How do methanotrophs handle the toxic effects of hydrogen sulfide?

Peer-Reviewed Publication

CARL R. WOESE INSTITUTE FOR GENOMIC BIOLOGY, UNIVERSITY OF ILLINOIS AT URBANA-CHAMPAIGN

 

IMAGE: M. CAPSULATUS BATH IS CURRENTLY USED COMMERCIALLY TO MAKE SINGLE CELL PROTEINS THAT ARE USED IN ANIMAL FEED. view more 

CREDIT: RAO LAB

Methanotrophs—organisms that grow by consuming methane—seem to be perfect for alleviating global warming, since methane accounts for about 30% of this effect. However, drilling sites, where the natural gas is mostly composed of methane, also contains hydrogen sulfide (H2S), which inhibits the growth of methanotrophs. In a new study, researchers have discovered that the methanotroph Methylococcus capsulatus Bath has an enzyme that helps it grow in the presence of small amounts of H2S.  

“Hydrogen sulfide is a major problem in oil and gas industries. If we are to develop biological solutions for addressing methane emissions, then we need to understand how methanotrophs respond to hydrogen sulfide,” said Christopher Rao (BSD/CABBI/GSE/MME), a professor of chemical and biomolecular engineering. “This study is one of the first investigations of how methanotrophs reprogram their metabolism in response to H2S.”

“Methanotrophs are the main methane sinks in nature since they use methane as their carbon source, unlike other bacteria, such as Escherichia coli, that use glucose,” said Sichong Pei, a former graduate student in the Rao and Mackie (MME) labs, and the first author of the paper. “By studying methanotrophs, we can understand and then engineer them to increase their methane consumption and help mitigate the greenhouse effects of methane.”

M. capsulatus Bath is currently used for commercial purposes where they are fed pure methane to make single cell proteins that are used in animal feed. Although the bacteria have been studied extensively for this purpose, it is unclear how M. capsulatus Bath performs on natural gas, which, in addition to methane, also contains carbon dioxide, nitrogen, and H2S.

“H2S is so toxic and corrosive that the petrochemical industry has to remove it from natural gas, in a step called ‘sweetening’,” Pei said. “However, we know that there are methanotrophs that live in hot springs, which have high concentrations of methane and H2S. These bacteria must have a natural resistance to sulfur compounds, which means that using these bacteria cuts out the sweetening process and saves money.”

Although other researchers have studied the inhibitory effects of H2S on M. capsulatus Bath, they only used physiological tests where they measured the growth rate of bacteria in the presence of the gas. In the current study, the group looked at transcription—the process by which cells use DNA to make messenger RNA—in the cell to further investigate the effects of H2S on the metabolism of these bacteria.

First, the researchers used different concentrations of H2S to see what concentrations were inhibitory. Although M. capsulatus Bath could grow with 0.1% H2S, the growth rate decreased at 0.5% and 0.75% concentrations, and they were completely inhibited at 1% H2S. “We were trying to find the sweet spot where the bacteria could tolerate H2S, without it being too stressful,” Pei said.

The researchers then grew the bacteria with different concentrations of H2S, including 0%, 0.1%, 0.5%, and 0.75%, and looked at the changes in RNA and small molecule levels. They found that at 0.75% H2S the bacteria switch from using the calcium dependent methanol dehydrogenase mxaF to the lanthanide-dependent methanol dehydrogenase xoxF.

“These bacteria grow on methane by first converting it to methanol, which is then converted to formaldehyde with the help of the enzyme methanol dehydrogenase,” Pei said. “The gene xoxF was identified a decade ago and it uses the element lanthanide. We saw that the transcription of xoxF increased fivefold compared to mxaF.”

Lanthanide is generally found in very low concentrations in nature—usually in the micromolar range. The question, then, is why would bacteria depend on an enzyme that uses lanthanide? “Three billion years ago, the Earth’s atmosphere mainly contained methane and H2S. It is likely that the ancient microorganisms contained enzymes that were accustomed to these harsh conditions. One hypothesis is that the bacteria inherited the xoxF gene, which produces this relatively ancient enzyme, allowing them to function under sulfide-rich conditions.”

