27 October 2014

Africa's Great Green Wall - towards a sustainable future

To highlight UNESCO’s World Science Day for Peace and Development on November 10th, Serene Hargreaves from the Millennium Seed Bank describes how Kew is working with communities in sub-Saharan Africa to build a ‘Green Wall’ that will contribute to their sustainable future.

A close up of a bright green leaf

What is desertification? 

Desertification threatens some of the world’s poorest people in many of the most politically unstable regions of the world. Sub-Saharan Africa is one such region and its inhabitants live with a fluctuating climate, soils of low fertility and limited access to land, technology, information and credit. These factors often culminate in unsustainable land management and the inappropriate use of marginal land. This increasing pressure on fragile resources results in continued land degradation or ‘desertification’, leading to a downward spiral into increasing poverty and further land degradation. The results of this vicious cycle are devastating.  

Africa’s solution 

Imagine a green ‘wall’ 8,000 km long and 15 km wide, running from Senegal in the west to the horn of Africa in the East. A British forester, St. Barbe Baker, was the first to propose this idea in 1954, picturing a wall of trees and shrubs blocking the ‘advancing’ desert (Baker, 1954). However, it is now known that desertification doesn’t refer to a moving desert as was once thought, rather to persistent land degradation due to climate change and over-exploitation of land. This initial idea has evolved into the Africa Great Green Wall Initiative, with the ‘wall’ now a metaphor for a mosaic of sustainable land use approaches. The initiative aims to improve livelihoods and help food security, while contributing to climate change mitigation and adaptation. The Food and Agriculture Organization of the Union Nations is taking the lead role in supporting the Africa Union to deliver this initiative, with numerous organisations, governments and other partners playing their part in this ambitious project. 

Kew’s role and commitment 

As part of this initiative the Royal Botanic Gardens, Kew, supported by the Dr Mortimer and Theresa Sackler foundation, is coordinating and providing technical assistance to Great Green Wall (GGW) partners in Mali, Burkina Faso and Niger. With evidence of deforestation in sub-Saharan Africa year on year (Rudel, 2013) and of decreasing biodiversity in existing woodlands (Gonzalez, 2001), Kew’s GGW team has so far supported agroforestry projects in over 60 engaged communities, and provided technical assistance to governments, forestry seed banks and local administrations. 

Identifying priority species for the Great Green Wall – a participatory approach 

Using Kew’s botanical information resources and plant expertise, as well as engaging with in-country partner specialists and local communities, Kew is helping to identify priority species for the GGW. First, communities are consulted to understand their needs and requirements. This collated information, supplemented with desk study, provides the basis for prioritising species in addition to information on technical capacity, knowledge of the species, seed availability and native distribution. Seeds and seedlings of selected species are then supplied, along with training on their collection and production, and monitoring plans are put in place with the local communities for their continued management.

Acacia senegal – an international commodity 

Around our partner communities much of the native woodland has been deforested due to overexploitation for grazing, fuel and charcoal. Acacia senegal, a small tree from the Leguminosae family is useful for fuel and charcoal, but can also provide money from the resin or gum it produces, known as gum arabic. This relatively innocuous looking substance is used in a vast range of everyday products, from preventing the sugar from crystallizing in soft drinks to ensuring that newspaper ink stays on the paper. This glue-like stabiliser is an economic commodity that can be sold for high prices, particularly when coupled with evidence of a sustainable supply chain. This species is in high demand for planting by communities. Providing requested economic species such as A. senegal for planting, followed by support for their propagation and development, will help to sustainably support the livelihoods of the communities in the area. 

Anogeissus leiocarpa – a species for the communities 

Anogeissus leiocarpa belongs to the Combretaceae family and is the only species of the genus Anogeissus found in West Africa. It has important economic and cultural values, with extracts of leaves and bark used traditionally for dyeing cotton fabrics and batiks. This species is often requested by the communities involved in the Africa Great Green Wall Initiative, although its planting is limited by low germination, with less than 5% germination of its seedlots. However, through research investigations using gravimetric sorting, Kew and partners in Mali have managed to separate out highly viable seeds (100%) from large quantities of seeds (Sanogo et al., 2015). These findings have enabled tree seed centres in Burkina Faso and Mali to sort their collections effectively, in order to obtain high quality seeds, and are helping with seedling production for the GGW reforestation and restoration plantings in West Africa. 

What lies ahead? 

The project has already resulted in the propagation of over 600,000 tree seedlings of useful species in local nurseries and worked with more than 60 communities in the four regions in which Kew is active. Now in its second year, Kew’s GGW project has helped these communities restore around 1,500 ha of land. The engagement of this project by local people is largely based on its participatory approach: consulting with local communities in all stages of the process, ensuring that the species planted are those requested, and implementing monitoring and management plans that are carried out with the communities themselves. The successes so far bode well for the pan-African initiative as a whole and opens up opportunities to expand Kew’s methods to new sites, new collaborators and new villages along the whole of the African GGW. 

Quality­ ­­­science ­education:­ securing­ a­ sustainable­ ­­­­future­ ­­­­­­­for ­all 

Scientific expertise, efficient technology transfer and capacity building in plant knowledge are the backbone of such successes. A vital and integral part of Kew’s Millennium Seed Bank (MSB) is its partnerships with local people across the globe, and its longstanding reputation for scientific education and capacity building in seed and plant knowledge. Kew’s MSB has a long history of providing specialist training, including practical courses in seed and herbarium specimen collections, seedbank techniques and national seed collecting programmes. For the GGW project, further and continuous training is being provided to partners ranging from farmers to university researchers, on plant conservation and sustainable use, technical data collection and management of botanical data. This training of local partners and communities has the ultimate aim of strengthening local capacity to run and manage their own plant conservation. For instance, this year we coordinated a course where trained specialists from Burkina Faso instructed farmers from Niger, as well as new farmers and other partners in Burkina, in methodologies for seed collecting of native species and seedling production in nurseries. This evidence of the dissemination of knowledge and cross-border cooperation sets a hopeful scene for the future of the GGW Initiative. 


Gonzalez, P. (2001). Desertification and a shift of forest species in the West African Sahel. Climate Research 17(2): 217-228. Available online 

Rudel, T. K. (2013). The national determinants of deforestation in sub-Saharan Africa. Philosophical Transactions of the Royal Society B: Biological Sciences 368: 20120405. Available online 

Sanogo, S., Sacande, M. & Van Damme, P. (2015). Gravimetric sorting improves germination of Anogeissus leiocarpa seedlots (under revision - New Forests). 

St. Barbe Baker, R. (1954). Sahara Challenge. The Camelot Press Ltd., London.