Chocolate Could Bring the Forest Back. (Mata Atlantica: Endangered Biome)

Article excerpt

The forests of Bahia, in eastern Brazil, are among the most diverse in the world. But in their current state, they are too fragmented to survive over the long term. Chocolate could help restore them.

I first encountered the witches' broom on a big farm in Bahia, Brazil's chocolate state (see map, page 10). Bahia is where about 85 percent of Brazil's cocoa is grown. This farm is one of several that belong to the family of my host, Eduardo Athayde. With Eduardo at the wheel of a rental car, we were bouncing down a rutted dirt road, peering info the wet, green confusion on either side. Dense stands of cacao, the little trees that bear the chocolate fruit, packed the understory of a patchy, towering rainforest. The cacao seemed like shrubbery sprouting in a ruined cathedral. And if you glanced up towards the vault, you could travel hundreds of years into the past. You look all the way up one of those buttressed, tan or cream-colored trunks, up to an island of foliage so high overhead it makes your neck hurt, and there it is: a fragment of the ancient, shattered canopy, crowded with epiphytes--arboreal plants that look like giant pineapple tops--and dangling liana vines, and who knows what else.

But the witch was in the cacao, not the canopy. I watched the little trees for its mark--the broom--and was soon rewarded. "There!" Eduardo stopped the car so I could plunge into the shrubbery and drizzle to inspect an ailing tree. It really didn't look that bad. Clumps of tender new stems had sprouted from several branches, then wilted and turned brown. The brooms looked as though they had grown too fast, the way an over-fertilized seedling looks. And then they had died. That's all. The witch might kill the whole tree, or it might not. But either way, the tree would no longer be commercially productive--even worse, it would be a factory of infection.

The witch is the fungus Crinipellis perniciosa. A "native disease" of cacao, it lives among the wild cacao trees in the northern and western portions of the Amazon basin. Unlike Bahia, that region is part of the tree's original range. In its native forests, wild cacao doesn't crowd the understory; it grows in loose patches, here and there. And the wild plants are extremely variable in their genetic characteristics, including their susceptibility to the fungus. So a fungal spore, adrift in a sea of moist, still Amazonian air, has relatively little hope of alighting on a susceptible host.

But in the plantations of Bahia, the cacao is so dense the trees often touch each other, and they carpet thousands of hectares of the countryside. So a fungal spore, drifting in the air of a Bahian plantation, can readily find susceptible tissue--a bud or young fruit pod on any of millions of genetically vulnerable trees. If the fungus colonizes a fruit pod, the pod's lode of cocoa beans will likely be spoiled. If it colonizes a bud, then about six weeks later the infected tissue will produce a broom, a sort of cancer that diverts the tree's energy from healthy growth. The broom itself will die, and then pink, flower-like structures called basidiocarps will emerge from it. Each basidiocarp will release up to 90 million new fungal spores.

The fungus's destructive potential in the dense plantation environment has long been understood, which is why Bahia has had a quarantine for many years on the movement of cacao from Amazonia. And the quarantine worked, until May 1989, when the fungus was discovered on a Bahian cocoa farm. How it got there remains a matter of speculation but in any case, this initial outbreak was suppressed when the infected 200-hectare stand was sprayed with fungicide and burned by officials from CEPLAC (the Comissao Executiva do Plano da Lavoura Cacaueira), Brazil's premier cocoa research agency. Towards the end of the year, however, a much larger infestation was discovered on another farm, where workers had apparently cut away some of the infected trees and thrown them in nearby rivers. …