1-мәтін
Banking on seeds
In a cold room cut into the side of a hill, rows of metal shelves hold thousands of small foil packets. Each packet contains seeds from a single plant variety, dried until they hold only a small amount of water and then frozen at minus eighteen degrees Celsius. At this temperature, the seeds of many crops can stay alive for decades, and some for more than a century. The room is part of a seed bank, one of more than a thousand such collections around the world.
The idea of storing seeds is far from new. Farmers have always kept part of each harvest to plant the following year, and in many villages families exchanged seeds to improve their crops. What changed in the twentieth century was the scale of the loss. As farms adopted a small number of high-yielding varieties, thousands of local types that had been grown for generations were simply abandoned. Scientists began to worry that useful characteristics, such as resistance to drought or disease, were disappearing with them.
Modern seed banks therefore have two main purposes. The first is insurance: if a variety is lost in the field because of war, flood or a sudden outbreak of disease, it can be grown again from stored samples. The second is research. Plant breeders who want to develop a wheat that survives hotter summers, for example, may search a collection for an old variety that already has this ability and then cross it with a modern one.
Running a seed bank is less simple than it sounds. Before seeds are stored, staff must check that they are clean, healthy and able to grow. A sample of each collection is tested every ten years or so, and when the number of seeds that sprout falls too low, the variety has to be planted again to produce fresh seed. For crops that are pollinated by wind or insects, this means growing them far away from related plants, otherwise the next generation may be a mixture of two varieties.
Not every plant can be saved in this way. The seeds of some tropical trees, as well as those of avocado and cocoa, are killed by drying, so they cannot survive the freezer. For these species, collections rely on living plants grown in field stations, or on small pieces of tissue kept in liquid nitrogen. Both methods are expensive, and critics point out that a living collection is exposed to exactly the same storms and diseases as the plants it is meant to protect.
Perhaps the greatest challenge is money. Many national seed banks depend on government budgets that can be cut at short notice, and a freezer that fails for even a few days can destroy years of work. To reduce this risk, a number of countries send duplicate samples to a global storage facility in the Arctic, where the natural cold would keep seeds frozen even if the power supply stopped. The facility does not own these samples; it simply holds them, rather like a safe deposit box in a bank, until the country that sent them asks for them back.