The Millennium Seed Bank was set up by the Royal Botanical Gardens at Kew as the world’s largest and most diverse genetic ‘ark’, on track to have collected 25 percent of global species by 2020 as part of a wider scheme with institutions around the world to store the world’s plants in seed banks to prevent them from extinction. According to Kew scientist John Dickie, "Ex-situ conservation of plants is more critical than ever, with many threats to plant populations including climate change, habitat conversion and plant pathogens, we need to make sure we're doing all we can to conserve the most important and threatened species.”
However, a new study published in Nature Plants presents research by scientists that found the seeds of over a third of critically endangered species cannot be frozen because they cannot survive the process of drying and deep freezing and produce ‘recalcitrant seeds’, which die in the dying process. 27 percent of endangered species produce these seeds that cannot be banked, along with 35 percent of plants considered to be "vulnerable" to extinction.
The study suggests this is a particular problem for trees, with 33 percent of all the world's species producing seeds that do not survive the drying process. In tropical moist forests, such as rainforests or cloud forests, as many as half the species of trees which create the canopy can be unsuitable for preserving in seed banks. The researchers warn it may be ‘somewhat naive’ to assume it is possible to conserve tropical plants and trees outside of their natural habitats and say protecting entire forests may be the only way of saving certain species. Kew, along with other banks around the world, aim to conserve 75 percent of the threatened species outside of their natural habitat by 2020.