Precipitation is essential for food production in Sub-Saharan Africa, where more than 80 % of agriculture is rainfed. Although ∼40 % of precipitation in certain regions is recycled moisture from Africa's tropical rainforest, there needs to be more knowledge about how this moisture supports the continent's agriculture. In this study, we quantify all moisture sources for agrarian precipitation (African agricultural precipitationshed), the estimates of African rainforest's moisture contribution to agricultural precipitation, and the evaporation from agricultural land across the continent. Applying a moisture tracking model (UTRACK) and a dynamic global vegetation model (LPJmL), we find that the Congo rainforest (>60 % tree cover) is a crucial moisture source for many agricultural regions. Although most of the rainforest acreage is in the DRC, many neighboring nations rely significantly on rainforest moisture for their rainfed agriculture, and even in remote places, rainforest moisture accounts for ∼10–20 % of agricultural water use. Given continuous deforestation and climate change, which impact rainforest areas and resilience, more robust governance for conserving the Congo rainforest is necessary to ensure future food production across multiple Sub-Saharan African countries.

The planetary boundaries framework defines a safe operating space for humanity. To date, these boundaries have mostly been investigated separately, and it is unclear whether breaching one boundary can lead to the transgression of another. By employing a dynamic global vegetation model, we systematically simulate the strength and direction of the effects of different transgression levels of the climate change boundary (using climate output from ten phase 6 of the Coupled Model Intercomparison Project models for CO₂ levels ranging from 350 ppm to 1000 ppm). We focus on climate change-induced shifts of Earth's major forest biomes, the control variable for the land-system change boundary, both by the end of this century and, to account for the long-term legacy effect, by the end of the millennium. Our simulations show that while staying within the 350 ppm climate change boundary co-stabilizes the land-system change boundary, breaching it (>450 ppm) leads to critical transgression of the latter, with greater severity the higher the ppm level rises and the more time passes. Specifically, this involves a poleward treeline shift, boreal forest dieback (nearly completely within its current area under extreme climate scenarios), competitive expansion of temperate forest into today's boreal zone, and a slight tropical forest extension. These interacting changes also affect other planetary boundaries (freshwater change and biosphere integrity) and provide feedback to the climate change boundary itself. Our quantitative process-based study highlights the need for interactions to be studied for a systemic operationalization of the planetary boundaries framework.

Quantifying fair national shares of the remaining global carbon budget has proven challenging. Here, we propose an indicator—additional carbon accountability—that quantifies countries’ responsibility for mitigation and CO₂ removal in addition to achieving their own targets. Considering carbon debts since 1990 and future claims based on countries’ emission pathways, the indicator uses an equal cumulative per capita emissions approach to allocate accountability for closing the mitigation gap among countries with a positive total excessive carbon claim. The carbon budget is exceeded by 576 Gigatonnes of fossil CO₂ when limiting warming below 1.5 °C (50% probability). Additional carbon accountability is highest for the United States and China, and highest per capita for the United Arab Emirates and Russia. Assumptions on carbon debts strongly impact the results for most countries. The ability to pay for this accountability is challenging for Iran, Kazakhstan and several BRICS+ members, in contrast to the G7 members.

Integrated assessment models that incorporate biodiversity and ecosystem services could be an important tool for improving our understanding of interconnected social-economic-ecological systems, and for analyzing how policy alternatives can shift future trajectories towards more sustainable development. Despite recent scientific and technological advances, key gaps remain in the scientific community’s ability to deliver information to decision-makers at the pace and scale needed to address sustainability challenges. We identify five research frontiers for integrated social-economic-ecological modeling (primarily focused on terrestrial systems) to incorporate biodiversity and ecosystem services: 1) downscaling impacts of direct and indirect drivers on ecosystems; 2) incorporating feedbacks in ecosystems; 3) linking ecological impacts to human well-being, 4) disaggregating outcomes for distributional equity considerations, and 5) incorporating dynamic feedbacks of ecosystem services on the social-economic system. We discuss progress and challenges along each of these five frontiers and the science-policy linkages needed to move new research and information into action.

Tropical rainforests rely on their root systems to access moisture stored in soil during wet periods for use during dry periods. When this root zone soil moisture is inadequate to sustain a forest ecosystem, they transition to a savanna-like state, losing their native structure and functions. Yet the influence of climate change on ecosystem's root zone soil moisture storage and the impact on rainforest ecosystems remain uncertain. This study assesses the future state of rainforests and the risk of forest-to-savanna transitions in South America and Africa under four Shared Socioeconomic Pathways (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5). Using a mass-balance-based empirical understanding of root zone storage capacity (S_r), defined as the maximum volume of root zone soil moisture per unit area accessible to vegetation's roots for transpiration, we project how rainforest ecosystems will respond to future climate changes. We find that under the end-of-the-21st-century climate, nearly one-third of the total forest area will be influenced by climate change. As the climate warms, forests will require a larger S_r than they do under the current climate to sustain their ecosystem structure and functions, making them more susceptible to water limitations. Furthermore, warming beyond 1.5–2 °C will significantly elevate the risk of a forest–savanna transition. In the Amazon, the forest area at risk of such a transition grows by about 1.7–5.8 times in size compared to the immediate lower-warming scenario (e.g. SSP2-4.5 compared to SSP1-2.6). In contrast, the risk growth in the Congo is less substantial, ranging from 0.7–1.7 times. These insights underscore the urgent need to limit the rise in global surface temperature below the Paris Agreement to conserve rainforest ecosystems and associated ecosystem services.

