When one asks how much an ecosystem has been
changed by human influence, the inevitable next question must be:
"changed in relation to what?" There is no simple answer to this.
Before we can analyze the ways people alter their environments, we
must first consider how those environments change in the absence of
human activity. This amateur investigation of the workings of
woods, rivers and grassland lead to the birth of ecology as a
scientific endeavour. In particular, as a biological science,
ecology from the outset has had to define what we mean by an
ecological "community.
The first generation of academic ecologists, led
by Frederic Clements, defined the communities they studied
literally as superorganisms which experienced birth, growth,
maturity, and sometimes death much as individual plants and animals
did. Under this model, the central dynamic of community change
could be expressed in the concept of "succession." Depending on its
region, a biotic community might begin as a pond, which was then
gradually transformed by its own internal dynamics into a marsh, a
meadow, a forest of pioneer trees, and finally to a forest of
dominant trees. This last stage was assumed to be stable and was
known as the "climax," a more or less permanent community which
would reproduce itself indefinitely if left undisturbed. Its
equilibrium state defined the mature forest "organism," so that all
members of the community could be interpreted as functioning to
maintain the stability of the whole. Here was an apparently
objective point of reference: any actual community could be
compared with the theoretical climax, and differences between them
could then usually be attributed to "disturbance." Often the source
of disturbance was human, implying that humanity was somehow
outside of the ideal climax community.
This functionalist emphasis on equilibrium and
climax had important consequences, for it tended to remove
ecological communities from history. If all ecological change was
either self-equilibrating (moving toward climax) or nonexistent
(remaining in the static condition of climax), then history was
more or less absent except in the very long time frame of climatic
change or Darwinian evolution. The result was a paradox. Ecologists
trying to define climax and succession for intensively settled
regions were faced with an environment massively altered by human
beings, yet their research programme demanded that they determine
what that environment would have been like without a human
presence. By peeling away the corrupting influences of human
settlement they could discover the original ideal community of the
climax. In the process historical change was defined as an
aberration rather than the norm."
In time, the analogy comparing biotic communities
to organisms came to be criticised for being both too monolithic
and too teleological. The model forced one to assume that any given
community was gradually working either to become or to remain a
climax, with the result that the dynamics of nonclimax communities
were too easily ignored. For this reason, ecology by the
mid-twentieth century had abandoned the organism metaphor in favour
of a less teleological "ecosystem." Now individual species could
simply be described in terms of their associations with other
species along a continuous range of environments; there was no
longer any need to resort to functional analysis in describing such
associations. Actual relationships rather than mystical
superorganisms could become the focus of study, although an
infusion of theory from cybernetics encouraged ecologists to
continue their interest in the self-regulating, equilibrating
characteristics of plant and animal populations.
With the imperatives of the climax concept no
longer so strong, ecologists were prepared to become at least in
part, scientific natural historians of the countryside for which
change was less the result of "disturbance" than of the ordinary
processes whereby wildlife communities maintained and transformed
themselves. Ecologists began to express a stronger interest in the
effects of human beings on their environment. What investigators
had earlier seen as an inconvenient block to the discovery of ideal
climax communities could become an object of research in its own
right. But accepting the effects of human beings was only part of
this shift toward a more historical ecology. Just as ecosystems
have been changed by the historical activities of human beings, so
too have they had their own less- recorded history: forests have
been transformed by disease, drought, and fire, species have become
extinct, and landscapes have been drastically altered by climatic
change without any human intervention at all. As we shall see, the
period of human postglacial occupation of the northern hemisphere,
even in the so-called North American wilderness, has seen
environmental changes on an enormous scale, many of them wholly
apart from human influence. There has been no timeless wilderness
in a state of perfect change-lessness, no climax forest in
permanent stasis.
But admitting that ecosystems have histories of
their own still leaves us with the problem of how to view the
people who inhabit them. Are human beings inside or outside their
systems? In trying to answer this question, appeal is too often
made to the myth of a golden age, as Thoreau sometimes seemed
inclined to do. If the nature of Thoreau's community environment in
Concord in the 1850s—a nature which many Americans now
romanticise as the idyllic —was as "maimed" and "imperfect"
as he said, what are we to make of the wholeness and perfection
which he thought preceded it? It is tempting to believe that when
the Europeans arrived in the New World they confronted Virgin Land,
the Forest Primeval, a wilderness which had existed for eons
uninfluenced by human hands. Nothing could be further from the
truth. The land was less virgin than it was widowed. Indians had
lived on the continent for thousands of years, and had to a
significant extent modified its environment to their purposes. The
destruction of Indian communities in fact brought some of the most
important ecological changes which followed the Europeans' arrival
in America. The choice is not between two landscapes, one with and
one without a human influence; it is between two human ways of
living, two ways of belonging to an ecosystem.
The riddle of the ecological view of nature
requires exploring why these different ways of living had such
different effects on New England ecosystems. A group of ecological
anthropologists has tried to argue that for many non-Western
societies, like those of the New England Indians, various ritual
practices have served to stabilize people's relationships with
their ecosystems. In effect, culture in this anthropological model
becomes a homeostatic, self-regulating system much like the larger
ecosystem itself. Thus have come the now famous analyses designed
to show that the slaughter of pigs in New Guinea, the keeping of
sacred cows in India, and any number of other ritual activities,
all function to keep human populations in balance with their
ecosystems. Such a view would describe precolonial New England not
as a virgin landscape of natural harmony, but as a landscape whose
essential characteristics were kept in equilibrium by the cultural
practices of its human community.
Unfortunately, this functional approach to
culture has the same penchant for teleology as does the organism
model of ecological climax. Saying that a community's rituals and
social institutions "function" unconsciously to stabilize its
ecological relationships can lead all too quickly into a static and
a historical view of both cultural agency and ecological change. If
we assume a priori that cultures are systems which tend
toward ecological stability, we may overlook the evidence from many
cultures— even preindustrial ones—that human groups
often have significantly unstable interactions with their
environments. When we say, for instance, that the New England
Indians burned forests to clear land for agriculture and to improve
hunting, we describe only what they themselves thought the purpose
of burning to be. But to go further than this and assert its
unconscious "function" in stabilising Indian relationships with the
ecosystem, is to deny the evidence from places like Boston and
Narragansett Bay that the practice could sometimes go so far as to
remove the forest altogether, with deleterious effects for trees
and Indians alike.
All human groups consciously change their
environments to some extent—one might even argue that this,
in combination with language, is the crucial trait distinguishing
people from other animals—and the best measure of a culture's
ecological stability may well be how successfully its environmental
changes maintain its ability to reproduce itself. But if we avoid
assumptions about environmental equilibrium, the instability
of human relations with the environment can be used to explain both
cultural and ecological transformations. An ecological history
begins by assuming a dynamic and changing relationship between
environment and culture, one is apt to produce contradictions as
continuities. Moreover, it assumes that the interactions of the two
are dialectical. Environment may initially shape the range of
choices available to a people at a given moment, but then culture
reshapes environment in responding to those choices. The reshaped
environment presents a new set of possibilities for cultural
reproduction, thus setting up a new cycle of mutual determination.
Changes in the way people create and re-create their livelihood
must be analyzed in terms of changes, not only in their
social relations but in their ecological ones as
well.