Can a 25-year trend in Soudano-Sahelian vegetation dynamics be interpreted in terms of land use change? A remote sensing approach

Bégué, Agnès; Vintrou, Élodie; Ruelland, Denis; Claden, M.; Dessay, Nadine

doi:10.1016/j.gloenvcha.2011.02.002

Cited by 130 publications

(82 citation statements)

References 35 publications

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“…The analysis showed only a few portions of the total area with significant positive trend at p-value < 0.07. Our observations are in agreement with those of Bégué et al, 2011, who observed a similar no significant rainfall trend in the same area during the period from 1982 to 2005 for almost the whole catchment.…”

Section: Trend In Vegetation and Rainfallsupporting

confidence: 93%

Assessing Long-Term Trends In Vegetation Productivity Change Over the Bani River Basin in Mali (West Africa)

Traoré¹,

Landmann²,

Forkuo³

et al. 2014

JGES

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Using time series of Normalized Difference Vegetation Index (NDVI) and rainfall data, we investigated historical vegetation productivity trends from 1982 to 2011 over the Bani River Basin in Mali. Statistical agreements between long-term trends in vegetation productivty, corresponding rainfall and rate of land cover change from Landsat time-series imagery was used to discern climate versus human-induced vegetation cover change. Spearman correlation was used to investigate the relationship between metrics of vegetation, rainfall trends and land cover change categories. The results show there is a positive correlation between increases in rainfall and some land cover classes, while some classes such as settlements were negatively correlated with vegetation productivity trends. Croplands and Natural Vegetation were positively correlated (r=0.89) with rainfall while settlements have a negative correlation with NDVI time series trend (r=-057). Despite the fact that rainfall is the major determinant of vegetation cover dynamics in the study area, it appears that other human-induced factors such as urbanization have negatively influenced the change in vegetation cover in the study area. The results show that a combined analysis of NDVI, rainfall and spatially explicit land cover change provides a comprehensive insight into the drivers of vegetation cover change in semi-arid Africa.

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Section: Trend In Vegetation and Rainfallsupporting

confidence: 93%

Assessing Long-Term Trends In Vegetation Productivity Change Over the Bani River Basin in Mali (West Africa)

Traoré¹,

Landmann²,

Forkuo³

et al. 2014

JGES

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show abstract

“…We thus used the wet season peak NDVI as a proxy for the year's rainfall and growing conditions, to correct the dry season NDVI and remove the effects of varying foliage density. If a significant relationship between wet season NDVI peak and dry season NDVI was observed, a regression was used to predict the dry season NDVI with the wet season peak NDVI, following the concept described in Bégué et al [27]. The residues between predicted and observed NDVI were used to remove the effects of rainfall.…”

Section: Estimating Woody Cover Dynamics From Sahel-wide In Situ Datamentioning

confidence: 99%

Woody Vegetation Die off and Regeneration in Response to Rainfall Variability in the West African Sahel

et al. 2017

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Abstract:The greening in the Senegalese Sahel has been linked to an increase in net primary productivity, with significant long-term trends being closely related to the woody strata. This study investigates woody plant growth and mortality within greening areas in the pastoral areas of Senegal, and how these dynamics are linked to species diversity, climate, soil and human management. We analyse woody cover dynamics by means of multi-temporal and multi-scale Earth Observation, satellite based rainfall and in situ data sets covering the period 1994 to 2015. We find that favourable conditions (forest reserves, low human population density, sufficient rainfall) led to a rapid growth of Combretaceae and Balanites aegyptiaca between 2000 and 2013 with an average increase of 4% woody cover. However, the increasing dominance and low drought resistance of drought prone species bears the risk of substantial woody cover losses following drought years. This was observed in 2014-2015, with a die off of Guiera senegalensis in most places of the study area. We show that woody cover and woody cover trends are closely related to mean annual rainfall, but no clear relationship with rainfall trends was found over the entire study period. The observed spatial and temporal variation contrasts with the simplified labels of "greening" or "degradation". While in principal a low woody plant diversity negatively impacts regional resilience, the Sahelian system is showing signs of resilience at decadal time scales through widespread increases in woody cover and high regeneration rates after periodic droughts. We have reaffirmed that the woody cover in Sahel responds to its inherent climatic variability and does not follow a linear trend.

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“…It is one of the world's largest water-limited environments (WLE). The region is often considered to be particularly vulnerable to climate change and human activities (1,2). Herders and farmers in the Sahel have long recognized the importance of short-term rainfall variability on farm and livestock production, with drought being the principal cause of food insecurity (3).…”

mentioning

confidence: 99%

On regreening and degradation in Sahelian watersheds

Kaptué

Prihodko

Hanan

2015

Proc. Natl. Acad. Sci. U.S.A.

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Over many decades our understanding of the impacts of intermittent drought in water-limited environments like the West African Sahel has been influenced by a narrative of overgrazing and human-induced desertification. The desertification narrative has persisted in both scientific and popular conception, such that recent regional-scale recovery ("regreening") and local success stories (community-led conservation efforts) in the Sahel, following the severe droughts of the 1970s-1980s, are sometimes ignored. Here we report a study of watershed-scale vegetation dynamics in 260 watersheds, sampled in four regions of Senegal, Mali, and Niger from 1983-2012, using satellite-derived vegetation indices as a proxy for net primary production. In response to earlier controversy, we first examine the shape of the rainfall-net primary production relationship and how it impacts conclusions regarding greening or degradation. We conclude that the choice of functional relationship has little quantitative impact on our ability to infer greening or degradation trends. We then present an approach to analyze changes in long-term (decade-scale) average rain-use efficiency (an indicator of slowly responding vegetation structural changes) relative to changes in interannual-scale rainfall sensitivity (an indicator of landscape ability to respond rapidly to rainfall variability) to infer trends in greening/degradation of the watersheds in our sample regions. The predominance of increasing rain-use efficiency in our data supports earlier reports of a "greening" trend across the Sahel. However, there are strong regional differences in the extent and direction of change, and in the apparent role of changing woody and herbaceous components in driving those temporal trends.Sahel | desertification | rain-use efficiency | drylands | West Africa

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Can a 25-year trend in Soudano-Sahelian vegetation dynamics be interpreted in terms of land use change? A remote sensing approach

Cited by 130 publications

References 35 publications

Assessing Long-Term Trends In Vegetation Productivity Change Over the Bani River Basin in Mali (West Africa)

Assessing Long-Term Trends In Vegetation Productivity Change Over the Bani River Basin in Mali (West Africa)

Woody Vegetation Die off and Regeneration in Response to Rainfall Variability in the West African Sahel

On regreening and degradation in Sahelian watersheds

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