Precipitation controls Sahel greening trend

Hickler, Thomas; Eklundh, Lars; Seaquist, Jonathan; Smith, Benjamin; Ardö, Jonas; Olsson, Lennart; Sykes, Martin T.; Sjöström, Martin

doi:10.1029/2005gl024370

Cited by 225 publications

(195 citation statements)

References 23 publications

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“…Hickler et al (2005) showed that a positive trend in satellite-measured NDVI greenness through the 1980s and 1990s was best explained by a positive trend in precipitation over this period. Expanding this analysis to 2002, using a spatially explicit approach, accounting for additional regional effects of human land use, did not significantly improve agreement between modelled vegetation patterns and satellite observations (Seaquist et al, 2009 Fig.…”

Section: Inter-annual Greenness Variability 1982-2006mentioning

confidence: 99%

“…Results from the model have been compared to ecosystem flux measurements, site measurements and satellite-based proxies of NPP, leaf area index (LAI) and biomass, spanning many of the world's biomes (Morales et al, 2005;Hickler et al, 2005Hickler et al, , 2006Hély et al, 2006;Smith et al, 2008;Ahlström et al, 2012a). LPJ-GUESS has been shown to be better than LPJ-DGVM at predicting potential natural vegetation, e.g.…”

Section: Dgvmmentioning

confidence: 99%

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Implications of accounting for land use in simulations of ecosystem carbon cycling in Africa

et al. 2013

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Abstract. Dynamic global vegetation models (DGVMs) are important tools for modelling impacts of global change on ecosystem services. However, most models do not take full account of human land management and land use and land cover changes (LULCCs). We integrated croplands and pasture and their management and natural vegetation recovery and succession following cropland abandonment into the LPJ-GUESS DGVM. The revised model was applied to Africa as a case study to investigate the implications of accounting for land use on net ecosystem carbon balance (NECB) and the skill of the model in describing agricultural production and reproducing trends and patterns in vegetation structure and function. The seasonality of modelled monthly fraction of absorbed photosynthetically active radiation (FPAR) was shown to agree well with satellite-inferred normalised difference vegetation index (NDVI). In regions with a large proportion of cropland, the managed land addition improved the FPAR vs. NDVI fit significantly. Modelled 1991-1995 average yields for the seven most important African crops, representing potential optimal yields limited only by climate forcings, were generally higher than reported FAO yields by a factor of 2-6, similar to previous yield gap estimates. Modelled inter-annual yield variations during 1971-2005 generally agreed well with FAO statistics, especially in regions with pronounced climate seasonality. Modelled land-atmosphere carbon fluxes for Africa associated with land use change (0.07 PgC yr −1 release to the atmosphere for the 1980s) agreed well with previous estimates. Cropland management options (residue removal, grass as cover crop) were shown to be important to the landatmosphere carbon flux for the 20th century.

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Section: Inter-annual Greenness Variability 1982-2006mentioning

confidence: 99%

Section: Dgvmmentioning

confidence: 99%

Implications of accounting for land use in simulations of ecosystem carbon cycling in Africa

et al. 2013

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“…Changes in precipitation were identified as the primary driver of the greening trend of the Sahel vegetation and its interannual variability between 1982 and 1998 (Hickler et al, 2005), although Anyamba and Tucker (2005) emphasize that the NDVI time series commenced ARTICLE IN PRESS during a historically intense drought (the early 1980s) and that the recent gradual recovery has likely not returned vegetation to pre-drought conditions of the 1950s and 1960s. However, the resilience of vegetation to rainfall is not evident everywhere and the idea of ''greening Sahel'' has been challenged by some authors (Hiernaux and Turner, 2002;Hountondji et al, 2006;Ozer and Ozer, 2005).…”

Section: Article In Pressmentioning

confidence: 99%

Fifty years of landscape evolution in Southwestern Mauritania by means of aerial photos

Niang

Ozer

2008

Journal of Arid Environments

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South-western Mauritania is located in a semi-arid environment exposed to large rainfall variations and affected by a severe drought since the mid-1960s. The studied area includes the right bank of the Senegal River and the southern extension of the Saharan sandy dunes and is based on the analysis of climatic data, field studies, and four aerial surveys realized since 1954.The climatic analysis shows that, after a strong decline of yearly rainfall started in the mid-1960s, a significant increase is observed from the early 1990s. In the meantime, dust storms frequency has dramatically increased while the threshold wind speed declined as a result of vegetation contraction. The comparison of the four mosaics of aerial photos reveals the major impact of both drought and human on recent environment changes with the strong decline of the forest, the reactivation of sandy soils and the apparition of large rice fields.If the increase of active dunes activity is likely to be a consequence of the persisting drought, forest decline is more likely to be attributed to fuel wood collection in a first time, then to the creation of rice fields since the late 1980s. Although the 2003 aerial photos show a timid return of vegetation in very limited and specific areas, field surveys show that wind erosion is still very important and water erosion is developing very rapidly because of the absence of vegetation cover. r

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“…In addition to influences from anthropogenic activity (e.g. changes in land use), vegetation changes in the region have been linked to changes in recorded climatic conditions, including the trend and interannual variability in precipitation (Herrmann et al, 2005;Hickler et al, 2005;Zhou et al, 2014), which in turn have been related to decadal-scale changes in regional circulation (Camberlin et al, 2001;Giannini et al, 2003). On longer timescales, anthropogenic climate change has the potential to cause profound structural and compositional changes in vegetation over Africa (Sitch et al, 2008;Scheiter and Higgins, 2009).…”

Section: Introductionmentioning

confidence: 99%

Vegetation–climate feedbacks modulate rainfall patterns in Africa under future climate change

Schurgers

Rummukainen

et al. 2016

Earth Syst. Dynam.

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Abstract. Africa has been undergoing significant changes in climate and vegetation in recent decades, and continued changes may be expected over this century. Vegetation cover and composition impose important influences on the regional climate in Africa. Climate-driven changes in vegetation structure and the distribution of forests versus savannah and grassland may feed back to climate via shifts in the surface energy balance, hydrological cycle and resultant effects on surface pressure and larger-scale atmospheric circulation. We used a regional Earth system model incorporating interactive vegetation-atmosphere coupling to investigate the potential role of vegetation-mediated biophysical feedbacks on climate dynamics in Africa in an RCP8.5-based future climate scenario. The model was applied at high resolution (0.44 × 0.44 • ) for the CORDEX-Africa domain with boundary conditions from the CanESM2 general circulation model. We found that increased tree cover and leafarea index (LAI) associated with a CO 2 and climate-driven increase in net primary productivity, particularly over subtropical savannah areas, not only imposed important local effect on the regional climate by altering surface energy fluxes but also resulted in remote effects over central Africa by modulating the land-ocean temperature contrast, Atlantic Walker circulation and moisture inflow feeding the central African tropical rainforest region with precipitation. The vegetation-mediated feedbacks were in general negative with respect to temperature, dampening the warming trend simulated in the absence of feedbacks, and positive with respect to precipitation, enhancing rainfall reduction over the rainforest areas. Our results highlight the importance of accounting for vegetation-atmosphere interactions in climate projections for tropical and subtropical Africa.

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Precipitation controls Sahel greening trend

Cited by 225 publications

References 23 publications

Implications of accounting for land use in simulations of ecosystem carbon cycling in Africa

Implications of accounting for land use in simulations of ecosystem carbon cycling in Africa

Fifty years of landscape evolution in Southwestern Mauritania by means of aerial photos

Vegetation–climate feedbacks modulate rainfall patterns in Africa under future climate change

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