Researchers from Switzerland have shown that patients with metabolic dysfunction-associated steatotic liver disease (MASLD) suffer poor sleep due to sleep fragmentation and wakefulness. Patients with the more severe form metabolic dysfunction–associated steatohepatitis (MASH) or with cirrhosis, but not healthy volunteers, experienced similar sleep disturbances. Whether poor sleep causes MASLD or vice versa isn’t yet clear. A single sleep hygiene education session proved insufficient to sustainably improve sleep quality and quantity.

The prevalence of MASLD (metabolic dysfunction-associated steatotic liver disease) is exploding in most regions of the world, boosted by increased obesity and sedentary lifestyles. MASLD (formerly known as non-alcoholic fatty liver disease) is already the most common liver disorder: it affects 30% of adults and between 7% and 14% of children and adolescents, and this prevalence is predicted to rise to more than 55% of adults by 2040. People with MASLD run a heightened risk of diabetes, hepatocellular carcinoma, non-liver cancers, chronic kidney disease, age-related muscle loss, and cardiovascular disease.

Earlier studies have implicated disturbances in the circadian clock and in the sleep cycle in the development of MASLD. But the American Academy of Sleep Medicine has recommended that objective measures – rather than subjective ones such as sleep questionnaires – be used to prove this hypothetical link between disorders of sleep and the circadian rhythm, MASLD, and MASH. MASH is a more severe form of MASLD, where the liver suffers damage from inflammation and tissue scarring, caused by abnormal accumulation of fat.

Don’t lose any sleep

Between 2019 and 2021, Schaeffer and colleagues recruited 46 adult women and men diagnosed with either MASLD, MASH, or MASH with cirrhosis. A further eight patients with non-MASH-related liver cirrhosis served as comparisons, while a second comparator group consisted of 16 age-matched healthy volunteers. Each study participant was equipped with an actigraph, to be worn at all times, which tracked light, physical activity, and body temperature.

Participants visited the clinic as outpatients at the start, midpoint, and end of the four-week follow-up. Both at the start and end of this period, they underwent clinical investigation, were interviewed through sleep questionnaires about their sleep habits. They also kept a sleep diary.

All patients with MASLD were obese, and 80% had metabolic syndrome. Patients with MASLD further had significantly higher levels of triglycerides, fasting glucose, and insulin in their blood than healthy participants, but lower levels of total cholesterol, ‘bad’ LDL cholesterol, and ‘good’ HDL cholesterol.

Rude awakening

Actigraph measurements didn’t reveal any differences between patients with MASLD and healthy participants when it came to things such as sleep duration or the amount of time spent in bed.

But importantly, the actigraphs showed that patients with MASLD woke 55% more often at night, and lay 113% longer awake after having first fallen asleep, compared to healthy volunteers. Patients with MASLD also slept more often and longer during the day. Sleep patterns and quality as measured by actigraph were similarly impaired in patients with MASH, MASH with cirrhosis, and non-MASH-related cirrhosis.

Subjectively, patients with MASLD self-reported their disrupted and inefficient sleep as shorter sleep with a delayed onset. In their sleep diaries, 32% of patients with MASLD reported experiencing sleep disturbances caused by psychological stress, compared to only 6% of healthy participants.

“We concluded from our data that sleep fragmentation plays a role in the pathogenesis of human MASLD. Whether MASLD cause sleep disorders or vice versa remains unknown,” said Schaeffer.

Sweetened drinks are bad for you — but an occasional slice of cake probably isn’t, scientists find. Researchers studying the effects that different types of sugar consumption have on health risks have found that although higher sugar intake raises your risk of certain cardiovascular diseases, sugary drinks in particular carry notably higher risks. Meanwhile, extremely low sugar consumption was also associated with poorer cardiovascular health. The lowest risks of cardiovascular diseases were found among people who ate occasional treats.

A little of what you fancy does you good… unless it’s a fizzy drink. Scientists studying the impact of sugar on the risk of cardiovascular disease have found that eating too much added sugar increases your risk of stroke or aneurysm, but eating a few treats is associated with a lower risk of cardiovascular diseases. Meanwhile, drinking sweetened beverages raises your risk of stroke, heart failure, and atrial fibrillation.

