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Biosphere 2, an ecosystem enclosed in steel and glass in the Arizona
desert near Tucson, is producing barely enough food for the eight people
living inside. During their first year sealed inside, the ‘biosphereans’
consumed an average of only 1784 calories a day. They have lost on average
almost 10 kilograms each, and have introduced strict food rationing.

Roy Walford, Biosphere 2’s resident doctor, says he and his comrades
have seen their levels of blood sugar, cholesterol and blood pressure fall
drastically. White blood cell counts have also fallen. Conditions inside
the Biosphere offer a unique opportunity to study the effects of a low-calorie,
low-fat diet in humans, says Walford. Studies with laboratory animals suggest
that those fed such diets are healthier and live longer.

So far, says Walford, the biological response of the biosphereans mirrors
the response observed in animals. Declining numbers of animals’ white blood
cells did not indicate a weakening immune system, he says. When challenged,
the animals’ immune systems responded more vigorously than normal. Stephen
O’Brien of the National Cancer Institute in Washington, a member of Biosphere
2’s scientific advisory committee, says Walford’s observations ‘may be the
best evidence so far that diet does regulate cholesterol levels’.

Walford, contacted by telephone inside Biosphere 2, said the experiment
was not planned. The biosphereans intended to eat well, although they were
always going to live largely on a vegetarian diet. But growing food on a
quarter of a hectare of land has turned out to be a struggle.

First, the steel and glass frame allowed in less light than expected.
Then, several key crops, including potatoes, failed when they were infected
with diseases or were attacked by pests. At one point the biosphereans tried
using portable hair dryers to drive mites off the leaves of potato plants
– without success.

Walford admits that ‘we may have lost a bit more weight than was optimal’.
O’Brien says he was worried enough about the rapid weight loss to consult
several nutritionists about it, but they told him there was ‘not too much
to worry about’. Walford says that the main consequence is a general loss
of energy, although it has not interfered with essential activities.

Besides the food shortage, the main worry for Walford and his fellow
inmates is a mysterious gradual decline in the concentration of oxygen in
the Biosphere’s atmosphere. Walford says the oxygen concentration has fallen
to a level found at an altitude of 3500 metres, just 100 metres lower than
the Tibetan capital of Lhasa. Tucson lies at an altitude of 700 metres.