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The possibility that the Amazon forest system could soon reach a tipping point, inducing large-scale collapse, has raised global concern1-3. For 65 million years, Amazonian forests remained relatively resilient to climatic variability. Now, the region is increasingly exposed to unprecedented stress from warming temperatures, extreme droughts, deforestation and fires, even in central and remote parts of the system1. Long existing feedbacks between the forest and environmental conditions are being replaced by novel feedbacks that modify ecosystem resilience, increasing the risk of critical transition. Here we analyse existing evidence for five major drivers of water stress on Amazonian forests, as well as potential critical thresholds of those drivers that, if crossed, could trigger local, regional or even biome-wide forest collapse. By combining spatial information on various disturbances, we estimate that by 2050, 10% to 47% of Amazonian forests will be exposed to compounding disturbances that may trigger unexpected ecosystem transitions and potentially exacerbate regional climate change. Using examples of disturbed forests across the Amazon, we identify the three most plausible ecosystem trajectories, involving different feedbacks and environmental conditions. We discuss how the inherent complexity of the Amazon adds uncertainty about future dynamics, but also reveals opportunities for action. Keeping the Amazon forest resilient in the Anthropocene will depend on a combination of local efforts to end deforestation and degradation and to expand restoration, with global efforts to stop greenhouse gas emissions.

Human actions compromise the many life-supporting functions provided by the freshwater cycle. Yet, scientific understanding of anthropogenic freshwater change and its long-term evolution is limited. Here, using a multi-model ensemble of global hydrological models, we estimate how, over a 145-year industrial period (1861–2005), streamflow and soil moisture have deviated from pre-industrial baseline conditions (defined by 5th–95th percentiles, at 0.5° grid level and monthly timestep over 1661–1860). Comparing the two periods, we find an increased frequency of local deviations on ~45% of land area, mainly in regions under heavy direct or indirect human pressures. To estimate humanity’s aggregate impact on these two important elements of the freshwater cycle, we present the evolution of deviation occurrence at regional to global scales. Annually, local streamflow and soil moisture deviations now occur on 18.2% and 15.8% of global land area, respectively, which is 8.0 and 4.7 percentage points beyond the ~3 percentage point wide pre-industrial variability envelope. Our results signify a substantial shift from pre-industrial streamflow and soil moisture reference conditions to persistently increasing change. This indicates a transgression of the new planetary boundary for freshwater change, which is defined and quantified using our approach, calling for urgent actions to reduce human disturbance of the freshwater cycle., Water Resources

To keep urban areas in the Netherlands inhabitable in the changing climate where extreme rainfall, drought, and heat occur increasingly often, they need to become more climate adaptive. The Deltaprogramma Ruimtelijke Adaptatie (DPRA) requires safety regions to carry out a climate stress test for locations that are at risk of water nuisance, drought, heat stress and flood risk. Based on this test municipalities can create a local adaptation strategy (LAS). Because climate adaptation is such an important and broad topic, different government levels need to collaborate to reach the desired results. Currently, there is no scientific framework on how the relevant government levels: water authorities, provinces and municipalities should collaborate to reach the climate adaptation goals. This research has focussed mostly on the collaboration between municipalities and water authorities. In depth research on the collaboration of Hoogheemraadschap de Stichtse Rijnlanden (HDSR) and fourteen municipalities within its management area has been conducted with the aim to provide HDSR with a set of actions they can take to assist municipalities in the creation of climate adaptation policy and the implementation of adaptation measures. In order to find this set of actions firstly the available climate adaptation policy of the municipalities was reviewed. Based on those results municipal representatives were interviewed to ask about their policy, difficulties, and what they desire and expect from HDSR. Secondly, possible actions HDSR could take were investigated. This concerned policy, capacity and budgetary aspects. Those possible actions were then linked to the main obstacles mentioned by the municipalities to come to a recommended course of action for HDSR. From the policy review, it became apparent that only eight of the fourteen municipalities have a clear climate adaptation policy document and for the other six municipalities it is either absent or fragmented over other documen

Extreme precipitation events and associated flash floods caused by synoptic cyclonic systems profoundly impact society and the environment, particularly in arid regions. This study brings forward a satellite-reanalysis-based approach to quantify extreme precipitation characteristics over the Sinai Peninsula (SiP) in Egypt from a statistical-synoptic perspective for the period of 2001-2020. With a multi-statistical approach developed in this research, SiP's wet and dry periods are determined. Using satellite observations of precipitation and a set of derived precipitation indices, we characterize the spatiotemporal variations of extreme rainfall climatologies across the SiP. Then, using the reanalysis datasets, synoptic systems responsible for the occurrence of extreme precipitation events along with the major tracks of cyclones during the wet and dry periods are described. Our results indicate that trends and spatial patterns of the rainfall events across the region are inconsistent in time and space. The highest precipitation percentiles (~20mm per month), frequencies (~15d per month with rainfall ≥10mmd-1), standard deviations (~9mmmonth per month), and monthly ratios (~18%) are estimated in the northern and northeastern parts of the region during the wet period, especially in early winter; also, a substantial below-average precipitation condition (drier trend) is clearly observed in most parts except for the south. Mediterranean cyclones accompanied by the Red Sea and Persian troughs are responsible for the majority of extreme rainfall events year-round. A remarkable spatial relationship is found between SiP's rainfall and the atmospheric variables of sea level pressure, wind direction, and vertical velocity. A cyclone-tracking analysis indicates that 125 cyclones (with rainfall ≥10mmd-1) formed within, or transferred to, the Mediterranean basin and precipitated over the SiP during wet periods compared to 31 such cyclones during dry periods. It is estimated aroun

