Abstract

Microplastics (MPs) and nanoplastics (NPs) are pervasive contaminants in agricultural soils, raising concerns over their environmental fate, food chain infiltration, and potential human health impacts. This review critically examines their primary sources—plastic mulching, biosolids, organic fertilisers, and atmospheric deposition—while distinguishing findings from laboratory, semi-field, and field studies. We assess their effects on soil health, microbial diversity, and crop productivity, emphasising methodological challenges in detecting and quantifying MPs. Plant and soil toxicity studies often use exaggerated MP concentrations (up to 50% by volume), whereas field data indicate much lower yet cumulatively significant levels (typically below 0.1% w/w). This discrepancy reveals the potential for long-term accumulative ecological risks and misrepresentations in many toxicity studies. Accurate toxicity assessments and analytical methodologies are crucial, as exaggerated MP concentrations in studies may misrepresent real-world risks. The review also evaluates plant uptake pathways, exploring bioaccumulation evidence and research discrepancies. In addition, we highlight the role of MPs as carriers of hazardous additives and pollutants, distinguishing their intrinsic effects from those of associated chemicals. A significant gap remains in standardised risk assessments and regulatory frameworks, limiting effective governance despite increasing environmental exposure. We propose future research priorities, including improved detection methods, long-term field studies, environmentally relevant toxicity studies and policy interventions, to mitigate the risks MPs and NPs pose in soil-based food systems. This review highlights the urgent need for coordinated scientific and regulatory efforts to address the growing challenges of agricultural plastic contamination.

Abstract

Following a nuclear war, destruction would extend well beyond the blast zones due to the onset of a nuclear winter that can devastate the biosphere, including agriculture. Understanding the damage magnitude and preparing for the folly of its occurrence are critical given current geopolitical tensions. We developed and applied a framework to simulate global crop production under a nuclear winter using the Cycles agroecosystem model, incorporating ultraviolet (UV)-B radiation effects on plant growth and adaptive selection of crop maturity types (shorter cycle the lower the temperature). Using maize (Zea maize L.) as a sentinel crop, we found that annual maize production could decline from 7% after a small-scale regional nuclear war with 5 Tg soot injection, to 80% after a global nuclear war with 150 Tg soot injection, with recovery taking from 7 to 12 years. UV-B damage would peak 6–8 years post-war and can further decrease annual maize production by 7%. Over the recovery period, adaptive selection of maize maturity types to track changing temperatures could increase production by 10% compared to a no-adaptation strategy. Seed availability may become a critical adaptation bottleneck; this and prior studies might underestimate food production declines. We propose that adaptation must include the development of Agricultural Resilience Kits consisting of region- and climate-specific seed and technology packages designed to buffer against uncertainty while supply chains recover. These kits would be congenial with the transient conditions during the recovery period, and would also be applicable to other catastrophes affecting food production.

Significance

The productivity of staple crops is a key factor shaping the affordability of food and the amount of land and other resources used in agriculture. We synthesize evidence on how the weather faced by these crops has changed and how these changes have affected productivity. Most cropping regions have experienced both rapid warming and atmospheric drying, with significant negative global yield impacts for three of the five crops. Models can largely reproduce these changes and impacts with two important exceptions—they overstate warming and drying in North America and understate drying in most other temperate regions. These insights can help to guide adaptation efforts and model improvements.

Abstract

Efforts to anticipate and adapt to future climate can benefit from historical experiences. We examine agroclimatic conditions over the past 50 y for five major crops around the world. Most regions experienced rapid warming relative to interannual variability, with 45% of summer and 32% of winter crop area warming by more than two SD (σ). Vapor pressure deficit (VPD), a key driver of plant water stress, also increased in most temperate regions but not in the tropics. Precipitation trends, while important in some locations, were generally below 1σ. Historical climate model simulations show that observed changes in crops’ climate would have been well predicted by models run with historical forcings, with two main surprises: i) models substantially overestimate the amount of warming and drying experienced by summer crops in North America, and ii) models underestimate the increase in VPD in most temperate cropping regions. Linking agroclimatic data to crop productivity, we estimate that climate trends have caused current global yields of wheat, maize, and barley to be 10, 4, and 13% lower than they would have otherwise been. These losses likely exceeded the benefits of CO2 increases over the same period, whereas CO2 benefits likely exceeded climate-related losses for soybean and rice. Aggregate global yield losses are very similar to what models would have predicted, with the two biases above largely offsetting each other. Climate model biases in reproducing VPD trends may partially explain the ineffectiveness of some adaptations predicted by modeling studies, such as farmer shifts to longer maturing varieties.

