, a U-M research specialist and co-author of the new report.

Geographically, the team found that triple exposure was most pronounced in Appalachia, an area devastated by flooding following Hurricane Helene. The team’s study was in the final stages of review before its publication when Helene made landfall in the U.S.

“Unfortunately, this paper has become timely,” Gounaridis said.

The areas hit hardest by the floods caused by Hurricane Helene, including Asheville, North Carolina, were just west of the Appalachian triple exposure hotspot the researchers found. But the team said the disaster underscores how dangers become magnified when people don’t fully appreciate their risks.

“Asheville was supposed to be a climate haven,” Newell said — a location that would be insulated from the worst consequences of climate change.

“It’s clear from our paper that it, or at least the region around it, is not. I think this really highlights the need for preparation in these high-risk areas and the urgency of doing that work.”

To identify areas facing triple exposure, the team combined what Gounaridis characterized as dozens of layers of data. That included results from a national Yale University survey on climate attitudes, data from a federal social vulnerability index and household level flood risk estimates from the nonprofit First Street Foundation, which is regarded as more modern and robust than FEMA’s.

This not only revealed areas facing outsized flood risks, but also opportunities to help communities in those regions bolster their preparedness and resilience, said Wanja Waweru, who worked on the project while earning her master’s degree at U-M.

“That could be education campaigns to help folks better understand climate change or policies that help lift people out of poverty so they can have the extra funds in their pockets to evacuate or rebuild after a disaster,” she said.

“I think agencies and organizations in these areas should continue their efforts to help folks understand their risks. Hopefully, this research can illuminate ways to meet them where they are.”

Nadja Drabon, an early-Earth geologist and assistant professor in the Department of Earth and Planetary Sciences, is insatiably curious about what our planet was like during ancient eons rife with meteoritic bombardment, when only single-celled bacteria and archaea reigned — and when it all started to change. When did the first oceans appear? What about continents? Plate tectonics? How did all those violent impacts affect the evolution of life?

A new study in Proceedings of the National Academy of Sciences sheds light on some of these questions, in relation to the inauspiciously named “S2” meteoritic impact of over 3 billion years ago, and for which geological evidence is found in the Barberton Greenstone belt of South Africa today. Through the painstaking work of collecting and examining rock samples centimeters apart and analyzing the sedimentology, geochemistry, and carbon isotope compositions they leave behind, Drabon’s team paints the most compelling picture to date of what happened the day a meteorite the size of four Mount Everests paid Earth a visit.

“Picture yourself standing off the coast of Cape Cod, in a shelf of shallow water. It’s a low-energy environment, without strong currents. Then all of a sudden, you have a giant tsunami, sweeping by and ripping up the sea floor,” said Drabon.

The S2 meteorite, estimated to have been up to 200 times larger than the one that killed the dinosaurs, triggered a tsunami that mixed up the ocean and flushed debris from the land into coastal areas. Heat from the impact caused the topmost layer of the ocean to boil off, while also heating the atmosphere. A thick cloud of dust blanketed everything, shutting down any photosynthetic activity taking place.

But bacteria are hardy, and following impact, according to the team’s analysis, bacterial life bounced back quickly. With this came sharp spikes in populations of unicellular organisms that feed off the elements phosphorus and iron. Iron was likely stirred up from the deep ocean into shallow waters by the aforementioned tsunami, and phosphorus was delivered to Earth by the meteorite itself and from an increase of weathering and erosion on land.

Drabon’s analysis shows that iron-metabolizing bacteria would thus have flourished in the immediate aftermath of the impact. This shift toward iron-favoring bacteria, however short-lived, is a key puzzle piece depicting early life on Earth. According to Drabon’s study, meteorite impact events — while reputed to kill everything in their wake (including, 66 million years ago, the dinosaurs) — carried a silver lining for life.

“We think of impact events as being disastrous for life,” Drabon said. “But what this study is highlighting is that these impacts would have had benefits to life, especially early on … these impacts might have actually allowed life to flourish.”

These results are drawn from the backbreaking work of geologists like Drabon and her students, hiking into mountain passes that contain the sedimentary evidence of early sprays of rock that embedded themselves into the ground and became preserved over time in the Earth’s crust. Chemical signatures hidden in thin layers rock help Drabon and her students piece together evidence of tsunamis and other cataclysmic events.

The Barberton Greenstone Belt in South Africa, where Drabon concentrates most of her current work, contains evidence of at least eight impact events including the S2. She and her team plan to study the area further to probe even deeper into Earth and its meteorite-enabled history.

More than 5% of the Arctic show signs of human activity

An international research team led by Gabriela Schaepman-Strub from the Department of Evolutionary Biology and Environmental Studies at the University of Zurich (UZH) has now shed light on this question. Together with US colleagues from NASA and the University of Wisconsin-Madison, the UZH researchers used data of nighttime artificial light observed from satellites to quantify the hotspots and evolution of human activity across the Arctic from 1992 to 2013. “More than 800,000 km² were affected by light pollution, corresponding to 5.1% of the 16.4 million km² analyzed, with an annual increase of 4.8%,” says Schaepman-Strub. With the new, standardized approach the researchers were able to spatially assess human industrial activity across the Arctic, independent of economic data.

