Calvin Sperling Biodiversity Memorial Lectureship.

Climate change and crop diversity. Future climate change is considered to be a major threat to the conservation of crop diversity. Paradoxically, the use of crop diversity is an essential element to climate change adaptation. A few major crops have been collected extensively, but gene bank holdings of most crops are incomplete. I will discuss new work on geographic modeling to identify gaps in gene bank collections to prioritize future collection and conservation in the context of climate change. Modeling approaches include ecological niche modeling for crop wild relatives, and spatial flow models of genetic distance in cultivated species. Crop wild relatives contain a large amount of useful genetic diversity but they are generally poorly represented in gene banks. Climate change, as well as habitat conversion, appears to be a major threat to their survival in nature. However, uncertainty abounds in the projections, and further field-based, physiological, and modeling research is urgently needed. To predict how climate change might affect the diversity of cultivated species, and the livelihood of subsistence farmers who depend on it, we need to understand better the spatial and temporal dynamics of the distribution of diversity, and the role farmers play in its creation and management. With climate change, adaptation to increased drought and heat stress will be particularly important in the semi-arid tropics, but climate change will also spur demand for many other traits, including increased pest and disease resistance. It is therefore important to assure that crop collections contain the broad patterns of diversity, as well as specific traits that will likely be in high demand. Identifying accessions with specific traits from geographic or environmental data appears to be less straightforward than previously thought, and extensive and rigorous evaluation of gene bank accessions should remain a priority.