Spring in Chinese cities is pulling away from spring in the countryside — and warmth alone does not explain it

Across 354 Chinese cities, urban green-up advanced faster than rural green-up in four of five cases; a study in The Innovation traces the gap to a faster decline in the heat plants must accumulate

Innovation Press

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Graphical abstract. On the left, rural vegetation: green-up advances slowly because the heat requirement — the accumulated warmth a plant must absorb before it breaks dormancy — changes little, and the spring phenology timeline is long. On the right, urban vegetation: the heat requirement falls further, so the same warming delivers leaf-out sooner and the timeline is short. Insets show green-up date against year for urban and rural vegetation and the magnitude of heat-requirement change for each. Graphical abstract of the published article, distributed by the journal with the pape.

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Credit: He C., Wang X., Peñuelas J., et al., (2026). Heat requirement, not warming, governs the urban-rural disparity in spring phenology advancement. The Innovation 7(9), 101343. https://doi.org/10.1016/j.xinn.2026.101343

Spring reaches a Chinese city before it reaches the fields around it, and the head start is growing. A study in The Innovation tracked the spring green-up date across 354 Chinese cities from 2001 to 2020 and found urban vegetation advancing faster than rural vegetation in 80.4% of them. Where the gap was significant, cities pulled ahead by about 0.37 days a year — a week over the record.

The obvious answer is heat. Cities run warmer than the land around them, and earlier work credited a stronger temperature response. The authors tested that three ways — ridge regression, ordinary least squares and a log-log model — against five definitions of the rural buffer. Urban and rural sensitivity to temperature, rainfall and radiation came out statistically indistinguishable.

Green-up dates came from NASA's MCD12Q2 product at 500 m, and the analysis was repeated on 30-m Landsat imagery for Beijing, Shenyang and Changchun, where urban vegetation advanced 3.00 ± 1.28 days a year against 2.64 ± 1.41 in farmland. The team then ran 11 chilling models and five heat-requirement models, fed 17 environmental variables into an XGBoost model read through SHAP values, and used convergent cross mapping to test which way causation runs.

Heat requirement won. Its partial correlation with green-up reached 0.86 ± 0.03 in cities against 0.81 ± 0.04 in the countryside, while chilling sat at 0.69 on both sides and matched observed trends in only 4 of 11 models where spring was delaying. At 30 m the heat signal held (r = 0.91 urban, 0.90 rural) as chilling fell to 0.70. Vegetation structure then tunes the response: species richness is the strongest spatial predictor in cities, tree density in farmland, where canopy shade and evaporative cooling buffer the local climate.

Four standard models — growing degree day, spring warming, sequential and parallel — were asked to reproduce the record. Observed urban trends ran at −0.94 ± 0.08 days a year against −0.83 ± 0.07 in rural areas; the models produced −0.62 to −0.42, and only the parallel model separated the two (p = 0.004). Pixel by pixel the gap widened further: 36.1% of urban pixels carried significant trends, against fewer than 7% under any model.

The result is a hierarchy rather than a single cause. Urbanisation sets the stage, vegetation structure tunes the answer, and the heat threshold does the work — which matters for what gets planted. Richer urban greenspace tracks climate more closely but swings more between years; denser rural woodland is steadier and slower to adapt.

A spring that moves a week in 20 years also moves everything timed to it: the pollinators that arrive with the first flowers, the migrants that land for the flush of insects, the shade that decides how hot a street gets in June.

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Journal

The Innovation

DOI

10.1016/j.xinn.2026.101343

Method of Research

Observational study

Subject of Research

Not applicable

Article Title

Heat requirement, not warming, governs the urban-rural disparity in spring phenology advancement

 

Extreme heat creates hurdle for athletes getting carbohydrates into muscles

Nearly 30% of ingested carbs remained ‘unburned’ during exercise trial, even after participants took part in heat acclimation

University of Birmingham

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Endurance sport has seen a renaissance in the understanding of carbohydrates for fuel in recent years. Advances in sports science have led to much higher levels of carbohydrates either eaten or drunk during exercise, with some top sports stars consuming 120g or more per hour during a race. This step change has contributed to the first competitive sub 2hr marathon, and record-breaking triathlon and cycling race times.

 

While scientists have known that high temperatures stop athletes from fully using these high levels of carbohydrates as fuel during intense exercise, the mechanisms that are stopping this from happening have been poorly understood.

