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DEVELOPING AND APPLYING
ECOLOGICAL THEORY TO
MANAGEMENT OF ECOSYSTEMS
Session Summary
W.H. Moir, Chair1
The human species, approaching Jl population of 6 billion on
Earth, is one of Earth's most efficient predators. Effects of
are analyses of ecosystem function appropriate (Salwasser,
Urban, Wessman and Nel)? How do functions at one scale
influence functions at another scale?
Ecosystem patterns are affected by periods and intensities of
disturbance regimes at whatever scales (Urban). For example,
an ant can harvest green leaves from certain trees in a tropical
forest, or a hurricane can level thousands of hectares of forests.
A small activity, local in space and of short time intelVal, can
have cumulative effects far more than the arithmetic sum of the
individual activities. A complex interaction of disturbances with
space-time scales can affect long-tenn ecosystem equilibria (e.g.
the condition around which they tend to fluctuate in biotic and
abiotic conditions). Some ecosystems may behave chaotically
under certain conditions (Moir and Mowrer), and some may flip
from one equilibrial state to another, such as pinyon-juniper
woodlands of the American Southwest (Jameson).
'
Ecosystem analysis is very much complicated by the necessity
to include interactions or disciplines that are difficult to quantify
or measure. Three papers in this section illustrate the importance
of cultural, political, economic, and sociological nature of human
activities for ecosystem analysis. Salwasser discusses how
"founding principles" of ecosystem management must come
from the social sciences as well as from the biological and
physical sciences. The paper by Ayn Shlisky, based on work by
Nancy Diaz and Dean Apostol, shows how a blend of ecosystem
analysis and landscape design can result in a culturally
acceptable, functional, and sustainable landscape. Their analysis
transfonns narrative landscapes of desired future conditions into
concrete form at a local community or watershed scale, although
the analysis must necessarily also consider effects of
management at other space-time scales. At a more regional scale
in the Sierra Madre Occidental of northern Mexico,
Aguirre-Bravo shows how cultural factors of ecosystem analysis
are more limiting and problematical than biological factors. The
region is currently in tumultuous disequilibrium as forest,
woodland, agricultural, and pastoral ecosystems suffer intense
human commodity demands. There are also cultural
human activities ripple in complex ways throughout the
planetaly ecosystem. Cities swollen with humans are great
heterotrophic sinks, concentrating nutrients and pouring forth
respiratory and industrial gases. Their autotrophic countetpart,
the vast agricultural land systems, are an essential production
base to support great cities. Globally, both the utban and
agricultural regions are expanding ever more into remnant
wildlands and forcing many other of Earth's inhabitants into
marginal environments, if not outright extinction (some species
are highly adaptive to human ways). Global effects of human
activities influence Earth's continents, great rivers, oceans, and
atmosphere. Some effects, such as radioactively contaminated
sites, will last long into the future. Great issues arise about
human dominance. What is the nature of the global ecosystem
that will support Earth's human population at some sustainable
level and at some quality of life? How is this global ecosystem
composed of hierarchically organized parts? How do we keep
these ecosystems sustainable, resilient to change, and
productive?
Papers in this session all play upon the above themes. At the
global scale we must monitor the movement of nutrients and
keep track of primaIy productivity (from photosynthesis) along
. major climatic and nutrient gradients (Wessman and Nel). Each
presentation in this session addresses the need to understand
ecological processes and effects at scales of space and time
ranging from macro to micro. This is a recurrent theme of
ecosystem management: that the effects of populations (not just
humans) upon ecosystems in which they function can vary,
depending upon the scales of space and time. At what scales
1 Ecologist, USDA Forest Service, Rocky Mountain Forest and
Range Experiment Station, Fort Collins, Colorado.
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insensitivities that threaten ecological balances and well-being
of people, plants, and animals. Dysfunctional rural ecosystems
display ethnic hostilities, drug trafficking, political unrest, and
execution of local leaders. Other biological consequences
include loss of biological diversity and loss of the productive
base of ecosystems, including soil erosion and loss of human
know-how about maintenance and values of indigenous crops
and medicine.
. ~.
The papers which follow, therefore, illustrate the breadth,
difficulty, and urgency of ecosystem management viewed
holistically. The reader is challenged to the near impossibility
of truly understanding ecosystems in all their great complexity.
In learning this lesson, we may arrive at the conclusion that the
human species must first come to a deeper understanding about
itself. We must be able to distinguish greed, which can lead to
ecological dysfunction, from true need, which links humans into
supportive and sustainable ecosystems.
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