The European Arctic and the oil and gas extraction regions of Alaska, USA, and Russia were hotspots of human activity, with up to one-third of the land area illuminated. Compared to these regions, the Canadian Arctic was largely dark at night. “We found that, on average, only 15% of the lit area in the Arctic contained human settlements, which means that most of the artificial light is due to industrial activities rather than urban development. And this major source of light pollution is increasing in both area and intensity every year,” says first author Cengiz Akandil, a doctoral student in Schaepman-Strub’s team.

Effects on terrestrial ecosystems and regional sustainability

According to the researchers, these data provide an essential basis for future studies on the impact of industrial development on Arctic ecosystems. “In the vulnerable permafrost landscape and tundra ecosystem, even just repeated trampling by humans, and certainly tracks left by tundra vehicles, can have long-term environmental effects that extend well beyond the illuminated area detected by satellites,” says Akandil.

The negative impacts of industrial activities and light pollution are absolutely critical for the Arctic biodiversity. For example, artificial light at night reduces the ability of Arctic reindeer to adapt their eyes to the extreme blue color of winter twilight, which allows them to find food and escape predators. It also delays leaf coloration and breaking leaf buds, which is critical for the Arctic species where the growing season is limited. Furthermore, human activities foster the expansion of invasive species in the Arctic, and oil and gas extraction frequently lead to environmental pollution — as does the mining industry, which is also expanding.

Documenting industrial activity is crucial for sustainable development

The effects of rapid climate change in the Arctic require local communities to adapt quickly, and the industrial development might further increase the need for adaptation — and enhance the costs on society and the environment. The direct impacts that human activity has on Arctic ecosystems could exceed or at least exacerbate the effects of climate change in the coming decades, the researchers estimate. If the growth rate of industrial development between 1940-1990 is maintained, 50-80% of the Arctic may reach critical levels of anthropogenic disturbance by 2050.

“Our analyses on the spatial variability and hotspots of industrial development are critical to support monitoring and planning of industrial development in the Arctic. This new information may support Indigenous Peoples, governments and stakeholders to align their decision-making with the Sustainable Development Goals in the Arctic,” concludes Gabriela Schaepman-Strub.

The study, led by the University of East Anglia (UEA) and published today in Science, grouped areas of the world into ‘pyromes’ — regions where forest fire patterns are affected by similar environmental, human, and climatic controls — revealing the key factors driving recent increases in forest fire activity.

It is one of the first studies to look globally at the differences between forest and non-forest fires, and shows that in one of the largest pyromes, which spans boreal forests in Eurasia and North America, emissions from fires nearly tripled between 2001 and 2023.

Significant increases were seen more broadly across the extratropical forests and amounted to an additional half a billion tonnes of CO₂ per year, with the epicentre of emissions shifting away from tropical forests and towards the extratropics.

Increased emissions were linked to a rise in fire-favourable weather, such as the hot-dry conditions seen during heatwaves and droughts, as well as increased rates of forest growth creating more vegetation fuels. Both trends are aided by rapid warming in the high northern latitudes, which is happening twice as fast as the global average.

The study reveals a worrying increase in not only the extent of forest wildfires over the last two decades, but also their severity. The carbon combustion rate, a measure of fire severity based on how much carbon is emitted per unit of area burned, increased by almost 50% across forests globally between 2001 and 2023.

The work involved an international team of scientists — from the UK, the Netherlands, US, Brazil, and Spain — who warn that further expansion of forest fires can only be averted if the primary causes of climate change, such as fossil fuel emissions, are tackled.

Lead author Dr Matthew Jones, of the Tyndall Centre for Climate Change Research at UEA, said: “Increases in both the extent and severity of forest fires have led to a dramatic rise in the amount of carbon emitted by forest fires globally. Startling shifts in the global geography of fires are also underway, and they are primarily explained by the growing impacts of climate change in the world’s boreal forests.

“To protect critical forest ecosystems from the accelerating threat of wildfires, we must keep global warming at bay and this underscores why it is so vital to make rapid progress towards net zero emissions.”

Threats to carbon storage

Forests are of worldwide importance for carbon storage, with their growth helping to remove CO₂ from the atmosphere and reduce rates of global warming. They also play a crucial role in meeting international climate targets, with reforestation and afforestation schemes being implemented to remove carbon from the atmosphere and offset human CO₂ emissions from hard-to-abate sectors such as aviation and certain industries.

The success of these schemes relies on carbon being stored in forests permanently, and wildfires threaten that. Extratropical fires are already emitting half a billion tonnes more CO₂ than two decades ago, and the long-term effect depends on how forests recover. More widespread and severe forest fires are a sign that emissions are now out of balance with the carbon captured by post-fire recovery.

Dr Jones, a NERC Independent Research Fellow, said: “The steep trend towards greater extratropical forest fire emissions is a warning of the growing vulnerability of forests and it poses a significant challenge for global targets to tackle climate change.

