Global Soil Erosion – Future projections
Land use and climate change impacts on global soil erosion by water (2015-2070)
We use the latest projections of climate and land use change to assess potential global soil erosion rates by water to address policy questions; working towards the goals of the United Nations working groups under the Inter-Governmental Technical Panel on Soils of the Global Soil Partnership. This effort will enable policy makers to explore erosion extent, identify possible hotspots, and work with stakeholders to mitigate potential impacts. In addition, we also provide insight into the potential mitigating effects attributable to conservation agriculture and the need for more effective policy instruments for soil protection. Scientifically, the modeling framework presented adopts a series of methodological advances and standardized data to communicate with adjacent disciplines and move towards robust, reproducible and open data science.
- Modelled area: 143 million Km2 which is about ~95.5% of Earth's land
- 202 countries included in the study
- Three alternative (2.6, 4.5 & 8.5) Shared Socioeconomic Pathway and Representative Concentration Pathway (SSP-RCP) scenarios
- 14 General Climate Circulation Models (GCMs) used to assess future rainfall erosivity scenarios
- The baseline model (2015) predicts global potential soil erosion rates of 43 (-7 , +9.2) Pg yr-1
- Climate projections indicate an overall trend moving towards a more vigorous hydrological cycle, which could increase global water erosion up to more than +60% (SSP5-RCP8.5).
Soil erosion is a major global soil degradation threat to land, freshwater and oceans. Wind and water are the major drivers, with water erosion over land being the focus of this work; excluding gullying and river bank erosion. Improving knowledge of the probable future rates of soil erosion, accelerated by human activity, is important both for policy makers engaged in land-use decision-making and for earth-system modelers seeking to reduce uncertainty on global predictions. Here we predict future rates of erosion by modelling change in potential global soil erosion by water using three alternative (2.6, 4.5 & 8.5) Shared Socioeconomic Pathway and Representative Concentration Pathway (SSP-RCP) scenarios. Global predictions rely on a high spatial resolution RUSLE-based semi-empirical modeling approach (GloSEM). The baseline model (2015) predicts global potential soil erosion rates of 43 (-7 , +9.2) Pg yr-1, with current conservation agriculture (CA) practices estimated to reduce this by ~5%. Our future scenarios suggest that socio‐economic developments impacting land use will either decrease (SSP1-RCP2.6 -10%) or increase (SSP2-RCP4.5 +2%, SSP5-RCP8.5 +10%) water erosion by 2070. Climate projections, for all global dynamics scenarios indicate a trend, moving towards a more vigorous hydrological cycle, which could increase global water erosion (+30 to +66%). Accepting some degrees of uncertainty, our findings provide insights into how possible future socio‐economic development will affect soil erosion by water using a globally consistent approach. This preliminary evidence seeks to inform efforts such as those of the United Nations to assess global soil erosion and inform decision makers developing national strategies for soil conservation.
The study area comprises the land surface of 202 countries for which FAOSTAT currently offers statistics. The modeling area totals about 143 million km2 (~95.5% of the Earth’s land surface), currently providing living space for a global population of ca. 7.5 billion people and estimated to rise to about 9 billion around 2070.
With some degree of uncertainty, GloSEM allows prediction of both state and change of soil erosion, identifying hot spots thanks to its high resolution (250 × 250 m) and, for the first time, predicting future variation based on projections of change in land use, soil conservation practices and climate change. Its estimates provide a useful knowledge base to support decision-makers in considering the development of more resilient agricultural systems, such as agroforestry, regenerative agriculture or other emerging techniques able to go beyond current CA strategies. These need to take into consideration that we may need to deal with important changes to climate now, and in the coming decades. Both SSP1-RCP2.6 and SSP5-RCP8.5 scenarios provide clues on possible future local conditions requiring adaptation to drastic climate change conditions. These appear to be mainly located within highly populated tropical countries. The ability of GloSEM to identify hotspots, and areas of concern, at the global scale provides the basis for a more strategic approach in directing local monitoring/ modeling. In addition, the dynamic nature of the model makes it suitable for both ex-ante and ex-post policy evaluation. Scientifically, the way forward for GloSEM is to produce free and easily accessible knowledge on global soil erosion dynamics to be shared with adjoining disciplines. The modeling framework presented in this study adopts standardized data in an adequate format to communicate with adjacent disciplines and moves us towards robust, reproducible and open data science. It aims at facilitating the consideration of soil erosion processes and deriving land degradation impacts in the next assessment reports of the Intergovernmental Panel on Climate Change (IPCC).
Data and additional material
The global soil erosion data for all the 3 (2.6, 4.5 & 8.5) Shared Socioeconomic Pathway and Representative Concentration Pathway (SSP-RCP) scenarios and 14 General Climate Circulation Models (GCMs) are provided. The data is provided as 0.25° by 0.25° gridded degree, spatially consistent with the Harmonization of Global Land-Use (LUH2) data. The baseline modelling year is 2015. Future projections refer to 2070 and are provided considering only land use change and land use change + climate change combined.
Borrelli P., Robinson D.A., Panagos P., Lugato E., Yang J.E., Alewell C., Wuepper D., Montanarella L., Ballabio C. 2020. Land use and climate change impacts on global soil erosion by water (2015-2070). Proceedings of the National Academy of Sciences (PNAS), 117(36), 21994–22001; doi: 10.1073/pnas.2001403117
Figure. Global annual changes in agricultural area between the reference period 2015 and the 2070 projections (RCP 2.6, IMAGE model; RCP 4.5, MESSAGE-GLOBIOM model; and RCP 8.5, REMIND-MAGPIE model).
Figure. Flow diagramm of the projected land use and climate change scenarios.