immediately. But it may take quite a while for a forest to fully “relax,” and
even small, remnant populations can persist for a long time, depending
on the roll of the survival dice. The difference between the number of
species that have been doomed by some sort of environmental change and
the number that have actually vanished is often referred to as the
“extinction debt.” The term implies there’s a lag to the process, just as
there is to buying on credit.
Another possible explanation is that habitat lost to deforestation isn’t
really lost. Even forests that have been logged for timber or burned for
pasture can and do regrow. Ironically enough, a good illustration of this
comes from the area right around the BDFFP. Not long after Lovejoy
convinced Brazilian officials to back the project, the country suffered a
paralyzing debt crisis, and by 1990 the inflation rate was running at thirty
thousand percent. The government canceled the subsidies that had been
promised the ranchers, and thousands of acres were abandoned. Around
some of the BDFFP’s square fragments, the trees grew back so vigorously
that the plots would have been swallowed up entirely had Lovejoy not
arranged to have them re-isolated by cutting and burning the new
growth. Though primary forest continues to decline in the tropics,
secondary forest in some regions is on the rise.
Yet another possible explanation for why observations don’t match
predictions is that humans aren’t very observant. Since the majority of
species in the tropics are insects and other invertebrates, so, too, are the
majority of anticipated extinctions. But as we don’t know, even to the
nearest million, how many tropical insect species there are, we’re not
likely to notice if one or two or even ten thousand of them have vanished.
A recent report by the Zoological Society of London notes that “the
conservation status of less than one percent of all described invertebrates
is known,” and the vast majority of invertebrates probably have not yet
even been described. Invertebrates may, as Wilson has put it, be “the little
things that run the world,” but little things are easy to overlook.
* * *