After a dry period with prolonged droughts in the 1970s and 1980s, recent scientific outcome suggests that the decades of abnormally dry conditions in the Sahel have been reversed by positive anomalies in rainfall. Various remote sensing studies observed a positive trend in vegetation greenness over the last decades which is known as the re-greening of the Sahel. However, little investment has been made in including long-term ground-based data collections to evaluate and better understand the biophysical mechanisms behind these findings. Thus, deductions on a possible increment in biomass remain speculative. Our aim is to bridge these gaps and give specifics on the biophysical background factors of the re-greening Sahel. Therefore, a trend analysis was applied on long time series (1987–2013) of satellite-based vegetation and rainfall data, as well as on ground-observations of leaf biomass of woody species, herb biomass, and woody species abundance in different ecosystems located in the Sahel zone of Senegal. We found that the positive trend observed in satellite vegetation time series (+36%) is caused by an increment of in situ measured biomass (+34%), which is highly controlled by precipitation (+40%). Whereas herb biomass shows large inter-annual fluctuations rather than a clear trend, leaf biomass of woody species has doubled within 27 years (+103%). This increase in woody biomass did not reflect on biodiversity with 11 of 16 woody species declining in abundance over the period. We conclude that the observed greening in the Senegalese Sahel is primarily related to an increasing tree cover that caused satellite-driven vegetation indices to increase with rainfall reversal
Tag: heterogeneity
Agrifood supply chain, private-sector standards, and farmers’ health: evidence from Kenya
This article evaluates the impact of adoption of European Union (EU) private-sector standards on farmers health in rural Kenya. The study utilizes cross-sectional farm household-level data collected in 2006 from a randomly selected sample of 439 small-scale export farmers.We estimate the casual impact by utilizing a two-stage Poisson regression model, two-stage standard treatment effect model, as well as by regression based on propensity score, to assess the robustness of the results.Using these techniques, we demonstrate that the pesticide-ascribed incidence of acute illness symptoms and the associated cost of illness significantly decrease with the adoption of standards. Ceteris paribus, farmers who adopt standards experience 70% lesser incidence of acute illness and spent about 5060% less on restoring their health than nonadopters. Although standards can potentially prevent resource-poor smallholders from maintaining their position in lucrative export markets, they can also result in positive changes in the health of those farmers who do adopt them, as shown by these results. This implies that, if adopted on a large scale, standards may reduce production externalities, corroborating the view that they may serve as a catalyst to transform production systems in developing countries.