Earth System Models underestimate natural terrestrial nitrogen fixation by up to 18%

Science China Press

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a, Isotope-based BNF estimate; b–i, BNFs simulated by ESMs in CMIP6. The areas of managed croplands and pastures were excluded in their analysis and are represented by grey regions.

 

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Credit: ©Science China Press

The research team, led by Professor Shushi Peng from Peking University, has delivered an observation-driven isotope-based estimate of global biological nitrogen fixation (BNF) for natural land ecosystems, revealing substantial biases in widely used Earth System Models (ESMs). Their findings indicated that the BNF in current ESMs may need to be better represented, and the parameterization may need to be constrained by many observations.

Grounded in nitrogen isotope (δ¹⁵N) mass-balance theory of a plant–soil system, the authors derived a theoretical negative relationship between the fraction of plant external N demand met by symbiotic fixation (fBNFs) and the isotope fractionation of plant N uptake (eU). Combining this framework with machine-learned global maps built from thousands of plant and soil δ¹⁵N observations, they estimated the spatial pattern of BNF and quantified key environmental controls.

Mean annual temperature (MAT) was identified as the primary predictor of symbiotic fixation, increasing monotonically from cold to warm regions and explaining ~29% of the spatial variability. Natural abundance of ectomycorrhizal fungi (ECM) explained ~14% of the variability, and MAT and ECM could interact to affect the fixation. 

Among the 11 ESMs participating the CMIP6 ensemble runs, only MPI-ESM-1-2-HAM can produce spatial pattern of BNF close to the isotope-based map, while the other models have either too large (ACCESS-ESM1-5) or too flat (CESM2, EC-Earth3-Veg, NorESM2-MM, MIROC-ES2L, UKESM1-0-LL, and TaiESM1) latitudinal gradients.

The team estimated global natural terrestrial BNF at 83.0 (78.2–89.8) Tg N yr-1, indicating ~18% underestimation in CMIP6 models with a multi-model mean of ~67.7 Tg N yr-1. To improve the model performance in the next phase of CMIP, the team suggest adding temperature and ECM into the representation of BNF, and also to constrain the parameters with N isotope measurements.

“By embedding real-world isotope constraints into a Bayesian framework, we reveal a larger natural nitrogen inputs than many models assume,” said Prof. Shushi Peng. “Incorporating temperature, abundance of mycorrhizal fungi and isotope constraints could improve model performance substantially.”

 

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Journal

National Science Review

DOI

10.1093/nsr/nwaf459 

Method of Research

Computational simulation/modeling

 

Why is the stunting rate higher among children in Tanzania’s breadbasket regions?

Higher Education Press

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Credit: Mosses LUFUKE 1, 2, Xu TIAN 3

Tanzania’s “Breadbasket Regions (BBRs)” are the core of the country’s food supply, contributing over 38% of Tanzania’s national maize production. However, the 2018 National Nutrition Survey revealed a paradox: the five regions with the highest rates of child stunting and severe malnutrition in the country are all located within these high-agricultural-yield areas. This “breadbasket paradox” has raised concerns: why are children in major food-producing regions more prone to growth issues than those in non-food-producing regions?

Recently, Professor Xu Tian from the College of Economics and Management at China Agricultural University, in collaboration with Mosses Lufuke from the Department of Economics at the University of Dodoma in Tanzania, uncovered the underlying reasons through data analysis. The related article has been published in Frontiers of Agricultural Science and Engineering (DOI: 10.15302/J-FASE-2025645).

The research team utilized comprehensive data from Tanzania’s 2017–2018 National Household Budget Survey, 2020–2021 National Integrated Labor Force Survey, and 2020–2021 National Panel Survey, covering 7360 households, to analyze the relationship between crop production and children’s growth status. Unlike previous studies that relied on descriptive statistics, this study employed Propensity Score Matching (PSM) and instrumental variable models, controlling for confounding factors such as household income, household size, and urban-rural differences, to verify the authenticity of the “breadbasket paradox” from a statistical perspective.

The results showed that the stunting rate among children in BBRs was significantly higher than that in non-BBRs. More importantly, there were regional differences in the impact of crop production on child nutrition: in non-BBRs, higher food production significantly reduced the risk of child stunting and improved height development; however, in BBRs, this positive effect was not significant—even with increased production, children’s growth status did not improve accordingly.

To explore the causes of this paradox, the research team analyzed two potential mechanisms. The first was “maternal working hours”: does higher production lead mothers to participate more in agricultural work, thereby reducing the time spent caring for children? Data showed that there was no significant correlation between crop production and mothers’ out-of-home working hours in either BBRs or non-BBRs, so this hypothesis was not supported.

The second mechanism was “dietary diversity”: does higher production result in a more monotonous household diet? The study found that in non-BBRs, increased food production did lead to greater household dietary diversity, which was directly related to improved nutrition; however, in BBRs, despite higher production, there was no significant increase in household dietary diversity. This may be related to the high degree of agricultural commercialization in BBRs—farmers tend to cultivate single cash crops for sale rather than growing a variety of foods for their own consumption, leading to the phenomenon of “high production but monotonous diet”.

The study pointed out that simply increasing food production is insufficient to solve the problem of child malnutrition, especially in regions with a high degree of agricultural commercialization. Tanzania’s current agricultural policies may overemphasize production increases while neglecting the key role of dietary diversity in children’s growth. The study suggested that future policies could be adjusted in three aspects: first, encouraging farmers in BBRs to grow a variety of crops to balance economic benefits and household consumption; second, strengthening the construction of agricultural product markets to enable farmers to obtain income by selling cash crops to purchase a variety of foods; third, specifically improving the allocation of household resources, such as helping women reduce the burden of non-agricultural work like water-fetching, to ensure they have time to prepare nutritious food.