 

But now, a new study from the University of Birmingham which worked with trained cyclists has investigated the scale of how much heat stops ingested carbohydrates from being available to fuel exercise.

 

In the paper published in the Journal of Physiology, amateur cyclists were tested during a 90-minute sub-maximal cycle ride on a static bike to see how much glucose that they consumed was able to be used as fuel under different heat conditions. 17 participants took part in the study, which included two tests performed under very hot temperatures of 40C and 20% humidity, and one at a controlled 20C. Prior to the second ‘hot’ test, participants took part in a nine-day period of heat acclimation, exercising in similar conditions.

 

Across the study, participants on average were able to use 27% less ingested carbohydrate in hot conditions, regardless of whether they had done heat acclimation. Analysis of the findings suggest that heat is creating a barrier that stops the ability of all carbohydrates in the blood from being transferred into or used by the muscle and other body systems for fuel.

 

Professor Gareth Wallis, from the University of Birmingham and senior author of the study, said: “Endurance athletes are taking on significantly higher amounts of carbohydrate during sport by rule. As some of the top events around the world are being held in increasingly oppressive heat, understanding what heat does to our bodies and how it uses carbohydrates is crucial – and could make the difference between podium places among the very best competitors.

 

“The headline findings are significant. With nearly 30% of glucose not being able to be used to fuel aerobic performance, extreme heat could be having a significant effect on endurance athletes’ ability to hit their best speeds.”

 

What is reducing the body’s use of carbs in hot conditions?

 

The team of sports scientists analysed data on carbohydrate use taken during the test. They found that this reduction in the ability to burn carbs as fuel was not due to a reduced ability to process carbs in the gut, as was thought previously.

 

Instead, the team discovered that there is a mechanism of action stopping a typical amount of glucose that would be taken up from circulation by muscles and being used as energy. A combination of blood and muscle biopsy analysis, and the use of stable-isotope tracers, enabled the researchers to measure how carbohydrates consumed during the trial were absorbed and used during exercise.

 

While the team thought that heat acclimation might have a benefit in making more ingested glucose available under hot conditions, there was no observed difference. After heat acclimation, participants showed expected signs of adapting to the heat. Their core temperature was lower both at rest and during exercise in the heat, their blood plasma volume expanded, and they had lower heart rates and found the exercise less hard and less uncomfortable.

 

Professor Gareth Wallis continued: “We have observed for the first time that heat is creating a barrier that is affecting how the body removes glucose from blood and uses it as energy. While we can’t yet say exactly what is stopping the full transfer of glucose into systems to fuel exercise performance, we have shown that the issue exists at the point of transfer out of the blood supply and subsequent use rather than from the gut into the blood stream.

 

“We have also been able to show that heat acclimation, despite improving people's ability to cope with the heat, did not rescue the reduction in capacity to use ingested carbohydrates. The same mechanisms that are creating a barrier affecting the transfer and use of glucose from the blood supply were not alleviated with acclimation - this was contrary to what we and most would expect.”

 

The findings taken from hot conditions of 40C and 20% humidity suggest that athletes should not reduce their carbohydrate intake during exercise as they look to prioritise consuming enough liquid for cooling core body temperature during extreme heat conditions. Future studies will identify the precise barrier that stops the muscles from being able to use the full glucose load.

 

Dr Tim Podlogar from Exeter University and lead author of the study said: "The key message for athletes is simple: do not cut back on carbs in the heat. Your gut is still absorbing them, so they are getting into your body, and eating less would only leave you with even less fuel. Aim for a similar carbohydrate intake as you would in cooler conditions and make sure you are drinking enough to allow the body to produce sweat and cool you down. Getting both in can be challenging when it is hot, so practise your race fuelling and drinking in training, ideally in warm conditions, to get your gut used to it. And use the usual tricks to stay cool, like cold drinks, ice slushies, ice socks, and pouring water over yourself.”

 

The study has been led by the team involved in a personalised carbohydrate test for performance athletes. Launched by Professor Gareth Wallis, fuelsync® shows exactly how much carbohydrate taken during exercise is converted into usable energy. Validated in a peer reviewed paper published in Performance Nutrition, the fuelsync® test demonstrates how athletes can have an optimum amount of glucose intake that is up to 25% more or less than current academic-led guidelines.

 

The study received financial support from the U.S. Army Medical Research and Development Command.