Although these bacteria have xoxF, they primarily depend on mxaF because it is more efficient. However, the researchers showed that when these bacteria are exposed to sulfide, they switch to using xoxF. “Previously, this switch was only seen when researchers added lanthanide,” Pei said. “I believe that there is an intriguing mechanism behind the switch and this is just one piece of the puzzle.”

The study “Systems analysis of the effect of hydrogen sulfide on the growth of Methylococcus capsulatus Bath” was published in Applied Microbial and Cell Physiology and can be found at https://doi.org/10.1007/s00253-022-12236-y. The study was funded by Shell International Exploration and Production, Inc.

 

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DOI

10.1007/s00253-022-12236-y 

METHOD OF RESEARCH

Experimental study

SUBJECT OF RESEARCH

Cells

ARTICLE TITLE

Systems analysis of the effect of hydrogen sulfide on the growth of Methylococcus capsulatus Bath

Forests can help manage water amid development, climate change

Peer-Reviewed Publication

NORTH CAROLINA STATE UNIVERSITY

In areas near Raleigh projected to see heavier future development, keeping buffers of trees or other greenery around waterways could help slow rushing streams during wet conditions, and keep them flowing during dry ones. However, North Carolina State University researchers behind a recent study warned these so-called “riparian buffers” would not be a magic bullet for managing water as development increases and the climate grows warmer and wetter.

“Buffers are good for watersheds – there’s a lot of literature that shows that they’re great for water quantity and also for quality,” said the study’s lead author Elly T. Gay, a graduate student in forestry and environmental resources at NC State. “But in the future, buffers in isolation may not be viable as the only option to mitigate negative consequences that increased development and more variable climate might have on water quantity; they need to be coupled with other management strategies.”

Forests can filter water, and they can also slow water down to prevent floods or keep water levels up during droughts, said the study’s co-author Katherine Martin, assistant professor of forestry and environmental resources at NC State. Alternatively, stream flows can be more extreme in urban areas with more paved surfaces. Riparian buffers are one tool to help manage water in urban areas.

“Urban hydrology is a lot more flashy,” Martin said. “When it rains, and you have an area with a lot of buildings and roads, the rainfall goes immediately into the streams. There’s not a lot of time for it to seep into the ground. In forests, the water is filtered through the soil, and used by plants. It’s a slower process of getting the water to the stream, even if it’s not raining. That’s important for aquatic species, so they have enough water. When stream levels are low, pollutants get concentrated.”

In the study, researchers projected average stream flow between 2017 and 2060 for the Upper Neuse River Watershed, the watershed that starts in Durham, feeds into Falls Lake to supply water to Raleigh, and drains through to Goldsboro. They modeled the impact of three different scenarios for riparian buffers to see how they’d impact stream flow: They tested a “business as usual” scenario with existing forest or greenspace, which includes a 50-foot state mandated buffer area, as well as many areas that were exempted. They also looked at a scenario with 50 feet of forested buffers throughout the entire watershed; and a scenario where forest buffers were extended to 100 feet.

They also projected the impact of climate change on precipitation and temperature, and if low-intensity development were to continue to grow.

“We modeled a higher greenhouse gas emissions scenario, but precipitation was not particularly extreme,” said Martin. “We were also interested in testing how expanded development would affect stream flow because of this link between increased impervious surface, and the impact it has on water quantity and quality.”

They found that on average, daily streamflow across the watershed would increase. They projected average daily stream flow to increase by as much a 28% in some areas without buffers.

In wetter conditions, they saw that buffers linked with larger reductions in stream flow in some of the most developed areas.

During dry spells, they saw that buffers had mixed results. In some areas, buffers were actually linked with reductions in daily stream flow during dry spells – so the opposite of what they would hope to see. But, buffers did seem to help maintain water levels in areas at either end of the development spectrum: buffers helped maintain stream flow in an area of the watershed with the highest amount of future development, and they also helped maintain water levels in areas that are not yet developed.

“We found that buffers can increase flow during the lowest flow events, and they can decrease flow during the highest flow events in more localized areas,” Gay said. “These localized areas are typically in the places with the highest levels of development – we found buffers had the largest effect in those areas.”

