Earths Future最新文献

Less than 6% of US farmlands are cover cropped, an on-farm management practice with potential to sequester carbon and provide environmental co-benefits (e.g., improved soil health and water quality). Despite their promise as a nature-based climate solution that can enhance soil carbon storage, cover crops remain underutilized, in part due to farmer perceptions that benefits are not assured and management risk is high. This scoping review synthesizes research from multiple disciplines to identify persistent knowledge gaps that limit both the effectiveness and sustained adoption of cover cropping. We focus on Midwestern US agroecosystems, where scientists generally agree that cover cropping has the potential to increase soil organic carbon and contribute to long-term carbon sequestration. Our synthesis reveals critical challenges across domains: carbon outcomes are highly variable across space and time; water and nutrient dynamics exhibit tradeoffs and context dependence; economic returns remain difficult to quantify; and adoption patterns are shaped by feedbacks between perceived risk, observed outcomes, system constraints, and social factors such as norms and identity. We use Ostrom's social-ecological systems framework to structure our analysis across biophysical, economic, and social domains, linking scientific uncertainty to real-world implementation barriers. The review culminates in a set of research priorities designed to advance transdisciplinary work on cover cropping, clarify its climate mitigation potential, improve the design of private and public interventions, and support adaptive management.

Groundwater irrigation plays a crucial role in sustaining India's food security and rural livelihood. However, the carbon footprint of its energy (72% coal-based) requirement is also equally alarming. Under such scenarios, the Farm Power Subsidy (FPS) policy for groundwater irrigation, one of India's costliest public support systems, needs a relook, keeping in view the Sustainable Development Goals (SDGs). Although aimed at bridging social disparities, it is observed that FPS encourages simplification and intensification of the food production system, leading to inter-state and district scale inequality in income. States implementing FPS, even if experiencing physical water scarcity, are growing water guzzling crops for economic benefits. Conversely, without adequate access to energy, states reeling from economic water scarcity are witnessing low farm incomes. India consumes about a quarter of the world's groundwater for irrigation, and also leads the energy use. Notably, since the mid-2000s large-scale implementation of the FPS policy, the CO₂ emission (equivalent) has been rising by 5.77 million tons annually, now surpassing 100 million tons. These outcomes bear testimony to the globally accepted view that those least responsible for causing greenhouse gas emissions are the hardest hit. We suggest repurposing of agricultural policies, without compromising farmers' income, for efficient management of energy and water.

Carbon emissions from land use change (LUC) play a critical role in the global carbon budget and serve as a fundamental basis for national land-use planning. However, existing estimates are typically derived from direct human activities, while the environmental indirect effects driven by both natural and anthropogenic factors are often overlooked. To date, no studies have explicitly differentiated between the direct and environmental indirect effects of interannual LUC. This omission may bias estimates of LUC-induced carbon emissions and undermine the effectiveness of carbon reduction policies. Here, we proposed a novel accounting method that employed a process-based dynamic vegetation model to quantify interannual LUC-induced carbon fluxes (LUCF) in China from 1990 to 2020, further distinguishing them into direct (LUCF-d) and environmental indirect fluxes (LUCF-ind). The results indicate that China's overall LUCF from 1990 to 2020 functioned as a carbon source, with a trend shifting from a source in the 1990s to a sink in the past decade. Over the past 30 years, LUCF-ind sequestered 1.39 ± 1.05 TgC yr⁻¹, offsetting approximately 25% of the emissions from LUCF-d. The South and Central regions are the primary areas for the trade-off between LUCF-d and LUCF-ind, with indirect environmental effects reducing direct emissions by 13.3% and 13.7%, respectively. This study aims to enhance the effectiveness of national-level land use carbon reduction policies by integrating environmental indirect effects and providing methodological references for other countries.

