What Four Decades of Earth Observation Tell Us about Land Degradation in the Sahel?

Mbow, Cheikh; Brandt, Martin; Ouédraogo, Issa; Leeuw, Jan De; Marshall, Michael

doi:10.3390/rs70404048

Cited by 87 publications

(70 citation statements)

References 73 publications

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“…Changes in tree cover attributes (e.g., canopy cover and tree density) have primarily been analysed using high or medium resolution RS data in order to separate trees and shrubs from the herbaceous vegetation that dominate the RS signal during the growing season. However, recent research by Horion et al (2014) and has shown that coarse resolution NDVI data acquired during the dry season is an interesting alternative for analysing tree cover changes over larger spatial extents (Brandt et al 2015). …”

Section: Research Topicmentioning

confidence: 99%

“…The second most common variable for vegetation change analysis in the SSZ is vegetation productivity derived from time series of coarse resolution RS data (e.g., AVHRR). Knauer et al (2014) and Mbow et al (2015) provide detailed descriptions of the many different approaches have been used to detect changes in vegetation productivity using coarse resolution RS data in the SSZ. Considerably less research has analysed changes in tree cover attributes and vegetation phenology using RS data.…”

Section: Research Topicmentioning

confidence: 99%

“…Knauer et al (2014) present a detailed overview of how RS has been used to analyze vegetation dynamics in West Africa, and conclude that most of the research has been focusing on areas in the SSZ. Lastly, Mbow et al (2015) provide a critical assessment of the research that has used RS for detecting desertification and land degradation in the Sahel. Together, these three papers provide a comprehensive description of the technological and methodological advancement of RS for vegetation observation in the SSZ, where the main focus is on the strengths and weaknesses of different RS systems and analytical methods.…”

Section: Introductionmentioning

confidence: 99%

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Remote sensing of vegetation in the Sudano-Sahelian zone: A literature review from 1975 to 2014

Karlson

Ostwald

2016

Journal of Arid Environments

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Scarcity of in situ vegetation data inhibits research and natural resource management in the Sudano-Sahelian zone (SSZ). Satellite and aerial remote sensing (RS) constitute key technologies for improving the availability of vegetation data, and consequently the preconditions for scientific analysis and monitoring. The aim of this paper was to investigate how the hands-on application of RS for vegetation analysis has developed in the SSZ by reviewing the scientific literature published between 1975 and 2014. The paper assesses the usages and the users of RS by focusing on four aspects of the material (268 peer-reviewed articles), including publication details (time of publication, scientific discipline of journals and author nationality), geographic information (location of study areas and spatial scale of research), data usage (application of RS systems and procedures for accuracy assessments), and research topic (scientific objective of the research). Three key results were obtained: i) the application of RS to analyze vegetation in the SSZ has increased consistently since 1977 and it seems to become adopted by a growing number of scientific disciplines; ii) the contribution of African authors is low, potentially signaling a need for an increased transfer of knowledge and technology from developed countries; iii) RS has primarily been used to analyze changes in vegetation productivity and broad vegetation types, whereas its use for studying interactions between vegetation and environmental factors has been relatively low. This calls for stronger collaborative RS research that enables the mapping of additional vegetation variables of high relevance for the environmental problems facing the SSZ. Remotely sensed vegetation data are needed at spatial scales that suits the requirements of both research and natural resource management in order to further enhance the usefulness of this technology.

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Section: Research Topicmentioning

confidence: 99%

Section: Research Topicmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Remote sensing of vegetation in the Sudano-Sahelian zone: A literature review from 1975 to 2014

Karlson

Ostwald

2016

Journal of Arid Environments

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“…Medium to low spatial resolution remote sensing data (250 m -4 km pixel size) enable the detection of trends and anomalies of remotesensing derived indices or biophysical variables over large areas. Applications in the Sahel include studies on the dynamics of vegetation, land use, and land degradation (Dardel et al, 2014;Brandt et al, 2014a;Horion et al, 2014;Mbow et al, 2015), water bodies and wetlands (Moser et al, 2014) and precipitation (Nicholson, 2005). Yet, such data is insufficient to elucidate more specific social-land use practices (Turner, 2003), for which the use of high to very high spatial resolution data is required (Elmqvist and Khatir, 2007;Brandt et al, 2014b).…”

