Modeling Species Distribution with GIS - Research Techniques in Animal Ecology - page 392

minor changes, be used in other fields. The very nature of GIS makes it essen-
tial that specialists in different scientific disciplines contribute to the general
effort of setting up and maintaining common data sets.
One drawback is that in the early phases of tool development (such as GIS ),
people who master the new tool tend to become generalists, invading other
fields of science without having the necessary specific background. This may
cause problems both in the solutions provided, which generally tend to be too
simplistic, and in terminology, because the same term or concept can be used
with slightly different meanings in different disciplines. This is the case, for
instance, with use of the concept of scale. For the cartographer, large scale per-
tains to the domain of detailed studies covering small portions of the earth's
surface (Butler et al. 1986), whereas for the ecologist large scale means an
approach that covers regional or even wider areas (Edwards et al. 1994). Obvi-
ously this derives from the fact that cartographers use scale to mean the ratio
between a unit measure on the map and the corresponding measure on the
earth's surface, whereas the ecologist uses it in the sense of proportion or
extent. For example, the relationship between the geographic scale and the
extension of ecological studies supplied by Estes and Mooneyhan (1994) high-
lights that large scale in ecology is often associated with small geographic scale:

Site = 1:10,000 or larger
Local = 1:10,000 to 1:50,000
National or regional = 1:50,000 to 1:250,000
Continental = 1:250,000 to 1:1,000,000
Global = 1:1,000,000 or smaller

In ecology it would be better to use the adjectives f ine or broad (Levin 1992),
which places the term scale more in the context of its second meaning.
If the confusion arising from the two uses of large scale seems trivial (at least
from the ecologists' point of view), we believe that the different uses that have
been made of the word habitat give rise to major misunderstandings and thus
need to be clarified (Hall et al. 1997).

Habitat Definitions and Use

j

The term habitat 3 forms a core concept in wildlife management and the dis-
tribution of plant and animal species. The fact that the actual sense in which it