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Journal

The Journal of Physiology

DOI

10.1113/JP289304

Method of Research

Experimental study

Subject of Research

People

Article Title

Heat acclimation does not alleviate the reduction in exogenous glucose oxidation that occurs when exercising in hot conditions

Article Publication Date

11-Nov-2026

 

Even in record-breaking high temperatures, schoolchildren in Arizona continue to play outside—with higher perceived and measured outside temperatures surprisingly associated with increased physical activity at recess

The findings indicate a potential mismatch between children’s behavior and heat-related risk

PLOS

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Children playing outdoors during school recess

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Credit: Arizona State University Heat Futures Lab

In a survey of 170 elementary students in the Phoenix, AZ metropolitan area over August-September 2024 (average maximum temperature during this period was 97°F), students reported feeling “a lot hot” directly after recess in 45% of surveys—and higher perceived heat was associated with greater physical activity intensity, according to a study published November 11, 2026 in the open access journal PLOS Global Public Health by Kylie Wilson from University of Arizona Cancer Center, United States, and colleagues.

Extreme heat can impact how and if children play outside while at school. Children younger than 10 may be uniquely vulnerable to heat-related illness during extreme temperatures for both physiological and behavioral reasons.. In this study, the authors examined if children’s perceptions of heat while playing outside corresponded with actual air temperatures, as well as whether their perceptions of outdoor heat were related to changes in their recess activity over time.

Wilson and colleagues surveyed children at five elementary schools in the Phoenix Metropolitan Region (Arizona, United States) during the first six weeks of the 2024-2025 school year (August-September). During this period, Phoenix experienced extreme heat: its hottest September, its hottest year (2024) to date, and the longest run of days with maximum temperatures at or above 100°F (37.8°C). Across the four schools included in analyses, average outdoor shade canopy coverage ranged from 13.5% to 53.9%.

Immediately after outdoor lunch recess, students self-reported the intensity of their physical activity on a 3-point scale: sedentary (not breathing hard at all), light physical activity (breathing hard a little), and moderate-to-vigorous physical activity (breathing hard a lot). Students also reported their perceived heat levels on a 3-point scale: “not at all hot,” “a little hot,” or “a lot hot” immediately after recess. Daily air temperature data at scheduled recess times were obtained from the nearest weather station.

170 students completed 981 surveys, with individual participation ranging from 2 to 11 surveys per student (mean = 5.8 surveys). Outdoor air temperatures during recess across the study period for schools in the sample ranged from 90°F (32.2°C) to 108°F (42.2°C); the mean temperature was 97.9°F (36.6°C). Across schools, students reported that an average of 34.5% of recesses were predominantly spent sedentary, 42.5% in light physical activity, and 23.1% in moderate-to-vigorous physical activity. These distributions remained relatively consistent over the six-week period. Students also reported feeling “a lot hot” in 45% of observations. Higher perceived heat was associated with greater physical activity intensity, and the authors also found that perceived heat did not meaningfully alter activity trajectories over the study period.

The authors note that the positive association between perceived heat and activity does not indicate causal directionality: because the surveys happened directly after recess, children’s responses may likely reflect feeling especially hot after intense physical exertion, as opposed to higher heat encouraging intense play.

Regardless, their findings highlight a disconnect between children’s activity and environmental heat risk during outdoor recess: children continued to engage in intense physical activity under extreme heat, even when they reported feeling hot, and did not change activity intensity across repeated heat exposures. The authors conclude: “Because children in school settings have limited capacity to independently regulate their thermal environment and may not have full access to critical protective resources (e.g., shade, water), these findings underscore the importance of proactive, adult-guided strategies to support heat-adaptive physical activity in schools rather than reliance on children’s self-regulation.”

The authors add: “One of the most interesting findings was that children continued to engage in physical activity, including moderate-to-vigorous activity, at a pretty consistent rate even when outdoor temperatures were extreme and they reported feeling very hot. These results highlight an important challenge for schools - rather than simply eliminating outdoor activity during hot weather, we need proactive strategies to help schools determine when and how children can safely remain active.”

This project was supported by the 2023 Heat and Health CHS Pilot Grant Initiative at Arizona State University. Wilson was supported by the University of Arizona Cancer Center Office of Cancer Research Training & Education Coordination (CRTEC) during a portion of this work. Poulos and Vanos were also supported by funding from the National Science Foundation (NSF GEO/RISE-2521935). Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the NSF.

