Re-greening in Niger, Sahel region

This post was greatly inspired by my colleague Kexin who focused on the Sahel region and mentioned the regreening of the Sahel which piqued my interest. From there I looked into the integration of trees into Annual Cropping systems.

Site

Niger is located in West Africa at the centre of the Sahel band (Figure 1). The Sahel has a semi-arid climate and has an average rainfall of less than 200mm. Its rainy season is during the summer due to the annual northward movement of the ITCZ (see this post). Most of its agriculture is based on smallholder, subsistence farming in the south, usually relying on groundwater due to the lack of surface water streams. As water is a precious resource, communities often search for innovative ways to fulfil necessary demand.

Figure 1. Map of average annual rainfall in the Sahel region and West Africa, 1981-2016 (Sahara and Sahel Observatory 2019)

Challenge

From the 1960s to the 1980s, Niger experienced severe episodes of drought and famine which drove livestock and crop losses, high mortality, and displacement. Soil degradation and vegetation loss gave warning bells of desertification if nothing was to be done. What made it even more of a challenge is the high rainfall variability every year with heterogeneous soils and bedrock (Sendzimir et al., 2011). From then on the Sahel was continuously hit by severe droughts in 2005, 2010, 2012, 2014 and 2015 (OCHA, 2017). 

Despite large investments from the global west, conventional reforestation showed to have little impact on improving agricultural livelihoods in the area. The Sahel continued to experience more extreme and erratic rainy seasons and land degradation.

Adaptation

In the late 1980s, ‘Farmer Managed Natural Regeneration’ (FMNR) was widely utilised in southern Niger, “adapting centuries-old methods of woodland management to produce continuous harvests of trees for fuel, building materials, food and fodder without the need for frequent, costly replanting” (WRI 2008). FMNR consisted of selecting tree stumps in their cropland, then selecting the best stems to prune and protect, removing unwanted stems and sidebranches, then finally removing the new stems to be replanted. These techniques were adapted to each farmer’s situation and objectives, some creating woodlands by regrowing many more stems per stump. These practices were formalised and distributed by Serving in Mission, an international NGO, which identified and experimented with these insights (Sendzimir et al., 2011).

By 2008 5 million hectares of tree cover was created through this agroforestry method (Tougiani et al. 2009). This generated a sustainable forest-based market (Tougiani et al. 2009), reaping multiple benefits such as fodder for livestock, firewood, fruit, and medicinal products for self use or selling. This effectively decreased overall sensitivity to drought by the production systems compared to other areas in Niger (Niang et al. 2014). 

Figure 2. NDVI trends over the Sahel, showing locations of re-greening (Dardel et al., 2014).

One species in particular is favoured for agroforestry: Faidherbia albida. It not only provides tree products but also tree services such as reducing wind speed and evapotranspiration, protecting crops from being buried by sand, and holding soil moisture (Reij et al. 2009). F. albida has an unusual habit of shedding its leaves during cropping season and regrowing during the dry season. The leaves provide mulch, increasing soil fertility, and because there are no leaves it doesn’t compete for water or nutrients during cropping season, instead, it preserves water during the dry season (Mokgolodi et al., 2011). 

It has been proposed that the onset of vegetation fed into vegetation-rainfall feedback loops, amplifying rainfall variability in the Sahel and shifting the direction of these loops away from desertification. One example is the moisture recycling mechanism. In theory, the increase in vegetation increases the amount of evapotranspiration, which in turn increases precipitated water. Because the energy is primarily used for evapotranspiration instead of heating the bare ground, less energy hits the ground directly which in turn increases surface temperature

Figure 3. Diagram of climate-vegetation interaction feedback loops (Zhang et al., 2014)

The success of this scheme has been credited to many factors including increased rainfall, rural to urban migration, bottom up community participation, changes in local management in resources and a reform in top-down policy. Unlike previous schemes that called for forestry plantations, the success of regreening was not implemented by a single actor, policy or practice, but by multiple actors, institutions and processes that operated at different levels and scales. In a sense, this institutional change affected livelihoods, which changed the biophysical environment, and now, that environment is sustaining the former two, forming its own social-physical feedback loop that will hopefully continue to bring benefit to Niger’s local communities (Sendzimir et al., 2011).