Conservation planning for priority crop wild relatives in the SADC region

Solanum catombelense in South Africa.
Credit: SANBI

The SADC region is important for its diversity of wild relatives of a number of food and beverage crops of particular food security and/or economic value in the region ‒ including coffee, cottonseed oil, cowpea, eggplant, millets, pigeonpea, rice, sorghum and watermelon.

Some of these crops are also of particular global value in terms of their direct contribution to food security in other regions ‒ notably millets, rice and sorghum. In addition to the development of National Strategic Actions Plans in three pilot countries in the region, the project has developed a proposal for a strategy to conserve the unique and important CWR diversity across the SADC region, taking into account priorities for food and economic security in the region as a whole. This strategy will be important to ensure that the conservation of priority CWR diversity in the region is optimized and that the diversity is available for future sustainable use.

Some results of the analysis and modeling of CWR diversity in the SADC region are presented below, the full analysis will be available in a peer review publication in preparation (Magos Brehm et al. [in preparation]).

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).

Figure 1. Number of regional priority wild relatives of crops selected on the basis of their particular food security and/or economic value in the region

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.

Map Layers
Number of taxa

References

  • Hijmans RJ, Cameron SE, Parra JL, Jones PG, Jarvis A (2005) Very high resolution interpolated climate surfaces for global land areas. International Journal of Climatology 25:1965–1978.
  • Hijmans RJ, Spooner DM (2001) Geographic distribution of wild potato species. American Journal of Botany 88:2101–2112.
  • Magos Brehm J, Gaisberger H, Kell S, Thormann I, Dulloo ME, Maxted N [in prep] Conservation planning for crop wild relative diversity in the SADC region.
  • Phillips SJ, Anderson R, Schapire RE (2006) Maximum entropy modeling of species geographic distributions. Ecological Modelling 190:231–259.
  • Ramírez-Villegas J, Khoury C, Jarvis A, Debouck DG, Guarino L (2010) A gap analysis methodology for collecting crop genepools: a case study with Phaseolus beans. PLoS ONE 5:e13497.