A spoonful of sugar

Although most public health bodies recommend limiting sugar consumption to protect your teeth and improve your diet, there has previously been limited evidence regarding the impact of sugar intake on cardiovascular diseases. These diseases are the leading cause of death and disease in Europe, and changing your diet is a comparatively easy way to reduce your risk.

To understand how sugar consumption affects cardiovascular disease risk, and whether consuming different kinds of sugar changes those risks, the scientists collected data from two major cohort studies, the Swedish Mammography Cohort and the Cohort of Swedish Men. These studies had diet questionnaires administered in 1997 and 2009, allowing the scientists to monitor participants’ diets over time.

Once exclusions had been made to ensure the two cohorts shared the same inclusion criteria and to remove independent risk factors for cardiovascular diseases, the scientists were left with a sample of 69,705 participants. They looked at three classes of sugar consumption — toppings like honey, treats like a pastry, or sweetened beverages like fizzy drinks — and seven cardiovascular diseases: two different types of stroke, heart attacks, heart failure, aortic aneurysms, atrial fibrillation, and aortic stenosis.

The participants were monitored until they died, were diagnosed with one of the cardiovascular diseases, or reached the end of the follow-up period in 2019. During this period, 25,739 participants were diagnosed with a cardiovascular disease. The scientists then used this data to break down how the different types of sugar intake affect the risk of different cardiovascular diseases.

Affairs of the heart

They found that consuming sweet drinks was worse for your health than any other form of sugar: drinking more sweetened drinks significantly increased the risk of ischemic stroke, heart failure, atrial fibrillation and abdominal aortic aneurysm.

“Liquid sugars, found in sweetened beverages, typically provide less satiety than solid forms — they make you feel less full — potentially leading to overconsumption,” said Janzi. “Context also matters — treats are often enjoyed in social settings or special occasions, while sweetened beverages might be consumed more regularly.”

Different cardiovascular diseases were affected differently by increased sugar intake, possibly because consuming additional sugar affected participants’ individual risk profile differently. Increased sugar in general raised the risk of ischemic stroke and abdominal aortic aneurysm, as well as increasing the risk of heart failure in participants with a normal BMI.

However, the highest risks of a negative health outcome arose in the lowest intake category for treats. Consuming occasional treats was associated with better outcomes than no treats at all.

“This might reflect underlying dietary behaviors — individuals consuming very little sugar might have very restrictive diets or might be limiting sugar due to pre-existing health conditions,” suggested Janzi. “While our observational study cannot establish causation, these findings suggest that extremely low sugar intake may not be necessary or beneficial for cardiovascular health.”

However, the scientists noted that more work will be needed to understand the mechanisms involved in the differential effects of different types of sugar consumption. They also pointed out that diet is highly demographically and culturally specific.

“Our findings are based on a Swedish population, which may have dietary habits and lifestyle factors that differ from those in other populations,” said Janzi. “Particularly relevant in this context is the social custom of ‘fika’ — regular coffee and pastry breaks that are deeply embedded in Swedish culture. These results may not directly translate to other populations with different dietary cultures.”

Increasing heat, droughts, floods, and salinization caused by climate change are lowering the amount of edible food produced by our staple crops. Since taking over more land for agriculture isn’t sustainable, our only path forward is to adapt the crops themselves to the new conditions. We have two options—domestication of crops’ wild relatives which are more resilient but have a lower yield, or including resilience genes in modern high-yield crops. Writing in Frontiers in Science, researchers discuss these possibilities and the critical need for more funding, research, and public understanding.

Feed the world?

Our current agricultural system produces very large amounts of food through the intensive use of fertilizers and high-production monocultures. This has absorbed the demands of our global population for decades, but we now recognize it as unsustainable. The fertilizers we are reliant on damage the environment when they are produced and pollute the environment when they are used. At the same time, due to the stresses caused by the climate crisis, key staple crops are producing less food.

