Geoscience Reference
In-Depth Information
tation developed to focus more on interactions between these components, with the
gradual realisation that the natural environment was more complex than at fi rst
supposed. Scientifi c enquiry generally focused on relatively fi ne-scale biological
subjects (e.g., the human body, medicine) or much larger-scale physical subjects
(e.g., hydrology, geology, astrophysics). Increasingly, these investigations found
fundamental laws that could be applied to nature (e.g., the laws of thermodynamics,
motion, relativity) but also that the
systems
under investigation were more variable,
stochastic or chaotic than at fi rst supposed (e.g., Gleick, 1987; Benson, 2000). This
was also the case for the science of ecology and the study of ecosystems in the 19th
and 20th centuries (see Golley, 1993; Benson, 2000).
Through much of ancient and pre-modern history, humans have generally managed
ecosystems to obtain several resources at one time rather than being geared around
the production of just one (e.g., Power and Campbell, 1992). For example, prior to
the agricultural revolution in the mid-18th century European farming methods
focused on using a single area of land to produce a range of food and other resources.
Monoculture of a single crop was undesirable and uneconomic due to small popula-
tion centres, limited ability to transport and preserve goods, and the possibility of
disease or poor weather leading to excessive losses of a specifi c crop (Power and
Campbell, 1992; Richardson, 2005). Until relatively recently, population pressure on
ecosystems was also much lower, so that intensive exploitation of an ecosystem for
a specifi c resource was unlikely to signifi cantly infl uence the functional integrity of
the ecosystem (e.g., Warner et al., 1996). It was only with the Agricultural and Indus-
trial Revolutions of the 18th and 19th centuries when ecosystems were 'refi ned' for
the intensive production of a specifi c resource that substantial modifi cation of the
structure and processes of ecosystems began. Consequently, understanding the
dynamics of the desirable resources became a management priority. Other ecosystem
components and processes (unless directly related) were typically seen as unimport-
ant, irrelevant or tangential at best (e.g., Gaichas, 2008).
It was against this background of modifi ed ecosystems and disrupted processes
that modern ecological thought developed. Specifi c concepts of 'ecosystem' (an
interactive system of biota and abiota), 'ecological community' (an assemblage of
species with associated resource requirements) and 'ecosystem services' (functions
provided by ecosystems which are of benefi t to humans and the environment in
general) developed in the 19th and 20th centuries as the discipline of ecology formed
and ecologists became concerned with fundamental theoretical questions relating to
how biotic and abiotic components of ecosystems interact and change (e.g., Pickett
et al., 1994). This, in turn, led to increased experimentation into and quantifi cation
of ecosystem structure, processes, and variability (see, e.g., Gaichas, 2008).
The dynamical nature of ecosystems had been apparent for centuries, although
this dynamism was poorly understood and its extent underrated (Pahl-Wostl, 1995).
It was early theoretical ecologists such as Clements (1916) and Tansley (1935) who
fi rst began to consider the mechanisms of dynamism and to attempt to identify
universal ecological laws that would enable ecosystem changes to be predicted (see
Golley, 1993). Early ecological investigations were concerned mainly with changes
in biodiversity, community composition, and the structure and arrangement of
organisms within ecosystems, and focused primarily on plants (easily observable,
sedentary organisms) as indicators of ecosystem change. Clements suggested that
particular species would associate together to form a specifi c community. He con-
ceptualised ecosystem seral dynamics as the simple replacement of particular com-
