Researchers refine the clock of Earth’s early complex animal life

University of Lausanne

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The researchers focused on exceptionally well-preserved sedimentary rocks deposited on ancient seafloors in what is now southern Sweden.

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Credit: Unil

How can we measure time more than 500 million years into the past? A study recently published in Nature Communications by researchers at the University of Lausanne presents a new geological “rock clock” that allows major climate events from the dawn of complex animal life to be dated with unprecedented precision.

The Cambrian Period (approximately 539 to 487 million years ago) represents a pivotal chapter in Earth’s history, marked by the rapid diversification of complex animal life in the oceans. Understanding this evolutionary turning point requires precise constraints on the timing of environmental changes that shaped early ecosystems. Until now, however, dating such ancient events remain challenging, as many sedimentary archives lack direct age markers.

To overcome this limitation, the researchers focused on exceptionally well-preserved sedimentary rocks deposited on ancient seafloors in what is now southern Sweden. These rocks accumulated continuously over millions of years and retain both fossil remains and chemical signatures of past environmental conditions. Using a drill core, the team carried out high-resolution geochemical analyses that capture subtle variations in chemistry and carbon isotopes, central component of Earth’s climate system.

The key advance came from combining these measurements with cyclostratigraphy, a method that identifies the imprint of regular climate cycles driven by small, predictable variations in Earth’s orbit around the Sun. These orbital cycles influence climate in a rhythmic way and leave repeating patterns in sedimentary rocks. By recognizing and quantifying these patterns, the researchers transformed a long sequence of rock strata into a precise, internally consistent timeline anchored directly in the geological record.

This new “rock clock” has made it possible, for the first time, to determine the timing and duration of a major global climate disturbance known as the DrumIan Carbon isotope Excursion (DICE). Beyond refining the geological timescale of the Cambrian, the results allow rock layers and fossil records from different continents to be correlated more accurately. They also provide new insights into how Earth’s climate system and early animal ecosystems responded to natural climate change in a greenhouse world, half a billion years ago.

Funded by an Ambizione grant from the Swiss National Science Foundation (SNSF), the study was carried out at the University of Lausanne in collaboration with researchers from partner institutions in Danemark (University of Copenhagen, Geological Survey of Denmark and Greenland), the United States (George Mason University) and Belgium (University of Liège).

Source : V. Jamart, Damien Pas, Linda A. Hinnov, Jorge E. Spangenberg, Thierry Adatte, Arne T. Nielsen, Niels H. Schovsbo, Nicolas Thibault, Michiel Arts & Allison C. Daley, Astronomical calibration of the middle Cambrian in Baltica: global carbon cycle synchronization and climate dynamics . Nature Communication (2026).

 

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Journal

Nature Communications

DOI

10.1038/s41467-026-70651-5 

Article Title

Astronomical calibration of the middle Cambrian in Baltica: global carbon cycle synchronization and climate dynamics

Article Publication Date

13-Mar-2026

 

Trace levels of food pathogen do not always translate to health risk, says study

Ultra-sensitive food safety tests may drive food waste and unavailability with limited public health benefit, according to a Frontiers in Science study

Frontiers

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These food safety measures and ultra-sensitive tests may drive edible food being thrown away, excessive packaging, and extra costs for consumers. 

The international team of researchers make it clear that food safety is an important concern, as foodborne pathogens account for approximately 420,000 deaths and 600 million cases of illness each year. However, the authors argue that food systems will be more sustainable, while continuing to protect public health, if “zero-detection” expectations are replaced with evidence-based targets for “sufficiently safe” food. 

Their new article sets out how regulators might find trade-offs with other important factors, such as food supply security, sustainability, and nutritional health. 

“Although the public expects food to be completely safe, there will always be some risk of foodborne illness. Zero risk doesn’t exist, and we shouldn’t be aiming for that either. Just as we don’t limit highway speeds to 10 miles per hour to minimize road deaths, we need to take a balanced approach that considers possible negative consequences of extreme food safety measures,” said lead author Prof Martin Wiedmann from Cornell University. 

Impact of aiming for zero risk 

The study’s authors highlight several situations where excessive caution can cause harm. 

Many rules and purchasing standards rely heavily on detecting a pathogen, sometimes treating any detection as unacceptable without fully considering dose, exposure, the food’s ability to support microbial growth, or who is most at risk. 

For example, a food product might be considered contaminated if it tests positive for the bacterium Listeria monocytogenes, regardless of levels. 

These alarms can result from ultra-sensitive tests detecting small amounts of microbes unlikely to cause disease in humans. In some cases, the concerns may come from bacteria that are not harmful themselves, but are an indirect indicator of contamination. 

Throwing away such food reduces the available food supply and wastes resources. Similarly, recalling food products from consumers can damage consumer trust, pushing people away from otherwise healthy products. 

Other protective measures, such as storage temperatures, packaging, and heat treatment, can waste energy, increase costs, and reduce nutritional content. While these are all important safety measures, they should only be applied if needed and associated trade-offs should be considered. 