Atmospheric rivers (ARs) are key drivers of hydrological change, but their role in sustaining and reshaping hydrological responses in Chinese river basins remains insufficiently quantified. We detect ARs for 1950–2023 using integrated water vapor transport (IVT) dual percentile thresholds with morphological filtering for elongated, persistent features; attribute precipitation, extreme precipitation, runoff, and soil moisture via a 1.5° axis buffer; model contributions with zero-inflated beta (ZIB) regression; and trace moisture sources during AR-driven floods with TROVA. Results reveal a south-to-north contrast, with southern basins exhibiting high summer IVT (∼600–1,100 kg m⁻¹ s⁻¹) from long ARs (∼13,000 km) that sustain antecedent wetness and amplify floods, while since the 1980s ARs have shortened and weakened, and hydrologic responses have declined in central and northern basins. Basin mean ARs contributions peak in the Huai River Basin (16.5%, 70.0%, 17.9%, 3.2%) and are lowest in the Southwest Basin (0.1%, 0.8%, 0.1%, 0.04%) for precipitation, extreme precipitation, runoff, and soil moisture, respectively. ZIB indicates a declining mean AR influence on soil moisture in the east and increasing shares of extremes in the southeast; antecedent soil moisture is the strongest covariate of AR-induced precipitation. During floods, dominant sources can reach 74.7% from the East Asia Monsoon (Yangtze River Basin, 1998), 55.6% from the West Pacific Tropics (Pearl River Basin, 2009), and 32.5% from the South Asia Monsoon (Pearl River Basin, 1985). These findings show that ARs sustain water availability and reshape hydrological responses, informing flood risk management and water security planning in a warming climate.

There is an increasing interest amongst policymakers in understanding the implications of high-impact low-likelihood (HILL) risks for climate mitigation, adaptation and resilience. Whilst extreme sea level rise scenarios have been used and there is awareness of some HILL risks, in practice there are currently few scenarios which can be applied in risk assessments. Here we present two sets of HILL climate scenarios for the UK, complementing existing UK climate projections. Both are based around storylines describing physically-plausible changes, were developed using observations, models and theory, and describe HILL drivers of change as inputs to impact models or stress tests. The storylines provide a narrative framework for understanding risk, and indicative quantifications provide the basis for quantitative risk assessments. One set describes six storylines for transient climate change to 2100 and beyond, reflecting plausible forcings and system responses outside the range conventionally assumed. These describe enhanced global warming, rapid reductions in aerosol emissions, volcanic eruptions, enhanced Arctic Amplification, changes to ocean circulation, and accelerated sea level rise. The other set describes extreme monthly and seasonal anomalies, representing hot, cold, wet, dry and windy extreme years. This set includes storylines describing persistently anomalous weather.

In a global-scale nuclear war, massive explosions, intense heat, and radioactive fallout would cause extensive harm to humanity and ecosystems. Further, previous studies of even regional-scale nuclear conflicts show that the smoke from large-scale fires caused by such weapons could lead to global-scale ozone loss. However, combustion studies show that urban fires release key ozone-depleting substances that were not previously considered in nuclear war studies, particularly chlorine and bromine compounds. Recent wildfire studies have also shown that high solubility of hydrochloric acid in oxidized organic smoke particles can greatly enhance chlorine-driven ozone loss. For the first time, here we simulate the impacts of a nuclear war on the ozone layer using a chemistry-climate model that accounts for fire-related halogen emissions as well as HCl solubility and heterogeneous chemistry in smoke particles. Our results show that a regional war scenario with 5 Tg of soot could result in a ∼40% reduction in the global ozone burden, nearly twice as much as previous studies. The calculated ozone losses exceed ∼80% over the Arctic, comparable to those observed when the Antarctic ozone hole was discovered and hence represent an Arctic ozone hole. Ozone losses also reach ∼50% over mid-latitudes in the Northern Hemisphere, including highly populated areas. The enhanced ozone loss compared to previous studies is attributable to combined non-linear effects from the incorporation of halogen emissions and updated heterogeneous chemistry in smoke particles. Such ozone losses lead to a large increase in surface ultraviolet exposure, posing grave risks to humanity and ecosystems.

