Genetic diversity in agricultural crops began to erode as the political and social changes of the industrial era transformed agriculture. As a result genetic conservation began early this century when foresighted agriculturists saw that the loss of primitive varieties or "landraces" meant loss of genetic variation essential for sustained crop improvement.
For plants, the best ex situ gene bank is an arboretum or an experimental garden, farm, or forest, in any of which the growing conditions resemble as closely as possible the various species' natural habitats.