Environmental Engineering Reference
In-Depth Information
from far away. Arab seafarers took bananas from New Guinea to Africa around two thousand years
ago, probably along with mangoes and yams. Avocados, plantains, and pineapples crossed the Atlantic
from the Amazon and penetrated deepest Africa. Mangoes came from South Asia, cassava from Central
America, and goats from the Middle East. Malaysians first brought rice to Madagascar a thousand years
ago.
systems remain distinct and limited by geology and climate. But species come and go so much, as a
result of both human and natural forces, that conventional hard distinctions about what belongs where
have long been all but meaningless.
So much has been moved so many times in much of Asia, for instance, that nobody would even try
to make the distinction. Such is the confusion that even native Asian weeds are sometimes thought of as
foreign. After American forces sprayed millions of tons of Agent Orange to defoliate rain forest during
the Vietnam War, a tough local grass called cogon moved into the clearings. It provided ground cover
until the native trees got going again. But locals associated it with the bombardment and called it the
“American weed.” It was never an American weed—though it may soon become one. It has invaded the
United States in the packaging of houseplants from Southeast Asia.
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Or take the ecology of the island of Borneo, shared today by Indonesia, Malaysia, and Brunei. Until
recently, it was regarded as one of the most untamed regions of Asia, an almost mythological jungle-in-
fested place, visited by daring adventurers and the supposed home of circus freaks like the “wild men
of Borneo.” Yet all is not what it seems. Many of its endangered orangutans, though feted as symbols of
the untouched rain forest, are probably the descendants of animals kept captive for their meat centuries
ago, whereas the pigs and cattle farmed there turn out to be mostly the descendants of wild natives.
12
The omnipresent water buffalo may look local, but the species was actually introduced from the Asian
mainland after being domesticated some five thousand years ago. Fish like the snakehead are domest-
icated and have been farmed in irrigation canals for at least two millennia, and many birds fluttering in
the forest canopy have returned to the wild after being transported as caged birds and then escaping. The
Java sparrow is one example.
Farmers in Borneo, as in most places, grow mostly foreign crops. Rice came from southern China,
coconuts from the western Pacific islands. Black pepper, from the Western Ghats in India, was brought
to Indonesia by Hindu colonists two thousand years ago. The swamp sago, a long-standing staple food
here, has made many human-sponsored journeys through the region. More recently, peanuts came to
Borneo from Bolivia, and coffee and cassava came from Africa, while Europeans brought plantation
crops like rubber, acacia, and eucalyptus. A local culinary specialty is the American bullfrog (
Lithobates
catesbeianus
), caught in the canals of the city of Kuching.
Most such introductions were intentional, but many were accidental. Small creatures and seeds
found it easy to slip ashore unnoticed amid ships' cargo. Vessels arriving in Virginia in the early seven-
teenth century gave a ride to rats, which thanked their new hosts for their hospitality by eating their way
through grain stores and leaving the settlers starving.
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Ships reaching New England around the same
time brought the first earthworms to live in soils there since the last glaciation. The pioneers probably
wriggled free from soil loaded as ballast in Cornwall in South West England. They soon began eating
leaf litter that had previously built up on the floor of woodlands, changing forest ecosystems for good.
Nobody takes much notice of earthworms' movements, not even biologists. We know little about
their global journeys, but they have undoubtedly been extensive. More than a hundred species are wide-
spread around the world, probably mainly thanks to humans. Paul Hendrix of the University of Georgia,
who hosts a group called the International Symposium on Earthworm Ecology, says “introduced exotic
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