genetic diversity that has no immediate production or market value are minimum. Weaknesses of ex situ conservation include: 1) it is costly to maintain seeds and germplasm healthily in perpetual storage, or in field collections; 2) Coverage of the diversity of neglected and underutilized crops or crop wild relatives is currently very limited. Genebanks have largely focused on the conservation of major staple crops while non-staple crops and crop wild relatives are poorly represented; 3) There are species with ‘recalcitrant’ seeds, which means they cannot be stored long term; 4) Specialized infrastructure and staff are needed. In situ conservation In situ conservation means "the conservation of ecosystems and natural habitats and the maintenance and recovery of viable populations of species in their natural surroundings and, in the case of domesticated or cultivated species, in the surroundings where they have developed their distinctive properties". In situ conservation comprises both conservation of trees and crop wild relatives in situ in the wild, and conservation of landraces and neglected and underutilized species on farm in farmers' fields. Conserving agrobiodiversity in situ has the benefit that species can continue to evolve in response to natural and human pressures. In the case of crops, a large amount of diversity is retained in developing countries by smallholder farmers, particularly for many crops in their centers of domestication and diversity. There, farmers continue to grow landraces and maintain traditional knowledge and seed management practices in a process known as de facto conservation. Home gardens too are repositories of high levels of species diversity, and traditional landraces contain wide genetic diversity. For forest trees, in situ conservation is considered the most appropriate method since most tree seeds cannot be conserved ex situ, and because there are 60,000 tree species, each with multiple populations, so too many to identify and collect. Having limited access to synthetic inputs, resource-poor farmers' fields are often organic by default. A meta-analysis of studies comparing biodiversity noted that, when compared to organic cropping systems, conventional systems had significantly lower species richness and abundance (30% greater richness and 50% greater abundance in organic systems, on average), though 16% of studies did find a greater level of species richness in conventional systems. In situ conservation is relatively low cost for high levels of biodiversity, particularly crop wild relatives, neglected and underutilized species, landraces, trees, fish and livestock. However, species and varieties conserved in situ can be