A deep dive for environmental data on coastal oceans

New research addresses lack of information on the potential presence of human-generated carbon dioxide in these saltwater ecosystems

University of Delaware

 

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A recent study from Wei-Jun Cai’s lab group at the University of Delaware looked to address the issue of the amount of anthropogenic carbon dioxide, as well as where that anthropogenic carbon dioxide comes from with observational data in coastal oceans.

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Credit: Tammy Beeson/ University of Delaware

Excess carbon dioxide emitted by human activities – such as fossil fuel burning, land-use changes and deforestation – is absorbed by the world’s oceans. While this absorption helps mitigate global warming, it also has adverse effects on marine life, including fish and plants.

While the impact of what is known as anthropogenic carbon dioxide on the open oceans has been extensively studied, there has been limited observational data on its presence and sources in coastal oceans, the broad range of saltwater ecosystems, from estuaries to coral reefs, that link the land and sea.

A recent study from Wei-Jun Cai’s lab at the University of Delaware, titled “The Source and Accumulation of Anthropogenic Carbon in the U.S. East Coast,” published in Science Advances, addresses this gap.

The lead author, Xinyu Li, earned her doctorate from UD’s School of Marine Science and Policy in 2023 and is now a postdoctoral researcher at the Pacific Marine Environmental Laboratory. Wei-Jun Cai, associate dean for research and the Mary A.S. Lighthipe Chair Professor of Earth, Ocean, and Environment, was Li’s advisor and supervised the study. Co-authors include Zelun Wu, a dual-degree doctoral student at UD and Xiamen University, and Zhangxian Ouyang, a postdoctoral researcher at UD.

The researchers analyzed a high-quality carbonate dataset from five research cruises conducted between 1996 and 2018. This dataset covers the East Coast of the United States’ Mid-Atlantic Bight, a coastal region stretching from Massachusetts to North Carolina.

The 1996 dataset, provided by Doug Wallace, a professor of oceanography at Dalhousie University, allowed the researchers to track changes in carbon dioxide levels over time. Except for the 1996 cruise, the data were collected by members of Cai’s group under the Ocean Acidification Program of the National Oceanic and Atmospheric Administration (NOAA).

The researchers used this data to investigate where and how much anthropogenic carbon dioxide is entering coastal waters, which are crucial to the global carbon budget.

Surface water – the top 200 meters of the ocean – showed the highest increase in anthropogenic carbon dioxide due to its direct contact with the atmosphere, which leads to greater absorption of atmospheric CO2.

Cai noted that an intriguing aspect of the study was analyzing the proportions of natural versus anthropogenic CO2 in the water and how water age affects anthropogenic carbon accumulation.

Surface water, being newer and arriving via the Gulf Stream from the Gulf of Mexico, exhibited high levels of anthropogenic carbon dioxide but relatively low levels of naturally occurring carbon dioxide.

In contrast, the middle layer of water (below 200 meters) had high concentrations of natural carbon dioxide and lower levels of anthropogenic carbon dioxide. 

“The surface water has very high anthropogenic carbon dioxide but the middle layer water, that water that comes from the Southern Ocean and is called the Antarctic Intermediate Water, that water travels a long time, maybe 100 years from the Southern Ocean to the East Coast,” said Cai. “That water has a lot of natural carbon dioxide because of microbial decomposition but that water has very low amounts of anthropogenic carbon.” 

Below these layers lies the North Atlantic Deep Water, which sinks in winter and travels from the Labrador Sea to the East Coast over two decades. “This water has an intermediate level of anthropogenic carbon dioxide,” Cai said. “Each water mass has a recorded level of carbon dioxide from its time of formation,  and this gave us a history of these changes. It’s interesting to see that the more recent waters had the highest levels of anthropogenic carbon.” 

Li described this distribution as a “sandwich structure,” with high anthropogenic carbon on the surface, low anthropogenic carbon in the middle layers, and intermediate levels deeper down. 

“This distribution is closely related to water age, when it comes in contact with the atmosphere on the surface and absorbs carbon dioxide from the atmosphere,” Li said.

