Biology Reference
In-Depth Information
Baltzer, captured on film a Javan rhino reaching up to nibble a tree branch. The image was
seen around the world, but depressing news accompanied it: Gert and Mike's final surveys
in 2006 put the total number of Javan rhinos at fewer than a dozen in Cat Loc. Interestingly,
Cat Loc, a forested area with no formal protection, is very close to Cat Tien National Park.
A dense, thorny thicket of spiny palm draped the hilly terrain of Cat Loc. Professor Giao's
rhinos had become ghosts within it. Of concern was that no one had seen small footprints
signifying a calf. Biologists sought explanations for the population's perilous drop from the
dozen or more thought to still be resident in Cat Loc. One immediate speculation was that
they had been poached for their valued horn. Another was collateral damage from the bom-
bardment some years earlier. But in order to understand what happened to them and the other
rare large mammals, we need to revisit the war years and make inferences based on a bit of
human epidemiology.
Defoliant. The soft, gentle sound of this noun suggests a home beauty product rather than
a deadly toxin that kills tree leaves. As General Giap mentioned over lunch in Hanoi during
my first trip to Vietnam, he and his troops used the forest strategically and hid within it; de-
foliant was designed to expose them. The American strategy from the mid-1960s to 1971 in-
cluded an unprecedented spraying campaign intended to halt the infiltration of soldiers from
the north and shift the course of the war. By 1971, more than 75 million liters of a defoliant
dubbed Agent Orange (from the identifying orange stripe on the steel storage containers) had
descended on about 57,000 square kilometers of inland tropical forest, an area about twice
the size of the state of Massachusetts. Almost 1,300 square kilometers of coastal mangroves
were also affected.
Agent Orange did much more than strip leaves from trees. Dioxin, a chemical generated
during the synthesis of the growth hormone forming the defoliant's major ingredient, turned
out to be highly carcinogenic. Soldiers on both sides of the conflict absorbed Agent Orange
and stored it in their tissues. Because dioxin remains stable for decades, it is a persistent pub-
lic health risk. Worse, it is able to cross the placental wall into the embryo, so postwar off-
spring were often affected.
Exposure to dioxin is linked to at least twenty-eight serious diseases, including a fatal type
of leukemia. Because symptoms can take years to develop, government officials at first dis-
missed the claims of veterans who reported severe health problems from exposure. An out-
of-court settlement between the companies producing Agent Orange and the 2.4 million Vi-
etnam veterans filing suit against them led to a $180 million fund to pay veterans' health
claims. The fund was quickly exhausted, however. A 2003 US Supreme Court decision en-
abled many more veterans to receive treatment.
So little was known about the effects of Agent Orange on wildlife that a survey was called
for, to the displeasure of the US government. Among the first to investigate the ecological
effects of the war was one of the leading ecologists of our day, Gordon Orians. Traveling as a
