Agroforestry as an innovation
The available scientific information confirms that climate change is already affecting forest ecosystems and the services they provide including ecosystem sustainability and the maintenance of biodiversity. It is also expected to have increasing effects both positive and negative on the ecosystems and socio-economic development in the future. For example while deforestation is responsible for about 18 percent of greenhouse gases, forests currently still absorb more carbon (C) than they emit and an increased tree growth is foreseen in some regions bringing new opportunities for forest industry and forest-dependent communities. However, over the long-term, some of the anticipated benefits linked to increased forest cover could be offset if climate change continues at the current pace . For countries, especially those in the South, the paramount issue will be, on the one hand, to strengthen the capacities of their populations to adapt to climate change and, on the other, to commit wholeheartedly to sustainable development and social equity and increasing investments in research to expand the knowledge base for climate change projection, impact and mitigation within agroforestry systems.
Agroforestry systems could also be linked to Payments for Environmental Services (PES) within the framework of climate accords for the Reduction in Emissions from Deforestation and forest Degradation (REDD). At present, though, these services are insufficiently valued and the advantages are insufficiently known as they depend on species, methods of management, on the environment and still have to be adequately researched and elaborated. Nair et al  reported on carbon sequestration studies in five countries including Mali which showed that tree based agricultural systems store significantly more C in deeper layers of soils under comparable conditions and that soil organic content is higher in the upper layers of soil with higher species richness and tree density. Their work underpins the role of agroforestry systems in climate change mitigation.
The slash-and-burn technique of cultivation as a system of exploiting agricultural lands worked well in satisfying human needs while still conserving the balance of the cultivated ecosystems, but only as long as human pressures on natural resources remained manageable. However, the growth in populations and scientific and technological progress in the last century – have given rise to a cascading succession of factors that have tilted this balance. To reverse this trend, the reintroduction of trees and shrubs in the rural landscape appears to be a serious alternative to current systems of agricultural, pastoral and forest-based production. Agroforestry systems, in the form of linear plantation of trees and shrubs, fallows, improved tree parks and reforestation of all types, can thus contribute to reducing soil erosion, limiting loss of soil organic matter, and engender an overall improvement in soil function by being a part of the plots’ biodiversity . Isolated trees also form forest  nuclei which accelerate the ultimate reconstitution of the continuous forest cover . Thus, agroforestry addresses effects of climate change by preventing or alleviating some of them.
Towards a peri-urban agroforestry?
Emerging or developing tropical countries all have rapidly expanding cities and a growing peri-urban agriculture. However, land availability is very limited on the periphery of cities. One response to climate change consists of promoting the development of short supply chains with production taking place as close as possible to areas of consumption, leading to reduced CO2 emissions related to the transport of merchandise. In such areas, where usable plots tend to become scarcer due to the growth of cities (rural exodus, economic development, etc.), it becomes imperative to utilize the available surfaces to the best possible extent.
To succeed in a better integration of trees and human activities on city outskirts is thus an issue for the future: improving the urban dweller’s quality of life, increasing revenues from cultivated plots in peri-urban areas, product diversification, etc. The peri-urban space, i.e., on the outskirts of cities and under their direct influence, is susceptible to the impact of nearby human activity. Special care should therefore be taken in the production methods adopted; they should imperatively be sustainable in nature. The tree then serves as a biodiversity reservoir in increasingly urbanizing areas and could also be a factor in limiting pollution caused by leaching and runoff of chemical fertilizers used by farmers, a significant problem with peri-urban agriculture. This requires further study.
Outstanding research questions
Whenever trees and agroforestry are introduced in fields near seasonal crops, the problem of competition between trees and crops arises. Research is necessary to answer these essential questions: under what conditions do agroforestry systems make optimum use of resources? What are the biophysical mechanisms that govern the functioning of these systems? What is and how to best measure, their performance in terms of production, productivity and of environmental services? Other questions relate to the domestication of trees, to genetic improvement and to methods of increasing the value of agroforestry products at all levels. In addition, innovation will be required to develop better monitoring and evaluation tools for measuring the impact of these different forms of agroforestry on biodiversity and means of subsistence.
Climate change does not impact only average biophysical conditions (thermic, pluviometric) but also intra- and inter-annual variability and the occurrence and frequency of extreme climatic events. Increased hazards call for the implementation of new mechanisms of economic and biophysical resilience: only an inclusive and systemic approach can lead to the formulation of effective development strategies in the face of climate change and associated factors. Scientific research has an obligation of the highest order to come up with results and products that can encourage decision-makers to take the necessary actions and producers to innovate. It has to demonstrate that the adoption of viable agroforestry techniques that respect the environment constitute at least part of the solution to the global problem of climate change. Urgent efforts are required to make political decision makers understand that agroforestry is both a tool to be distributed widely as well as a different way of production.
 Flamboyant is the most influential organ for information and dialogue between members of the International network on tropical trees. Recent issues of Flamboyant are now downloadable from its website: http://www.silva-riat.fr/derniers_numeros_flamboyants.html
 Adaptation of forests and people to climate change, A global assessment report Prepared by the Global Forest Expert Panel on Adaptation of Forests to Climate Change, Panel Chair :Prof. Risto Seppälä, 2009
 Les orphelins de la forêt, IRD Editions, 2003, Stéphanie Carrière
 Effet de nucléation (Yarranton and Morrison, 1974)