The study also found that anthropogenic carbon decreases from offshore to nearshore waters, correlating with lower salinity. This suggests that there is no net increase in the export of anthropogenic carbon dioxide from nearshore areas like estuaries and wetlands to the open ocean.

“When we extrapolate our results to low salinity waters, like the water coming out of the Delaware Bay and the Chesapeake Bay, we found that there is actually very little anthropogenic carbon dioxide increase in very low salinity waters,” Cai explained. “That water has a lot of natural carbon dioxide but there’s very little anthropogenic carbon dioxide there.” 

This finding supports previous research indicating that net anthropogenic carbon dioxide transport from estuaries and wetlands to the continental shelf is essentially zero, or even negative. Possible reasons include low buffer capacity and short residence times in estuarine waters, which limit their ability to absorb anthropogenic CO2. Additionally, the loss rate of North American wetlands is three times its growth rate, reducing the opportunity for carbon uptake and transport to coastal waters.

Cai highlighted the broader implications of these findings for the global carbon cycle. “This paper clarifies conflicting views from terrestrial studies,” he said. “There is a big debate about whether there is an increase of transport of anthropogenic carbon dioxide from terrestrial systems to the coastal ocean. Our conclusion is that there is no natural transport of anthropogenic carbon and that anthropogenic carbon in the coastal waters is really all mixed in from the offshore water masses and comes locally from the atmosphere above it. A majority of the latter is then exported to the ocean.”

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Journal

Science Advances

DOI

10.1126/sciadv.adl3169 

Article Title

Excess carbon dioxide emitted by human activities – such as fossil fuel burning, land-use changes and deforestation – is absorbed by the world’s oceans. While this absorption helps mitigate global warming, it also has adverse effects on marine life, including fish and plants. While the impact of what is known as anthropogenic carbon dioxide on the open oceans has been extensively studied, there has been limited observational data on its presence and sources in coastal oceans, the broad ra

 

Killing giant ragweed just got harder for some Wisconsin farmers

University of Illinois College of Agricultural, Consumer and Environmental Sciences

 

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From left: Felipe Faleco, University of Wisconsin-Madison, hands a bag of PPO-resistant giant ragweed seeds to Pat Tranel, University of Illinois Urbana-Champaign. The team identified the first cases of multiple-herbicide-resistant giant ragweed in Wisconsin and the first ever incidence of Group 14-resistance in these weeds.

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Credit: Rodrigo Werle, University of Wisconsin-Madison

URBANA, Ill -- When giant ragweed takes hold in a crop field, the towering weed reduces yield and sends plumes of its famously allergy-inducing pollen into the air. There are few tools available to thwart the menace, especially for farmers growing non-GMO soybeans. Now, some Wisconsin farmers are left with even fewer options. 

New research from the University of Wisconsin-Madison and the University of Illinois Urbana-Champaign shows some giant ragweed populations in Wisconsin have evolved resistance to a crucial class of post-emergence herbicides known as protoporphyrinogen oxidase (PPO) inhibitors (Group 14 herbicides).  

“It’s hard to control giant ragweed with pre-emergence herbicides, in part because it's a larger seed and can emerge from greater depths. So farmers depend on post-emergence products. For folks growing non-GMO soybean, those POST products are ALS and PPO, and we already have fairly widespread ALS resistance in giant ragweed,” said study co-author Pat Tranel, professor in the Department of Crop Sciences in the College of Agricultural, Consumer and Environmental Sciences (ACES) at Illinois. 

“Losing PPOs means you're basically out of chemical options,” he added.

The results won’t surprise some Wisconsin farmers. Study co-author Rodrigo Werle, associate professor and Extension weed scientist at UW-Madison, says farmers started mentioning in 2018 that PPOs weren’t working as well. 

“We thought they had issues with application timing, that they were missing the ideal window for application,” Werle said. “But the growers we were working with are very knowledgeable and did everything by the book. Small plants were regrowing after being sprayed, which can be a sign of resistance.” 