Changes in evaporation over land affect terrestrial precipitation via atmospheric moisture recycling and, consequently, freshwater availability. Although global moisture recycling at regional and continental scales is relatively well understood, the patterns of local moisture recycling and the main variables that impact it remain unknown. We calculate the local moisture recycling ratio (LMR) as the fraction of evaporated moisture that precipitates within a distance of 0.5° (typically 50 km) of its source, identify variables that correlate with it over land globally, and study its model dependency. We derive the seasonal and annual LMR using a 10-year climatology (2008-2017) of monthly averaged atmospheric moisture connections at a scale of 0.5° obtained from a Lagrangian atmospheric moisture tracking model. We find that, annually, an average of 1.7% (SD of 1.1%) of evaporated moisture returns as precipitation locally, although with large temporal and spatial variability, and the LMR peaks in summer and over wet and mountainous regions. Our results show that wetness, orography, latitude, convective available potential energy, wind speed, and total cloud cover correlate clearly with the LMR, indicating that wet regions with little wind and strong ascending air are particularly favourable for a high LMR. Finally, we find that spatial patterns of local recycling are consistent between different models, yet the magnitude of recycling varies. Our results can be used to study the impacts of evaporation changes on local precipitation, with implications for, for example, regreening and water management.

To keep urban areas in the Netherlands inhabitable in the changing climate where extreme rainfall, drought, and heat occur increasingly often, they need to become more climate adaptive. The Deltaprogramma Ruimtelijke Adaptatie (DPRA) requires safety regions to carry out a climate stress test for locations that are at risk of water nuisance, drought, heat stress and flood risk. Based on this test municipalities can create a local adaptation strategy (LAS). Because climate adaptation is such an important and broad topic, different government levels need to collaborate to reach the desired results. Currently, there is no scientific framework on how the relevant government levels: water authorities, provinces and municipalities should collaborate to reach the climate adaptation goals. This research has focussed mostly on the collaboration between municipalities and water authorities. In depth research on the collaboration of Hoogheemraadschap de Stichtse Rijnlanden (HDSR) and fourteen municipalities within its management area has been conducted with the aim to provide HDSR with a set of actions they can take to assist municipalities in the creation of climate adaptation policy and the implementation of adaptation measures. In order to find this set of actions firstly the available climate adaptation policy of the municipalities was reviewed. Based on those results municipal representatives were interviewed to ask about their policy, difficulties, and what they desire and expect from HDSR. Secondly, possible actions HDSR could take were investigated. This concerned policy, capacity and budgetary aspects. Those possible actions were then linked to the main obstacles mentioned by the municipalities to come to a recommended course of action for HDSR. From the policy review, it became apparent that only eight of the fourteen municipalities have a clear climate adaptation policy document and for the other six municipalities it is either absent or fragmented over other documen

This chapter assesses scientific evidence for tipping points across the biosphere, which comprises Earth’s ecosystems. Human-driven habitat loss, pollution, exploitation and, increasingly, climate change are degrading ecosystems across the planet, some of which can pass tipping points beyond which a ‘regime shift’ to an alternative (and often less diverse or beneficial) ecosystem state occurs.Evidence for tipping points emerges across many biomes. In forests,large parts of the Amazon rain forest could tip to degraded forest or impoverished savanna, while tipping in boreal forests is possible but more uncertain, and whether current temperate forest disturbance could lead to tipping is unclear. In open savannas and drylands,drying could lead to desertification in some areas, while in others encroachment by trees and shrubs could see these biodiverse ecosystems shift to a forested or degraded state. Nutrient pollution and warming can trigger lakes to switch to an algae-dominated low-oxygen state. Coral reefs are already experiencing tipping points, as more frequent warming-driven bleaching events, along with pollution,extreme weather events and diseases, tip them to degraded algae-dominated states. Mangroves and sea grasses are at risk of regional tipping, along with kelp forests, marine food webs and some fisheries,which are known to be able to collapse.Together, these tipping points threaten the livelihoods of millions of people, and some thresholds are likely imminent. Stabilising climate is critical for reducing the likelihood of widespread ecosystem tipping points, but tackling other pressures can also help increase ecological resilience, push back tipping and support human well being.