However, researchers said the effects weren’t as striking as they expected, and there was little difference when they compared the 50-foot and 100-foot buffers.

“This suggests there is a role for buffers in mitigating extremes for stream flow, but it can’t be the only strategy,” Martin said. “We need a comprehensive plan for the future if we want to maintain high water quality that includes not only riparian buffers, but more, and larger, green spaces, which have an abundance of benefits beyond just water.”

The study, “Riparian buffers increase future baseflow and reduce peakflows in a developing watershed,” was published online in Science of The Total Environment. Co-authors included Peter V. Caldwell, Ryan E. Emanuel, Georgina M. Sanchez and Kelly M. Suttles. The work was funded by the USDA Forest Service Joint Venture Agreement No. 18-JF-11330155-036.

 

-oleniacz-

Note to Editors: The study abstract follows.

 

Riparian buffers increase future baseflow and reduce peakflows in a developing watershed

 

Authors: Elly T. Gay, Katherine L. Martin, Peter V. Caldwell, Ryan E. Emanuel, Georgina M. Sanchez and Kelly M. Suttles.

 

Published: Dec. 9, 2022, Science of The Total Environment

 

DOI: 10.1016/j.scitotenv.2022.160834

 

Abstract: Land conversion and climate change are stressing freshwater resources. Riparian areas, streamside vegetation/forest land, are critical for regulating hydrologic processes and riparian buffers are used as adaptive management strategies for mitigating land conversion effects. However, our ability to anticipate the efficacy of current and alternative riparian buffers under changing conditions remains limited. To address this information gap, we simulated hydrologic responses for different levels of buffer protection under a future scenario of land/climate change through the year 2060. We used the Soil and Water Assessment Tool (SWAT) to project future streamflow in the Upper Neuse River watershed in North Carolina, USA. We tested the capacity of riparian buffers to mitigate the effects of future land use and climate change on daily mean streamflow under three buffer treatments: present buffer widths and fully forested 15 m and 30 m buffers throughout the basin. The treatments were tested using a combination of a future climate change scenario and landcover projections that indicated a doubling of low-intensity development between 2017 and 2060. In areas with >50 % development, the 30 m buffers were particularly effective at increasing average daily streamflow during the lowest flow events by 4 % and decreasing flow during highest flow events by 3 % compared to no buffer protection. In areas between 20 and 50 % development, both 15 m and 30 m buffers reduced low flow by 8 % with minimal effects on high flow. Results indicate that standardized buffers might be more effective at a local scale with further research needing to focus on strategic buffer placement at the watershed scale. These findings highlight a novel approach for integrating buffers into hydrologic modeling and potential for improved methodology. Understanding the effects of riparian buffers on streamflow is crucial given the pressing need to develop innovative strategies that promote the conservation of invaluable ecosystem services.

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JOURNAL

Science of The Total Environment

DOI

10.1016/j.scitotenv.2022.160834 

METHOD OF RESEARCH

Computational simulation/modeling

ARTICLE TITLE

Riparian buffers increase future baseflow and reduce peakflows in a developing watershed

School garden-based interventions can improve blood sugar, reduce bad cholesterol in children

Peer-Reviewed Publication

UNIVERSITY OF TEXAS HEALTH SCIENCE CENTER AT HOUSTON

School garden-based interventions can improve metabolic parameters such as blood sugar and cholesterol in children, according to a new study from UTHealth Houston.

A cluster randomized controlled trial conducted by researchers with UTHealth Houston School of Public Health and The University of Texas at Austin found that Texas Sprouts – a gardening, nutrition, and cooking intervention implemented in elementary schools in Austin – improved glucose control and reduced bad cholesterol in high-risk minority youth. The results were published today in JAMA Network Open.

“The Dietary Guidelines for Americans recommends 2.5 cups of vegetables per day for children 9 to 13 years old,” said Adriana Pérez, PhD, senior author of the study and professor of biostatistics and data science with the Michael & Susan Dell Center for Healthy Living at UTHealth Houston School of Public Health. “Texas Sprouts incorporates nutrition, gardening, and cooking components that improved glucose control and reduced bad cholesterol in children.”

