Conservation Priorities in Naturally
Fragmented and Human-Altered Riparian
Habitats of the Arid West
David J. Krueper
Abstract—Riparian ecosystems are critically valuable to wildlife
in arid regions of the western United States. They are particularly
valuable in the lowlands, primarily below 5,000 feet, where they
provide direct sustenance for a variety of animal species. They also
provide a connection between all other habitats, including mountains, forests, prairies, and deserts. Although western riparian
ecosystems historically have been structurally fragmented, discontinuous, and highly variable in size and shape, nearly all species of
western nongame migratory birds identified as conservation priorities by Partners In Flight have been recorded within them. Unfortunately, owing to habitat alteration and degradation, this critical
habitat is now among the rarest of forest types in western North
America, where it makes up less than 5% of the total land mass. To
retain or restore the values of this sensitive and extremely limited
habitat under continued anthropogenic pressure, I recommend:
that Riparian habitat issues be viewed in terms of modern conservation principles; that a conservation strategy and mechanism to
implement the strategy be developed; and that the traditional
paradigms that have guided riparian management in past years be
critically evaluated and amended.
Riparian habitats are vegetative communities or ecosystems associated with perennial, intermittent, or ephemeral
surface or subsurface water (Krueper 1993). They are among
the rarest habitat types in North America, constituting less
than 5% of the continental land mass. Traditionally, lowland
riparian ecosystems have been the western habitat type that
is most heavily affected by human overuse, abuse, and
neglect (Fleischner 1994; Ohmart 1994; Krueper 1996).
Within the past 100 years, an estimated 95% of this habitat
has been altered, degraded, or destroyed by a wide range of
human activities including river channelization, unmanaged
livestock grazing, clearing for agriculture, water impoundments, urbanization, timber harvest, exotic plant invasion,
recreational impacts, groundwater pumping, and fire. Together, these activities have dramatically altered the structural and functional integrity of western riparian habitats
(Johnson and others 1977; Dobyns 1981; Bock and others
1993; Krueper 1993; Fleischner 1994; Horning 1994; Ohmart
1994, 1995; Cooperrider and Wilcove 1995; Krueper 1996).
At present, natural riparian communities persist only as
In: Bonney, Rick; Pashley, David N.; Cooper, Robert J.; Niles, Larry,
eds. 2000. Strategies for bird conservation: The Partners in Flight planning process; Proceedings of the 3rd Partners in Flight Workshop; 1995
October 1-5; Cape May, NJ. Proceedings RMRS-P-16. Ogden, UT: U.S.
Department of Agriculture, Forest Service, Rocky Mountain Research
Station.
David J. Krueper, Bureau of Land Management, San Pedro Riparian
National Conservation Area, 1763 Paseo San Luis, Sierra Vista, AZ, 85635.
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isolated remnants of vast, interconnected webs of rivers,
streams, marshes, and vegetated washes.
Nonetheless, up to 80% of vertebrate species in the arid
West use western riparian habitats at some stage of their
lives. The high density and diversity of wildlife within these
habitats results from the availability of water and prey
items, and from high vegetative density, diversity, and
structure. More than 50% of the bird species in the American
Southwest breed in riparian habitats (Johnson and others
1977; Krueper 1996). More than 60% of the nongame migratory bird species identified as conservation priorities by
Partners in Flight (PIF), including tens of millions of individuals, regularly use western riparian areas for breeding,
migration, or wintering habitat (Krueper 1993).
Major obstacles to management of riparian areas for
wildlife include mixed ownership patterns, high economic
value in arid landscapes, and polarization between consumptive and nonconsumptive users. Land management
agencies such as the USDA Forest Service, the Bureau of
Land Management, and various state agencies are mandated to administer public lands in a multiple-use manner, provided that the impacts do not jeopardize their
continued sustainable use. The challenge of responsible
riparian habitat management is thus to strike a balance
between consumptive and nonconsumptive public needs.
This balance can be accomplished only through a consensus, problem-solving process, in which management techniques and implementation methodologies are agreed
upon by all affected parties.
Ecosystem management has been the supposed “guiding
principle” behind land management during the past decade.
