12.5 Comparison of Existing Ecosystem Management DSS
175
goals at the various intermediate levels, and a special goal, which may be called a desired future condition, at the bottom (Saaty, 1992; Keeney and
Raiffa, 1993). A desired future condition (DFC) is
a goal statement containing a single variable measuring some observable state or flow of the system
being managed (Nute et aI., 1999). DFCs are the
lowest level of the goal hierarchy. They are directly
connected to the management alternatives being
considered (Saaty, 1992). Furthermore, DFCs precisely define the measurable variables that each alternative must contain (Mitchell and Wasil, 1989).
In other words, each DFC provides a measure of
the degree to which any given ecosystem state, current or simulated future, meets the goal statement
(InfoHarvest, 1996).
For example,
Goal: Freshwater Fishing Opportunities Exist IF
DFC(I): pH of all (> = 90%) freshwater lakes> 5
AND
DFC(2): popular game fish are plentiful AND
DFC(3): access to all (> = 90%) freshwater lakes is
adequate.
Given that "plentiful" and "adequate" are further
defined so that they are measurable, the three DFCs
above define three attributes, that is, pH, popular
game fish, and access to freshwater lakes, that each
alternative under consideration must have. Otherwise, it will be impossible to determine whether the
alternative can satisfy the goal "Freshwater Fishing Opportunities Exist." DFCs should be objective in nature. That is, there should exist a commonly understood scale of measurement, and the
application of that scale to the ecosystem should
yield roughly the same results no matter who makes
the measurement. DFC(I) is objective in this sense.
On the other hand, DFC(2) and DFC(3) are using
subjective, binary scales for "plentiful" and "adequate." Research results indicate that subjectively
developed scales can be reliably used by qualified
professionals (Keeney and Raiffa, 1993, p. 40). An
operationally practical DFC should (1) provide the
appropriate information on theoretical grounds and
(2) also be obtainable. In other words, a DFC
should accurately define the lowest-level subgoal
and be measurable in practice.
Unlike goals, which depend primarily on value
judgments, defining how to achieve a goal with a
set of DFCs depends primarily on factual knowledge (Keeney, 1992). A set of DFCs that defines a
lowest-level goal is not generally unique (Keeney
and Raiffa, 1993). There are usually alternative
ways to define the same lowest-level goal, and no
a priori tests exist to show that one way is better
or worse than another. This disparity typically results from competing scientific theories or professional judgment. Consequently, it is important to
document the justification for defining the lowestlevel goal in any particular way.
Constraints, like goals, have a standard that is either met or not (Keeney, 1992). This standard is
meant to screen unacceptable goals, objectives, alternatives, and management prescriptions from
consideration. Requirements are equivalent to constraints, but are phrased differently. Logically, "you
must" do something is exactly the same as "you
must not" do something else. Permissions are the
logical inverse of constraints. Permissions make it
explicitly clear that certain goals, objectives, alternatives, and silvicultural prescriptions are allowed
if they naturally surface in the management
process. Permissions are not mandatory; if they
were, they would be requirements.
The development of a goal hierarchy, the constraint network, and the specification of DFCs for
a complex decision problem is more art than science. Although no step by step procedures are possible, some useful guidelines have been developed
and summarized by Keeney and Raiffa (1993),
Clemen (1996), and by InfoHarvest (1996).
Alternatives are the courses of action open to a
decision maker for satisfying the goal hierarchy
(Holtzman, 1989). In ecosystem management, each
alternative contains a set of action-location-time
triples that is intended to change the landscape so
that goal satisfaction is improved. These triples,
called prescriptions, embody the purposeful application and expenditure of monetary, human, material, and knowledge resources that define ecosystem management.
The design of alternatives, like the design of the
goal hierarchy, is largely an art that relies heavily
on decision science expertise, along with an expertlevel understanding of forest ecosystem management (Klein and Methlie, 1990; Clemen, 1996). It
is also very much an iterative process. Highquality decisions require the design of a set of
promising, distinct alternatives to evaluate (Holtzman, 1989; Keeney, 1992). Given knowledge about
(1) the current condition of the forest ecosystem;
(2) the goals and DFCs; (3) the standards, guides,
best management practices, and constraints in force
at any given time; and (4) available management
prescriptions, an experienced manager can craft alternatives that represent reasonable answers to the
question of what state of organization we want for
this forest ecosystem so that we can best meet the
goals. The human mind is the sole source of alternatives (Keeney, 1992).
