Environmental Health Perspectives
Vol. 10, pp. 243-245, 1975
Biological Consequences of Land Use
by R. E. Munn*
The primary goals of land-use planning are enunciated. A plea is made for consideration
of the total biosphere and not just its separate components. The environmental impact
statement process is reviewed and some suggestions made for its strengthening. Moves
for international adoption of this process are noted, as well as the concept of eco-develop-
ment currently under examination by UN agencies.
Introduction Goals of Land-Use Planning
Whenever a tree is cut or a house is built,
the physical environment is changed, which
in turn affects the biological environment.
The changes may be substantial but in gen-
eral they are rather local.
Sometimes with a single stroke of the pen,
however, rather large areas are rezoned
from rural to suburban, from residential to
industrial, or from forest to reservoir. These
rezonings may have a major influence on
both the local and the regional environments,
particularly in cases where the land-use
change is a stimulus and focal point for
additional development.
It will be assumed in this paper that major
land-use changes do have an effect on the
environment and thus have biological con-
sequences. (It is interesting to note that the
Ontario Air Management Branch receives
more citizen complaints from rural than from
urban areas, the major source of annoyance
being odors from large farm operations.)
The emphasis will therefore be placed on
the problems associated with predicting the
magnitude and importance of these conse-
quences.
* Atmospheric Environment Service, Downsview,
Ontario, Canada.
The primary goals of land-use planning
should be to maximize the carrying capacity
of the biosphere and to maximize the assimi-
lative capacity of the biosphere. These goals
are hardly ever achieved because: joint
maximization of the carrying and the
assimilative capacities may not be theoreti-
cally possible; suboptimal solutions of each
may be required; the scientific basis for solv-
ing the problem posed above is usually lack-
ing; society has other goals (economic
growth, recreational facilities, etc.) which
often conflict with the two primary goals.
In connection with the carrying capacity
of the biosphere, a distinction is usually
made between renewable and nonrenewable
resources. However, note should be made of
the fact that the so-called renewable re-
sources are not necessarily renewable. For
example, when fertile land is replaced by a
shopping center or a drive-in theater, the
carrying capacity of the biosphere is re-
duced in a way that is irreversible for all
practical purposes. Other examples include
overgrazing and pine reforestation (which
may acidify the soil).
Mention should also be made of the fact
that the second primary goal of land-use
planning is to maximize the assimilative
April 1975 243

capacity of the total biosphere, not just of
the atmosphere. The pathways of trace sub-
stances through the environment are so com-
plex and poorly understood that optimum
recycling solutions are difficult to find or to
verify. Although it may be tempting to ex-
ploit the assimilative capacity of the atmos-
phere alone (through tall chimneys, meteoro-
logical episode control, or land-use planning),
this may in some cases lead to long-term
degradation of other environmental reser-
voirs (soils, lakes, etc.).
Presentation of Alternatives through the En-
vironmental Impact Assessment Process
In the United States and increasingly in
other parts of the world, the environmental
impact assessment process is being used as
an institutional instrument to ensure that
environmental considerations are included
at an early stage of planning for large
development projects.
Recognizing the needs of assessors and
their staffs for technical guidance on inter-
disciplinary investigations, an international
workshop was organized at Victoria Har-
bour, Canada in February 1974 by SCOPE
(Scientific Committee on Problems of the
Environment), a component of ICSU (Inter-
national Council of Scientific Unions). The
workshop produced a book entitled, "En-
vironmental Impact Assessment: Principles
and Procedures" (1). Some of the main work-
shop conclusions related to land-use plan-
ning are summarized below.
Presentation of Alternatives
An environmental impact assessment
should provide the decision-maker with alter-
native environmental management strate-
gies, including that of taking no action. The
assessment should include examination of a
wide spectrum of physical, biological, eco-
nomic, and social factors and should be
undertaken at a very early stage of regional
planning, in parallel with engineering and
economic feasibility studies. However, the
assessor should avoid the temptation of pro-
ducing a "telephone directory" of the quality
of the regional environment. Finally, an
impact assessment should not be an adver-
sary document but should present unbiased
estimates of the environmental consequences
of several alternative proposals.
