Geoscience Reference
In-Depth Information
which measurements are made. 'Small scale', in this context, typically denotes a
fi ner resolution, while 'large scale' indicates a large extent; practical constraints
generally dictate a small extent for fi ne-grained studies and a coarse grain for studies
that have a large extent. Combining a fi ne grain with a large extent is diffi cult
because a fi ne grain captures greater variability, which in turn necessitates larger
sample sizes, even at a small or medium extent. Often, grain and extent are con-
strained by the technical capacities of available instruments for measurement (and
of computers for analysing the resulting data): If one has only a meter stick, for
example, the grain can be no smaller than a millimeter, and extents of greater than,
say, fi fty meters are likely to be impractical. Likewise with temporal scale: annual
rainfall, for example, is too coarse a resolution to understand vegetation patterns
where seasonal variability is high. Choosing one's grain and extent carefully is
important precisely because 'patterns that appear at one level of resolution or extent
may be lost at lower or higher levels' (Gibson et al., 2000, p. 221). Conversely, the
advent of new observational tools and technologies can strongly affect the kinds of
questions that scholars pose and the theories they construct. As Church (1996,
p. 153) puts it: 'The space and time scales of observation constrain the structure
and physical content of functionalist theories [in geomorphology] through their
control of the resolution of information in the theory. Our theoretical construction
of order in nature is bound by the tyranny of the scales'.
Observational scale is principally an epistemological issue, but subsequent work
in ecology and biophysical geography indicates that scale may have ontological
implications as well.
Operational scale
refers to the idea that phenomena occur at
determinate spatial (and temporal) scales in the real world: that scale is an actual,
material property of processes, not simply a matter of how they are observed. The
Coriolis force, for example, determines patterns of winds and weather systems at
very large scales: It is why low-pressure systems rotate counterclockwise in the
northern hemisphere and clockwise in the southern hemisphere. However, contrary
to popular belief, it does not affect which way water spins down the drain, a process
at much smaller spatial and temporal scales. Similarly, tectonic drift occurs over
very long time periods and very large areas, but at smaller scales it is, practically
speaking, not only invisible but generally irrelevant. For both ecologists and bio-
physical geographers, operational scale is ontologically real.
A key point of agreement among geographers and ecologists is that no single
'correct' scale exists for either fi eld: different processes operate at different scales
and must be studied accordingly. Identifying the operational scales of processes and
reconciling them with observational scales are therefore central challenges of
research. The former may be termed the
ontological moment
of scale, the latter its
epistemological moment
(Sayre, 2005)
.
One must work back and forth between the
two moments (dialectically or, at the least, hermeneutically), incrementally reducing
epistemological obstacles and thereby strengthening ontological insights. Over time,
the observational scales utilised by scientists should more closely refl ect the opera-
tional scales of material processes.
Scale as Level
That different processes have different operational scales raises diffi cult questions
about their interactions. If the Coriolis force can give direction to something as
big and powerful as a hurricane, shouldn't it also affect water going down the