Section: Using Geospatial Analysis In a Contested Landscapementioning

confidence: 99%

The production of contested landscapes: Enclosing the pastoral commons in Niger

Snorek

Moser

Renaud

2017

Journal of Rural Studies

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a b s t r a c tDivergent adaptation to climate variability produces unequal adaptive capacities between user groups and contributes to a contested landscape. This article examines divergent adaptations in the context of land tenure shifts in the pastoral zone of Niger. The management of the pastoral commons is shifting from a commonly-shared to private regime as former pastoralists take up new livelihoods, such as irrigated gardening. A method combining political ecology and remote sensing is used to study social ecological system (SES) dynamics in order to demonstrate the relationship between divergent adaptation, water-based conflict, land tenure shifts and land use/land cover change. Examining pastoral and agro-pastoral users' historical perceptions of land use and tenure change, results indicate that disputes over the access to and use of commonly shared natural resources are linked to increasing enclosures of ephemeral and permanent lakes in the pastoral zone of Niger. Remote sensing-derived information is used to identify and quantify the area and volume of enclosures around commonly shared water sources in the northern pastoral zone of Niger from 2003 to 2013. The study identifies the government-supported development of irrigated gardens in the pastoral zone as a divergent adaptation with its related conflict dynamics between user groups and highlights the land tenure shifts from a commonly to a privately managed regime. The findings have broader implications for the wider Sahel and provide recommendations as to how adaptation programs could be better designed and implemented in the pastoral system.

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“…Much of these investigations have aimed to refine methodological issues in order to accurately track land degradation in vulnerable areas, reduce uncertainties and explain inconsistencies among studies. For instance, a wide array of satellite-derived data, such as vegetation indices, normalized surface reflectance, brightness temperature or biomass net primary production derivatives (Mbow et al, 2015), have been utilized to appraise desertification effects in the Sahel (Mbow et al, 2015;Fensholt et al, 2013) and also in other African countries such as Kenya (Omuto, 2011), Somalia (Omuto et al, 2010), South Africa (Thompson et al, 2009) or Zimbabwe (Prince et al, 2009). Likewise, desertification in the Mediterranean region has been studied through satellite imagery in Greece (Bajocco et al, 2012), Israel (Shoshany and Karnibad, 2015) and the Iberian Peninsula (del Barrio et al, 2010).…”

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confidence: 99%

Can land degradation drive differences in the C exchange of two similar semiarid ecosystems?

et al. 2018

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Abstract. Currently, drylands occupy more than one-third of the global terrestrial surface and are recognized as areas vulnerable to land degradation. The concept of land degradation stems from the loss of an ecosystem's biological productivity due to long-term loss of natural vegetation or depletion of soil nutrients. Drylands' key role in the global carbon (C) balance has been recently demonstrated, but the effects of land degradation on C sequestration by these ecosystems still need to be investigated. In the present study, we compared net C and water vapor fluxes, together with satellite, meteorological and vadose zone (CO 2 , water content and temperature) measurements, between two nearby (∼ 23 km) experimental sites representing "natural" (i.e., site of reference) and "degraded" grazed semiarid grasslands. We utilized data acquired over 6 years from two eddy covariance stations located in southeastern Spain with highly variable precipitation magnitude and distribution. Results show a striking difference in the annual C balances with an average net CO 2 exchange of 196 ± 40 (C release) and −23 ± 2 g C m −2 yr −1 (C fixation) for the degraded and natural sites, respectively. At the seasonal scale, differing patterns in net CO 2 fluxes were detected over both growing and dry seasons. As expected, during the growing seasons, greater net C uptake over longer periods was observed at the natural site. However, a much greater net C release, probably derived from subterranean ventilation, was measured at the degraded site during drought periods. After subtracting the nonbiological CO 2 flux from net CO 2 exchange, flux partitioning results point out that, during the 6 years of study, gross primary production, ecosystem respiration and water use efficiency were, on average, 9, 2 and 10 times higher, respectively, at the natural site versus the degraded site. We also tested differences in all monitored meteorological and soil variables and CO 2 at 1.50 m belowground was the variable showing the greatest intersite difference, with ∼ 1000 ppm higher at the degraded site. Thus, we believe that subterranean ventilation of this vadose zone CO 2 , previously observed at both sites, partly drives the differences in C dynamics between them, especially during the dry season. It may be due to enhanced subsoil-atmosphere interconnectivity at the degraded site.

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What Four Decades of Earth Observation Tell Us about Land Degradation in the Sahel?

Cited by 87 publications

References 73 publications

Remote sensing of vegetation in the Sudano-Sahelian zone: A literature review from 1975 to 2014

Remote sensing of vegetation in the Sudano-Sahelian zone: A literature review from 1975 to 2014

The production of contested landscapes: Enclosing the pastoral commons in Niger

Can land degradation drive differences in the C exchange of two similar semiarid ecosystems?

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