Agroforestry systems towards rehabilitation of West Africa marginal areas through an integrated green biotechnology approach

To achieve the goals set by the 2030 agenda for Sustainable Development, it is imperative to create sustainable solutions to recovery marginal lands (e.g. landfills or abandoned mining areas) and create conditions for agriculture activities, but most importantly is a concern that deserves political priority. Landfills, poses health and environmental concerns due to the presence of potentially hazardous elements (PHE), among other contaminants that cannot be degraded leading to soil and water contamination, with increasing concern in the African continent. In 2018, a Report to the United Nations Framework Convention on Climate Change by the Republic of Guinea-Bissau reported that waste management is one of the major problems that the country faces. Thus, it is essential to create solutions, beyond contaminated wastes management, such as the rehabilitation of such areas. A potential rehabilitation strategy is the combination of phytostabilization with Technosols. Phytostabilization uses plants to decrease mobility or immobilize PHE in the rhizosphere. These plants should also have low PHE translocation factors from the soil/roots to the shoots. For the Technosols construction it can be used a mixture of different kinds of wastes from different origins (e.g. landfill, construction) to obtain a anthropic soil whose properties (e.g. fertility, water-holding capacity, structure) decrease PHE availability and promote plant growth, minimizing the risk to both human health and the environment. A possible strategy for the rehabilitation of contaminated areas, could be the establishment of an agroforestry system - by intercropping legumes, towards phytostabilization, using cashew as a case study due to its importance as a revenue commodity in West Africa countries (e.g.Guinea-Bissau). However, it is of utmost importance to identify the nature/quantity of PHE and wastes as well as climatic conditions for each contaminated/degraded site, before creating an agroforestry system in those areas, thus ensuring the sustainability of the phyto-geo-technology towards food security. Furthermore, potential alternative revenues obtained from the agroforestry system arise. As such, we present a potential rehabilitation agroforestry system that can in the future be useful for African countries attain the goals set for 2030 and beyond.