The research team asked farmers to collect and send seeds from plants in affected fields. 

“We evaluated fomesafen (a PPO inhibitor) at 1x and 3x the label rate, and a lot of plants survived. Then we evaluated the dose response for fomesafen and lactofen (another PPO). We determined one population had almost 30-fold resistance to fomesafen and almost four-fold resistance to lactofen,” said lead study author Felipe Faleco, a doctoral student at UW-Madison.  

Faleco let plants that survived the 1x rate of fomesafen grow to maturity, then collected seeds and handed them off to Tranel, who had previously determined the molecular basis of ALS and PPO resistance in common ragweed, a close relative of the giant variety.

“We sequenced the genes for the PPO target enzyme and found the same mutation that we’d seen in common ragweed,” Tranel said. “There were really no other mutations, so that is likely the basis of resistance in giant ragweed, too.”

Tranel’s group went farther, developing a molecular tool diagnostic labs can use to detect PPO resistance, offering farmers quick answers.

The Wisconsin team also tested for resistance to acetolactate synthase (ALS) inhibitors and glyphosate, finding four populations with resistance to ALS and two populations with resistance to glyphosate. These types of resistance had already been documented in giant ragweed, but the team also found one population with resistance to both.

“For us in Wisconsin, this is the first time we’ve documented two types of resistance in a single population in giant ragweed,” Werle said. “It shows that it’s not only waterhemp that is evolving multiple resistance. We also have some other weeds we have to keep an eye on.”

Resistance to glyphosate affects GMO soybean growers, who turn to PPO and ALS herbicides in those cases. Similarly, non-GMO growers who can’t use glyphosate rely on these chemistries.  The authors say with ALS and PPO resistance — essentially, zero chemical options — more non-GMO growers may switch to GMO soybeans.

“Farmers plant non-GMO soybeans for the premiums; there’s a financial reason to go that route even though weed control is more difficult,” Werle said. “But if a farmer knows they're dealing with this type of resistance, that could prevent them from growing a non-GMO crop in a sustainable or a profitable way.”

In addition to the potential impacts on farm management and profits, the findings matter for allergy sufferers. 

“As farmers struggle with control, more ragweeds are going to escape and shed pollen,” Tranel said. “So if you're living in a semi-rural area with corn and soybean fields around, it’s likely there's going to be more pollen in the air.”

The study, “Resistance to protoporphyrinogen oxidase inhibitors in giant ragweed (Ambrosia trifida),” is published in Pest Management Science [DOI: 10.1002/ps.8349]. Authors include Felipe Faleco, Filipi Machado, Lucas Bobadilla, Pat Tranel, David Stoltenberg, and Rodrigo Werle. The Wisconsin Soybean Marketing Board supported Faleco’s graduate studies.

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Journal

Pest Management Science

DOI

10.1002/ps.8349 

 

Legal challenges in human brain organoid research and its applications

Institute for the Advanced Study of Human Biology (ASHBi), Kyoto University

 

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Human brain organoids are three-dimensional neural tissues derived from stem cells that can mimic some aspects of the human brain. Their use holds incredible promise for medical advancements, but this also raises complex ethical and legal questions that need careful consideration.

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Credit: WPI-ASHBi/Kyoto University

A recent study has explored the legal and ethical challenges expected to arise in human brain organoid research.

Human brain organoids are three-dimensional neural tissues derived from stem cells that can mimic some aspects of the human brain. Their use holds incredible promise for medical advancements, but this also raises complex ethical and legal questions that need careful consideration.

Seeking to examine the various legal challenges that might arise in the context of human brain organoid research and its applications, the team of researchers, which included a legal scholar, identified and outlined potential legal issues. Notably, the study has evaluated the urgency of these issues, thereby establishing regulatory priorities for the future. The complexities involved in this area have often been overlooked, making this study a crucial step forward.

Legal challenges were categorized into five key themes: consciousness, legal status, consent, ownership, and transplantation. One of the most debated concerns is whether human brain organoids could become conscious. This raises profound ethical and legal questions, even though the realization of such concerns may be distant. The researchers explored the legal implications of different levels of consciousness—from basic sensory experiences to more advanced cognitive functions—suggesting that future legal protections might be necessary.

