Green water, or plant-available soil moisture, is a substantial subset of terrestrial fresh water. Land use change alters green water dynamics through interactions on the micro-level (i.e. between the soil and vegetation) and on the macro-level (i.e. between the land surface and atmosphere). Ongoing global deforestation, and growing interest in reforestation projects, begs the question whether such large-scale land use changes have major eco-hydrological impacts via the process of terrestrial moisture recycling (TMR). This requires a systematic, mechanistic understanding of green water dynamics in relation to land use change. Hence, this literature review addresses the above question via a scoping review that draws from papers covering empirical observations and simulated approximations on the hydrological effects of land use change from different parts of the world. The results show that some regions are more vulnerable to land use change than others and can affect local as well as distant hydrology of landscapes. Furthermore, we find that many studies focus on the global level or on tropical rainforests, through which we identify a knowledge gap for temperate regions and drylands. We derive analytical tools and directions for further research that can improve understanding of the effects of land use change on moisture recycling patterns in order to minimize unexpected hydrological impacts for nature and society.

A review of the literature on water governance reveals that most studies focus on blue water governance; while there is some literature on green and atmospheric water, explicit literature on how to govern green and atmospheric water is lacking. Hence, this paper addresses the question: What are the arguments for governing green and atmospheric water? In order to address this question, we have undertaken a scoping analysis of the literature on green and atmospheric water. We conclude that water governance must proactively address green and atmospheric water since: (a) blue water represents only a part of the available fresh water; (b) blue river basins represent only a subset of the wider systemic nature of water; (c) land use change has significant impacts on various water flows, which all may need to be governed; (d) climate variability and change influences blue, green, and atmospheric water availability; (e) an understanding of the socio‐ecological uses of the different colors of water is critical for a more optimal and legitimate governance of water; (f) new water technologies make it increasingly possible to modify the use of green and atmospheric water; and (g) global trade infrastructures pressurize local green water resources. Neglecting the need for explicit governance of green and atmospheric water could create new forms of “water grabbing” that would impact water availability beyond the basin scale.This article is categorized under: Human Water > Water Governance Science of Water > Hydrological Processes Water and Life > Stresses and Pressures on Ecosystems

Ambitious climate change mitigation in all economic sectors is crucial for limiting global warming. Cost-effective mitigation pathways to keep global average temperature increases below 1·5°C by the end of the 21st century often rely on land-based greenhouse gas (GHG) emission reductions, increased land-based carbon uptake and biomass supply to other sectors (eg, energy and transport), and demand-side changes in the food system. To evaluate the broader sustainability of land-based climate change mitigation action, we evaluated synergies and trade-offs of individual and combined supply-side mitigation measures across five planetary boundaries. We also examined the role of a food demand transformation aligned with the dietary recommendations of the updated planetary health diet defined in the forthcoming EAT-Lancet Commission 2.0 report in shaping planetary boundary outcomes. In this modelling study, we used the dynamic land-system modelling framework MAgPIE to assess the consequences of land-based GHG reductions, increased land-based carbon uptake, increased biomass supply to other sectors, and a food-system transformation towards the planetary health diet including food waste reductions on five planetary boundary domains (climate change, nitrogen, land-system change, freshwater use, and biosphere integrity) relative to a reference scenario without land-system mitigation throughout the century. For each planetary boundary control variable, we calculated the level of planetary boundary transgression (ie, the extent to which scenario outcomes exceeded the defined safe operating space) and assessed the contributions of land-based mitigation strategies to reducing planetary boundary transgressions projected for the reference scenario. Our projections show that a food-system transformation together with ambitious land-system and energy-system climate change mitigation can limit global warming to below 1·5°C by 2100, while also reducing planetary boundary transgression (particularly for the climate change, land-system change, biosphere integrity, and nitrogen planetary boundaries). However, a safe operating space was not achieved through these mitigation measures, as most planetary boundaries were still projected to remain transgressed by the end of the 21st century. Increased bioenergy supply alone worsened planetary boundary transgression when only looking at land-system impacts, but combining increased bioenergy supply with GHG pricing in the land system alleviated these trade-offs. Food waste reductions and dietary shifts towards the planetary health diet were projected to ease pressures on the land system and reduce planetary boundary transgression of all assessed planetary boundaries. This research highlights the importance of considering multiple planetary boundaries and the interactions between various mitigation strategies when assessing climate mitigation action in the land system to avoid negative consequences for other aspects of the environment. Following an ambitious climate change mitigation pathway compatible with the Paris Agreement results in a transgression of all assessed five planetary boundaries by 2100. However, the combination of the land-system mitigation measures included in this study produced a substantial shift towards the safe operating space for humanity. EAT-Lancet Commission 2.0.

Global environmental pressures from food systems threaten biodiversity and the stability of the Earth system, yet the safe operating space for food systems is unknown. Here we calculate food system boundaries as shares of planetary boundaries, proposing budgets for the food system across nine boundaries. Our results indicate that food systems are a critical driver of planetary boundary transgressions, dominating at least four transgressed boundaries (that is, biosphere integrity, land system change, freshwater change and biogeochemical flows) while strongly contributing to the transgression of two more (that is, climate change and novel entities). Moreover, global food systems are currently beyond all nine food system boundaries; moving to the safe operating space requires reducing related greenhouse gas emissions substantially, halting the conversion of intact nature to agriculture, redistributing fertilizer inputs, limiting pesticide and antibiotic use, and preserving critical freshwater flows without negatively affecting yields.

The redistribution of biological (transpiration) and non‐biological (interception loss, soil evaporation) fluxes of terrestrial evaporation via atmospheric circulation and precipitation is an important Earth system process. In vegetated ecosystems, transpiration dominates terrestrial evaporation and is thought to be crucial for regional moisture recycling and ecosystem functioning. However, the spatial and temporal variability in the dependency of precipitation on transpiration remains understudied, particularly in sparsely sampled regions like Africa. Here, we investigate how biological and non‐biological sources of evaporation in Africa contribute to rainfall over the major watersheds in the continent. Our study is based on simulated atmospheric moisture trajectories derived from the Lagrangian model FLEXPART, driven by 1° resolution reanalysis data over 1981–2016. Using daily satellite‐based fractions of transpiration over terrestrial evaporation, we isolate the contribution of vegetation to monthly rainfall. Furthermore, we highlight two watersheds (Congo and Senegal) for which we explore intra‐ and interannual variability of different precipitation sources, and where we find contrasting patterns of vegetation‐sourced precipitation within and between years. Overall, our results show that almost 50% of the annual rainfall in Africa originates from transpiration, although the variability between watersheds is large (5%–68%). We conclude that, considering the current and projected patterns of land use change in Africa, a better understanding of the implications for continental‐scale water availability is needed.