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Drought-induced regime shift and resilience of a Sahelian ecohydrosystem
- Source :
- Environmental Research Letters, Environmental Research Letters, IOP Publishing, 2019, 14 (10), pp.105005. ⟨10.1088/1748-9326/ab3dde⟩, Environmental Research Letters, 14. IOP Publishing, Environmental Research Letters, 2019, 14 (10), pp.105005. ⟨10.1088/1748-9326/ab3dde⟩
- Publication Year :
- 2019
- Publisher :
- HAL CCSD, 2019.
-
Abstract
- International audience; The Sahel (a semi-arid fringe south of the Sahara) experienced a long and prolonged drought from the1970s to the mid-1990s, with a few extremely severe episodes that strongly affected ecosystems andsocieties. Long-term observations showed that surface runoff increased during this period, despite therainfall deficit. This paradox stems from the soil degradation that was induced by various factors,either directly linked to the drought (impact on vegetation cover), or, in places, to human practices (land clearing and cropping). Surface runoff is still increasing throughout the region, suggesting that Sahelian ecohydrosystems may have shifted to a new hydrological regime. In order to explore this issue, we have developed a simple system dynamics model incorporating vegetation–hydrology interactions and representing in a lumped way the first order processes occurring at the hillslope scale and the annual timestep. Long term observations on a pilot site in northern Mali were used to constrain the model and define an ensemble of plausible simulations. The model successfully reproduced the vegetation collapse and the runoff increase observed over the last 60 years. Our results confirmed that the system presents two alternative states and that during the drought it shifted from a high-vegetation/low-runoff regime to the alternative low-vegetation/high-runoff one, where it has remained trapped until now. We showed that the mean annual rainfall deficit was sufficient to explain the shift. According to the model, vegetation recovery and runoff reduction are possible in this system, but the conditions in which they could occur remain uncertain as the model was only constrained by observations over the collapse trajectory. The study shows that the system is also sensitive to the interannual and decadal variability of rainfall, and that larger variability leads to higher runoff. Both mean rainfall and rainfall variability may increase in central Sahel under climate change, leading to antagonist effects on the system, which makes its resilience uncertain.
- Subjects :
- 010504 meteorology & atmospheric sciences
rainfall
Climate change
alternative stable states
010501 environmental sciences
01 natural sciences
Alternative stable state
Soil retrogression and degradation
Sahel
Clearing
Ecosystem
Regime shift
[SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment
ComputingMilieux_MISCELLANEOUS
0105 earth and related environmental sciences
General Environmental Science
2. Zero hunger
regime shifts
rainfall variability
Renewable Energy, Sustainability and the Environment
variability
Public Health, Environmental and Occupational Health
Vegetation
15. Life on land
13. Climate action
Climatology
[SDE]Environmental Sciences
eco-hydrology
Environmental science
Surface runoff
Subjects
Details
- Language :
- English
- ISSN :
- 17489326
- Database :
- OpenAIRE
- Journal :
- Environmental Research Letters, Environmental Research Letters, IOP Publishing, 2019, 14 (10), pp.105005. ⟨10.1088/1748-9326/ab3dde⟩, Environmental Research Letters, 14. IOP Publishing, Environmental Research Letters, 2019, 14 (10), pp.105005. ⟨10.1088/1748-9326/ab3dde⟩
- Accession number :
- edsair.doi.dedup.....5fcfa268d9b34c8ae3059b6591c2f639