From 2016 to 2019, researchers analyzed 16 low-income elementary schools in the greater Austin area with majority Hispanic student populations. The schools were randomly assigned to either Texas Sprouts intervention or delayed intervention.

Texas Sprouts spanned the nine-month school year and involved the formation of a Garden Leadership Committee; a quarter-acre outdoor teaching garden; a series of 18 student gardening, nutrition, and cooking lessons taught by trained educators throughout the school year; and nine monthly parent lessons. The delayed intervention was implemented the following academic year and received an identical intervention.

The team measured students’ height, weight, and body mass index (BMI) parameters, as well as their glucose, insulin, insulin resistance, and lipid panel – a blood test that measures the amount of certain fat molecules known as lipids in the blood – via an optional fasting blood draw.

Compared to schools in the control group, Texas Sprouts schools saw a 0.02% reduction in HbA1c, or mean blood sugar levels over the past three months, and a 6.4 mg/dL reduction in bad cholesterol, indicating a reduced risk of diabetes and prediabetes among this population. There were no intervention effects on glucose, insulin, insulin resistance, or other lipid parameters.

Based on the study results, Perez said more elementary schools should incorporate garden-based interventions.

“Small increases in dietary fiber and vegetable intake, as well as reductions in added sugar intake, may have combined effects on lowering bad cholesterol and improving glucose control,” said Pérez, who is based in Austin.

Other co-authors from UTHealth Houston School of Public Health Austin Campus included Deanna M. Hoelscher, PhD, RDN, campus dean and director of the Michael & Susan Dell Center for Healthy Living; and Alexandra E. van den Berg, PhD, MPH, professor in the Department of Health Promotion and Behavioral Sciences and associate director of the center.

Additional co-authors, all with The University of Texas at Austin, were Jaimie N. Davis, PhD, RD; Matthew J. Landry, PhD, RDN; Sarvenaz Vandyousefi, PhD, MS, RD; Matthew R. Jeans, MS, MM; and Erin A. Hudson. Landry is also with Stanford University, while Vandyousefi is also with New York University School of Medicine and Jeans is affiliated with The Health Management Academy in Virginia.

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JOURNAL

JAMA Network Open

DOI

10.1001/jamanetworkopen.2022.50375 

ARTICLE TITLE

Effects of a School-Based Nutrition, Gardening, and Cooking Intervention on Metabolic Parameters in High-risk Youth

ARTICLE PUBLICATION DATE

10-Jan-2023

Effects of school-based nutrition, gardening, cooking intervention on metabolic outcomes in high-risk youth

JAMA Network Open

Peer-Reviewed Publication

JAMA NETWORK

About The Study: In this secondary analysis of a randomized clinical trial of 695 children, a school-based gardening, nutrition, and cooking intervention resulted in improved glucose control and reduced low-density lipoprotein cholesterol in high-risk youth. These findings suggest that elementary schools should incorporate garden-based interventions as a way to improve metabolic parameters in children. 

Authors: Jaimie N. Davis, Ph.D., R.D., of the University of Texas at Austin, is the corresponding author. 

Editor’s Note: Please see the article for additional information, including other authors, author contributions and affiliations, conflict of interest and financial disclosures, and funding and support.

#  #  #

Embed this link to provide your readers free access to the full-text article This link will be live at the embargo time http://jamanetwork.com/journals/jamanetworkopen/fullarticle/10.1001/jamanetworkopen.2022.50375?utm_source=For_The_Media&utm_medium=referral&utm_campaign=ftm_links&utm_term=011023

About JAMA Network Open: JAMA Network Open is an online-only open access general medical journal from the JAMA Network. On weekdays, the journal publishes peer-reviewed clinical research and commentary in more than 40 medical and health subject areas. Every article is free online from the day of publication.

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JOURNAL

JAMA Network Open

Fluid on the lungs: Relatively little known hazard linked to open water swimming

Older age, swimming long distances, cold water, female sex among risk factors. Often occurs in those who are otherwise fit and healthy, doctors warn

Peer-Reviewed Publication

BMJ

Fluid on the lungs, or pulmonary oedema as it’s formally known, is a relatively little known hazard associated with open water swimming, warn doctors in the journal BMJ Case Reports after treating a woman with the condition.

