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Gap Analysis provides a regional perspective on the
distribution of several elements of biodiversity, notably, plant
communities and vertebrate species. The maintenance of much
biodiversity will depend on balanced management of multiple-use
wildlands. Special management areas however, are a necessary
component of an overall biodiversity management strategy, since
they serve as a haven for those species and communities
incompatible with multiple use management and provide control
areas to assess the success of various management prescriptions
outside of special management areas.
In their 1994 book, Saving Nature's Legacy, Reed Noss and Allen
Cooperrider conclude, "The United States has no national
strategy to conserve biodiversity." Aside from the
opportunistic protection of scenic wilderness, habitat protection
in the USA largely has been focused on areas inhabited by game
species or endangered species. Although the recovery needs of
species on the brink of extinction are legitimate components of
an overall strategy to maintain biological diversity, they must
be complemented by a proactive approach to land use planning that
ensures that the bulk of biodiversity never becomes endangered in
the first place. In an ideal world, an objective consideration of
the distribution of biodiversity would lead to the identification
of priority areas which would then be managed for their natural
values in order to minimize future anthropogenic extinctions.
This, of course, has never been the case. In reality, most
natural areas have been set aside because they have little
economic value, because of their scenic appeal, and because the
opportunity to designate them presented itself. The primary
danger of opportunistic development of a special management area
network is that options to establish new special management areas
could be exhausted before all elements of biodiversity are
represented in the special management area system.
Developing a natural area network is a multiple step process.
First, the distribution of the known elements of biodiversity
must be assessed. Next, a set of areas is identified in which all
elements of biodiversity are represented. This is an exercise in
applied biogeography. Then, potential natural areas are more
intensively studied to determine their condition and the
feasibility of special management area designation. Sites meeting
criteria for natural areas are then chosen. This process is
commonly referred to as special management area selection.
Following special management area selection, the principles of
conservation biology are applied to delineate natural area
boundaries sufficient to maintain viable populations and
ecosystem processes. This step is commonly referred to as special
management area design and draws on the disciplines of ecology,
population biology, hydrology, and natural areas management. The
spatial questions involved in identifying natural area networks
in which biodiversity will be completely represented should not
be confused with the practical and biological questions that need
to be addressed when designing individual natural areas for long
term viability of their constituent biodiversity elements and
processes.
This entire process is complicated because of our incomplete
knowledge of the occurrence and abundance of the elements of
biodiversity, as well as an incomplete understanding of
ecological processes. Our lack of knowledge is basic. We do not
even have names for all species. Although estimates vary, perhaps
90 % of the world's species are unnamed. It is only for some of
the higher vertebrates (large mammals, birds) that we have
reasonably complete record. For others, especially invertebrates,
we have a much less complete list of species. When it comes to
more detailed ecological studies, such as distribution,
abundance, demographics, and habitat association, we are far more
ignorant. The same is true for process. Thus, while ideally
identification, selection, and design of special management area
areas should be based on complete knowledge, we are hindered by
our ignorance of taxonomy and ecology of the species and the
ecological processes occurring in the systems in which they live.
However, we must not use lack of complete information as an
excuse not to act on what biologically defensible information we
do have. If we fail to do so, we will lose much of what we have.
Special management area Identification
Rather than focusing on locations of rare species or
difficult-to-classify landscapes, biodiversity can be most
efficiently represented if maps of several biodiversity elements
are examined in hierarchical manner. First, areas in which all
plant communities are represented are identified, corresponding
to the "coarse filter" approach of The Nature
Conservancy. Then, species-rich areas that are most complementary
to one another are identified. Finally, areas containing species
still unrepresented are located, a "fine filter" that
catches species not represented in areas identified by the
"coarse filter" approach.
A subset of areas from a state or region in which all
biodiversity elements are represented can be identified using one
of a variety of stepwise algorithms. This approach to
conservation planning has been most fully developed in Australia.
One algorithm, called the "greedy heuristic," proceeds
as follows: The presence of plant communities or species becomes
an attribute of an area; areas with the largest number of
attributes are identified, then areas with the largest number of
attributes not already present in the previous choice are
identified, and so on. This stepwise approach maximizes
complementarity in each successive selection and results in the
efficient selection of a special management area network. Since
many areas will share biodiversity attributes, alternative
choices usually exist at each step, leading to the identification
of different configurations of special management area networks,
any one of which would be completely representative. Of course,
areas containing unique attributes must be included in all
potential special management area networks. These areas are
irreplaceable (i.e., they must be included in all networks).
Designing and managing natural areas for the long term
persistence of species and communities are important but
fundamentally different issues than selecting potential special
management area networks. No amount of management will maintain
species or ecosystems not present in a natural area network in
the first place. However, the presence of a species or natural
community in an area implies nothing about the potential of the
area to maintain that species or community.
Special management area Selection
Once potential areas containing target species or communities
have been identified, further information about the quality of
each area needs to be gathered and compared with the biological,
physical, and spatial requirements for long term persistence of
the target species or communities. There are many established
protocols for sampling plant and animal populations, and the
intensity of sampling necessary to select the best natural area
has not been systematically investigated and is likely to differ
between ecosystem types. In some cases, a rapid assessment by
trained biologists will suffice, in others, multi-year sampling
of a number of populations will be necessary.
Social and economic factors are often more critical than
biological factors when selecting among a set of potential
special management areas. Cost, community attitudes, and
projected changes in human land use in surrounding areas all
contribute to the selection process. Possible ways to integrate
these factors into special management area selection are being
explored by Gap Analysis Programs.
Special management area Design
Population, community, ecosystem, and landscape processes are all
important factors in special management area design. Furthermore,
beyond the physical and biological components of special
management area design, the size and shape of a natural area have
considerable relevance to practical details of special management
area management. Four areas of special management area design
become relevant after potential natural areas are selected: 1)
minimum area requirements for viable populations; 2)
community-level interactions; 3) patch dynamics and other
ecosystem processes; and 4) interactions between special
management area design and management.
Natural areas are expected to maintain biodiversity for
centuries. The long term expenses of management can easily
outweigh the costs of special management area establishment.
Making boundary adjustments to minimize management costs is as
important to special management area viability as those necessary
to maintain population, community, and ecosystem processes.
Conclusions
A clear understanding of the differentiation between identifying
a representative natural area network and designing individual
viable natural areas will assist development of a national
strategy to conserve biodiversity. Regional biodiversity
distribution data bases are not intended to convey information
about population or ecosystem processes. By definition, these
processes are dynamic and can be accurately described only for
small areas and short time periods. Special management area
designers use detailed information about these local processes to
make determinations about the special management area size and
shape they hope will endow long term viability on particular
natural areas. Recognizing the distinction between biogeographic
analyses for natural area network identification and the
biological, ecological, and practical analyses that constitute
special management area design is the first step toward a
consensus for developing a national biodiversity conservation
strategy.
Blair Csuti
Idaho Cooperative Fish and Wildlife Research Unit
University of Idaho