Geoenvironment Management and Sustainability - Sustainable Practices in Geoenvironmental Engineering - page 5

The term ecosystem refers to a system where the various individual elements and organ-
isms interact singly or collectively to the advantage or detriment of the whole. The rela-
tionships formed between these elements and organisms can be symbiotic or antagonistic.
For an ecosystem to be self-sustaining, the relationships between the communities in
the ecosystem need to be symbiotic, and furthermore, the interactions must be mutu-
ally beneicial. The various ecosystems that exist in the geoenvironment have functions,
uses, resources, and habitats that are crucial to the production of goods and the means for
ensuring life support.
The biological component within the ecosystems that comprise the terrestrial ecosystem
do not fall within the purview of this topic except insofar as they contribute to the persis-
tence, transformation and fate of pollutants in the ground. In particular, we will be concen-
trating on the land aspects of the terrestrial ecosystem, and more speciically with the land
surface (landscape), the soil ecosystem, and subsurface systems. The term pollutants is used
to denote contaminants that have been classiied by regulatory agencies as toxic or noxious
substances that are threats to the health of humans and the environment. Contaminants are
substances that are not indigenous to the location under consideration. All pollutants are
contaminants, but not all contaminants are pollutants.
1.2.1 Ecozones and Ecosystems
Ecology is generally deined as the study of the relationship between living and nonliving
organisms and their environment. The study of these relationships is facilitated by estab-
lishing ecozones or ecosystems. Strictly speaking, ecozones are zones that are delineated
according to some sets of established ecological characteristics. They are essentially basic
units of the land or marine environment that are distinctly characterized by the living
and nonliving organisms within that region. Ecozones are geographical units that are usu-
ally several hundreds of square kilometers in spatial extent. The ecosystem or ecosystems
bounded or resident within an ecozone deals with the mutual interactions between the
living and nonliving organisms in this zone. An ecosystem is deined herein as a discrete
system that (a) contains all physical (i.e., material) entities and biological organisms and
(b) includes all the results or products of the interactions and processes of all the enti-
ties and organisms in this system. With this classiication scheme, one can distinguish
between the two primary ecosystems constituting the ecosphere, namely the land and
aquatic ecosystems. The delineation of ecozones and ecosystems is somewhat arbitrary
and can be performed or undertaken according to several guidelines. The boundaries
demarking the ecozones are not ixed.
Classiication and characterization of these land ecosystems can be performed according
to various standards or guidelines. Classiication according to the physiographic nature of
the land is one of the more popular schemes available. Under such a scheme, one has there-
fore such ecosystems as alpine, desert, plains, coastal, arctic, boreal, prairie, etc. Another
popular scheme for classiication is the resource-based method of classiication. This
approach is based on the identiication of the sets of activities or the nature of the primary
or signiicant resources constituting the speciic land environment under consideration—
such as agro ecosystem and forest ecosystem. Within each ecosystem, there exist numer-
ous elements and activities that can be examined and documented in respect to before and
after ecosystem impact. One of the primary reasons for classiication of any of the ecosys-
tems is to deine, bound, or document the sphere of inluence or examination wherein all the
elements of the ecosystem interact, and are dependent on the welfare of each individual element for
the overall state, beneit, and function of the ecosystem.