Even if droughts don’t kill plants, high temperatures lower the yield. To overcome this, farmers irrigate their crops — but irrigation water usually has a high salt content, because freshwater is too much in demand. This raises the salinity of the soil, which lowers the yield of most crops that grow in it. Finally, flooding caused by extreme weather events leaves plants standing in water, creating hypoxic conditions that stop plants absorbing oxygen through their roots. This also lowers the yield of most plants.

“The problem of a sustainable diet has scientific, social, and political facets,” said Shabala. “A broader acceptance of novel technologies and a willingness to accept some cultural shifts is needed. A good example may be rice: it is a main staple food for a high percentage of the population, but many parts of the world may become unsuitable for its production. A switch to other, more resilient, crops may be needed, and I am not sure the public is ready to accept it.”

Many wild plants, including the ancestors and relatives of staple crops, are better able to cope with environmental stresses than modern crops. For our crops to survive climate change, we need to reintroduce those resilient traits.

The seeds of success

Shabala and colleague Prof Michael Palmgren from the University of Copenhagen lay out two options. The first is that we could introduce genes which support resistance to environmental stress into existing high-yield crops. This is easier where there is a close relative to borrow genes from, or where the gene remains in the plant’s DNA but has been deactivated. However, many genes contribute to resistance to environmental stress, and including multiple additional novel traits in a new varietal is difficult.

The second option is that we could domesticate wild plants which are resistant to environmental stresses but have lower yields than modern crops. This has been successful in comparatively simple cases where only small changes need to be made, but it’s unclear whether there are enough simple cases to help assure our food supply.

It’s too early at this point to know which strategy will succeed, the scientists say. However, the same critical elements are essential to the success of both: innovative gene-editing and other precision breeding technologies driven by accurate cell-based phenotyping and public acceptance of the new crops.

“One of the current challenges is to match recent scientific advances with public perception of new technologies,” cautioned Shabala. “The issue is highly politicized and there are significant commercial interests involved. And due to a lack of specific knowledge, the general public cannot distinguish the subtle differences amongst various technologies, and relies on opinions in the media.”

While hunting, an orca (identified as pod matriarch Dakota) propels a dusky dolphin into the air. Image by Maikol Barrera.

Scientists have managed to track a mysterious population of orcas living off the coast of Chile and learn more about them, starting with their food supply. Orcas divide into different ecotypes based on their hunting specialisms: new data suggests that the Chilean orcas are incredibly skilled mammal-hunters, chasing down dusky dolphins and sharing the food amongst themselves. This could mean they belong to the Type A ecotype — a potentially important piece of the puzzle for understanding and conserving orca populations in the southern hemisphere.

Off the coast of Chile, in waters filled with krill and anchovy by the Humboldt Current system, live an elusive and little-known population of orcas. Thanks to citizen science and years of dedicated surveillance, a team of scientists led by Dr Ana García Cegarra of the Universidad de Antofagasta are unveiling their secrets — starting with dinner.

García Cegarra’s team, who previously observed these orcas using fishing boats to help them capture sea lions, have now spotted them successfully hunting dusky dolphins for the first time and sharing the food among the pod. This new evidence about their eating habits may help experts understand how populations of orcas in the southern hemisphere are linked, promoting conservation efforts.

“Studying orcas in their natural environment is very challenging as they are marine top predators, travelling long distances and living offshore, which makes observation difficult,” said García Cegarra, lead author of the study in Frontiers in Marine Science. “But understanding their role in the marine environment is crucial for the conservation of this poorly-known species in the Humboldt Current.”

You are what you eat

Orcas are apex predators with an impressively varied diet — but not all orcas eat the same things. Populations can be assigned to different ecotypes based on their preferred foods, acoustics, and genetics, so understanding what the orcas of the Humboldt Current eat is a major step towards understanding where they fit in among the other orcas of the world. Five different ecotypes are reported in the southern hemisphere: some, like Type A and Type B1 orcas, focus on marine mammals, while other types prefer fish. Understanding where the Humboldt Current animals fit in would help us understand the way these populations relate to each other more broadly and conserve them for the future.