Older age, swimming long distances, cold water, and female sex are among the risk factors,  as are high blood pressure and pre-existing heart disease. But it frequently occurs in those who are otherwise fit and healthy, highlight the authors.

Open water swimming has become very popular, with more than 3 million enthusiasts in England in 2021 alone. But mounting evidence points to a link between the activity and a condition called swimming-induced pulmonary oedema, or SIPE for short.

First reported in 1989, SIPE leaves swimmers struggling to draw breath and depletes their blood of vital oxygen. It affects an estimated 1-2% of open water swimmers, but cases are likely to be underreported, say the authors.

The woman in question was in her 50s and a keen competitive long distance swimmer and triathlete.

Otherwise fit and well, she was struggling to breathe and coughing up blood after taking part in an open water swimming event at night in water temperatures of around 17°C while wearing a wetsuit. Her symptoms started after swimming 300 metres.

She had no medical history of note, but experienced breathing difficulties during an open water swim a fortnight earlier which had forced her to abandon the event and left her feeling breathless for some days afterwards. 

On arrival at hospital, her heartbeat was rapid, and a chest x-ray revealed pulmonary oedema. Further scans revealed that fluid had infiltrated the heart muscle, a sign of strain known as myocardial oedema. But she had no structural heart disease. 

Her symptoms settled within 2 hours of arrival at hospital. And after careful monitoring, she was discharged the following morning. 

It’s not clear exactly what causes SIPE. But it likely involves increases in arterial pressure in the lungs secondary to centralisation of blood volume in a cold environment, combined with an exaggerated constriction of these blood vessels in response to the cold and increased blood flow during physical exertion.

But recurrence is common and has been reported in 13%-22% of scuba divers and swimmers, suggesting a predisposition to the condition, say the authors. 

They advise swimming at a slower pace, accompanied, in warmer water, without a tight-fitting wetsuit, and avoidance of non-steroidal anti-inflammatories, such as ibuprofen, to minimise the risk.

For those experiencing symptoms for the first time, the authors recommend stopping swimming and getting out of the water straight away, then sitting upright, and calling for medical assistance if required.

This is just one case, emphasise the authors, whose aim in reporting it is to raise awareness among doctors and swimmers of a relatively little known condition. 

“The UK Diving Medical Committee has published guidance for divers. However, at present, there are no formal national medical guidelines concerning the recognition and management of this complex condition,” they note.

 

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JOURNAL

BMJ Case Reports

DOI

10.1136/bcr-2022-251274 

METHOD OF RESEARCH

Case study

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Myocardial oedema in the setting of immersion pulmonary oedema - Cause or effect?

ARTICLE PUBLICATION DATE

9-Jan-2023

Consumption of fast food linked to liver disease

Risk of liver damage is highest for those with obesity or diabetes

Peer-Reviewed Publication

UNIVERSITY OF SOUTHERN CALIFORNIA - HEALTH SCIENCES

 

IMAGE: ANI KARDASHIAN, MD, A HEPATOLOGIST WITH KECK MEDICINE OF USC, IS THE LEAD AUTHOR OF A NEW STUDY SHOWING THAT FAST-FOOD CONSUMPTION IS LINKED TO LIVER DISEASE. view more 

CREDIT: RICARDO CARRASCO III

LOS ANGELES — The new year has begun, and with it, resolutions for change.

A study from Keck Medicine of USC published today in Clinical Gastroenterology and Hepatology gives people extra motivation to reduce fast-food consumption.

The study found that eating fast food is associated with nonalcoholic fatty liver disease, a potentially life-threatening condition in which fat builds up in the liver.

Researchers discovered that people with obesity or diabetes who consume 20% or more of their daily calories from fast food have severely elevated levels of fat in their liver compared to those who consume less or no fast food. And the general population has moderate increases of liver fat when one-fifth or more of their diet is fast food.