Uncertainty
An impact assessment is not an exact fore-
cast but contains two types of uncertainty.
The prediction may be seriously in error be-
cause of an inadequate understanding of the
behavior of the biosphere and/or because of
insufficient environmental data concerning
the region under investigation. The predic-
tion of the precise time of occurrence of a
significant but rare event may not be possi-
ble (e.g., forecasting the year of occurrence
of an earthquake, flood, or drought of a
given magnitude), although statistical pre-
dictions of the probability that such events
will occur sometime in the next 100 years
can be made with some confidence. Methods
of dealing with the second type of uncer-
tainty are well-known, although even in this
case, the decision-maker must accept a finite
risk of failure when he decides to build a
dam or to irrigate a region.
Methods for evaluating the first type of
uncertainty are generally lacking. On the
one hand, the decision-maker does not appre-
ciate "waffling ;" on the other hand, the
assessor may may wish to hedge, due to the
complexity of the environmental problem he
is trying to solve.
Irreversibility
A biological system is able to survive
across a rather wide range and variety of
environmental stresses. Nevertheless, there
are outer limits beyond which an ecosystem
"flip-flops" to another, and usually simpler
form in an irreversible way. These outer
limits define the resilience of an ecosystem
(2), which is evidently an important con-
sideration in impact assessments.
Environmental Health Perspectives244

Magnitude versus Importance of
Environmental Effects
The assessor has a responsibility to esti-
mate the magnitudes of environmental
effects. However, some large effects may not
be very important to the public, or vice
versa, depending upon the priorities estab-
lished or accepted by society. Furthermore,
these priorities may change over the years.
The ways in which environmental effects
are related to human concerns through sets
of so-called impact indicators are described
in-the SCOPE publication (1). Admittedly,
methodologies for ranking the relative worth
of various indicators of environmental qual-
ity are not yet well developed, and current
practices are controversial.
Post-Audit of Impact Assessments
How accurate are impact assessments? It
is almost unbelievable that no systematic
post-audit program exists in any country
with impact-assessment experience.
The Concept of Eco-Development
Within the United Nations, the concept of
eco-development is currently being examined
as a possible midterm strategy for the Third
World (3). The concept also has relevance
for developed countries such as the United
States and Canada.
Each region of the world has a rather
unique environment (mesoclimate, physiog-
raphy, natural resources, etc.). Eco-develop-
ment is a form of planned growth that at-
tempts to exploit the locally available natural
resources, within the constraints of the local
environment. In terms of land-use practices,
eco-development tries to maximize the carry-
ing and assimilative capacities of the bio-
sphere.
As a simple example, suppose that irriga-
tion is introduced into a semi-arid region at
great expense. The land becomes productive,
but because of the need for marketing and
service facilities, a town is created. Without
rational planning, the town may compete
with agriculture for fertile land, and the
carrying capacity of the region may become
seriously impaired within a generation or so.
As an alternative scenario in the above
example, the irrigated land may require the
intensive use of fertilizers in order to be-
come productive. This may lead in a few
decades to salinization of the soil and again
to an impairment of the carrying capacity
of the region.
Environmental impact assessments are
recommended in cases such as these, as an
instrument for providing insight into the
nature of the options and tradeoffs open to
the decision-maker.
REFERENCES
1. SCOPE. Environment impact assessment: prin-
ciples and procedures. SCOPE 5, ICSU-SCOPE,
(51 Boulevard de Montmorency, Paris 75016,
France) 1975, $4.50.
2. Holling, C. S. Resilience and stability of eco-
logical systems. Ann. Rev. Ecol. Systematics 4:
1 (1973).
3. UNEP. Report by the Executive Director to the
Second Session of the Governing Council, UNEP,
Nairobi, Kenya, 1973, UNEP/GC/14 Add. 2,
p. 135.
April 1975 245