Agricultural biodiversity is a sub-set of general biodiversity. It includes all forms of life directly relevant to agriculture: rare seed varieties and animal breeds (farm biodiversity), but also many other organisms such as soil fauna, weeds, pests, predators, and all of the native plants and animals (wild biodiversity) existing on and flowing through the farm. However, most attention in this field is given to crop varieties and to crop wild relatives. Cultivated varieties can be broadly classified into “modern varieties” and “farmer’s or traditional varieties”. Modern varieties are the outcome of formal breeding and are often characterized as 'high yielding'. For example, the short straw wheat and rice varieties of the Green Revolution. In contrast, farmer’s varieties (also known as land