Geoscience Reference
In-Depth Information
Laws:
universal statements that are deterministic and so well corroborated
that everyone accepts them as part of the scientific background of
knowledge. There are laws in physics, chemistry, and genetics but not
in ecology.
Principles:
universal statements that we all accept because they are mostly
definitions or ecological translations of physicochemical laws. For
example, “no population increases without limit” is an important eco-
logical principle that must be correct in view of the finite size of the
planet Earth.
Theories:
an integrated and hierarchical set of empirical hypotheses that
together explain a significant fraction of scientific observations. The
theory of island biogeography is perhaps the best known in ecology.
Ecology has few good theories at present, and one can argue strongly
that the theory of evolution is the only ecological theory we have.
Hypotheses:
universal propositions that suggest explanations for some
observed ecological situation. Ecology abounds with hypotheses, and
this is the happy state of affairs we discuss in this chapter.
Models:
verbal or mathematical statements of hypotheses.
Experiments:
a test of a hypothesis. It can be mensurative (observe the sys-
tem) or manipulative (perturb the system). The experimental method is
the scientific method.
Facts:
particular truths of the natural world. Philosophers endlessly discuss
what a fact is. Ecologists make observations that may be faulty, and
consequently every observation is not automatically a fact. But if I tell
you that snowshoe hares turned white in the boreal forest of the south-
ern Yukon in October 1996, you will probably believe me.
Ecology went through its theory stage prematurely from about 1920 to
1960, when a host of theories, now discarded, were set up as universal laws
(Kingsland 1985). The theory of logistic population growth, the monoclimax
theory of succession, and the theory of competitive exclusion are three exam-
ples. In each case these theories had so many exceptions that they have been
discarded as universal theories for ecology. Theoretical ecology in this sense is
past.
It is clear that most ecological action is at the level of the hypothesis, and I
devote the rest of this chapter to a discussion of the role of hypotheses in eco-
logical research.
