Day 161 — Listening: Seed Banks — Insurance or Illusion? — Section 4（講義）

（色付きは解答後の確認用。青＝根拠、黄＝distractor）

Good morning, everyone. Last week we looked at in situ conservation, that is, protecting plants in the places where they grow naturally. Today I want to turn to the alternative, ex situ conservation, and in particular to seed banks, which are often presented as a kind of insurance policy for world agriculture. I'm going to argue that they're essential, but that they're far less of a complete solution than the headlines suggest.

Let's start with the basic principle. Most crop seeds are what botanists call orthodox seeds: if you dry them and keep them cold, they can stay alive for decades, in some cases for centuries. The international standard, set out by the Food and Agriculture Organization, is to dry seeds to between three and seven per cent moisture and then store them at minus eighteen degrees Celsius. You'll sometimes see minus twenty quoted in newspaper articles, but eighteen is the figure the gene banks actually work to.

The best-known facility is, of course, the Svalbard Global Seed Vault, which opened in 2008 on a Norwegian island well inside the Arctic Circle. The press likes to call it the doomsday vault, but I think that's rather misleading. Svalbard doesn't carry out research, and it doesn't hand out seeds to farmers. It works on what's called a black box arrangement: the gene bank that deposits the seeds keeps ownership of them, and only that gene bank can take them out again. So a better comparison isn't a library, which lends things to anyone with a card, but a safety deposit box.

That backup function was tested for the first time in 2015. The International Center for Agricultural Research in the Dry Areas, usually shortened to ICARDA, had its main gene bank near Aleppo, in Syria. When the civil war made that site impossible to operate, ICARDA withdrew its duplicate samples from Svalbard. And here's the part that tends to get left out of the news stories: the seeds weren't simply handed to farmers. They were planted in fields in Lebanon and Morocco, multiplied, and then a portion was sent back to the vault, so that the backup existed again.

Now, the site was chosen partly because of the permafrost, which was supposed to keep the seeds cold even if the power failed. But in October 2016, after an unusually warm spell, meltwater ran into the access tunnel. I should stress that no seeds were affected; the water never got near the storage chambers. Even so, the operators spent the next few years waterproofing the tunnel and removing heat sources from it. A small incident, but a symbolic one: a building meant to protect us from the effects of climate change turned out to be exposed to them itself.

So, what are the limitations? I'd highlight three.

The first is biological. Not every seed is orthodox. A large group, known as recalcitrant seeds, simply die if they're dried. That group includes many tropical trees and some important crops: cocoa, avocado and mango, for example. For these species the main alternative is cryopreservation, where instead of the whole seed you store just the embryo, or a tiny piece of the shoot tip, in liquid nitrogen at around minus one hundred and ninety-six degrees. It does work, but it's labour-intensive, and the method has to be worked out species by species.

The second limitation is what I'd call genetic freezing. A seed sitting in a vault doesn't evolve. Out in the field, meanwhile, pests and pathogens keep adapting, and the climate keeps shifting too. A variety that resisted a particular fungus in the 1970s may have no resistance at all to the strains that are around today. For me, that's the strongest argument for keeping farmers' own seed systems going alongside the banks, not replacing them.

The third limitation is perhaps a surprising one. The real cost isn't storage, which is relatively cheap once the building exists. It's regeneration. Even orthodox seeds gradually lose viability, so every sample has to be tested for germination and, every so often, grown out again to produce fresh seed. Surveys of national gene banks have repeatedly found large backlogs of samples that are overdue for this. And a seed bank with a backlog like that isn't really a bank at all. It's a slow archive of material that is quietly dying.

Let me finish with the question of who these seeds belong to. The International Treaty on Plant Genetic Resources for Food and Agriculture was adopted in 2001, and it came into force in 2004. It places a list of major crops in a shared multilateral system, and in return, users agree to share the benefits. I'll leave the legal detail for Thursday's seminar, but keep in mind that conservation is never only a technical question.

So, to sum up: seed banks are indispensable, but they're a complement to living diversity, not a substitute for it.