Another important consideration is the legal status of human brain organoids, which are currently regarded as property, similar to other human-derived materials. However, as research advances, the potential for brain organoids to be integrated into information processing systems and other applications could challenge this classification, possibly leading to discussions about legal personhood.

Consent and ownership also pose unique and pressing challenges. The researchers emphasized the need for appropriate and specific consent from cell donors, especially given the sensitive nature of the research. Ownership disputes may arise as donors might feel a personal connection to the brain organoids or perceive them as belonging to them, particularly as the monetary value of brain organoids increases.

Finally, transplantation of human brain organoids into animals and potentially humans raises another set of ethical and legal issues. Ensuring the welfare of host animals is an urgent concern requiring stringent regulation. In the distant future, addressing the consciousness and welfare of transplanted brain organoids may also be significant concerns.

“Our main finding is that we have, for the first time, thoroughly categorized the legal challenges associated with human brain organoid research on a global scale,” says Dr. Tsutomu Sawai, one of the researchers. This categorization is a significant step toward developing a comprehensive legal framework to improve the research environment for brain organoids.

Looking to the future, the researchers aim to use their findings to guide regulatory action and policy, ensuring responsible and ethical advancement in the field. They encourage public engagement and discussion, emphasizing that diverse perspectives are essential for navigating the complex ethical dimensions of this research. “The results of this research have the potential to bring various benefits to society. While the issues may be complex, we encourage the public to engage with our work, understand the ethical dimensions, and participate in discussions where appropriate,” Dr. Sawai added. “Contributions from different perspectives are essential for the responsible advancement of science.”

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Journal

Journal of Bioethical Inquiry

DOI

10.1007/s11673-024-10349-9 

Article Title

Human Brain Organoid Research and Applications: Where and How to Meet Legal Challenges?

 

WHITE US Congress members’ wealth statistically linked with ancestors’ slaveholding practices

Study provides new evidence that past slaveholding practices might continue to affect people today

Peer-Reviewed Publication

PLOS

 

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Sehgal and Sehgal examined the net worth of members of the U.S. Congress and its relationship with being a descendant of slave owners. Legislators whose ancestors enslaved 16 or more individuals had $3.93 million higher net worth compared to legislators whose ancestors were not slave owners, a five-fold increase. 

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Credit: Anne-Lise Paris, (www.in-graphidi.com), PLOS, CC-BY 4.0

Per a new study, as of April 2021, US Congress members whose ancestors enslaved 16 or more people had a net worth that was five times higher than that of legislators whose ancestors did not have slaves. Neil Sehgal of the University of Pennsylvania, US, and Ashwini Sehgal of Case Western Reserve University, US present these findings in the open-access journal PLOS ONE on August 21, 2024. 

Prior research has linked slavery’s intergenerational effects to contemporary inequality, poverty, education, voting behavior, and life expectancy in the US However, the extent to which past slavery in the US contributes to today’s social and economic conditions remains unclear. 

In 2023, Reuters released an investigative series that captured information on slaveholder ancestry for all 535 individuals who were US Congress members as of April 15, 2021. To boost understanding of US slavery’s potential contemporary effects, Sehgal and Sehgal cross-referenced information from that report with legislators’ self-disclosed finances. 

Statistical analysis of the data revealed that the net worth of US Congress members whose ancestors had 16 or more slaves was about five times higher than that of legislators whose ancestors did not have slaves—even after accounting for demographic factors that could also be linked to net worth, including age, sex, race, ethnicity, and education. 

The researchers note that legislators are not personally responsible for their ancestors’ actions. Nonetheless, the findings provide new evidence suggesting the possibility that past slaveholding practices in the US may continue to affect people today. 

