Geology Reference
In-Depth Information
them? If the former is true, then we will need to protect entire ecological communities
in order to preserve the ecosystem services they provide. If the latter is the case, then we
need only bother to look after the key players, or to introduce those of our own choos-
ing.
These questions occupied the minds of the founding fathers of ecology in the first
half of the 20th century. The American ecologist Frederick Clements, one the most in-
fluential ecologists of his day, studied how plants colonise bare ground. He noticed that
there was a series of stages, beginning with an inherently unstable plant community and
ending up in a stable climax community in balance with its environment. In Devon,
from where I write, bare ground is first colonised by annual herbaceous plants, then by
brambles and shrubs, and eventually by oak forest, which grows here because the mix
of soil, temperature, rainfall and wind are just right. For Clements, the development of
vegetation resembled the growth process of an individual living being, and each plant
was like an individual cell in our own bodies. He thought of the climax community as
a
complex organism
in which the member species work together to create an emergent
self-regulating network, in which the whole is greater than the sum of the parts.
Within the scientific community, a struggle ensued between the organismic views of
Clements and the objectivist approach of the Oxford botanist Sir Arthur Tansley. Tans-
ley declared that plant communities couldn't be superorganisms because they are noth-
ing more than random assemblages of species with no emergent properties. He found
Clements' views difficult to accept because they challenged our legitimacy as humans
to remake nature as we liked. Tansley wanted to remove the word 'community' from the
ecologist's vocabulary because he believed, in the words of Donald Worster that “There
can be no psychic bond between animals and plants in a locality. They can have no true
social order.” Tansley represented a breed of ecologists who wanted to develop a com-
pletely mechanistic understanding of nature, in which, according to Worster, nature is
seen as “a well-regulated assembly line, as nothing more than a reflection of the modern
corporate state”. For Tansley, agricultural fields were no better or worse than wild plant
communities. To paraphrase Worster, the reduction of nature to easily quantified com-
ponents removed any emotional impediments to its unrestrained exploitation. Ecology,
he says, took on the economic language of cost-benefit analysis, but economics learned
nothing from ecology.
Which approach best describes biotic communities: organism, or mechanism? Out
in the flatlands of Minnesota, at a place called Cedar Creek, a long-term experiment
is in progress that could have a bearing on these questions. A strange chequerboard of
metre-square plots filled with prairie plants dots the landscape, tended by David Tilman,
one of the world's leading ecologists, who has spent years investigating the relation-
ship between biodiversity in his plots and the ability of the small ecological communit-