García Cegarra and her colleagues used a combination of their own surveys and citizen science data collection from whale-watching trips and fishing vessels to monitor the population and track their hunting choices. Observers recorded the presence of orcas, group composition and location, and took pictures and videos which the scientists could cross-reference with catalogues of known individuals. By combining this data with their own systematic surveys and drone footage, the scientists built up a map of orca presence in the area and tracked pods’ behavior and prey choices.

This allowed the researchers to capture evidence of the Menacho pod of orcas catching dusky dolphins — a species no orcas in this area have ever been reported successfully hunting. Dramatic images show the matriarch, Dakota, tossing a dusky dolphin into the air.

These sightings could indicate that these orcas may belong to the mammal-hunting Type A ecotype. Their prey, and their small pod sizes, would be consistent with this hypothesis, although their white eye patches are smaller than is typical of Type A orcas. They have also never been recorded in Patagonia with other Type A orcas.

“We wish we could obtain skin biopsy samples to analyze their genetic data, as there is no genetic information for orcas in this region of the south-east Pacific,” said García Cegarra. “However, they are very elusive and intelligent, which makes it difficult to approach them in the boat for biopsies.”

Sharing the spoils

The scientists’ observations of the dusky dolphin hunting also revealed that the Menacho pod were sharing their food. Food sharing is recorded among many populations of orcas, sometimes to help feed kin, and sometimes because the pod hunts cooperatively and everyone gets a share. In this case, García Cegarra and her colleagues suggest that the Menacho pod were sharing food with kin, similar to Type A orcas who hunt sea lions by deliberately stranding: female orcas were seen sharing meat with group members, allowing closer relations to eat first.

García Cegarra emphasized that much more information and systematic study is necessary to fully understand and protect this secretive population of orcas. “The fact that we have observed newborn calves is important, because it indicates that they are having offspring, but we don’t know their survival rate,” she said. “Thanks to citizen science, we can follow the presence of killer whales along thousands of kilometers of the coast of northern Chile — but most orca sightings are opportunistic.”

Planting Abies religiosa (Sacred fir) seedlings under the shade of pre-existing shrubs (Senecio cinerarioides, narrow green-greyish foliage) as protective “nurse plants”. Large trees on background are adult Pinus hartwegii, the pine that reaches the timberline. Abies religiosa is completely absent in this site at 3800 meters of elevation, northeaster slope of Nevado de Toluca volcano, central Mexico, because it is too high in elevation. Planters personnel are locals of Native Indian origin. Image credit: Cuauhtémoc Sáenz-Romero, UMSNH

Migrating monarch butterflies depend on mountain forests of sacred firs in Mexico as overwintering sites. These forests are under threat from global warming. But researchers from Mexico have now shown that seedlings derived from their original range can be transplanted successfully to a new site further east, on the higher and colder volcano Nevado de Toluca. The resulting new stand of sacred firs could ultimately serve as the overwintering sites of the future.

The migration of the monarch butterfly is one of the wonders of the natural world. Each autumn, a new generation of monarch butterflies is born in the northern United States and southern Canada. Hundreds of millions of these butterflies then fly to the mountains of Central Mexico, between 4,000km and 4,800km away. There, they overwinter in forests of the sacred fir Abies religiosa at high altitudes. Without these sacred firs, the monarchs couldn’t survive their grueling migration.

But under global warming, these forests are predicted to slowly move up the slopes. By approximately 2090 they will run out of mountain. It will thus be necessary to create new forests outside their current geographic range: for example on mountains further east, which are higher.

“Here we show the feasibility of planting new sacred fir forests on a nearby volcano, Nevado de Toluca, at altitudes between 3,400 and 4,000 meters,” said Dr Cuauhtémoc Sáenz-Romero, a professor at the Universidad Michoacana de San Nicolás de Hidalgo in Mexico, and the lead author of a new study in a new study in Frontiers in Forests and Global Change.

“We call this ‘assisted migration’: planting seedlings grown from seeds from existing sacred fir populations to new sites whose climate by 2060 is predicted to become similar to that at today’s overwintering sites due to global warming.”