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Journal

Frontiers of Agricultural Science and Engineering

DOI

10.15302/J-FASE-2025645 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Unraveling the paradox of child growth in Tanzania’s breadbasket regions: impact of household food production

 

Trade risk of beautiful birds - how aesthetics drive wild bird exploitation for trade

University of Helsinki

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Orange-banded Ground-thrush (Geokichla peronii).

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Credit: Simon Brusland

A new global study finds that the visual beauty of birds – their colours and shapes – predicts which wild species are traded by people. By analysing data for over 9000 bird species, researchers discovered that the birds people find most aesthetically appealing are also the most likely to appear in wildlife markets.

“The results show a correlation between a species’ aesthetic value and its likelihood of being traded, particularly in live markets, where birds are commonly sold as pets or for display”, says Anna Haukka, lead author of the study from the University of Helsinki. 

The study also found that this aesthetic-driven trade varies by region and product type. Visually attractive live birds are more frequently traded in international markets, while domestic trade shows a weaker connection. Aesthetic appeal also influences the trade of bird products like clothing and ornaments, though it plays a lesser role in markets for meat or traditional medicine.

Beyond beauty, other factors such as body size and geographic range also contribute to a species’ trade risk. Larger birds with wider ranges are more likely to be exploited internationally, while smaller species might tend to appear more often in local markets.

“Our findings highlight a troubling pattern: people’s preference for visual beauty may unintentionally increase conservation risks for certain species,” says Haukka. “Parrots, colourful songbirds, and birds of prey that are often considered especially beautiful, are disproportionately represented in trade, sometimes at unsustainable levels.”

Understanding drivers of demand in trade informs early conservation efforts

The authors emphasize that understanding how aesthetic appeal influences demand can help predict future trade targets and inform early conservation efforts. They also call for region-specific strategies, noting that policies like the European Union’s wild bird import ban have reshaped market dynamics and the role of aesthetics in trade.

“Perhaps it does not seem surprising that more attractive species are traded more, but the bird trade is dynamic in geography and fashion. Understanding what people find attractive in birds for trade will enable us to predict which species might be targeted in the future,” says Simon Bruslund from Copenhagen Zoo, coauthor of the study.    

Ultimately, the study underscores a critical message: the allure of beauty can come at a steep ecological cost. By illuminating the link between aesthetics and exploitation, the research offers valuable insights for designing targeted conservation measures, demand-reduction campaigns, and conservation planning and policy to protect some of the world’s most admired and vulnerable bird species.

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Journal

Biological Conservation

DOI

10.1016/j.biocon.2025.111572 

Article Title

Aesthetic values predict bird trade, but the association varies across product types and trade regions

Article Publication Date

8-Nov-2025

 

Hi-tech viticulture: the Politecnico di Milano has created virtual vineyards for self-driving tractors

Politecnico di Milano

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new methodologies to simulate and independently control vineyard operations for more efficient and sustainable agriculture

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Credit: Politecnico di Milano

 

Milan, 11th November 2025 - While grapes are being harvested throughout Italy, the Politecnico di Milano is looking to the future of viticulture with an innovative approach that combines mechanics, IT and digital simulation. A team of researchers from the Departments of Mechanical Engineering and Electronics, Information and Bioengineering at the Politecnico di Milano has developed a system to test and optimise self-driving strategies for agricultural tractors in a virtual environment.

The study, published in AgriEngineering (Scenario Generation and Autonomous Control for High-Precision Vineyard Operations, doi: 10.3390/agriengineering7020046), presents a complete methodology for creating realistic vineyard scenarios and evaluating control algorithms for autonomous driving. The goal is not simply to reduce the human presence, but to provide a high-fidelity digital environment in which to develop, verify and safely improve agricultural automation solutions based on sensors and predictive algorithms.

The research has made it possible to create a “digital twin” of the vineyard, capable of reproducing slopes, soil irregularities and row layout. Tractors equipped with low-cost GNSS and IMU sensors and guided by advanced algorithms have been tested in this virtual environment, vehicles capable of moving autonomously between rows and of performing off-field turning manoeuvres with the utmost precision.

“Our approach combines terrain modelling, advanced control and realistic sensors in a single simulation environment. This speeds up research and reduces the risks and costs of real field tests,” says Federico Cheli, professor at the Politecnico di Milano, Department of Mechanical Engineering, and project coordinator.

According to the researchers, the use of realistic simulations not only reduces the risks and costs of field tests, but can also become a useful tool for operator training. It can accelerate the adoption of new agricultural technologies.

The project stems from the partnership between researchers at the Politecnico di Milano and the company Soluzioni Ingegneria s.r.l. that develops software for dynamic vehicle simulation. It is part of a broader context of cooperation with industrial companies engaged in research on automation and sustainability in agriculture.

Ruiz Mayo, C.; Cheli, F.; Arrigoni, S.; Paparazzo, F.; Mentasti, S.; Pezzola, M.E. Scenario Generation and Autonomous Control for High-Precision Vineyard Operations. AgriEngineering 2025, 7(2), 46. https://doi.org/10.3390/agriengineering7020046

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Journal

AgriEngineering

DOI

10.3390/agriengineering7020046 

Method of Research

Computational simulation/modeling

Subject of Research

Not applicable

Article Title

Scenario Generation and Autonomous Control for High-Precision Vineyard Operations