The authors outline a number of limitations of their study. For instance, the findings do not point to any specific mechanism by which slave ownership by ancestors might affect contemporary legislators’ wealth. In addition, the dataset is small, does not account for ancestors’ history of slavery prior to the founding of the U.S. in 1776, and may lack certain financial assets and information that legislators are not required to disclose. And because US Congress members tend to be wealthier, the findings cannot be extrapolated to other US politicians or the general public. 

Additional research in these areas could help clarify links between slaveholder ancestry and current wealth, which may aid efforts to address contemporary social and economic disparities. 

The authors add: “Members of Congress hold significant power to shape policies and set national agendas. Understanding the wealth disparities within this influential group can drive conversations about economic equity and motivate legislators to support policies addressing historical injustices.” 

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In your coverage please use this URL to provide access to the freely available article in PLOS ONE: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0308351 

Citation: Sehgal NKR, Sehgal AR (2024) Slaveholder ancestry and current net worth of members of the United States Congress. PLoS ONE 19(8): e0308351. https://doi.org/10.1371/journal.pone.0308351  

Author Countries: USA 

Funding: The author(s) received no specific funding for this work. 

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Journal

PLoS ONE

DOI

10.1371/journal.pone.0308351 

Method of Research

Observational study

Subject of Research

People

Article Publication Date

21-Aug-2024

AMERIKA

Homicide rates are a major factor in the gap between Black and White life expectancy

The racial life expectancy gap in 2020 and 2021 was driven by homicide rates even more than by COVID-19 deaths

PLOS

 

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S1 Fig. Differences in homicide death rates between Black and White men, 1990–2021. 

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Credit: Light et al., 2024, PLOS ONE, CC-BY 4.0 (https://creativecommons.org/licenses/by/4.0/)

Homicide is a major reason behind lower and more variable reduction in life expectancy for Black rather than White men in recent years, according to a new study published August 21, 2024 in the open-access journal PLOS ONE by Michael Light and Karl Vachuska of the University of Wisconsin-Madison, USA.  

The COVID-19 pandemic precipitated a staggering drop in U.S. life expectancy and substantially widened Black-White disparities in lifespan. It also coincided with the largest one-year increase in the U.S. homicide rate in more than a century, with Black men bearing the brunt of these. Despite these trends, there has been limited research on the contribution of homicide to Black-White disparities in life expectancy during the pandemic.  

In the new study, researchers used mortality data and multiple cause of death data files from the National Vital Statistics System division of the National Center for Health Statistics. The data spanned 2019 to 2021, and causes of death were organized into 20 main groupings.  

Whereas Black men were expected to live on average 71.4 years in 2019, this dropped to 67.7 years in 2020. For White men, the corresponding decline was only from 76.4 years to 74.9 years. As a result, the life expectancy racial gap jumped from 5.0 to 7.2 fewer years  for Black relative to White men. 

The researchers found that in 2020 and 2021, homicide was the leading contributor to inequality both in life expectancy and in lifespan variability between Black and White men. Homicide accounted for far more of the racial gap in longevity and lifespan variability than deaths due to COVID-19. In 2021, for instance, the impact of homicide on the racial gap in lifespan variability was nine times greater than deaths from COVID-19. 

The authors conclude that addressing homicides should be at the forefront of any public health discussion aimed at promoting racial health equity. 

The authors add: “Increased homicide is one of the principal reasons why lifespans have become shorter for Black men than White men in recent years. In 2020 and 2021, homicide was the leading contributor to inequality in both life expectancy and lifespan variability between Black and White men, accounting for far more of the racial gap in longevity and variability than deaths from COVID-19.” 

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In your coverage please use this URL to provide access to the freely available article in PLOS ONE: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0308105  

Citation: Light MT, Vachuska K (2024) Increased homicide played a key role in driving Black-White disparities in life expectancy among men during the COVID-19 pandemic. PLoS ONE 19(8): e0308105. https://doi.org/10.1371/journal.pone.0308105  

Author Countries: United States 

Funding: This research is supported by the Romnes Faculty Fellowship provided by the University of Wisconsin-Madison Office of the Vice Chancellor for Research and Graduate Education with funding from the Wisconsin Alumni Research Foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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Journal

PLoS ONE

DOI

10.1371/journal.pone.0308105 

Method of Research

Observational study

Subject of Research

People

Article Publication Date

21-Aug-2024

 

Human-wildlife overlap expected to increase across more than half of land on Earth by 2070

University of Michigan

ANN ARBOR—As the human population grows, more than half of Earth's land will experience an increasing overlap between humans and animals by 2070, according to a University of Michigan study.