For related information, please visit ASU Heat Futures Lab, Active Schools & Communities Lab at Arizona State University, HUM.LAB, or HeatReadyTM Schools

 

In your coverage please use this URL to provide access to the freely available article in PLOS Global Public Health:https://plos.io/4sNnhav

 

Citation: Wilson K, Vanos J, Lim CC, Poulos A (2026) Children’s physical activity during six weeks of school recess in hot weather: Associations with perceived and measured heat. PLOS Glob Public Health 6(11): e0007432. https://doi.org/10.1371/journal.pgph.0007432

Author Countries: United States

Funding: This work was supported by the 2023 Heat and Health CHS Pilot Grant Initiative at Arizona State University (AP and JV) which provided project support for recruitment incentives, materials, and supplies. No salary support was provided through this funding source. KW received salary support during a portion of this work from the University of Arizona Cancer Center Office of Cancer Research Training & Education Coordination (CRTEC). AP and JV received salary support during a portion of this work from the National Science Foundation (NSF 2521935). CL received salary support during a portion of this work from the National Institute of Environmental Health Sciences of the National Institutes of Health (R01ES034740, P20ES036112, P30ES006694, and P42ES00494). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

 

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Journal

PLOS Global Public Health

DOI

10.1371/journal.pgph.0007432

Article Publication Date

11-Nov-2026

 

Forests in Japan shift toward trees adapted to warmer climates

Climate-related changes in forest structure and tree composition revealed by long-term monitoring

Osaka Metropolitan University

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The progressive replacement of certain forest tree species by others, particularly in boreal coniferous forests mixed with deciduous broadleaved trees. 

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Credit: Osaka Metropolitan University

Climate change has caused substantial alterations in forest ecosystems worldwide through changes in temperature and precipitation patterns. A new study from Osaka Metropolitan University (OMU) suggests that these effects are also evident in Japan, where forests are undergoing changes in structure and shifts towards tree types adapted to warmer climates.

A research group led by Associate Professor Tetsuro Yoshikawa and Professor Yayoi Takeuchi of OMU investigated forest changes by compiling long-term monitoring data from 191 forest plots across Japan from the 1950s to 2020. 

"Japan spans a wide range of climatic zones and contains diverse forest biomes, making it an ideal setting for investigating forest change," Associate Professor Yoshikawa, the first author of the study, explained. 

The researchers analyzed annual rates of change in Total Basal Area (TBA), the sum of tree trunk cross-sectional areas measured at chest height within a plot. TBA reflects both tree size and density and provides a measure of the forest’s structure. They also investigated the changes in the relative dominance of four major tree groups: boreal conifers, deciduous broadleaved trees, temperate conifers, and evergreen broadleaved trees. 

They found that changes in forest structure were closely associated with climate change, as greater increases in mean annual temperature were associated with increases in TBA. On the other hand, more rapid increases in annual precipitation were associated with decreases in TBA.  

As increased precipitation can be associated with more severe typhoon disturbances, the findings support the hypothesis that such disturbances have contributed to the decline in TBA in recent years.  

The researchers also found that the relative dominance of the cold-adapted boreal conifers declined, while that of warm-adapted deciduous broadleaved trees increased in some regions. This pattern is consistent with a phenomenon known as thermophilization: an increase in dominance of species adapted to warmer climates in communities.  

"These changes suggest that warming is affecting not just the growth of individual trees but also the composition of Japan's forests," Professor Takeuchi said. "Over time, such changes could contribute to shifts in the distribution of forest biomes." 

Overall, the findings highlight the complex effects of climate change on forests in Japan.  

“Although our findings capture changes that occurred in Japanese forests up to 2020, the impacts of climate change are expected to become even more pronounced in the future,” Associate Professor Yoshikawa concluded. “Continued long-term monitoring of forest ecosystems will be increasingly important for detecting ecological changes and improving our ability to predict their consequences for forest environments and people's lives.” 

The findings were published in Forest Ecosystems. 

Plots were located on the four main islands (Hokkaido, Honshu, Shikoku, and Kyushu) and nearby islands, including the Ryukyus.  

Circles show old-growth forests, and triangles denote secondary forests.  

Colors indicate the most dominant type of tree in the plots: blue, BC: boreal conifer; green, DB: deciduous broadleaved tree; orange, TC: temperate conifer; red, EB: evergreen broadleaved tree. 