175
goals at the various intermediate levels, and a special goal, which may be called a desired future condition, at the bottom (Saaty, 1992; Keeney and
Raiffa, 1993). A desired future condition (DFC) is
a goal statement containing a single variable measuring some observable state or flow of the system
being managed (Nute et aI., 1999). DFCs are the
lowest level of the goal hierarchy. They are directly
connected to the management alternatives being
considered (Saaty, 1992). Furthermore, DFCs precisely define the measurable variables that each alternative must contain (Mitchell and Wasil, 1989).
In other words, each DFC provides a measure of
the degree to which any given ecosystem state, current or simulated future, meets the goal statement
(InfoHarvest, 1996).
For example,
Goal: Freshwater Fishing Opportunities Exist IF
DFC(I): pH of all (> = 90%) freshwater lakes> 5
AND
DFC(2): popular game fish are plentiful AND
DFC(3): access to all (> = 90%) freshwater lakes is
adequate.
Given that "plentiful" and "adequate" are further
defined so that they are measurable, the three DFCs
above define three attributes, that is, pH, popular
game fish, and access to freshwater lakes, that each
alternative under consideration must have. Otherwise, it will be impossible to determine whether the
alternative can satisfy the goal "Freshwater Fishing Opportunities Exist." DFCs should be objective in nature. That is, there should exist a commonly understood scale of measurement, and the
application of that scale to the ecosystem should
yield roughly the same results no matter who makes
the measurement. DFC(I) is objective in this sense.
On the other hand, DFC(2) and DFC(3) are using
subjective, binary scales for "plentiful" and "adequate." Research results indicate that subjectively
developed scales can be reliably used by qualified
professionals (Keeney and Raiffa, 1993, p. 40). An
operationally practical DFC should (1) provide the
appropriate information on theoretical grounds and
(2) also be obtainable. In other words, a DFC
should accurately define the lowest-level subgoal
and be measurable in practice.
Unlike goals, which depend primarily on value
judgments, defining how to achieve a goal with a
set of DFCs depends primarily on factual knowledge (Keeney, 1992). A set of DFCs that defines a
lowest-level goal is not generally unique (Keeney
and Raiffa, 1993). There are usually alternative
ways to define the same lowest-level goal, and no
a priori tests exist to show that one way is better
or worse than another. This disparity typically results from competing scientific theories or professional judgment. Consequently, it is important to
document the justification for defining the lowestlevel goal in any particular way.
Constraints, like goals, have a standard that is either met or not (Keeney, 1992). This standard is
meant to screen unacceptable goals, objectives, alternatives, and management prescriptions from
consideration. Requirements are equivalent to constraints, but are phrased differently. Logically, "you
must" do something is exactly the same as "you
must not" do something else. Permissions are the
logical inverse of constraints. Permissions make it
explicitly clear that certain goals, objectives, alternatives, and silvicultural prescriptions are allowed
if they naturally surface in the management
process. Permissions are not mandatory; if they
were, they would be requirements.
The development of a goal hierarchy, the constraint network, and the specification of DFCs for
a complex decision problem is more art than science. Although no step by step procedures are possible, some useful guidelines have been developed
and summarized by Keeney and Raiffa (1993),
Clemen (1996), and by InfoHarvest (1996).
Alternatives are the courses of action open to a
decision maker for satisfying the goal hierarchy
(Holtzman, 1989). In ecosystem management, each
alternative contains a set of action-location-time
triples that is intended to change the landscape so
that goal satisfaction is improved. These triples,
called prescriptions, embody the purposeful application and expenditure of monetary, human, material, and knowledge resources that define ecosystem management.
The design of alternatives, like the design of the
goal hierarchy, is largely an art that relies heavily
on decision science expertise, along with an expertlevel understanding of forest ecosystem management (Klein and Methlie, 1990; Clemen, 1996). It
is also very much an iterative process. Highquality decisions require the design of a set of
promising, distinct alternatives to evaluate (Holtzman, 1989; Keeney, 1992). Given knowledge about
(1) the current condition of the forest ecosystem;
(2) the goals and DFCs; (3) the standards, guides,
best management practices, and constraints in force
at any given time; and (4) available management
prescriptions, an experienced manager can craft alternatives that represent reasonable answers to the
question of what state of organization we want for
this forest ecosystem so that we can best meet the
goals. The human mind is the sole source of alternatives (Keeney, 1992).