Environmental Engineering Reference
In-Depth Information
Box 3.1 Climate-Space Analysis
A climate-space analysis is an approach that quantifies how solar radiation, envi-
ronmental temperature, and physical and physiological processes (conduction,
convection, evaporative cooling) influence the exchange of heat energy between
an individual organism and its environment. A climate-space delineates the range
of environmental conditions that an individual species can tolerate and still
survive.
The approach generates a climate envelope on a graph (see below) relating
ambient air temperature and absorbed solar radiation (Qa) by species. Qa is deter-
mined by characteristics of a species such as surface color, thickness of fur, body
shape, and thickness of body fat in conjunction with the level of direct and indirect
solar radiation striking the body surface of the species. In the envelope, lines with
positive slope represent combinations of minimum nighttime (top left line) and
maximum daytime (bottom right line) temperature and solar radiation that can be
tolerated. The lines on the left and right sides of the envelope are combinations of
temperature and solar radiation that can be tolerated when the animal has
attained the minimum (left line) and maximum (right line) allowable body temper-
atures. The animal incurs injurious, if not lethal, effects when body temperatures
exceed these limits. The climate-space approach has been validated with numer-
ous small-scale experiments and field observations (see Gates 1980).
The climate-space approach can be tested at the geographic scale of species
distributions. The figure below depicts the range
distribution (light gray area) of a hypothetical
species that lives in southwestern Canada. If the
climate-space gave correct insight, then meas-
ures of ambient temperature and absorbed solar
radiation at explicit locations within a species
current range distribution (light gray circles)
should fall within the climate envelope. Values
measured outside the geographic range (dark
gray circles) should fall outside the envelope. This has indeed been shown to be
the case (Johnston and Schmitz 1997).
