Synopsis (short abstract)Farm specialisation and the general abandonment of mixed farming is a significant factor in the declines of biodiversity, including genetic resources for food and agriculture and wildlife, and of the disintegration of traditional and community-based management. The adoption of high-yielding, uniform cultivars has led to a considerable reduction in the number of genetically viable species used in agriculture. Many food crop varieties have virtually disappeared from their centres of diversity. There is now an increasing body of evidence that organic agriculture supports much higher level of biodiversity than conventional farming systems, including species that have significantly declined. This paper addresses the contribution of organic agriculture to agricultural biodiversity, including genetic resources for food and agriculture. The positive impact of organic agriculture on wildlife (e.g. soil organisms, arable flora, predatory invertebrates, pollinators, birds) and in creating and connecting habitats that enhance nature conservation is outside the scope of this paper. The adverse impact of genetically modified organisms on organic agriculture is also outside the scope of this paper. The cases presented in this document illustrate how organic agriculture, to be viable, is reversing the decline in species diversity as well as abundance of each species. If biodiversity is to be maintained, it should be an integral part of a healthy landscape where not only diversity but al so abundance is a fundamental factor.