Making a stand

In 2017, Sáenz-Romero and colleagues gathered seeds from cones from eight stands of sacred fir in the Monarch Butterfly Biosphere Reserve (MBBR) in Mexico, at altitudes between 3,100 and 3,500 meters. They grew seedlings from these, at first for two years in a shade-house at 1,900 meters altitude, and then for another year in a nursery at 3,000 meters. In July 2021, they transplanted the seedlings to four sites along an elevational gradient on the northeast slope of Nevado de Toluca.

The researchers chose this mountain because it is the closest to the MBBR and has a summit 1,130 meters higher than the highest occurrence – at 3550 meters – of sacred firs there. It is also a Protected Natural Area.

They planted 960 seedlings at four altitudes: 3,400, 3,600, 3,800, and 4,000 meters. The latter is the timberline of Nevado de Toluca, and was included to find the highest elevation at which sacred firs can survive in the present climate. Seedlings were distributed over 30 spatial blocks per altitude, taking care to include equal numbers from each original stand in the MBBR.

Colder and higher

The results showed that the performance of the transplanted seedlings decreased as the ‘ecological distance’ – the weighted difference across a range of climate variables such as temperature, precipitation, and dryness – between the original and the planting site increased. Overall, survival and growth worsened when seedlings were transplanted to sites colder and higher than the original stand in the MBBR. At 4,000 meters, growth was approximately nil, while many seedlings showed frost damage.

Between 3,600 and 3,800 meters, seedlings had 54% less vertical growth, 27% less biomass, and 27% less survival than at the baseline of 3,400 meters. The authors judged this survival rate to be ‘very acceptable’.

“These planted stands could ultimately serve as overwintering sites for the Monarch butterfly under warmer climates,” concluded Sáenz-Romero.

“In fact, monarch butterflies have over recent year established new and large colonies at colder places within the Nevado de Toluca, which suggests that they already are searching for new places to overwinter, as their historic sites inside the MBBR are now too warm. Once our seedlings are fully grown, they will hopefully discover our planting site, too.”

“We stress that creating new areas for monarch butterflies is not mutually exclusive with continuing efforts to conserve their current habitat in the Monarch Butterfly Biosphere Reserve. Both approaches should be complementary, with equal priority.”

This paper reviews decommissioning and abandonment in Nigeria, looks at candidate identification strategies, breaks down the methods and best practices involved, and examines the requirements for openhole and cased-hole abandonment.

All oil and gas assets—including wells, flowlines, production facilities, and all surface structures installed as part of the network of facilities required for the safe exploration, development and production of hydrocarbons—are required by law to be properly decommissioned at the end of their useful life and the environment restored to its original form.

Of particular significance are the considerations given to oil and gas well decommissioning and abandonment (D&A) because of their extensive subsurface footprint. Achieving acceptable D&A requires significant planning during the early stages of a project and involves projections and decisions being made around funding, timing, and the extent of the decommissioning that needs to be done, including proper zonal abandonment of respective reservoirs, retrieval of well construction hardware, and subsurface plugging of the well to ensure hydrocarbon never finds its way to the surface after abandonment.

The requirement and extent of oil and gas asset D&A is a statutory requirement governed by the legislature in countries of operation and governed by international best practices. These best practices ensure environmental sustainability. Provisions for D&A must be made in each operator’s financial statements to recognize the liability for D&A. This is mandated by international financial reporting standards.

The D&A process is fraught with technical and nontechnical challenges, which require significant upfront identification and robust risk identification and mitigation.

This paper reviews D&A in Nigeria, looks at candidate identification strategies, breaks down the methods and best practices involved in D&A operations for wells, and examines the requirements for openhole and cased-hole abandonment as well as the logging and testing requirements that guide decision-making.

The risks involved in D&A projects are analyzed with insights into how they tie back to the mitigations put in place to ensure successful decommissioning and restoration and how these all connect back to nature with a view to sustaining global best practices for returning our environment to its clean and green state.

Analysis by S&P shows that the annual growth in absolute emissions was less than 1% for the third consecutive year.