“Healthy livers contain a small amount of fat, usually less than 5%, and even a moderate increase in fat can lead to nonalcoholic fatty liver disease,” said Ani Kardashian, MD, a hepatologist with Keck Medicine and lead author of the study. “The severe rise in liver fat in those with obesity or diabetes is especially striking, and probably due to the fact that these conditions cause a greater susceptibility for fat to build up in the liver.”

While previous research has shown a link between fast food and obesity and diabetes, this is one of the first studies to demonstrate the negative impact of fast food on liver health, according to Kardashian.

The findings also reveal that a relatively modest amount of fast food, which is high in carbohydrates and fat, can hurt the liver. “If people eat one meal a day at a fast-food restaurant, they may think they aren’t doing harm,” said Kardashian. “However, if that one meal equals at least one-fifth of their daily calories, they are putting their livers at risk.”

Nonalcoholic fatty liver disease, also known as liver steatosis, can lead to cirrhosis, or scarring of the liver, which can cause liver cancer or failure. Liver steatosis affects over 30% of the U.S. population.

Kardashian and colleagues analyzed the most recent data from the nation’s largest annual nutritional survey, the 2017-2018 National Health and Nutrition Examination Survey, to determine the impact of fast-food consumption on liver steatosis.

The study characterized fast food as meals, including pizza, from either a drive-through restaurant or one without wait staff.

The researchers evaluated the fatty liver measurement of approximately 4,000 adults whose fatty liver measurements were included in the survey and compared these measurements to their fast-food consumption.

Of those surveyed, 52% consumed some fast food. Of these, 29% consumed one-fifth or more daily calories from fast food. Only this 29% of survey subjects experienced a rise in liver fat levels.

The association between liver steatosis and a 20% diet of fast food held steady for both the general population and those with obesity or diabetes even after data was adjusted for multiple other factors such as age, sex, race, ethnicity, alcohol use and physical activity.

“Our findings are particularly alarming as fast-food consumption has gone up in the last 50 years, regardless of socioeconomic status,” said Kardashian. “We’ve also seen a substantial surge in fast-food dining during the COVID-19 pandemic, which is probably related to the decline in full-service restaurant dining and rising rates of food insecurity. We worry that the number of those with fatty livers has gone up even more since the time of the survey.”

She hopes the study will encourage health care providers to offer patients more nutrition education, especially to those with obesity or diabetes who are at higher risk of developing a fatty liver from fast food. Currently, the only way to treat liver steatosis is through an improved diet.

Jennifer Dodge, MPH, assistant professor of research medicine and population and public health sciences at the Keck School of Medicine of USC and Norah Terrault, MD, MPH, a Keck Medicine gastroenterologist and division chief of gastroenterology and liver diseases at the Keck School, were also authors on the study.

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For more information about Keck Medicine of USC, please visit news.KeckMedicine.org.

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JOURNAL

Clinical Gastroenterology and Hepatology

DOI

10.1016/j.cgh.2022.11.040 

METHOD OF RESEARCH

Data/statistical analysis

SUBJECT OF RESEARCH

People

ARTICLE TITLE

Quantifying the Negative Impact of Fast-Food Consumption on Liver Steatosis Among U.S. Adults with Diabetes and Obesity

ARTICLE PUBLICATION DATE

10-Jan-2023

It would take 23 million years for evolution to replace Madagascar’s endangered mammals

“Now or never” for preventing extinction

Peer-Reviewed Publication

FIELD MUSEUM

 

IMAGE: BROWN MOUSE LEMUR, ONE OF THE 104 SPECIES OF LEMURS THAT ARE CURRENTLY THREATENED WITH EXTINCTION. A TOTAL OF 17 SPECIES OF LEMURS HAVE GONE EXTINCT SINCE HUMANS ARRIVED ON MADAGASCAR. view more 

CREDIT: © CHIEN C. LEE

In many ways, Madagascar is a biologist’s dream, a real-life experiment in how isolation on an island can spark evolution. About 90% of the plants and animals there are found nowhere else on Earth. But these plants and animals are in major trouble, thanks to habitat loss, over-hunting, and climate change. Of the 219 known mammal species on the island, including 109 species of lemurs, more than 120 are endangered. A new study in Nature Communications examined how long it took Madagascar’s unique modern mammal species to emerge and estimated how long it would take for a similarly complex set of new mammal species to evolve in their place if the endangered ones went extinct: 23 million years, far longer than scientists have found for any other island.

