Trees inside and outside forests contribute to food security in Africa in the face of climate variability and change. They also provide environmental and social benefits as part of farming livelihoods. Varied ecological and socio-economic conditions have given rise to specific forms of agroforestry in different parts of Africa.
"Big" plant genera, those of 500 or more species, have not only occasioned interest among systematic botanists, but for geographical, ecological or horticultural reasons, have also become well-established popular concepts. Their size has rendered them difficult, if not impossible, to study in their entirety; there have been few full revisions since the nineteenth century.