Human pressures have pushed the Earth system deep into the Anthropocene, threatening its stability, resilience and functioning. The Planetary Boundaries (PB) framework emerged against these threats, setting safe levels to the biophysical systems and processes that, with high likelihood, ensure life-supporting Holocene-like conditions. In this Review, we synthesize PB advancements, detailing its emergence and mainstreaming across scientific disciplines and society. The nine PBs capture the key functions regulating the Earth system. The safe operating space has been transgressed for six of these. PB science is essential to prevent further Earth system risks and has sparked new research on the precision of safe boundaries. Human development within planetary boundaries defines sustainable development, informing advances in social sciences. Each PB translates to a finite budget that the world must operate within, requiring strengthened global governance. The PB framework has been adopted by businesses and informed policy across the world, informing new thinking about fundamental justice concerns, and has inspired, among other concepts, the planetary commons, planetary health and doughnut economics. Future work must increase the precision and frequency of PB analyses, and, together with Earth observation data analytics, produce a high-resolution and real-time state of planetary health.

The Loess Plateau in China has experienced a remarkable greening trend due to vegetation restoration efforts in recent decades. However, the response of precipitation to this greening remains uncertain. In this study, we identified and evaluated the main moisture source regions for precipitation over the Loess Plateau from 1982 to 2019 using a moisture tracking model, the modified WAM-2layers model, and the conceptual framework of the precipitationshed. By integrating multiple linear regression analysis with a conceptual hydrologically weighting method, we quantified the effective influence of different environmental factors for precipitation, particularly the effect of vegetation. Our analysis revealed that local precipitation has increased on average by 0.16 mm yr−1 and evaporation by 5.17 mm yr−1 over the period 2000–2019 after the initiation of the vegetation restoration project. Regional greening including the Loess Plateau contributed to precipitation for about 0.83 mm yr−1, among which local greening contributed for about 0.07 mm yr−1. Local vegetation contribution is due to both an enhanced local evaporation as well as an increased local moisture recycling (6.9% in 1982–1999; 8.3% in 2000–2019). Thus, our study shows that local revegetation had a positive effect on local precipitation, and the primary cause of the observed increase in precipitation over the Loess Plateau is due to a combination of local greening and circulation change. Our study underscores that increasing vegetation over the Loess Plateau has exerted strong influence on local precipitation and supports the positive effects for current and future vegetation restoration plans toward more resilient water resources managements.

The achievement of several sustainable development goals and the Paris Climate Agreement depends on rapid progress towards sustainable food and land systems in all countries. We have built a flexible, collaborative modeling framework to foster the development of national pathways by local research teams and their integration up to global scale. Local researchers independently customize national models to explore mid-century pathways of the food and land use system transformation in collaboration with stakeholders. An online platform connects the national models, iteratively balances global exports and imports, and aggregates results to the global level. Our results show that actions toward greater sustainability in countries could sum up to 1 Mha net forest gain per year, 950 Mha net gain in the land where natural processes predominate, and an increased CO₂ sink of 3.7 GtCO₂e yr⁻¹ over the period 2020–2050 compared to current trends, while average food consumption per capita remains above the adequate food requirements in all countries. We show examples of how the global linkage impacts national results and how different assumptions in national pathways impact global results. This modeling setup acknowledges the broad heterogeneity of socio-ecological contexts and the fact that people who live in these different contexts should be empowered to design the future they want. But it also demonstrates to local decision-makers the interconnectedness of our food and land use system and the urgent need for more collaboration to converge local and global priorities.

The Anthropocene is characterized by the strengthening of planetary-scale interactions between the biophysical Earth system (ES) and human societies. This increasing social-ecological entanglement poses new challenges for studying possible future World-Earth system (WES) trajectories and World-Earth resilience defined as the capacity of the system to absorb and regenerate from anthropogenic stresses such as greenhouse gas emissions and land-use changes. The WES is currently in a non-equilibrium transitional regime of the early Anthropocene with arguably no plausible possibilities of remaining in Holocene-like conditions while sheltering up to 10 billion humans without risk of undermining the resilience of the ES. We develop a framework within which to conceptualize World-Earth resilience to examine this risk. Because conventional ball-and-cup type notions of resilience are hampered by the rapid and open-ended social, cultural, economic and technological evolution of human societies, we focus on the notion of 'pathway resilience', i.e. the relative number of paths that allow the WES to move from the currently occupied transitional states towards a safe and just operating space in the Anthropocene. We formalize this conceptualization mathematically and provide a foundation to explore how interactions between ES resilience (biophysical processes) and World system (WS) resilience (social processes) impact pathway resilience. Our analysis shows the critical importance of building ES resilience to reach a safe and just operating space. We also illustrate the importance of WS dynamics by showing how perceptions of fairness coupled with regional inequality affects pathway resilience. The framework provides a starting point for the analysis of World-Earth resilience that can be extended to more complex model settings as well as the development of quantitative planetary-scale resilience indicators to guide sustainable development in a stabilized ES.

This planetary boundaries framework update finds that six of the nine boundaries are transgressed, suggesting that Earth is now well outside of the safe operating space for humanity. Ocean acidification is close to being breached, while aerosol loading regionally exceeds the boundary. Stratospheric ozone levels have slightly recovered. The transgression level has increased for all boundaries earlier identified as overstepped. As primary production drives Earth system biosphere functions, human appropriation of net primary production is proposed as a control variable for functional biosphere integrity. This boundary is also transgressed. Earth system modeling of different levels of the transgression of the climate and land system change boundaries illustrates that these anthropogenic impacts on Earth system must be considered in a systemic context.