“We know that forests rebound poorly after the most severe fires, so there is huge interest in how the observed increases in fire severity will influence carbon storage in forests over the coming decades. This demands our close attention.”

Escalating wildfire impacts masked until now

Significantly, the increased emissions from forest fires contrasts with the reduced burning of the world’s tropical savannahs during the same period. Previous studies have shown that, since 2001, the area burned by all fires (forest and non-forest) fell by a quarter globally, mainly due to this.

The latest findings are important because forest fires burn more severely and release larger amounts of harmful smoke to the atmosphere than savannah grassland fires, presenting major threats to those living near fires and to more distant communities exposed to poor air quality caused by smoke.

The authors say the study debunks the narrative that falling overall annual area burned by fire globally means falling wildfire impact.

“Until now, reduced burning in the already fire-prone savannahs and grasslands has masked increases in forest fire extent and severity that are hugely consequential for society and the environment,” said Dr Jones. “Our work shows that fires are increasingly happening where we don’t want them to — in forests, where they present the greatest threat to people and to vital carbon stores.”

Managing wildfires

Machine learning was key to unlocking new observations about the shifting global geography of forest fires. It was used to group the world’s forest ecoregions into 12 distinct pyromes, allowing the researchers to isolate the effects of climate change from other influencing factors such as land use.

This knowledge also reveals new insights into which strategies can be most effective for mitigating wildfires and protecting forests. Dr Jones said: “Substantial financing is required to support strategic programs of forest management, stakeholder engagement, and public education, all of which represent a meaningful shift of fire management strategy from largely reactive to increasingly proactive.

“For example, priority areas for forest management and fire breaks must be defined based on proactive monitoring of forest productivity, particularly in the extratropics. Managing fuel loads in places where they could present greatest danger during fire-favourable weather is a key priority for limiting the severity and impact of fires when they do occur.” The work was supported by funders including the UK Natural Environment Research Council (NERC), European Commission Horizon 2020 programme, and European Space Agency.

The work was supported by funders including the UK Natural Environment Research Council (NERC), European Commission Horizon 2020 programme, and European Space Agency.

The scientists were investigating the hippocampus, a brain area that plays a key role in memory in humans and mice. Specifically, they focused on the CA2 region, which is significant for social memory, the ability to remember other individuals, and the CA1 region, which is important for remembering places.

In this new study, the researchers for the first time reveal that CA1 and CA2 respectively encode the locations and individuals linked with a threatening experience. The results show that, beyond simply recognizing individuals, CA2 helps record more complex aspects of social memory: in this case, whether another individual is safe or risky. The scientists published their findings on October 15 in the journal Nature Neuroscience.

“It’s vital to all species that live in social communities, including mice and humans, to have social memories that can help one avoid future experiences with others that might prove harmful while keeping ourselves open to individuals who may be beneficial,” saidPegah Kassraian, PhD, a postdoctoral research fellow in the Siegelbaum lab and lead author of the new study. “Fearful memories are important for survival and help to keep us safe.”

To investigate where fearful social memories originate in the brain, Dr. Kassraian and her colleagues gave individual mice a choice. They could scamper to one place, meet another mouse that was unknown to them, and receive a mild foot shock (much like a static electricity zap people might get after walking on a carpet and touching a doorknob). Scurrying in the opposite direction to meet a different stranger was safe. Normally, the mice quickly learned to avoid the strangers and locations that were associated with the shocks, and these memories lasted for at least 24 hours.

To determine where in the hippocampus these memories were stored, the researchers genetically altered the mice to enable them to selectively suppress the CA1 or CA2 regions. Surprisingly, turning off each region had very different effects. When the scientists silenced CA1, the mice could no longer remember where they were zapped, but they could still remember which stranger was associated with the threat. When they silenced CA2, the mice remembered where they were shocked, but became indiscriminately afraid of both strangers they met.

These new findings reveal that CA2 helps mice remember whether past encounters with others were threatening or safe. The results also are consistent with prior research detailing how CA1 is home to place cells, which encode locations.

Previous research has implicated CA2 in various neuropsychiatric conditions such as schizophrenia and autism. The new study suggests that further investigating CA2 might help scientists better understand social anxiety, post-traumatic stress disorder and other conditions that can lead to social withdrawal.

“It’s possible that social withdrawal symptoms are related to an inability to discriminate between who is a threat and who is not,” said Dr. Siegelbaum, who is also a professor and chair of the department of neuroscience at Columbia’s Vagelos College of Physicians and Surgeons. “Targeting CA2 could be a useful way of diagnosing or treating disorders linked with a fear of others.”

The paper, “The hippocampal CA2 region discriminates social threat from social safety,” was published online in Nature Neuroscience on October 15, 2024.

The full list of authors includes Pegah Kassraian, Shivani K. Bigler, Diana M. Gilly, Neilesh Shrotri, Anastasia Barnett, Heon-Jin Lee, W. Scott Young, and Steven A. Siegelbaum.

The authors report no conflicts of interest.