Whereas biologists may have an understanding of the concept, most land management agencies and public officials do
not have a clear working definition or understanding of
ecosystem management and the principles involved. In
many instances, agencies do have the understanding, but
conflicting mandates and political pressures have prevented
adherence to the concept. In an attempt to clearly define the
parameters of ecosystem management, Grumbine (1994)
critically evaluated peer-reviewed journals and public policy
documents from several federal and state management
agencies. He identified ten themes common among all sources
referenced, which he synthesized into this definition:
Ecosystem management integrates scientific knowledge of
ecological relationships within a complex sociopolitical and
values framework toward the general goal of protecting
native ecosystem integrity over the long term.
Using this definition, I present the following recommendations for conservation and preservation of western riparian
ecosystems and their dependent avian assemblages.
USDA Forest Service Proceedings RMRS-P-16. 2000
Recommendations ______________
Ecosystem Management
Adopt basic tenets of ecosystem management and conservation biology to help understand the principles behind
riparian habitat conservation and restoration.
1. Improve and expand current riparian habitat to the
maximum extent possible, and ensure that a proper spectrum of ecological assemblages exists. Large blocks of habitat, which can sustain several or many pairs of species of
concern, are preferable to smaller blocks. Large blocks of
continuous habitat are more valuable than blocks that are
fragmented or discontinuous. Historic destruction or alteration of western riparian habitats has resulted in highly
fragmented and discontinuous habitat patches of adequate
breeding habitat for a great number of nongame bird species.
Southwestern Willow Flycatcher (Empidonax traillii extimus)
and Western Yellow-billed Cuckoo (Coccyzus americanus
occidentalis) have undergone precipitous population and
range declines within the last century. These species and
many others have reached the critical stage where suitable
breeding habitat has become so fragmented and isolated
that genetic bottlenecks may have been created. Single
individuals cannot locate mates within the remaining suitable fragments of riparian habitat.
2. Tie patches of riparian habitat together to allow avian
species to recolonize areas where they have previously been
extirpated. Patches of habitats that are close together are
more valuable than patches that are isolated. Riparian
corridors are beneficial to migrating or dispersing animals.
3. Manage common species to keep them common, but
concentrate special management actions on habitats and species of concern. Avian species are less likely to become extinct
if they are common across large ranges. Conversely, species
with extremely limited ranges are more likely to become extinct
through habitat loss or other catastrophic events.
4. Involve all interested or affected parties in riparian
management implementation. Stanley (1995) determined
that the true concept of ecosystem management, under its
current definition, is superseded by human needs and desires.
He feels that to maintain or improve ecosystem integrity,
humanity must shift its anthropocentric thinking from believing that we are above natural processes to believing that
we are a part of nature. While this belief is noble, in reality,
it may never be adopted by humanity. Therefore, successful
riparian habitat management must accommodate “selfish”
human needs and values. Humans are an integral part of the
landscape, and to ignore their continued use of riparian
habitats is to ignore not only potential impacts, but also the
possibility of successful habitat management.
Conservation
Develop a conservation strategy for which the status of
riparian habitats is assessed, and management practices
and other conservation actions are identified.
1. Evaluate habitat fragments on the basis of size and
configuration, connectivity to adjacent habitats, and
importance to priority bird species. Determine the location,
quality, and extent of remaining riparian habitat. This
USDA Forest Service Proceedings RMRS-P-16. 2000
process is currently under way through the efforts of
several western states involved in the PIF conservation
planning process (Carter and others, this proceedings).
2. Determine the habitat requirements of priority avian
species, including issues of habitat quality and quantity.
Develop management strategies for the enhancement of all
threatened habitats and resources. Initiate (or complete)
inventories to determine the status of sensitive avian
species within western riparian habitats, identified in part
through the PIF species prioritization process. Identify the
bird species and locations of riparian habitats that are
rarest and/or most vulnerable.
3. Address the concept of “biotic impoverishment” of riparian ecosystems (Cooperrider and Wilcove 1995). Because
western riparian habitats have experienced intensive use
for many generations, any management scenario must consider the cumulative impacts of:
• range management (overgrazing, erosion, loss of native
vegetation)
• energy and mineral development
• recreation pressures
• displacement of native plant and animal species (exotic
plant invasion)
• habitat fragmentation
• suppression/interruption of natural fire regime
• urbanization
• vegetative and mechanical manipulation of riparian
habitats
• vegetative restoration efforts/needs
• forestry practices
• agricultural diversions
• traditional wildlife management practices
• information/education needs
4. Ensure that all parts and processes of riparian ecosystems function together. Consider energy flow, hydrologic
cycles, nutrient cycles, biotic interactions, and rare species,
as well as the connectivity, location, and configuration of
habitat and successional stages.
