Among all the scientific disciplines, one arguably has the greatest potential for providing human benefit on a global scale. Hundreds of millions of people in urban and rural areas in the poorest countries suffer from chronic hunger. Meanwhile, the world's great monocultures of staple grains -- rice, wheat and corn -- are at risk from novel pathogens, arising from sudden genetic alteration or from delivery by an agroterrorist.

The only line of defense depends on plant breeding, empowered by the new science of genomic analysis, which allows us to know far more about plant biology than ever before. But successful plant breeding requires the right resources accumulated over decades of painstaking effort -- and this resource is in danger of being lost.

The tools are the collections of crop genetic diversity, stored in the seed banks and crop diversity collections maintained by international centers and more than 150 nations. These collections hold samples of thousands upon thousands of crop varieties and their ancestors. Using the material in the collections -- a task now made easier by modern methods -- holds the prospect of fighting new plant diseases, dealing with drought and other consequences of climate change, and protecting us against the consequences of possible malevolent assaults on the crops that feed most of the world.

The problem is that these storehouses of diversity are being allowed to depreciate. Serious underfunding prevents adequate curation. In many banks, living seeds are waiting to be duplicated while the cooling systems that protect them break down because there is no money to repair them. New work to capture and preserve the results of breeding experiments fails for lack of support. Data collected by the U.N. Food and Agriculture Organization demonstrate that in the years between 1996 and 2000, 66 of the 100 nations studied saw the size of their collections shrink, while gene bank budgets either decreased or remained constant in 60 of the countries over the same period. And funding for the vitally important Consultative Group on International Agricultural Research, which maintains important international seed banks, has decreased dramatically. So, for that and other reasons, has the rate at which they are gaining access to important new genetic resources.

The International Treaty on Plant Genetic Resources, adopted in Rome last year, represents a legal commitment by governments to conserve and use their crop diversity in the interest of food security. The United States signed the treaty on Nov. 1. Nevertheless, the disconnect remains between the long-term requirement for crop diversity conservation and the short-term nature of most funding for such conservation.

Fortunately, there is a movement toward improvement. The Global Conservation Trust, which was established to strengthen and expand public and private resources in agricultural research, has made a good start on establishing an endowment to protect this global public good. The United Nations Foundation, other private donors and a number of European and Latin American nations have already made contributions to a fund targeted initially at $260 million. The United States has made a major commitment to support the trust.

In our effort to feed people, we have created a vulnerable enterprise: Its weakness emerges in our inadequate knowledge of how to help small farmers in the poorest countries and -- on the other hand -- in the liability of the monocultures of our major cereal grains. Both depend on our capacity to keep their genetic armaments in good shape. That will take serious support, and unless we get behind the Global Conservation Trust, the support may not be there.

The writer is editor in chief of Science magazine, president emeritus of Stanford University and a former commissioner of the U.S. Food and Drug Administration.