Recent trends in vegetation dynamics in the African Sahel and their relationship to climate

Herrmann, Stefanie M.; Anyamba, Assaf; Tucker, Compton J.

doi:10.1016/j.gloenvcha.2005.08.004

Cited by 745 publications

(658 citation statements)

References 60 publications

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“…Identifying the determining climate variables is the other factor required to establish of the optimal relationship (Herrmann et al, 2005). Previous studies have demonstrated that the influence of climate change on vegetation growth may have a time lag (Piao et al, 2003;Udelhoven et al, 2009).…”

Section: Restrend Analysismentioning

confidence: 99%

Human-induced grassland degradation/restoration in the central Tibetan Plateau: The effects of ecological protection and restoration projects

Cai

Yang

2015

Ecological Engineering

178

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A B S T R A C TEcological projects are an important and vital method to help ecosystem adaptation and restoration in response to the environment change and human interference. The accurate and objective assessment of ecological projects will assist ecosystem management and adaption. This study took the central Tibetan Plateau as the study area, where a series of ecological projects has been implemented since 2005 to prevent grassland degradation by protecting and restoring the grasslands. Our aim is to explore where and to what extent the ecological projects influenced the grassland variation, using SPOT NDVI-based residual trend as an indicator. The results indicated that before the projects (between 1998 and 2004), human-induced degradation characterized the grassland. However, a general grassland restoration was detected after the projects from 2005 to 2012. Moreover, over 60% of project plots had positive trends in the NDVI residuals. From the spatial patterns, project-induced restoration was detected in the western and northern regions, such as Maduo, Dongde and Xinghai counties. For the eastern regions, the human-induced degradation has been generally mitigated and yet not reversed after the projects. Our results indicated that ecological protection and restoration projects in the central Tibetan Plateau have mitigated the grassland degradation and even reversed the degradation in some areas, and also suggested that the NDVI-based residual trend is a useful indicator for assessing the effectiveness of the ecological projects in alpine regions.

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Section: Restrend Analysismentioning

confidence: 99%

Human-induced grassland degradation/restoration in the central Tibetan Plateau: The effects of ecological protection and restoration projects

Cai

Yang

2015

Ecological Engineering

178

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“…This rather unexpected finding further challenged the dominating narrative of environmental change in the SSZ, and is one of the main reasons for the large increase in RS research in the last 15 years shown in this review. Several researchers suggested that the greening-phenomenaon needed to be observed at higher levels of detail in order to establish the causative mechanisms and to better understand potential consequences Herrmann et al 2005). Time series of medium and high resolution RS data have been widely used for such analyses because fine scale processes, including human influences on vegetation, can be observed (e.g., Kelder et al 2013;Rasmussen et al 2014;Ruelland et al 2008;2010;Tappan et al 2000;.…”

Section: Vegetation and Environmental Factors And Vegetation Change)mentioning

confidence: 99%

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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“…The effect of this increase in rainfall was assessed by a long-term analysis of satellite observations, which shows a general re-greening of Sahel for the period 1982-2003 (Herrmann et al, 2005). On the other hand, Lebel and Ali (2009) concluded from an analysis of a longer time period ) that the initial 20-year wet period (1950)(1951)(1952)(1953)(1954)(1955)(1956)(1957)(1958)(1959)(1960)(1961)(1962)(1963)(1964)(1965)(1966)(1967)(1968)(1969) was followed by a 40-year dry period a tipping point in the rainfall regime observed by Lebel and Ali (2009), which may suggest the beginning of a longer wet period.…”

Section: Rainfall Patternsmentioning

confidence: 99%

“…In contrast, a study by Capecchi et al (2008) demonstrated that an increase in rainfall in West Africa between 1986 and 2000 had a positive effect 3583 on crop production, particularly on the production of millet. The 're-greening' of the Sahel since the mid-eighties that followed the great drought of the seventies was also attributed to rainfall increase (Herrmann et al, 2005).…”

Section: Introductionmentioning

confidence: 99%

A conceptual model for assessing rainfall and vegetation trends in sub‐Saharan Africa from satellite data

Hościło

Balzter

Bartholomé³

et al. 2014

Int. J. Climatol

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Policymakers, governments and aid agencies require operational environmental monitoring in support of evidence-based policy-making and resource deployment in crisis situations. For Africa, this is only feasible at sub-continental scale with a large network of automated meteorological stations, a large number of highly coordinated field observers or with satellite remote sensing. The challenge with satellite data lies in the derivation of meaningful environmental indicators. This article describes a conceptual framework for understanding satellite-derived indicators of rainfall and vegetation greenness trends over Africa. It attributes observed vegetation changes to climatic (i.e. rainfall linked) and non-climatic drivers. A decade of annual rainfall and vegetation data over sub-Saharan Africa was analysed using satellite-based rainfall estimates [Famine Early Warning System Rainfall Estimation 2.0 (FEWSNET RFE 2.0)] from National Oceanic and Atmospheric Administration's (NOAA's) Climate Prediction Centre and the Normalized Difference Vegetation Index (NDVI) obtained from the Satellite Pour l'Observation de la Terre Vegetation (SPOT-VGT) sensor. Rainfall and vegetation greenness trends were analysed for 759 administrative regions of sub-Saharan Africa to identify those regions that have experienced a negative, positive or stable rainfall/vegetation trend over the period [2001][2002][2003][2004][2005][2006][2007][2008][2009][2010]. The character of the relationship between the annual rainfall and max NDVI trends were examined to identify areas where the changes in greenness could be attributed to climatic (rainfall) and non-climatic (human land use or ecological disturbance) changes. Regions where increasing rainfall was associated with vegetation greening were found in West Africa, Central African Republic, West Cameroon and northeastern part of South Africa, whereas areas with evidence of 'climatic vegetation degradation' were located in Southern Madagascar, Nigeria, Kenya and the Garden Route region of South Africa.

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Recent trends in vegetation dynamics in the African Sahel and their relationship to climate

Cited by 745 publications

References 60 publications

Human-induced grassland degradation/restoration in the central Tibetan Plateau: The effects of ecological protection and restoration projects

Human-induced grassland degradation/restoration in the central Tibetan Plateau: The effects of ecological protection and restoration projects

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

A conceptual model for assessing rainfall and vegetation trends in sub‐Saharan Africa from satellite data

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