The incongruous juxtaposition of my title, “The Lighthouse and the Potato,” refers to two public goods of incalculable value – safe navigation and crop genetic resources. Neither lighthouse keepers nor the farmers who cultivate genetic diversity in potatoes and other crops provide their respective benefits to humankind without cost. The costs of lighthouses are relatively easy to measure – construction of the tower, fuel for the light, wages for the keeper. The costs of sustaining crop genetic resources are less evident, but can be viewed as the income foregone by not switching to new varieties, new crops, or other economic pursuits. This foregone income is the functional equivalent of the costs of building and operating a lighthouse to provide the public good of safe navigation. The increasing availability of more profitable alternatives to growing traditional crops means that society must find ways to sustain diverse crop genetic resources and the environments where they are created and maintained – the small farms of poor farmers. We have long recognized that we cannot simply depend on the goodwill of coastal dwellers to maintain lighthouses for ships at sea (Coase 1974, van Zandt 1993). Gradually, we are becoming aware that we cannot depend on the goodwill of farmers to conserve crop genetic resources.