Environmental Engineering Reference
In-Depth Information
view. Eugenics generated calls for societies to be cleansed of inferior, alien, and unfit humans. Clement-
sian ecology led to a similar view of alien species.
The two theories also had common adherents. Many conservationists of the first half of the twentieth
century were prominent proponents of eugenics. One was the American Garrett Hardin, inventor of one
of the central tenets of environmental thinking, the tragedy of the commons. He advocated forced ster-
ilization of less-intelligent people. Another was the Oxford biologist Julian Huxley, who feared a future
world made up of “the descendants of the least intelligent persons now living.”
20
The big problem for the Clementsian view of the balance of nature is not political, however. It is that it
simply doesn't fit reality. Its critics say nature simply isn't like that. Ecosystems are not so much com-
plex and coevolved machines as the results of accident and chance. Much of what most ecologists have
previously regarded as natural, pristine and permanent now seems to be artificial, accidental, and re-
cent, with different species constantly moving in and out. Notions of being “native” and “alien” have
little meaning. Dynamism and change are the norm in nature. Ecosystems that are unchanging may be
in trouble rather than in a state of perfection. And that messes up our old ideas of humans being in per-
petual conflict with the balance of nature. “We can no longer assume the existence of a static and benign
climax community in nature that contrasts with dynamic, but destructive human change,” wrote envir-
onmental historian William Cronon of the University of Wisconsin.
21
To make sense of this, we need a new image of how nature works. Increasingly, ecologists talk
not about the brilliance of evolution, or about grand processes of succession leading to climax ecosys-
tems, but about the more prosaic business of “ecological fitting,” a phrase coined by American ecologist
Daniel Janzen in 1980.
Janzen is a legendary figure. Born as World War II broke out, the son of a director of the US Fish
and Wildlife Service, he is an evolutionary ecologist and conservationist. Since 1963, he has inspired
and driven the management of one of the oldest habitat restoration projects in the world: the Santa Rosa
National Park in Guanacaste Province in northern Costa Rica. There he pondered a scientific mystery
concerning the Guanacaste tree (
Enterolobium cyclocarpum
), an abundant local tree with a huge canopy
that grows widely in sunny pastures, providing much-needed shade. It is the national tree of Costa Rica
and produces huge numbers of large fruit that contain seeds. But there are no native animals around
able to eat the fruit and disperse the seeds. The fruit mostly piles up on the forest floor unless taken and
planted by humans. This is a tragedy for the tree and the park, which is destined to change radically
unless the tree's reproductive strategy can be unraveled and revived.
Janzen needed a solution to the “riddle of the rotting fruit.” Which creatures were the lost dispersers?
They must have been large and herbivorous. His study of natural history discovered that they had been
around in the past: ground sloths, bison, camels, and the ancient horses of America among them. But
they died out long ago. To revive the forest, he needed to revive dispersal of the seeds of the Guanacaste
tree.
His solution was to introduce into the Santa Rosa National Park the modern horse, which had first
been brought to the Americas five hundred years ago by Spanish invaders. European horses, he found,
swallowed the fruit pulp without chewing up the seeds and made an ideal surrogate for the ancient but
inconveniently extinct herbivores. For some ecologists, this introduction of an alien into a protected area
was ecological heresy. Even if the aim was rehabilitation, it was not “natural.” For Janzen it was the
only long-term way of rebooting the local ecosystem to secure the tree's future.
22
Search WWH ::
Custom Search