Absolute greenhouse gas emissions (GHG) from Canadian oil sands production registered a nominal increase of less than 1% in 2023, even as total production grew, according to a new analysis by S&P Global Commodity Insights. Since 2020, absolute emissions growth from oil sands has slowed to average about 1% per year compared with 5% in the proceeding decade.

The slowdown in absolute emissions growth has occurred even as oil sands production continues to increase. Compared with 2019, absolute emissions were 3% higher (3 million metric tons of carbon dioxide) in 2023. Meanwhile, oil sands production grew by 9% (250,000 B/D) over the same period. By contrast, in the preceding decade (2010–19), absolute emissions increased, on average, by nearly 3 million mtpa carbon dioxide while production grew at an annual average of 200,000 B/D.

“The yearslong trend of declining greenhouse gas intensity, coupled with slower production growth, continues to slow the rise of absolute emissions,” said Kevin Birn, Canadian oil markets chief analyst at S&P Global Commodity Insights. “The fact that the rate of production additions is outstripping emissions growth indicates that the production that is coming forward is of a much lower intensity than the overall average.”

The S&P analysis found that the average GHG intensity of oil sands production fell to 58 kg of carbon dioxide equivalent per barrel (kgCO₂e/bbl) in 2023, the most recent year that S&P Global Commodity Insights estimates are available. Since 2009, the average GHG intensity of oil sands production has declined by nearly 28%, or nearly 23 kgCO₂e/b of marketable product.

S&P Global Commodity Insights previously noted that the lower pace of absolute emissions growth may indicate oil sands emissions could peak sooner and at a lower level than previously expected. The latest analysis, based on 2023 operations, continues to suggest this could be the case. Nevertheless, absolute emissions are still expected to rise in the near term because of more pronounced production additions expected in the next few years.

“Anticipated production additions are expected to outstrip intensity reductions in the near term, and that means that greater decarbonization efforts from the sector will likely be required to meet the proposed federal oil and gas emissions limit by 2030,” Birn said. “Bringing sufficient carbon and storage capacity online in just a few short years will be a challenge. However, the slower pace of emissions additions could make the proposed 2030 emissions limit more achievable.”

In space, astronauts are exposed to extreme stressors our bodies don’t experience on Earth. Microgravity, higher radiation, and a high workload can impact cognitive performance. To find out which cognitive domains are affected by spaceflight, researchers analyzed data from 25 professional astronauts. They found that while on the ISS, astronauts took longer to perform tasks concerned with processing speed, working memory, and attention, but that a six-month stay in space did not result in lasting cognitive impairment once crews returned to Earth.

A stay in space exerts extreme pressures on the human body. Astronauts’ bodies and brains are impacted by radiation, altered gravity, challenging working conditions, and sleep loss – all of which could compromise cognitive functioning. At the same time, they are required to perform complex tasks, and minor mistakes can have devastating consequences.

Little is known, however, about whether astronauts’ cognitive performance changes while in space. Now, working with 25 astronauts who spent an average of six month on the International Space Station (ISS), researchers in the US have examined changes in a wide range of cognitive performance domains. This dataset makes up the largest sample of cognitive performance data from professional astronauts published to date.

“We show that there is no evidence of any significant cognitive impairment or neurodegenerative decline in astronauts spending six months on the ISS,” said Dr Sheena Dev, a researcher at NASA’s Behavioral Health and Performance Laboratory and first author of the Frontiers in Physiology study. “Living and working in space was not associated with widespread cognitive impairment that would be suggestive of significant brain damage.”

Slower, but no less accurate

Astronauts underwent a series of tests developed to assess a range of cognitive domains using 10 subtests. For each of these tests, the researchers measured speed and accuracy at five time points: pre-mission, early and late flight respectively, as well as at 10 and 30 days after landing.

The results showed that responses to tasks assessing processing speed, working memory, and attention were slower than on Earth, but they were no less accurate. These changes, however, did not persist equally long. “Slowed performance on attention, for example, was only observed early during the mission while slowed performance on processing speed did not return to baseline levels until after the mission ended and crew were back on Earth,” Dev pointed out.