“A tremendous amount of food is wasted that would have been sufficiently safe to eat. Too often, trade-offs such as environmental or economic costs are only considered after a traditional microbial risk assessment. We cannot afford to carry on like this at a time when we desperately need to reduce our impact on the planet and assure not only food safety but food security,” said co-author Prof Sophia Johler at Ludwig Maximilian University of Munich, Germany. 

Focus on risk rather than hazard 

The current situation is driven by an emphasis on hazard-based assessments, according to the authors, where regulations focus on detecting pathogens, regardless of the threat to consumers. The researchers argue that the food system should move towards more flexible risk-based approaches, which assess the probabilities of harms and adjust the safety measures accordingly. 

Regulations that overemphasize stringent corrective actions (such as recalls) when swab samples from a food-processing facility test positive for an indicator, for example, could lead to undue corrective actions in areas that are unlikely to contaminate the food. The authors explain that this could be an opportunity cost that diverts resources away from more effective interventions and control strategies in high-risk areas. 

“There’s well-established evidence that focusing on end-product testing is generally ineffective to ensure safety. Overemphasis on end-product testing may distract from other food safety measures (e.g., applying validated and verified process controls), which can provide greater public health benefits,” said co-author Dr Sriya Sunil at Cornell University. 

Better tools to assess priorities 

Computational tools that incorporate vast amounts of information across the food production system could help with establishing acceptable risks. 

One challenge is how to prioritize different hazards. For example, in the US, norovirus causes thousands of times more cases than Listeria monocytogenes, yet Listeria monocytogenes causes more deaths per year.  

While there are trade advantages to having consistent international food safety standards, the balance between competing interests may vary between regions. This can become even more complex when factoring in the health and environmental implications of greenhouse gas emissions. 

“Specialists across social sciences, economics, and life sciences must work together to establish values that align with consumers’ priorities. Together with advanced models that build on geographic information, AI, and genomics, we can assess, manage, and communicate risks far more accurately,” said Wiedmann. 

 

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Journal

Frontiers in Science

DOI

10.3389/fsci.2026.1720772 

Method of Research

Literature review

Subject of Research

Not applicable

Article Title

Balancing food safety and sustainability: trade-off risk assessments and predictive modeling

Article Publication Date

17-Mar-2026

 

China’s nitrogen pollution control hits air-water asymmetry: Blue skies easier than clean water

Science China Press

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Nitrogen is a critical element for food production, with synthetic fertilizers feeding more than half of the global population. However, when excessive reactive nitrogen escapes into the environment, it triggers a cascade of ecological and health crises, including severe smog, water eutrophication, and groundwater contamination. The global nitrogen cycle is currently flashing red, standing out as one of the most severely surpassed “planetary boundaries”—a macro-level “health checkup” for the Earth.

Just as people of different heights and builds require different clothing sizes, regional ecosystems have vastly different carrying capacities for nitrogen pollution. A recent study published in the National Science Review abandons the traditional one-size-fits-all approach. A research team led by Prof. Baojing Gu from Zhejiang University has successfully established customized “regional safe nitrogen boundaries” for all 2,847 counties across China.

The nationwide diagnosis is alarming. In 2020, China’s cumulative nitrogen losses surpassed the safe boundaries for atmospheric release by 54%, surface water runoff by 262%, and groundwater leaching by 258%. Currently, 69% of China’s land area exceeds at least one of these critical boundaries. Even more concerning, these affected areas are home to 96% of the national population, or approximately 1.3 billion people, placing immense pressure on local environments and public health.

To combat this crisis, the researchers assembled a comprehensive “technological arsenal”. By analyzing 734 peer-reviewed publications, they compiled 72 technical mitigation measures across the agricultural, livestock, industrial, and human waste sectors to create a Cross-System nitrogen Management (CSM) strategy.

The study demonstrates that deploying this arsenal could cut total reactive nitrogen emissions by an impressive 46%. From an economic standpoint, this strategy is a highly lucrative investment: implementing the CSM would cost approximately $102 billion, but it would generate $256 billion in societal benefits—including avoided damages to ecosystems, human health, and climate, alongside an $11 billion boost in agricultural yields. Overall, the societal return is roughly 2.5 times the cost of implementation, proving the high economic feasibility of these measures.

However, the research uncovered a striking “asymmetry” in the fight against nitrogen pollution: clearing the air is relatively achievable, but purifying the water remains an arduous challenge. Under the CSM scenario, over 80% of Chinese counties could successfully bring their atmospheric nitrogen emissions back within safe limits. Yet, despite the exact same rigorous interventions, over half of the counties would still fail to meet the safety boundaries for surface and groundwater. This persistent water crisis stems from stricter water quality standards, complex historical pollution legacy, and fragmented management systems.

That is why the authors argue that technical upgrades alone will not be enough, especially in areas where water pollution remains far above safe limits. They suggest that deeper socioeconomic transformations will also be needed, including healthier diets with less animal protein, less food waste, better recycling of manure, and more integrated governance linking air and water pollution control.