That is, simply put, really bad news. “It's abundantly clear that there are whole lineages of unique mammals that only occur on Madagascar that have either gone extinct or are on the verge of extinction, and if immediate action isn't taken, Madagascar is going to lose 23 million years of evolutionary history of mammals, which means whole lineages unique to the face of the Earth will never exist again,” says Steve Goodman, MacArthur Field Biologist at Chicago’s Field Museum and Scientific Officer at Association Vahatra in Antananarivo, Madagascar, and one of the paper’s authors.

Madagascar is the world’s fifth-largest island, about the size of France, but “in terms of all the different ecosystems present on Madagascar, it’s less like an island and more like a mini-continent,” says Goodman. In the 150 million years since Madagascar split from the African mainland and the 80 million since it parted ways with India, the plants and animals there have gone down their own evolutionary paths, cut off from the rest of the world. This smaller gene pool, coupled with Madagascar’s wealth of different habitat types, from mountainous rainforests to lowland deserts, allowed mammals there to split into different species far more quickly than their continental relatives.

But this incredible biodiversity comes at a cost: evolution happens faster on islands, but so does extinction. Smaller populations that are specially adapted to smaller, unique patches of habitat are more vulnerable to being wiped out, and once they're gone, they're gone. More than half of the mammals on Madagascar are included on the International Union for Conservation of Nature Red List of Threatened Species, aka the IUCN Red List. These animals are endangered primarily because of human actions over the past two hundred years, especially habitat destruction and over-hunting.

An international team of Malagasy, European, and American scientists, including Goodman, collaborated to study the looming extinction of Madagascar’s endangered mammals. They built a dataset of every known mammal species to coexist with humans on Madagascar for the last 2,500 years. (Humans have lived on the island, perhaps intermittently, for the past 10,000 years, but have remained constant there for the last 2,500.) The scientists came up with the 219 known mammal species alive today, plus 30 more that have gone extinct over the past two millennia, including a gorilla-sized lemur that went extinct between 500 and 2,000 years ago.

Armed with this dataset of all the known Malagasy mammals that interacted with humans, the researchers built genetic family trees to establish how all these species are related to each other and how long it took them to evolve from their various common ancestors. Then, the scientists were able to extrapolate how long it took this amount of biodiversity to evolve, and thus, estimate how long it would take for evolution to “replace” all of the endangered mammals if they go extinct.

To rebuild the diversity of land-dwelling mammals that have already gone extinct over the past 2,500 years, it would take around 3 million years. But more alarmingly, the models suggested that if all the mammals that are currently endangered were to go extinct, it would take 23 million years to rebuild that level of diversity. That doesn’t mean that if we let all of the lemurs and tenrecs and fossas and other unique Malagasy mammals go extinct, that evolution will recreate them if we just wait around 23 million more years. “It would be simply impossible to recover them,” says Goodman. Instead, the model means that to achieve a similar level of evolutionary complexity, whatever those new species might look like, would take 23 million years.

Luis Valente, the study’s corresponding author, says he was surprised by this finding. “It is much longer than what previous studies have found on other islands, such as New Zealand or the Caribbean,” says Valente, a biologist at the Naturalis Biodiversity Center and the University of Groningen in the Netherlands. “It was already known that Madagascar was a hotspot of biodiversity, but this new research puts into context just how valuable this diversity is. These findings underline the potential gains of the conservation of nature on Madagascar from a novel evolutionary perspective.”

According to Goodman, Madagascar is at a tipping point for protecting its biodiversity. “There is still a chance to fix things, but basically, we have about five years to really advance the conservation of Madagascar’s forests and the organisms that those forests hold,” he says.

This urgent conservation work is made difficult by inequality and political corruption that keeps land-use decisions out of the hands of most Malagasy people, says Goodman: “Madagascar’s biological crisis has nothing to do with biology. It has to do with socio-economics.” But while the situation is dire, he says, “we can't throw in the towel. We’re obliged to advance this cause as much as we can and try to make the world understand that it’s now or never.”

