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GENE BANKS mean different things to different people. To conservationists,
they are somewhere to preserve every possible variation of every species
of plant. To plant breeders, a gene bank is a place to store varieties of
crop plants with characters that might one day have some commercial use.
The genes of unpromising, scrawny cousins might one day improve the hardiness,
flavour or yield of a valuable crop.

No gene bank is large enough to hold every variety of wheat, let alone
every variety of every plant that needs conserving. Priorities are necessary.
This often brings conservationists into conflict with those interested in
crops. But as the greenhouse effect begins to change the world’s climate,
a new priority will override all others. Today’s crops and forages may fail
in their new environment. And those parts of the world that suffer famine
most regularly now are likely to be hit hardest by drought and crop failures.

Global temperature is set to increase by about 3 Degree C in the next
50 years, with a smaller rise in the tropics and a larger rise towards the
poles. Climatologists find it more difficult to predict how patterns of
rainfall will change. Their models are too broad to say what will happen
in specific areas but some trends are evident.

Today’s grainbelts of North America and the Soviet Union will probably
shift north. Colder regions of Canada and the USSR might become suitable
for growing maize, while the Midwest of the US and the Ukraine become too
scorched. Such a shift might not lead to famine, but to a change of crop
and a change in the balance of producing and exporting countries.

The implications of global warming for the developing countries of the
world are more serious. The ‘Sahelian’ zone, a dry belt that encompasses
not only North

Africa but also dry regions of Brazil, India and Australia, is already
marginal for crops and forages. A warmer, drier climate will be devastating
for people in these areas. Other areas at risk are important centres of
genetic diversity that have in the past provided the raw material for many
crops and pastures. The montane forests of East Africa and Western China,
for example, might be squeezed out of existence as lowland species spread
up the mountains. The very plants that might have provided a crop, or the
raw material from which to breed a crop, that would grow in the hardest
hit areas could easily disappear.

At a meeting to discuss climate changes and plant genetic resources
held in Birmingham earlier this year, a large group of biologists, plant
breeders and climatologists agreed that the most urgent quest was for plants
that could survive the rigours of a drier tropical zone. Collecting anything
and everything that might come in useful is no longer sensible, said Trevor
Williams, director of the International Board for Plant Genetic Resources.
Each new accession must be screened properly to determine its every character
and how it will behave under different conditions.

One thing is certain: the world will need more gene banks to cope. Every
specimen will have to be organised and documented meticulously. Legumes,
for example, will become more important in the new conditions. But legumes
grow in association with nitrogen-fixing bacteria called rhizobia and so
collections of bacteria must accompany the plants.

Conservation of species in the wild, by protecting habitats, will become
more difficult as the climate changes, because plants may be prevented,
or simply be unable to migrate to where conditions suit them. This places
an even greater burden on gene banks and poses a problem in the long term.

Plants left in the wild evolve and maintain their variability. Once
in a gene bank, natural evolution ceases, and selection becomes the job
of the plant breeder. The climate in some parts of the world will be unlike
any they have experienced before. ‘There will be novel combinations of climatic
factors,’ said Peter Rowntree of the Meteorological Office. Today’s climatic
zones will not simply shift towards the poles: western Europe, for example,
will be hotter and drier but will not receive any more solar radiation than
it does now. Material deposited in gene banks may not have the characters
to flourish in entirely new conditions.

The richer countries of the world will undoubtedly find a way to cope,
but the price will be high. ‘Is it cheaper to prevent or delay climatic
change, or is it cheaper to adapt to it afterwards?’ asked Martin Parry
of the University of Birmingham. The question is an important one. The wealthy
countries of the world, which are almost wholly responsible for the greenhouse
effect, might choose to pay for adjustments to their agriculture. Poorer
countries may not have that option.