Thanks for asking. Louis' comments on ecology are always interesting. I did
not base my discussion in THE VULNERABLE PLANET on a CNS article by J.
Donald Hughes on "The Classic Maya Collapse" because I know of no such
article (maybe I missed it). My brief statement is based on my reading
mainly of the important work THE CLASSIC MAYA COLLAPSE (University of New
Mexico Press, 1973), edited by T. Patrick Culbert and put together by a team
of anthropologists all of them experts on Maya society. I had not read
Sharer's book for the simple reason that it was not published when I wrote
mine.
As to the real issues. My statement in the book is very general because the
issue of Maya collapse and the various theories of ecological collapse are
extremely complex and varied and the data both on the collapse and on the
nature of Maya agriculture (though we know a lot) is not all in. Let me
address the point logically first. I think it is safe to assume (and here I
will sound like the Marxist that I am) that Maya society collapsed for
material reasons. This does not tell us a lot, but it mostly rules out
purely spiritual or cultural influences. We do know that Maya society
collapsed; that its collapse was very complete, that it involved a
disappearance of "elite activities," manufacturing, writing, etc.; that this
occurred over a relatively short period of time (around 50 years of
crisis-collapse); that this was accompanied by an agricultural collapse and
famine (judging by skeletal remains); that there was massive depopulation of
both the countryside and ceremonial centers; and that the society and the
region never recovered. What could explain such a total collapse? There
are basically three types of explanation: ecological collapse, internal
social-political revolt; and external invasion. The social-political thesis
argues for a peasant revolt that devastated the elites and left no
civilization behind. The external revolt points to barbarian invaders on
the margins of the civilization. Neither of these two explanations seems to
be able to account for the massive decline in population and the failure of
the society to recover. At the same time it is known that there were all
sorts of ecological problems. Most convincing theories of collapse therefore
either focus on ecological factors exclusively or create a composite
explanation in which ecological failure plays a central role.
There are a number of different ecological crisis theories. The earliest
which focuses EXCLUSIVELY on swidden agriculture is no longer widely held.
There are others, however, that bring in the intensification of agriculture,
the erosion created by deforestation, the filling in of water basins and
diminishing water supplies, ecological problems associated with extensive
terracing, and the growth of savanna grass competition through deforestation
(a problem because the Mayans did not have the implements for turning the
soil). Insofar as most of the ecological crisis theories assume that Maya
agriculture was very productive and emphasize intensification of agriculture
as the cause of the eventual collapse it would appear that Sharer's points
don't constitute much of a refutation--given also the problematic nature of
his own statements. It is hard to imagine the "continuous field
agriculture" that he describes not leading to serious ecological problems.
Though he points to periodic flooding as a solution to this, I would be
surprised if this sort of hypothetical "Nile effect" was sufficient to
maintain agriculture in the Mesoamerican region given population pressures.
Naturally I am no expert in the area of the Maya collapse, but there is no
lack of evidence that ecological factors were crucial and any other
explanation seems to me to be lacking. Of course any ecological crisis or
crisis of agriculture would have gone hand in hand with social disruption,
invasion, etc. as a matter of course.