Overall, astronauts’ cognitive performance was stable, and the researchers did not find evidence that would suggest damage to the central nervous system during a six-month space mission.

Data for future space missions

The results showed that some cognitive domains were more susceptible to be impacted than others. “Even on Earth, processing speed, working memory, and attention are cognitive domains that can show temporary changes when an individual is under stress. Other domains, such as memory, are less vulnerable to stressors. For example, if you happen to have a really busy day but couldn’t get much sleep the night before, you might feel like it’s hard to pay attention or that you need more time to complete tasks,” explained Dev.

Astronauts are exposed to these stressors, too, but additional stressors that are unique to space also take their toll. “We found that the most vulnerable domains while astronauts are aboard the ISS are the same as those that are more susceptible to stressors on Earth,” Dev said.

The researchers said that their study can help them understand which changes in cognitive performance might be expected when humans go to extreme environments. What the study didn’t show, however, is why those changes happened, the researchers cautioned. It also didn’t set out to assess whether astronauts’ operational performance suffered. “It could be that even in areas with observed declines, astronauts were still able to compensate and effectively complete their tasks,” Dev said.

Once astronauts start traveling deeper into space – to the moon or Mars, for example – this data from the low Earth orbit can also provide a comparison which can help detect cognitive changes brought about by increased radiation exposure and extended communication delays more quickly, the researchers concluded.

Scientists from the US measured the relative amounts of ‘bioreactive’ iron in four sediment cores from the bottom of the Atlantic. They showed for the first time that the further dust is blown from the Sahara, the more iron in it becomes bioreactive through chemical processes in the atmosphere. These results have important implications for our understanding of the growth-promoting effect of iron on oceanic phytoplankton, terrestrial ecosystems, and carbon cycling, including under global change.

Iron is a micronutrient indispensable for life, enabling processes such as respiration, photosynthesis, and DNA synthesis. Iron availability is often a limiting resource in today’s oceans, which means that increasing the flow of iron into them can increase the amount of carbon fixed by phytoplankton, with consequences for the global climate.

Iron ends up in oceans and terrestrial ecosystems through rivers, melting glaciers, hydrothermal activity, and especially wind. But not all its chemical forms are ‘bioreactive’, that is, available for organisms to take up from their environment.

The core of the matter

Owens and colleagues measured the amounts of bioreactive and total iron in drill cores from the bottom of the Atlantic Ocean, collected by the International Ocean Discovery Program (IODP) and its earlier versions. IODP aims to improve our understanding of changing climate and oceanic conditions, geological processes, and the origin of life. The researchers selected four cores, based on their distance from the so-called Sahara-Sahel Dust Corridor. The latter ranges from Mauritania to Chad and is known to be an important source of dust-bound iron for downwind areas.

The two cores closest to this corridor were collected approximately 200km and 500km west of northwestern Mauritania, a third in the mid-Atlantic, and the fourth approximately 500km to the east of Florida. The authors studied the upper 60 to 200 meters of these cores, reflecting deposits over to the last 120,000 years – the time since the previous interglacial.

They measured the total iron concentrations along these cores, as well as concentrations of iron isotopes with a plasma-mass spectrometer. These isotope data were consistent with dust from the Sahara.

They then used a suite of chemical reactions to reveal the fractions of total iron present in the sediments in the form of iron carbonate, goethite, hematite, magnetite, and pyrite. The iron in these minerals, while not bioreactive, likely formed from more bioreactive forms through geochemical processes on the seafloor.

“Rather than focusing on the total iron content as previous studies had done, we measured iron that can dissolve easily in the ocean, and which can be accessed by marine organisms for their metabolic pathways,” said Owens.

“Only a fraction of total iron in sediment is bioavailable, but that fraction could change during transport of the iron away from its original source. We aimed to explore those relationships.”

Blowing in the wind

The results showed that the proportion of bioreactive iron was lower in the westernmost cores than in the easternmost ones. This implied that a correspondingly greater proportion of bioreactive iron had been lost from the dust and presumably been used by organisms in the water column, so that it had never reached the sediments at the bottom.