Greater human-wildlife overlap could lead to more conflict between people and animals, say the U-M researchers. But understanding where the overlap is likely to occur—and which animals are likely to interact with humans in specific areas—will be crucial information for urban planners, conservationists and countries that have pledged international conservation commitments. Their findings are published in Science Advances.

"We found that the overlap between populations of humans and wildlife will increase across about 57% of the global lands, but it will decrease across only about 12% of the global lands. We also found that agricultural and forest areas will experience substantial increases of overlap in the future," said Deqiang Ma, lead author of the study and a postdoctoral research fellow at the U-M Institute for Global Change Biology in the School for Environment and Sustainability. 

The study showed that the human-wildlife overlap will be driven by human population growth rather than climate change. That is, the increase of people settling in previously undeveloped areas will drive the overlap rather than climate change causing animals to shift where they live.

"In many places around the world, more people will interact with wildlife in the coming decades and often those wildlife communities will comprise different kinds of animals than the ones that live there now," said Neil Carter, principal investigator of the study and associate professor of environment and sustainability. "This means that all sorts of novel interactions, good and bad, between people and wildlife will emerge in the near future."

A human-driven issue

To calculate future human-wildlife overlap, the researchers created an index that combined estimates of where people are likely to populate land as well as the spatial distributions of 22,374 species of terrestrial amphibians, birds, mammals and reptiles. 

They drew information about the spatial distribution of vertebrates from previously published data that forecasts where species will live based on their climatic niches. Their estimates of where people are likely to live were based on projections of economic development, global society and demographics.

"The index we created showed that the majority of global lands will experience increases in human-wildlife overlap, and this increasing overlap is the result of the expansion of human population much more so than changes in species distributions caused by climate change," Ma said.

Specifically, the researchers found that areas that currently have and are projected to have high human-wildlife overlap in 2015 and 2070 are concentrated in regions where human population density is already high, including China and India.

In addition to those places where overlap is already high, "another area of major concern are forests, particularly in forests in Africa and South America where we're seeing a large increase in the overlap in the future," Carter said. "The reason that is concerning is because those areas have very high biodiversity that would experience greater pressure in the future."

The researchers also found that median species richness—the variety of species in a given area—is projected to decrease across most forests in Africa and South America. In South America, mammal richness is projected to decline by 33%, amphibian richness by 45%, reptile richness by 40% and bird richness by 37%. In Africa, mammal richness is projected to decline by 21% and bird richness by 26%.

The need for biodiversity

Preserving biodiversity in these zones of overlap has real benefits, Carter says. 

"There are cases of human-wildlife interactions that are both good and bad, but we anticipate that they're going to become more pronounced. For example, COVID19 was the result of human contact with wild animals, and there is concern that new diseases will emerge from greater encounters between people and certain wildlife species," he said. "But you also have species that provide important benefits to people, like reducing the abundances of pests."

For example, part of Ma's data analysis looked at birds that eat insects in agricultural areas and examined where those birds will go under climate change. He found that more than two-thirds of the croplands that will likely experience an increase of human-wildlife overlap by 2070 will see a decline in bird species that can help reduce crop pests.

"What we're doing is finding those areas and saying, if you have cropland or pastures here, are you going to have species move into those areas or species moving away from those areas," Carter said. "Are those new croplands or pastures going to be an additional threat to the species or could there be ecosystem services harnessed for free?"

Scavengers such as vultures and hyenas also play a critical role by cleaning waste from urban areas and other landscapes, Carter said. By clearing waste, scavengers can reduce the prevalence of some human diseases such as rabies, anthrax and bovine tuberculosis.