The 2024 Global Economic Prospects report by the International Monetary Fund highlighted the crucial role of emerging economies in driving global economic growth. Due to their active participation in global supply chains, these emerging economies generate large amounts of methane emissions to supply the required products to the global economy. While existing research has investigated the displacement of methane emissions between nations via interregional trade, the geospatial details of global methane footprint in emerging economies, which are crucial for pinpointing location-specific mitigation strategies, remain unknown. This study addressed this gap by connecting high-resolution methane emission maps from Emissions Database for Global Atmospheric Research with the Exiobase muti-regional input-output trade database, and generated spatially explicit hotspot maps of global methane footprint in emerging economies from 1995 to 2021. Results revealed that the methane footprint of global consumption in emerging economies is primarily concentrated in resource-rich, agriculture-intensive, and well-connected areas, with major regions contributing to 70% of total methane emissions in emerging economies. The displacement of methane emissions from economically-developed regions to emerging economies has consistently increased from 1995 to 2021, with the European Union, the United States, and the Rest of the World Europe collectively accounting for 70% of global methane emissions in 2021. Evolution trends and policy implications were presented for main sectoral agents including Fuel exploitation, Enteric fermentation, and Agricultural soil. The outcomes of this study can contribute to identifying emission hotspots in emerging economies and informing international cooperation efforts aimed at reducing methane emissions.

Urban green spaces (UGSs) are recognized beneficial for thermal comfort, yet its potential effects on air quality due to biogenic volatile organic compounds (BVOCs) emissions have received concerns. UGSs affect air quality through multiple pathways, some of which were generally missing in existing literature. Here we assess the impacts of UGSs on regional climate and air quality in the Pearl River Delta (PRD) with a more comprehensive framework. We consider the impacts of BVOCs emissions, dry deposition, radiative effects of produced aerosols, and transpiration effects. UGSs tend to elevate fine particulate matter (PM_2.5) concentrations by 5.11 μg/m³, dominated by evapotranspiration (4.62 μg/m³) that lowers mixing height and offset by additional dry deposition surfaces (−1.24 μg/m³). Although emitted BVOCs enhance ozone, evapotranspiration and dry deposition counterbalance the adverse effect by ∼87%. When considering the aerosol radiative effect, our findings indicate that both BVOC emissions and evapotranspiration contribute to mitigating the urban heat island effect between 14:00 and 16:00. Our results suggest that the air quality degradation will not be serious for cities with low aerosol concentrations if vegetations with less VOCs are planned. Additionally, UGSs can further help to alleviate urban warming.

Expansion of impervious surface area (ISA) in urbanizing regions often leads to vegetation area losses, a direct impact of urbanization. Many activities driven by economic growth, population increases, targeted urban greening investments, environmental policies, and major sports events change vegetation composition, structure, and function, leading to substantial indirect (positive or negative) impacts on vegetation in urban area. In this study, we analyzed the spatial-temporal dynamics of ISA, enhanced vegetation index (EVI), and gross primary production (GPP) in the Yangtze River Delta (YRD), China, over 2000–2020. Positive indirect impacts of urbanization on EVI and GPP surged after 2011, coinciding with China's Ecological Civilization Strategy. The concurrent increases of ISA, EVI, and GPP in the YRD provide an example for our society to work and advance the UN's Sustainable Development Goal #11, “Make cities inclusive, safe, resilient, and sustainable.”

Flash droughts have become a growing concern, as they can emerge rapidly and increase the risk of crop failure. Although past studies have investigated the meteorological drivers and future changes of flash drought, why flash drought is more frequent over humid and vegetated regions remains underexplored. This study delves further into the mechanism by which vegetation regulates flash drought and its future change using observations from multiple data sets and large ensemble simulations from three Earth system models. On an interannual timescale, both observations and simulations show robust increases in flash drought frequency and a higher flash-to-sub-seasonal drought ratio during spring or antecedent conditions with dense vegetation, supporting the important role of vegetation in flash drought occurrence, especially in the northern mid-to-high latitudes. In the latter regions, the large ensemble simulations show robust increases in flash drought (e.g., 67% and 46% increases in Eastern U.S. and North Asia in 2050–2100 relative to 1950–2000 under the high emission scenario), where the growing season is lengthening. Although greening might suggest reduced drought stress, it drives precipitation-soil moisture-evapotranspiration decoupling by increasing evapotranspiration partitioning to transpiration. As transpiration can access deep soil water through the plant root system, its increased portion can weaken the constraints of concurrent precipitation on evapotranspiration, thus accelerating soil moisture depletion under high evaporative demand, driving a slow-to-rapid drought transition. How vegetation regulates flash drought by regulating surface moisture budget is supported by observations and simulations. Although warming supports early planting, agriculture may increasingly be threatened by surging flash drought risk.