Implementation
Form a conservation delivery mechanism for those actions
that need to be implemented.
1. Develop a Western Riparian Ecosystem Management
Team, consisting of representatives of each state, to work
within the management subgroup of PIF.
2. Protect existing riparian habitat on state and federally
administered lands and, where necessary and feasible, add
to the amount of riparian habitat owned or managed by
conservation agencies or organizations.
3. On private lands, encourage land management practices that enhance the ecosystem values of riparian habitat.
This can be accomplished through outreach as well as
measures such as cooperative management agreements,
protective zoning, and taxes and other types of private
landowner incentives.
4. Restore vegetative structure, composition, and hydrologic dynamics, and thus productivity and biodiversity, of
degraded riparian habitat on public and private lands where
necessary and feasible.
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5. Assure that the network of high-quality riparian habitats that are maintained or restored are sufficient to support
a satisfactory distribution of healthy avian populations.
6. Monitor the results of implementation efforts and make
changes where appropriate. Monitoring should be an ongoing process so that progress can be successfully tracked.
Evaluation
Critically evaluate traditional paradigms.
1. Recognize that a problem exists. Address riparian
condition and restoration/recovery as the main objective in
land management practices.
2. Develop and encourage a concept of environmentally
responsible land management that puts the highest emphasis on properly functioning riparian ecosystems and their
dependent plant and wildlife resources.
3. Educate the public and agency resource managers
regarding the fragility and value of riparian habitats. Encourage public input through meetings and participation in
the decision-making process.
4. Stress interagency and public-private cooperation within
the context of ecosystem management. Where necessary, cooperate across state and international jurisdictional boundaries.
5. Endorse the legal mandates and spirit of legislation
such as the Endangered Species Act, Federal Land Policy
Management Act, National Environmental Policy Act, Public Rangelands Improvement Act, and the Clean Water Act.
These acts focus on the recovery of species and habitats and
supersede mandates of multiple-use management.
6. Stress that the primary goal of public land management
should be the preservation of functioning riparian ecosystems and their native flora and fauna.
7. Recognize that the interrelationships among hydrological processes, vegetative communities, sensitive wildlife
populations, and the fragility of riparian ecosystems are
integral to the management of all. Riparian ecosystems are
uniquely sensitive habitats and should be managed as such,
not as part of upland or other adjacent habitats.
8. View riparian habitats as endangered ecosystems
(Hunter and others 1987). Shift away from the view that
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they are “sacrificial areas” which can heal quickly if disturbance is minimized.
9. Change management emphasis from “single use” to a
more balanced concept, taking into account all species and
processes within a functioning ecosystem. Merge traditional
game and nongame programs to achieve a holistic and
ecological management approach for the benefit of riparian
habitats and all riparian-dependent species.
10. Do not assume that multiple-use mandates mean “all
uses in all habitats at all times.” Shift to a concept of
“appropriate uses in appropriate habitats at appropriate
times.” Employ objective, sound, and defensible science in
making management decisions.
11. Change the concept of “burden of proof.” Force consumptive users to show that proposed activities will not
damage a resource, including consideration of cumulative
impacts, rather than ask land managers to show proof of
potential damage or resource conflicts.
12. Hold land managers accountable for riparian ecosystem
health, viability, and restoration. Hold permittees and other
public land users responsible as well. Reward the public land
user who achieves desired goals of riparian ecosystem management, but penalize the public land user who is not achieving desired results, using fee increases or fines.
While many of these recommendations seem obvious to
biologists, if we are to ensure that lowland western riparian
ecosystems continue to exist and adequately function into
the 21st century, then we must do a better job of delivering
the management message to land managers, elected officials, and the American public. Riparian habitats are an
integral component of western biological ecosystems, and
their losses will permanently harm the integrity of the land
as well as everything that depends on it, including plant,
animal, and human populations. This fact alone should
place management and restoration of western riparian habitats as the primary goal of appropriate land management
agencies, all of which should strive to reverse the decline of
western riparian habitats, stabilize them, and finally increase their quality and quantity throughout the West.
USDA Forest Service Proceedings RMRS-P-16. 2000