"Hyenas and other species that are vilified or persecuted because they are scavengers provide a lot of disease reduction benefits," Carter said. "On one hand, they're viewed as a threat, but on the other hand, they're providing free health benefits.

Equitable conservation

Future conservation strategies will have to evolve, especially in regions that previously haven't seen much human settlement, according to the researchers. In the past, a core conservation strategy was to establish protected areas where human access is restricted. This is becoming harder to implement because there are fewer such places.

"There's also a significant environmental justice argument around the validity of telling communities that may have lived in a certain area for generations that they have to move," Carter said. "Our study suggests that with more areas of the world expected to be shared both by people and wildlife, conservation planning will have to get more creative and inclusive."

Conservationists will need to engage local communities to build interest in helping improve the conservation process. This process may include establishing habitat corridors to connect existing protected areas to potentially new areas or to create temporary protected areas during critical periods for wildlife, like breeding periods, as well as other conservation innovations.

"We care a lot about which areas can support populations of endangered species, like tigers, and how human communities interact with these species," Carter said. "In some places it's going to be really hard to do everything at once: to grow crops and have urban areas and protect these species and their habitats. But if we can start planning now, we have a lot of tools to help us promote sustainable coexistence."

Co-authors of the study include Briana Abrahms of the University of Washington, U-M ecologist Jacob Allgeier, Tim Newbold of the University College London and U-M evolutionary ecologist Brian Weeks.

 

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Journal

Science Advances

DOI

10.1126/sciadv.adp7706 

Method of Research

Data/statistical analysis

Subject of Research

Animals

Article Title

Global Expansion of Human-Wildlife Overlap in the 21st Century

Article Publication Date

21-Aug-2024

 

Study finds highest prediction of sea-level rise unlikely

Researchers question model of rapid polar ice collapse, but say retreat is still dire.

Peer-Reviewed Publication

Dartmouth College

In recent years, the news about Earth's climate—from raging wildfires and stronger hurricanes, to devastating floods and searing heat waves—has provided little good news.

A new Dartmouth-led study, however, reports that one of the very worst projections of how high the world's oceans might rise as the planet's polar ice sheets melt is highly unlikely—though it stresses that the accelerating loss of ice from Greenland and Antarctica is nonetheless dire.

The study challenges a new and alarming prediction in the latest high-profile report from the United Nations' Intergovernmental Panel on Climate Change (IPCC) to evaluate the latest climate research and project the long- and near-term effects of the climate crisis. Released in full last year, the IPCC's sixth assessment report introduced a possible scenario in which the collapse of the southern continent's ice sheets would make Antarctica's contribution to average global sea level twice as high by 2100 than other models project—and three times as high by 2300.

Though the IPCC designated this specific prediction as "low likelihood," the potential of the world's oceans rising by as much as 50 feet as the model projects earned it a spot in the report. At that magnitude, the Florida Peninsula would be submerged, save for a strip of interior high ground spanning from Gainesville to north of Lake Okeechobee, with the state's coastal cities underwater.

But that prediction is based on a new hypothetical mechanism of how ice sheets—the thick, land-based glaciers covering polar regions—retreat and break apart. The mechanism, known as the Marine Ice Cliff Instability (MICI), has not been observed and has so far only been tested with a single low-resolution model, the researchers report in the journal Science Advances.

The researchers instead test MICI with three high-resolution models that more accurately capture the complex dynamics of ice sheets. They simulated the retreat of Antarctica's Thwaites Glacier, the 75-mile-wide ice sheet popularly nicknamed the "Doomsday Glacier" for the accelerating rate at which it is melting and its potential to raise global sea levels by more than two feet. Their models showed that even the imperiled Thwaites is unlikely to rapidly collapse during the 21st century as MICI would predict.

Mathieu Morlighem, a Dartmouth professor of earth sciences and the paper's corresponding author, said that the findings suggest that the physics underlying the extreme projection included in the IPCC report are inaccurate, which can have real-world effects. Policymakers sometimes use these high-estimation models when considering the construction of physical barriers such as sea walls or even relocating people who live in low-lying areas, Morlighem said.