Credit

Tsutom Hiura, The University of Tokyo

 

About OMU  

Established in Osaka as one of the largest public universities in Japan, Osaka Metropolitan University is committed to shaping the future of society through the “Convergence of Knowledge” and the promotion of world-class research. For more research news, visit https://www.omu.ac.jp/en/ and follow us on social media: X, Instagram, LinkedIn. 

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Journal

Forest Ecosystems

DOI

10.1016/j.fecs.2026.100531

Method of Research

Meta-analysis

Subject of Research

Not applicable

Article Title

Long-term monitoring reveals differential climate and disturbance responses in Japanese forest biome composition

 

From Romania to Kazakhstan, summer droughts linked to less winter ice in two rapidly warming seas

Scientists show direct link between winter ice cover in Barents and Kara seas and summer drought in eastern Europe and central Asia

Frontiers

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This summer, with its scarce rainfall and repeated heatwaves, witnessed one of the most severe droughts in European history since 1540. The resulting wildfires across western Europe received considerable media attention, but eastern Europe was also heavily hit, worsening the humanitarian crisis caused by the war in Ukraine. Simulations have shown that such droughts are bound to become more frequent and severe in the future due to man-made global warming.

But what if such droughts could be predicted in advance? This would make it possible to take timely mitigating action. Exploring whether winter sea ice cover might offer an early clue to summer drought risk was the goal of a new study in Frontiers in Water.

"Here we show evidence of a directional, mechanistic link from reduced winter sea ice in the Barents and Kara Seas, in the Arctic, to more summer drought across a wide area of Eurasia, stretching from eastern Romania, Moldova and Ukraine, across the northern Black Sea and Caspian regions, into western Kazakhstan,” said lead author Dr Petru C Vaideanu, a scientist at the Centre of Excellence for Climate and Societal Changes at the University of Bucharest, Romania.

“If we have a winter with much less sea ice than usual, we have an early clue that drought is more likely in these regions the following summer."

Fastest warming seas on Earth

The researchers focused on the Barents and Kara Seas to look for a link with drought, because these waters have seen some of the Arctic’s steepest declines in winter sea ice since the 1980s. Unless measures are taken to reduce CO2 emissions, IPCC simulations project that by the end of this century, sea surface temperatures there could increase by 4°C to 5°C. This rapid warming is due to several interacting factors, including warmer Atlantic water entering the region, local feedbacks involving shrinking sea ice, changes in clouds, and other atmospheric processes.

Vaideanu and colleagues from the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research in Bremerhaven, Germany, retrieved historic records of sea ice in these waters from October through March. They used ERA5, a database from the European Centre for Medium-Range Weather Forecasts, which combines observations with a weather model to estimate monthly averages for atmospheric conditions across Eurasia from 1940 onwards. They calculated drought conditions separately, using records of precipitation and estimates of potential evapotranspiration. They then looked for areas with unusually dry conditions from May through September, reflecting less-than-average rainfall or greater atmospheric demand for moisture.

The authors took care to adjust for the long-term rise in atmospheric CO2 concentrations. This was important, as both sea ice cover and summer drought are known to change in response to the resulting warming of the climate, which could drive a spurious correlation between them.

With techniques borrowed from applied physics and economics, the authors found evidence that this discovery went beyond a mere association: rather, a reduction in winter sea ice is likely an important driver of summer drought.

Planetary waves

But how can a decline in Arctic sea ice lead to droughts thousands of kilometers away? Here, the researchers found an atmospheric pattern consistent with a possible role for Rossby or planetary waves, whose behavior is shaped in part by Earth’s rotation.

“Rossby waves appear as broad north–south bends, thousands of kilometers across, in the winds high above the Earth. In the northern hemisphere, northward bends called ‘ridges’ often favor warm, dry weather. In our data, winters with less sea ice in the Barents and Kara Seas were followed by a bendier pattern over the North Atlantic and Eurasia, consistent with a possible change in Rossby waves,” explained Vaideanu.

“Such a bendy atmospheric circulation pattern can bring relatively warm, dry air into our newly identified drought corridor in Eurasia and lead to stagnant weather. We also observed fewer clouds there, so more sunlight heats the land, potentially worsening the drought.”

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Journal

Frontiers in Water

DOI

10.3389/frwa.2026.1962329

Method of Research

Data/statistical analysis

Subject of Research

Not applicable

Article Title

Winter Barents–Kara sea ice loss preconditions a summer drought corridor across eastern Europe and Eurasia

Article Publication Date

12-Nov-2026