The study provides a new way to think about nitrogen management. Rather than asking how much nitrogen a country uses in total, it asks whether local losses have crossed what local ecosystems can safely tolerate. That shift, the researchers say, could help policymakers design more targeted and cost-effective strategies for protecting both food production and environmental quality.

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Journal

National Science Review

DOI

10.1093/nsr/nwag113 

Changing flight paths could slash aviation’s climate impact, study suggests

 ‘The climate opportunities and risks of contrail avoidance.’ 

University of Cambridge

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Small changes to aircraft flight paths to avoid the atmospheric conditions that create condensation trails – known as contrails – could reduce aviation’s global warming impact by nearly half, a new study suggests.

The study, led by researchers at the University of Cambridge, suggests that changing cruising altitude by a few thousand feet, either up or down, could prevent contrails from forming. Reducing or avoiding contrail formation in this way would also be faster and cheaper than other climate mitigation measures for the aviation industry, since the practice can be adopted with existing aircraft and fuel.

However, the researchers say that time is of the essence, and that the sooner airlines adopt contrail avoidance policies, the bigger the positive climate impact will be. Their results are reported in the journal Nature Communications.

Contrails are the thin white streaks seen behind aircraft flying at high altitude, and form when hot exhaust gases mix with cold, humid air at cruising altitude. Under the right conditions, the water vapour freezes into ice crystals, forming clouds that can persist for hours.

Contrails also trap heat in the atmosphere. Aviation contributes around 2–3% of global carbon dioxide emissions, but its total climate impact is larger because of non-CO₂ effects such as contrails. Interest in contrail avoidance has grown rapidly in recent years as governments and airlines search for ways to reduce aviation’s climate impact while the sector transitions to lower-carbon fuels.

“Contrail avoidance can often be as simple as changing the flight paths,” said lead author Dr Jessie Smith, from Cambridge’s Department of Engineering. “Often it’s even simpler than that – just moving slightly to a higher or lower altitude to avoid the areas of the atmosphere where contrails form.”

Smith and her colleagues modelled how altitude adjustments for contrail avoidance could affect aviation’s overall climate footprint. They found that such a programme, phased in between 2035 and 2045, could recover around 9% of the temperature budget the world has left before breaching the Paris Agreement’s 2°C limit.

However, they also found that if no action is taken, by 2050 aviation contrails will have added around 0.054°C of warming — 36% more than the warming attributable to aviation CO₂ over the same period.

“What surprised me was how quickly the temperature saving could be made,” said Smith. “Over a decade, you can take a really big chunk of aviation’s warming impact out very rapidly. That's unusual in climate science, where most changes take a very long time.”

The researchers also found that while rerouting aircraft can increase fuel use slightly, the reduction in warming from fewer contrails would more than offset the extra carbon dioxide emissions.

Implementing contrail avoidance would require airlines and air traffic controllers to adjust routes dynamically based on atmospheric conditions. Some aviation experts have raised concerns about whether such changes could increase workload for air traffic management systems, but the researchers say the adjustments required may be relatively modest.

Flights already alter their routes or altitude to avoid turbulence or bad weather, meaning similar systems could potentially be used to avoid contrail-forming regions.

“It's an operational change, not a technological one,” said Smith. “You don't need to modify aircraft. You just need to work out how it will operate, and then the system is already built for it — pilots do these manoeuvres all the time. That’s why we have more hope for this than for other interventions like sustainable aviation fuels, which face enormous infrastructure and supply-chain hurdles.”

Using a climate model that tracks temperature responses across 10,000 simulated scenarios, the researchers found that beginning contrail avoidance in 2035 rather than 2045 produces a temperature reduction at 2050 that is equivalent to roughly a 78% improvement in effectiveness. “In other words, waiting a decade has roughly the same effect as making the programme almost five times less efficient,” said Smith.

While more work is needed to improve forecasts of the atmospheric conditions that cause contrails and to better understand their climate effects, the researchers say that imperfect avoidance — even at 25% effectiveness — still delivers a meaningful climate benefit, and that starting early matters more than waiting for the technology to be perfected.

Scaling up contrail avoidance will require coordination from pilots, air traffic controllers, weather forecasters and policymakers, however. “The first step is demonstrating this works on a large scale through testing,” said Smith. “Once that's done, the policy can follow. But the modelling shows clearly that you do not want to wait for perfect conditions before you begin.”

Smith said the findings show the approach could play a major role in aviation’s climate strategy. “We’re not saying it solves everything,” she said. “But it could make a very big difference.”

Reference:
Jessie R. Smith et al. ‘The climate opportunities and risks of contrail avoidance.’ Nature Communications (2026). DOI: 10.1038/s41467-026-68784-8

 

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Journal

Nature Communications

DOI

10.1038/s41467-026-68784-8 

Article Title

The climate opportunities and risks of contrail avoidance

Article Publication Date

2-Mar-2026