Abstract
Drylands are home to more than two billion people and are characterised by frequent, severe droughts. Such extreme events are expected to be exacerbated in the near future by climate change. A potentially simple and cost-effective mitigation measure against drought periods is sand dams. This little-known technology aims to promote subsoil rainwater storage to support dryland agro-ecosystems. To date, there is little long-term empirical analysis that tests the effectiveness of this approach during droughts. This study addresses this shortcoming by utilising multi-year satellite imagery to monitor the effect of droughts at sand dam locations. A time series of satellite images was analysed to compare vegetation at sand dam sites and control sites over selected periods of drought, using the normalised difference vegetation index. The results show that vegetation biomass was consistently and significantly higher at sand dam sites during periods of extended droughts. It is also shown that vegetation at sand dam sites recovers more quickly from drought. The observed findings corroborate modelling-based research which identified related impacts on ground water, land cover, and socio-economic indicators. Using past periods of drought as an analogue to future climate change conditions, this study indicates that sand dams have potential to increase adaptive capacity and resilience to climate change in drylands. It therefore can be concluded that sand dams enhance the resilience of marginal environments and increase the adaptive capacity of drylands. Sand dams can therefore be a promising adaptation response to the impacts of future climate change on drylands.
Highlights
Drylands cover more than 41 % of the world’s surface (Safriel and Adeel 2005), and they are home to 2.3 billion people, or nearly 30 % of the world’s population (UNDP 2014)
It can be seen that throughout the 7-year observation period, Normalised difference vegetation index (NDVI) was consistently higher at sand dam sites
The overall treatment effect for all samples results in a highly significant statistical difference between mean NDVI values at sand dam sites compared to controls (F = 18.779, p = 0.005)
Summary
Drylands cover more than 41 % of the world’s surface (Safriel and Adeel 2005), and they are home to 2.3 billion people, or nearly 30 % of the world’s population (UNDP 2014). Climate models predict higher temperatures, decreased precipitation, and an increase in intensity and frequency of extreme events such as droughts and heavy rainfall (Sorensen et al 2008). Observational data suggests East African drylands are getting warmer with less rainfall, resulting in a drying effect that will increase with further climate change (Funk 2010). This threatens the ecosystems and people who depend on them, agroecosystems where humans are heavily reliant on ecosystem resources for their livelihoods (Boko et al 2007; Fischlin et al 2007; Speranza 2012; Kilroy 2015)
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