WMOD00593

• Contract/Permit #: 14-06-D-7052
• Title: Ecological Impacts of Snowpack Augmentation in the San Juan Mountains, Colorado
• Date: 3/1/1976
• State: CO
• Weather Modification - Doc Type: Report

INTRODUCTION TO GENERAL STUDIES l/
3.1
Jack D. Ives

As explained in Chapters I and II the greatest pro-
portion of the SJEP work effort was divided more or
less equally between two groups of studies, one con-
centrating on the alpine ecosystems, the other on the
forest ecosystems. It was realized that this approach
ran the danger of producing two rather independent
and disconnected reports. Furthermore, since it
would tend to force the viewpoint of the project
participants away from consideration of the San
Juan Mountains as a whole, towards specific process
studies, a set of investigations were required that
.would provide a regional overview. Under ideal cir-
cumstances there should be two types of overview
studies; one to provide a geographic framework to
describe the San Juan Mountain environments as they
were found essentially at the beginning of cloud
seeding experimentation (1970), the other to give a
temporal or historic framework to demonstrate the
pattern of ecologic and climatic change through time.
In this context two time scales are to be preferred:
secular or about 100 years (1870 to 1970 AD); and
Holocene, or Postglacial, about 10,000 years. .This
general philosophy was considered of substantial im-
portance at the inception of SJEP, so the underlying
thoughts will be explained in this introduction, and
will be followed by a discussion of why only partial
success was achieved.

In addition to the geographic and historic overviews,
a third type of overview was deemed necessary and
that of a much more highly specialized nature: the
study of the disposition and environmental effects of
silver iodide in the San Juan systems. This
third type of overview had two major components.
The first was the determination of the actual amounts of
silver iodide, with silver as the principal poten-
tially toxic substance, that entered forest and
tundra ecosystems. This was 'to include calculation
of the importance of the artificial addition of
silver in relation to the presence of naturally high
levels of silver already exis:ting in the ecosystems
of this mountain area. The second component was
based primarily on laboratory experiments and in-
volved the determination of levels of silver
toxicity in soil columns, soil microorganisms, and
individual plant species. In this way conclusions
could be reached regarding the significance of the
artificial silver being added to the San Juan area
as a by-product of cloud seeding.

!

r)
I

The geographical and historical overview subprojects
became the responsibility of the INSTAAR team, while
the silver studies were undertaken by the Colorado
State University team of Klein and Teller. All are
included in the general studies section because they
relate to the entire San Juan Mountain area rather
than to either of the primary ecosystems alone.

THE HISTORIC FRAMEWORK

Estimation of the long-term ecological impacts of
winter cloud seeding depends on the identification
of a stable environmental base. This would aid in
determination of the causes of subsequent ecological

change and particularly in differentiating between
natural change, as a response to climatic change,
and man-induced change. In part, this is a rational-
ization of the need for rigorous monitoring, by in-
strumental methods on a national and international
scale, of variations in the atmospheric circulation
and in specific mesoclimates and local climates. It
will be extremely difficult to detect the impact of
artificially-induced changes in weather or climate,
either deliberate or accidental, without a fairly
complete understanding of the direction and magnitude
of natural changes. Since the mid-point of the pres-
ent century it has become increasingly apparent that
the earlier northern-hemispheric warming trend has
ended and that we are now experiencing general cool-
ing. The duration of such a cooling trend cannot be
gauged, nor can we assume that the San Juan Mountain
climate is responding in phase with the hemispheric
shift. In fact Barry and Bradley (this vol. p. 43) show
that the San Juan climate is substantially out-of-
phase. Nevertheless, the value of determining
whether successful winter cloud seeding will augment
or offset a natural trend, and of assessing its com-
parative magnitude, should be self-evident.

On a somewhat longer time scale, we were concerned
with the climatic/ecologic shifts that have occurred
in the San Juan Mountains since the close of the
last Ice Age some 10,000 to 12,000 years ago.
Paleoecologic reconstruction for this time span
should provide a good indication of the broad limits
to which the local ecosystems have already responded
within the perspective of the theoretical impact of
cloud seeding. This in turn would relate to the
question of species plasticity (Webber, this vol. p.
201) and species adaptation through relatively
slight vertical migration (e.g. treeline changes in
elevation, Andrews, this vol. p. 87 ).

It was these considerations that prompted three of
the initial group of Institute of Arctic and Alpine
Research (INSTAAR) proposals: historical climatol-
ogy (Barry and Bradley); dendroecology (Krebs); and
palynology. By analysis of the instrumental record
that has been accumulating since the 1860's; Barry
and Bradley have provided a good indication of the
types and magnitude of climatic variation over the last
100 years. Their work was constrained by limited
available data, and virtual absence of instruments
above 2743 m, as well as by a very low funding
level and only two years duration of effort.
Bradley was able to extend his interests within the
context of doctoral and post-doctoral research to
treat the whole of the southwest United States
(Bradley, 1976 a and b). The dendroecology sub-
project (Krebs, this vol. p. 69 ) concentrated on
attempts to relate climatic variables to annual in-
crement of growth in ponderosa pine. Ponderosa1study
sites were located on the margins of the cloud seed-
ing target area. Aspen and Engelmann spruce were not
used because they are complacent species and not
suited to this kind of study. Finally, the palynology
subproject was eliminated, although some pollen and
macro-fossil analysis from peat bogs in the

l/ In Steinhoff, Harold W. and Jack D. Ives (Eds.) 1976. Ecological impacts of snowpack augmentation in the
San Juan Mountains, Colorado. Final Report, San Juan Ecology Project, Colorado State University Publ.,
Fort Collins.
2/ Present Address: INSTAAR, University of Colorado, Boulder, Colorado, 80309.

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