Priority CWR diversity in the SADC region

Among the more than 700 wild relatives of food and beverage crops found in the region, we prioritized 113 for immediate conservation action based on the regional food security and economic value of the crops to which they are related and their potential for utilization in crop improvement programmes (Figure 1). These taxa are distributed throughout the region but results of our analyses indicate taxon richness hotspots in Madagascar, Malawi, Mozambique, South Africa, Swaziland, Tanzania and Zimbabwe (see the taxon richness map, current climate, below).

Taxon richness and climate impact

We created potential distribution models for 110 of the priority wild relatives for which occurrence records were available. Only models that passed a cross-validation process (adapted from Ramirez-Villegas et al., 2010) were directly used whereas models for taxa that failed the cross-validation, due to insufficient and dispersed presence records, were instead mapped by creating a circular buffer of 50 km (CA50) around their occurrences (Hijmans and Spooner, 2001). Finally we created a taxon richness map under current climate (see below) for 110 priority CWR taxa by overlapping 75 stable potential distribution models and 35 CA50 buffers.

The impact of climate change on CWR distribution across the region was evaluated for 75 priority wild relatives (for which stable distribution models could be generated) using projected 2050 climatic conditions for two greenhouse gas emission scenarios. We overlapped the distribution models and compared the current versus the projected 2050 taxon richness (see the change in taxon richness maps, scenario RCP4.5 and RCP 8.5).

Conservation gap analysis

We undertook conservation gap analyses for 110 of the priority wild relatives for which occurrence records were available. Critically, the results reveal that the region’s important CWR diversity is poorly conserved both in situ and ex situ. Fifty-five (50%) of the priority wild relatives analysed are not conserved ex situ at all and of the 55 that are found in ex situ collections, 22 are represented by less than five populations and nine by only one, indicating that an inadequate range of genetic diversity is conserved. Nineteen (17%) do not occur within any protected area in the region, including wild relatives of coffee (4 taxa), millets (4), cowpea (2), brassicas (1), cotton seed oil (1), eggplant (1), rice (1), safflower (1), shea oil (1), sugarcane (1), sunflower (1), sweet potato (1), and winged bean (1). While 91 priority CWR do occur in protected areas, these populations are not monitored or actively managed and need to be incorporated into the site management plans.