An ecosystem is generally defined as the
union of the biological
community and its
habitat. The community (the
biotic) and the
habitat (the
abiotic) are intimately connected in a
reciprocal relationship. As an example of this reciprocity,
consider that physical factors shape the environment in which the
beaver
lives, while the beaver fundamentally changes the physical world in which
it lives.
The term was first proposed in print in 1935 by A. G. Tansley, who wrote:
The more fundamental conception (than biotic community) is, as it seems to
me, the whole system, including not only the organism-complex, but also
the whole complex of physical factors -- the habitat factors in the widest
sense."
Since its
conception, the ecosystem concept has had a fundamental role
in guiding
ecological and
environmental research. It has led
to a great deal of interdisciplinary research, as biologists, chemists,
geographers and geologists realize that their domains overlap and connect
in a fundamental way in nature. Much of the recent
theoretical work
performed in ecology approaches whole ecosystems, rather than populations
or communities by themselves.
One of the principal characteristics of the ecosystem is its scale-dependency. There are small (water-filled holes in tropical
trees) and large (the boreal forest) ecosystems, the latter
encompassing the former. Recent research has been focussed on not only
modeling energy flux in these ecosystems, but understanding how different
scales relate to one another. The rates at which biotic and abiotic
reactions occur are directly related to the scale of the ecosystem, and
the importance of one component to another is related to their similarity
in scale. For example, climate changes (which affect ecosystems at a
slow rate) have intense impacts on the forests but very little on the
microbial communities living in the soil.
The ecosystem concept has also greatly changed the basic
philosophies behind the management of natural resources.
Classical approaches considered only the impact a development would have
on the elements in question (for example, how a mine might affect the
local walleye population -- a popular sport fish). Currently, developers
and government agencies consider the role a development will play on all
the elements of the ecosystem. The assimilation of ecosystem theory into
management practices has changed the nature of environmental protection
laws from prophylactic to preventative.