Environmental Engineering Reference
In-Depth Information
beneath much of the African rain forest, suggesting that human disturbance has been one of the dom-
inant factors affecting forest structure and composition in recent millennia,” according to John Oates of
don's Kew Gardens, takes a similar view. “Much of this region [the Congo basin] underwent extensive
habitation, clearance and cultivation beginning around 3000 years ago and ending around 1600 years
ago,” she writes. Then something happened. There was certainly a population crash. Perhaps these in-
dustrial cultures ran out of trees. Perhaps climate changed. But whatever happened, the jungle closed
in.
10
This may have happened more than once. Barend van Gemerden of Wageningen University in the
Netherlands found that in the rain forests of southern Cameroon, almost all the trees that are more than
three hundred years old are of species that today grow only in clearings made by shifting cultivators.
But younger trees are of species that prefer closed forest. His conclusion is that the forests were once
full of farmers cutting and burning and cultivating on a large scale. The end came at around the time that
Europeans first showed up looking for slaves.
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What of the other jungle regions of the world? We know that the Angkor civilization ruled much of for-
ested Southeast Asia from the ninth to fifteenth centuries. The extraordinary Angkor Wat temple com-
plex on the lakeshore of Tonle Sap in Cambodia was the ceremonial heartland of a densely populated
area with networks of roads, canals, reservoir, and rice paddy fields that covered at least four hundred
square miles. The entire urban jungle must have housed hundreds of thousands of people. There were
miners and weavers, boat builders and blacksmiths, traders and priests.
Angkor was likely the pinnacle of a series of early urban societies in that region. The evidence
of widespread forest clearance and planting goes back thousands of years, says Chris Hunt of Queens
University Belfast in Northern Ireland. When he analyzed traces of pollen left in the forests from Thai-
land and Vietnam to the Indonesian islands of Borneo and Sumatra, he found “a pattern of repeated
disturbance of vegetation since the end of the last ice age.” In the highlands of Borneo they had been
burning the forest and planting fruit trees. On the coast, he found pollen from the sago palm shipped
there from New Guinea twelve hundred miles away and planted about ten thousand years ago. (He noted
angrily that laws in some Southeast Asian countries do not recognize the rights of indigenous groups,
such as the Penan in Borneo, because they leave no permanent mark on the landscape. Yet they have
been leaving their mark for ten thousand years.)
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Cut to Central America, where the most famous jungle remains come from the ancient Mayan civil-
ization. Giant pyramids loom out of the forest as a reminder of a culture that occupied large areas of
Guatemala, Honduras, and southern Mexico from some three thousand years ago. Population densities
in the area then were greater than today. The Mayans planted their forests with
Manilkara
trees, which
produce a latex that later became the basis for chewing gum, and millions of giant
Brosimum alicastrum
.
This relative of the mulberry tree yields nuts, now known as Maya nuts or breadnuts, which formed a
large part of the Mayan diet. The trees remain. But the descendants of the Mayans have forgotten about
this forest food so completely that they trample the fallen nuts underfoot and chop down the trees to
make room for fields of corn.
In 2006, I helped judge an environmental award given to Erika Vohman, an American who had re-
discovered the true worth of Maya nuts while working as a biologist in Guatemala. “It's the largest tree
in the rain forest—up to forty-five meters tall,” she said. “It is hard for some people to imagine that a
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