Perspective of the rehabilitation of marginal areas: the case of Lablab purpureus (L.) Sweet

It is estimated that the world population reach 9.1 billion in 2050 resulting in increasing food demand and consumption, but also waste production. Moreover, to help achieve the goals set by the 2030 Agenda for Sustainable Development, it is imperative to develop sustainable strategies for the recovery marginal lands (e.g. landfills or abandoned mining areas) and create conditions for agriculture activities. Thus, there is a need to increase agricultural production and to create sustainable waste management approaches. Several landfills pose health and environmental concerns associated to non-selective deposition of wastes, which present potentially hazardous elements (PHE), and inexistence of environmental management systems. Therefore, leachates rich-in PHE can spread to adjacent areas leading to soil and water contamination. This is particularly concerning considering the growing rate of Sub-Saharan African (SSA) population that will be living in urban or peri-urban areas, and practice subsistence farming in those areas. For SSA it is estimated that by 2050 about 50% of the population will be living in towns and cities. The recovery of landfills, in addition to other environmental management measures, can involve the development of a secure plant cover that creates conditions for agriculture activities, while protecting the food-chain, but also improve environmental and landscape impacts. Plant species selected for green cover should have the ability to decrease the mobility or immobilize PHE in the rhizosphere. Furthermore, these plant species should also have low PHE translocation factors from the soil/roots to the shoots. Plants with these characteristics are not common, and it is necessary to increase our efforts to identify them. Moreover, in the scope of SSA it is important that these species should be native and known by the population. The study of African crops behaviour, such as Lablab purpureus (L.) Sweet, can be a promising option since Lablab shows the ability to accumulate PHE in the roots and low translocation factors from the soil/roots to the shoots, resulting the concentrations present in the shoots safe for animal consumption. It is important to point that the characteristics of each landfill can be totally different as well as climatic conditions where is located the landfill, thus the initial and multidisciplinary characterization of the study area is crucial. Moreover, the ecophysiological plant behaviours, namely PHE accumulation in the edible part, depends on plant species and edafoclimatic conditions, so more studies should be done in order to assess the impact in the food-chain.