The critically endangered Verreaux’s Sifaka is one of the 109 species of lemurs that currently are extant on Madagascar. A total of 17 species of lemurs have already gone extinct.

CREDIT

© Chien C. Lee

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JOURNAL

Nature Communications

DOI

10.1038/s41467-022-35215-3 

ARTICLE TITLE

The macroevolutionary impact of recent and imminent mammal extinctions on Madagascar

ARTICLE PUBLICATION DATE

10-Jan-2023

Endangered mammals of Madagascar: Over 20 million years of evolution under threat

Peer-Reviewed Publication

UNIVERSITY OF GRONINGEN

 

IMAGE: LOWLAND STREAKED TENREC (HEMICENTETES SEMISPINOSUS). THIS IS A SPECIES OF TENREC, A DIVERSE AND UNIQUE GROUP OF MAMMALS FOUND ONLY ON MADAGASCAR. view more 

CREDIT: CHIEN C. LEE

A new study reveals that it would take 3 million years to recover the number of species that went extinct due to humans on Madagascar. However, if currently threatened species go extinct, recovering them would take more than 20 million years, much longer than what has previously been found on any other island.

From unique baobab species to lemurs, the island of Madagascar is one of the world’s most important hotspots of biodiversity. Approximately 90% of its species of plants and animals are found nowhere else. After humans settled on the island 2500 years ago, Madagascar experienced many extinctions, including giant lemurs, elephant birds and dwarf hippos. However, unlike most islands, Madagascar’s fauna is still relatively intact. Over two hundred species of mammals still survive on the island, including unique species such as the fossa and the ring-tailed lemur. Alarmingly, over half of these species are threatened with extinction, primarily due to human influence. How much have humans perturbed Madagascar away from its natural state, and what is at stake if environmental change continues?

Malagasy mammals

A team of biologists and paleontologists from Europe, Madagascar and the United States set out to answer these questions by building an unprecedented new dataset describing the evolutionary relationships of all species of mammals that were present on Madagascar at the time that humans colonized the island. The dataset includes species that have already gone extinct and are only known from fossils, as well as all living species of Malagasy mammals. The researchers identified 249 species in total, 30 of which already are extinct. Over 120 of the 219 species of mammals that remain on the island today are currently classified as threatened with extinction by the IUCN Red List, due to habitat destruction, climate change and hunting.

Using a computer simulation model based on island biogeography theory, the team, led by biologists from the University of Groningen (Netherlands), Naturalis Biodiversity Center (Netherlands) and the Association Vahatra (Madagascar) found that it would take approximately 3 million years to regain the number of mammal species that were lost from Madagascar in the time since humans arrived . However, if currently threatened species go extinct, it would take much longer: about 23 million years of evolution would be needed to recover the same number of species. Just in the last decade, this figure has increased by several million years, as human impact on the island grows.

Extinction wave imminent

The staggering time it would take to recover this diversity surprised the scientists: ”It is much longer than what previous studies have found on other islands, such as New Zealand or the Caribbean”, leading researcher Luis Valente says The results of this new research, published in the scientific journal Nature Communications, suggest that an extinction wave with deep evolutionary impact is imminent on Madagascar unless immediate conservation actions are taken. However, the study finds that with adequate conservation action we may still preserve over 20 million years of unique evolutionary history on the island. Valente: “It was already known that Madagascar was a hotspot of biodiversity, but this new research puts into context just how valuable this diversity is. These findings underline the potential gains of the conservation of nature on Madagascar from a novel evolutionary perspective.”

Reference: Nathan M. Michielsen, Steven M. Goodman, Voahangy Soarimalala, Alexandra A.E. van der Geer, Liliana M. Dávalos, Grace I. Saville, Nathan Upham, Luis Valente. “The macroevolutionary impact of recent and imminent mammal extinctions on Madagascar”. Nature Communications 10 January 2023.

The Madagascar Sucker-footed Bat (Myzopoda aurita) belongs to an ancient family of bats that is found only on Madagascar.

CREDIT

Chien C. Lee

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JOURNAL

Nature Communications

DOI

10.1038/s41467-022-35215-3