Notable shifts beyond pre-industrial streamflow and soil moisture conditions transgress the planetary boundary for freshwater change

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

5a. MaxEnt output - Raw

Raw data: MaxEnt results (csv) and haibitat suitability ascii fil

4. Correlation-check scripts

Matlab scripts to check for correlation between continuous variables and categorical variables (Cramers V). Input files for the categorical variables are provided, others can be found in <a href="https://doi.org/10.6084/m9.figshare.4668745" target="_blank">10.6084/m9.figshare.4668745</a

2. Eland Observation data

<div>Species observation data of eland (Taurotragus oyx) in Sneeuberg Nature Reserve, SA.</div><div><br></div>Content:<div><br>All_obs_long_latitude.csv = csv-file of all eland herd observation (longitude and latitue)<br>Eland_projected_UTM.xls = All data/meta data collected during ground census, with projected coordinated (WGS_1984_UTM_ZONE_35s)<div>MaxEnt input data.csv = eland observation data as was used to run MaxEnt (without duplicates)</div><div>CPE_ELAND.kmz = Google Earth file of eland observations <br><div><br></div></div></div

Contribution of the Sahel region to precipitation over the African continent

Redistribution of evapotranspiration from land via atmospheric circulation is an important Earth system process. Globally, evapotranspiration contributes significantly to terrestrial rainfall, on both regional and more remote scales. In wet, tropical regions (e.g. the Congo basin), transpiration and interception loss from the dense forest cover are the primary drivers of moisture recycling, which plays a crucial role in preserving regional ecosystem functioning. However, for semi-arid and arid regions, our knowledge on the extent and significance of evapotranspiration for moisture recycling is still very limited, despite the significance this may have for addressing challenges of desertification in times of rapid environmental change. Considering this, we are taking the Sahel region as a case study and investigate its contribution to precipitation in the African continent. In addition, we specifically study what fraction of the precipitation originates from vegetation in the Sahel through transpiration and interception loss. Our study is based on simulated atmospheric moisture trajectories derived from the Lagrangian model FLEXPART with a 1-degree resolution, driven by ECMWF reanalysis data over 1980–2016. Preliminary results show (1) the temporal variability in the contribution of the region to precipitation in African drylands, and (2) a significant contribution of local precipitation recycling. We conclude that consideration of the naturally and anthropogenically-driven greening of the Sahel, as well as land use and land cover changes in the region, may have both local and far-reaching impacts via the transport of moisture through the atmosphere

A planetary boundary for green water

Green water — terrestrial precipitation, evaporation and soil moisture — is fundamental to Earth system dynamics and is now extensively perturbed by human pressures at continental to planetary scales. However, green water lacks explicit consideration in the existing planetary boundaries framework that demarcates a global safe operating space for humanity. In this Perspective, we propose a green water planetary boundary and estimate its current status. The green water planetary boundary can be represented by the percentage of ice-free land area on which root-zone soil moisture deviates from Holocene variability for any month of the year. Provisional estimates of departures from Holocene-like conditions, alongside evidence of widespread deterioration in Earth system functioning, indicate that the green water planetary boundary is already transgressed. Moving forward, research needs to address and account for the role of root-zone soil moisture for Earth system resilience in view of ecohydrological, hydroclimatic and sociohydrological interactions

Towards a green water planetary boundary

Green water - soil moisture, evaporation, and precipitation over land - is fundamental to safeguard Earth system functioning. Nonlinear green-water driven changes in climate, ecosystems, biogeochemistry, and hydrology are becoming increasingly evident and widespread. Yet, considerations of continental to planetary scale green-water dynamics are yet to be assessed and incorporated in management and governance. Here, we propose a green water planetary boundary (PB) - as part of the planetary boundary framework that demarcates a global “safe-operating space” for humanity - for assessing green-water related changes that can affect the capacity of the Earth system to remain in Holocene-like conditions. We consider green-water related processes associated with all scales: spatially distributed units, regions or biomes, and the Earth system as a whole. The proposed green water PB variable is selected through expert elicitation based on a set of transparent evaluation criteria that consider both scientific and governability aspects. Finally, we clarify the appropriate use of a green water PB, outline remaining challenges, and propose a research agenda for future navigation and quantitative assessments of the biophysical Earth system scale boundaries of green water changes