“Our results suggest that during long-distance atmospheric transport, the mineral properties of originally non-bioreactive dust-bound iron change, making it more bioreactive. This iron then gets taken up by phytoplankton, before it can reach the bottom,” said Dr Timothy Lyons, a professor at the University of California at Riverside and the study’s final author.

“We conclude that dust that reaches regions like the Amazonian basin and the Bahamas may contain iron that is particularly soluble and available to life, thanks to the great distance from North Africa, and thus a longer exposure to atmospheric chemical processes,” said Lyons.

“The transported iron seems to be stimulating biological processes much in the same way that iron fertilization can impact life in the oceans and on continents. This study is a proof of concept confirming that iron-bound dust can have a major impact on life at vast distances from its source.”

As the climate crisis alters familiar growing conditions, we urgently need to find ways of protecting the world against famines. Currently, our food system is heavily dependent on pesticides—but these pesticides grow less effective as pests develop resistance to them, have a substantial carbon footprint, and can damage biodiversity. Induced resistance, using plants’ immune systems to build up their strength and fight pests, could be critical to reducing our reliance on pesticides and developing sustainable agriculture.

Food for thought

Right now, crops are mostly protected using pesticides and breeding for resistance genes, although there is a significant risk that pests will out-evolve plants intended to resist them. Induced resistance enhances abilities a plant already has to provide more sustainable and potentially broader-spectrum protection: defending against several pathogens and pests, not just one.

Induced resistance can take several different forms—for instance, plants releasing compounds which attract herbivores’ predators—but the best known and most widespread is defense priming. Defense priming takes place when part of a plant experiences a stress, and this weakly activates defense mechanisms which then activate fully when the plant undergoes another attack. Intriguingly, this priming seems to last so long that it can appear in the next generation of plants, potentially transmitted via epigenetic mechanisms.

However, induced resistance usually doesn’t offer complete protection, so must be combined with other measures. It also needs to be carefully calibrated to ensure that it doesn’t leave a plant open to other threats and doesn’t compromise growth by causing the plant to allocate too many resources to defense.

“Induced resistance is the result of a complex network of developmental and environmental pathways in the plant,” explained Mauch-Mani. “So safe and efficient exploitation of induced resistance is not as straightforward as the introgression of a single gene or spraying a single pesticide. We will need case-by-case evaluation of the optimal growth conditions, crop germplasm, and agricultural practices to capitalize on induced resistance’s multifaceted benefits.”

Seeds of the future

Once implemented, induced resistance could do more than just ward off pests. Some of the defense compounds that plants produce in response to induced resistance are linked to health benefits or higher-quality nutrition, meaning that we could benefit not just from avoiding pesticides but from eating healthier food. Induced resistance is also faster than traditional breeding, offering a quicker way to adapt to changing climatic conditions. It’s harder for evolving pests to evade, and it has the potential to offer broad-spectrum protection.

Combined with integrated pest management that uses pests’ natural enemies as crop protection, we could use induced resistance to cut pesticides to a bare minimum, making agriculture more sustainable. We could also secure much longer-lasting crop protection, once we develop a better understanding of the epigenetic mechanisms that transmit defense priming to a new generation.

To make induced resistance part of farmers’ and food scientists’ toolkits, the researchers said we urgently need more research that covers more real-world circumstances. We also need to understand how induced resistance performs under less controlled conditions and support the development of methods that can be scaled up to field trials and then into full-scale agriculture. The researchers also called for legislative support to establish quality standards, protecting producers and consumers.

“We strongly believe that fundamental research into induced resistance will be critical for the transition towards a truly sustainable food supply,” said Mauch-Mani. “However, there is an urgent need for better communication between discovery-focused research and other stakeholders who have the expertise to translate discovery into application.

“Governments need to create a research environment and funding climate that allows for more efficient knowledge exchange between scientists, policymakers, and industry. Like the biology underpinning it, successful exploitation of induced resistance relies on a multifaceted effort.”