Land rights remain, unsurprisingly, a hot topic in Southern Africa. One of the arguments I hear again and again is that secure individual land tenure is a prerequisite for farmers (including small-scale and large-scale commercial farmers) to invest in farming activities and avoid exploitative practises that will, for example, cause soil erosion.
My sense of it, based on quite a lot of time spent in rural areas, is that farmers are investing in their land and farming activities anyway, even in South Africa where most small-scale farmers have no land tenure and large-scale farmers are engaged in a long-running cold war with government over land reform, expropriation and private property laws. The little bit of empirical research that exists on small-scale farming in South Africa seems to back this up, but it's not that recent and not much of it exists.
But here is a blog post and a new research paper on Madagascar that finds no empirical link between formal land rights and productivity. Fascinating and super-important in the ongoing backwards and forwards on land rights and ownership in SADC countries.