"These projections are actually changing people's lives. Policymakers and planners rely on these models and they're frequently looking at the high-end risk. They don't want to design solutions and then the threat turns out to be even worse than they thought," Morlighem said.

"We're not reporting that the Antarctic is safe and that sea-level rise isn't going to continue—all of our projections show a rapid retreat of the ice sheet," he continues. "But high-end projections are important for coastal planning and we want them to be accurate in terms of physics. In this case, we know this extreme projection is unlikely over the course of the 21st century."

Morlighem worked with Dartmouth's Hélène Seroussi, associate professor in the Thayer School of Engineering, along with researchers from the University of Michigan, the University of Edinburgh and the University of St. Andrews in Scotland, and Northumbria University and the University of Stirling in England.

The idea behind MICI is that if an ice shelf—the floating extension of the land-based ice sheet—collapses rapidly, it would potentially leave the ice cliffs that form the outer edge of the ice sheet exposed and unsupported. If these cliffs are tall enough, they would break under its own weight, exposing an even taller cliff and leading to rapid retreat as the ice sheet collapses inward toward the interior like a row of dominos. The loss of this ice into the ocean where it would melt is what would lead to the projected dramatic sea-level rise.

But the authors of the Science Advances study find that the glacial collapse is not that simple or that fast. "Everyone agrees that cliff failure is real—a cliff will collapse if it's too tall. The question is how fast that will happen," Morlighem said. "But we found that the rate of retreat is nowhere near as high as what was assumed in these initial simulations. When we use a rate that is better constrained by physics, we see that ice cliff instability never kicks in."

The researchers focused on Thwaites Glacier because it has been identified as especially vulnerable to collapse as its supporting ice shelf continues to break down. The researchers simulated Thwaites' retreat for 100 years following a sudden hypothetical collapse of its ice shelf, as well as for 50 years under the rate of retreat actually underway.

In all their simulations, the researchers found that Thwaites' ice cliffs never retreated inland at the speed MICI suggests. Instead, without the ice shelf holding the ice sheet back, the movement of the glacier toward the ocean accelerates rapidly, causing the ice sheet to expand away from the interior. This accelerated movement also thins the ice at the glacier's edge, which reduces the height of the ice cliffs and their susceptibility to collapse.

"We're not calling into question the standard, well-established projections that the IPCC's report is primarily based on," Seroussi said. "We're only calling into question this high-impact, low-likelihood projection that includes this new MICI process that is poorly understood. Other known instabilities in the polar ice sheets are still going to play a role in their loss in the coming decades and centuries."

Polar ice sheets are, for example, vulnerable to the established Marine Ice Sheet Instability (MISI), said study coauthor Dan Goldberg, a glaciologist at Edinburgh who was a visiting professor at Dartmouth when the project began. MISI predicts that, without the protection of ice shelves, a glacier resting on a submerged continent that slopes downward toward the interior of the ice sheet will retreat unstably. This process is expected to accelerate ice loss and contribute increasingly to sea-level rise, Goldberg said.

"While we did not observe MICI in the 21st century, this was in part because of processes that can lead to the MISI," Goldberg said. "In any case, Thwaites is likely to retreat unstably in the coming centuries, which underscores the need to better understand how the glacier will respond to ocean warming and ice-shelf collapse through ongoing modeling and observation."

The paper, "The West Antarctic Ice Sheet may not be vulnerable to Marine Ice Cliff Instability during the 21st Century," was published in Science Advances on Aug. 21, 2024. This work was supported by the National Science Foundation (grant no. 1739031) and Natural Environment Research Council (grant nos. NE/S006745/1 and NE/S006796/1).

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Journal

Science Advances

DO

10.1126/sciadv.ado7794 

Method of Research

Computational simulation/modeling

Subject of Research

Not applicable

Article Title

The West Antarctic Ice Sheet may not be vulnerable to Marine Ice Cliff Instability during the 21st Century

Article Publication Date

21-Aug-2024