Abstract

HFC-23 (trifluoromethane) is a potent greenhouse gas released to the atmosphere primarily as a by-product of HCFC-22 (chlorodifluoromethane) synthesis. Since 2020, the Kigali Amendment to the Montreal Protocol has required Parties to destroy their HFC-23 emissions to the extent possible. Here, we present updated HFC-23 emissions estimated from atmospheric observations. Globally, emissions fell to 14.0 ± 0.9 Gg yr-1 in 2023 from their maximum in 2019 of 17.3 ± 0.8 Gg yr-1, but remained five times higher than reported in 2021. Atmospheric observation-based emissions for eastern China, the world’s largest HCFC-22 producer, were also found to be substantially higher than 2020-2022 reported emissions. We estimate that potential HFC-23 sources not directly linked to HCFC-22 production explain only a minor, albeit highly uncertain, fraction of this discrepancy. Our findings suggest that HFC-23 emissions have not been destroyed to the extent reported by the Parties since the implementation of the Kigali Amendment.

Abstract

The pressures humanity has been placing on the environment have put Earth’s stability at risk. The planetary boundaries framework serves as a method to define a ‘safe operating space for humanity’1,2 and has so far been applied mostly to highlight the currently prevailing unsustainable environmental conditions. The ability to evaluate trends over time, however, can help us explore the consequences of alternative policy decisions and identify pathways for living within planetary boundaries3. Here we use the Integrated Model to Assess the Global Environment4 to project control variables for eight out of nine planetary boundaries under alternative scenarios to 2050, both with and without strong environmental policy measures. The results show that, with current trends and policies, the situation is projected to worsen to 2050 for all planetary boundaries, except for ozone depletion. Targeted interventions, such as implementing the Paris climate agreement, a shift to a healthier diet, improved food, and water- and nutrient-use efficiency, can effectively reduce the degree of transgression of the planetary boundaries, steering humanity towards a more sustainable trajectory (that is, if they can be implemented based on social and institutional feasibility considerations). However, even in this scenario, several planetary boundaries, including climate change, biogeochemical flows and biodiversity, will remain transgressed in 2050, partly as result of inertia. This means that more-effective policy measures will be needed to ensure we are living well within the planetary boundaries.

Abstract

Mass loss from ice sheets in Greenland and Antarctica has quadrupled since the 1990s and now represents the dominant source of global mean sea-level rise from the cryosphere. This has raised concerns about their future stability and focussed attention on the global mean temperature thresholds that might trigger more rapid retreat or even collapse, with renewed calls to meet the more ambitious target of the Paris Climate Agreement and limit warming to +1.5 °C above pre-industrial. Here we synthesise multiple lines of evidence to show that +1.5 °C is too high and that even current climate forcing (+1.2 °C), if sustained, is likely to generate several metres of sea-level rise over the coming centuries, causing extensive loss and damage to coastal populations and challenging the implementation of adaptation measures. To avoid this requires a global mean temperature that is cooler than present and which we hypothesise to be closer to +1 °C above pre-industrial, possibly even lower, but further work is urgently required to more precisely determine a ‘safe limit’ for ice sheets.

Abstract

Carbon storage in soils is important in regulating atmospheric carbon dioxide (CO2). However, the sensitivity of the soil-carbon turnover time (τsoil) to temperature and hydrology forcing is not fully understood. Here, we use radiocarbon dating of plant-derived lipids in conjunction with reconstructions of temperature and rainfall from an eastern Mediterranean sediment core receiving terrigenous material from the Nile River watershed to investigate τsoilin subtropical and tropical areas during the last 18,000 years. We find that τsoil was reduced by an order of magnitude over the last deglaciation and that temperature was the major driver of these changes while the impact of hydroclimate was relatively small. We conclude that increased CO2 efflux from soils into the atmosphere constituted a positive feedback to global warming. However, simulated glacial-to-interglacial changes in a dynamic global vegetation model underestimate our data-based reconstructions of soil-carbon turnover times suggesting that this climate feedback is underestimated.