Wetland Ecotones and the Role
of the Private Sector in Conservation and Management of the Pantanal
(Excerpts from the paper presented in the "uncorrected, advance proof" of The
Pantanal of Brazil, Bolivia and Paraguay, Hudson MacArthur Publishers,
copyright 2000 by Waterland Research Institute.)
The development of aquatic conservation as a discipline
has clearly lagged behind terrestrial conservation, both temporally and
intellectually. The great lakes of the East African rift and Lake Baikal
in Russia have been recognized since the beginning of the twentieth century
as globally unique aquatic sites because of extensive species' endemism,
and extensive research programs first appeared in the 1960's to develop
management strategies for temperate lakes undergoing progressive cultural
eutrophication in Europe and North America. It was not until
the 1970's that wetland protection received any appreciable attention globally.
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Effective conservation and management of the Pantanal
requires: 1) detailed understanding of the structure and functional processes
of the ecosystem, 2) promulgation of laws and regulations based on sound
science, and 3) effective law enforcement. The earliest detailed scientific
investigations of tropical wetlands were conducted on the Chaco of Paraguay
in the 1920's (Carter and Beadle 1930). Unfortunately, the scientific endeavors
that have followed have been scant and limited primarily to structural
elements of the ecosystem (Por 1995). Recently, however, several Brazilian
groups, separately and in conjunction with an expansion of the decades
long investigations of the Amazon River and its floodplain by the German
Max Planck Institut fur Limnologie based in Manaus, have contributed significantly
to understanding of ecosystem functional processes in addition to structure
(Junk and Da Silva 1995, Heckman 1998). Incomplete understanding of the
structure and function of the Pantanal and their relationship to changing
watershed land use and associated alterations in hydrology, erosion rates
and nutrient release has hindered development of policy applicable to more
than small subregions of the Pantanal. Sound management schemes and regulations
applicable to the whole Pantanal based on detailed knowledge of the structure
and function of the whole ecosystem are currently lacking.
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While the Pantanal is clearly recognized as the
largest wetland in the world, estimates of its size range from 80,000 to
250,000 km2 (Por 1995) depending to a large degree on the extent
of flooding during the wet season. Accepting an estimated size of 140,000
km2 for the Pantanal (Heckman 1994), the total watershed area
draining into it would be 256,800 km2, located predominately
to the north and east of the wetland (Figure 1). The world considers the
Pantanal as one intact ecosystem.
It is hard to visualize a single ecosystem that
is roughly the size of the State of Florida and 39% of the area of Germany.
The Pantanal is at its maximum extent and totally flooded during the wet
season and is characterized by hydrological sheetflow from the north towards
its narrow discharge zone into the Paraguay River. Even then, the Pantanal
does not act as a single ecosystem because waters still tend to maintain
their subbasin chemical integretity (Por 1995).
The habitat heterogeneity of the Pantanal is visibly
evident during the drier portions of the year when the landscape is transformed
into a matrix of isolated freshwater lagoons, salinas, wetlands and rivers.
One could argue convincingly that each of these aquatic components is functioning
as independent ecosystems, at least during the dry season.
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Not only is it difficult to define whether wet
or dry conditions define the Pantanal ecosystem, it is equally difficult
to delineate the areal extent of the Pantanal that is affected by individual
watershed practices and human incursions into the wetland for extraction
of resources including ornamental fish, birds and furs. Small to intermediate-sized
wetlands are sometimes viewed as ecotones, transition zones between fully
terrestrial and fully aquatic ecosystems, rather than a distinct ecosystem
type unto themselves. By extension, any alteration in watershed export
of sediments or nutrients will affect the entire wetland.
While this is not likely the case for the Pantanal
due to its immense size and hydrological subbasins, interaction zones between
the Pantanal and its watershed have not been defined adequately for either
the wet or dry seasons. Rivers entering the Pantanal integrate erosion
products, chemical contaminants and nutrients (nitrogen and phosphorus)
from urban, agriculture, and mining practices (Figure 2). The interaction
zone of the river with the Pantanal is limited to a narrow riparian corridor
during the dry season, but expands at the end of the river course associated
with deltaic sheetflow and development of secondary stream networks. While
rivers act to maximize the zone of influence of watershed practices into
the wetland, the upland-aquatic interaction zone along most of the perimeter
of the Pantanal is rather narrow and limited to non-point pollution sources
from agriculture and mining and the ability of humans to penetrate the
wetland for extraction of natural resources. Roads, like rivers, expand
the interaction zone deep into the interior of the Pantanal, but unlike
the latter, their influence is unlikely to expand in areal extent at their
terminus. Within the interior of the Pantanal, larger wetlands likely maintain
an inner core area that is sufficiently spatially and hydrologically isolated
that it is little affected by cattle grazing and other human activities
during the dry season, while smaller systems are completely controlled
by terrestrially derived activities. Such distinctions in the extent of
ecotonal interactions, both between the Pantanal and its watershed and within
the Pantanal proper, are likely overridden by flooding regimes during the
wet season. Quantification of ecotonal processes for both the wet and dry
seasons is considered basic for development of any sound management plan
for the Pantanal.
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At the time of the first Earth Day in 1970, humans
were not seen as a natural component of ecosystems, but rather as an invasive
element altering ecosystem structure and function in purely negative ways.
Today, there is a different reality that recognizes that humans are an
integral component of ecosystems and that even the most "pristine" areas
of the world have been and most certainly are influenced currently by humans.
The archaeological/paleolimnological record has documented multiple periods
of forest clearance and abandonment by humans throughout the tropics, especially
Latin America (Binford et al. 1987, Islebe et al. 1996). Today, the concept
of pristine is problematic given that the atmosphere is extremely effective
at dispersing human produced contaminants for ultimate deposit in distant
ecosystems throughout the biosphere.
It is difficult to ascertain the extent to which
the current landscape features of the Pantanal are the direct result of
over 200 years of ranching activities. Approximately 95% of the Pantanal
is under private ownership as cattle ranches. Traditionally, most ranches
averaged 100,000 hectares, but recently some have been subdivided into
smaller units of 5,000 hectares or less (Wade et al. 1993). In addition
to an estimated three to eight million cattle, large sections of the Pantanal
are burned annually to stimulate growth of fresh pasture, and a few ranches
have attempted to introduce non-native grasses for increased pasture production.
Although it is likely that the structure of the
Pantanal has been altered by 200 years of ranching operations, it is unclear
either whether this is irreversible or if critical ecosystem functional
aspects of the Pantanal have been compromised significantly. We must now
ask what role traditional cattle ranching should play in the conservation
of the Pantanal.
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Obviously, it is in the best interest of the fazendeiros
(ranchers) to maintain the integrity of the Pantanal as it has been for
at least 200 years so long as it is economically feasible. It is now critical
to develop additional economic incentives for conserving the Pantanal including
development of natural products extracted from the Pantanal and examination
of the feasibility and carrying capacity of ecotourism. Several organizations
are trying to promote economically viable operations to develop value-added
products based on the sustainably extractable natural resources of the
Pantanal.
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Ecotourism is developing rapidly in the Pantanal
and provides economic return both to the fazendeiros and service providers
in urban centers of the upper watershed. There are, however, negative aspects
of such operations. Ecotourism has the potential to drive the zone of high
intensity human impact (ecotone) deeper into the Pantanal than ever before.
Serious questions still remain regarding the impact of heavy vehicular
traffic on wetland soils and the disposal of sewage and solid wastes. In
addition, with increased ecotourism, there is an associated increased demand
for accomodations within the Pantanal and service personnel. In short,
the carrying capacity for ecotourism activities in the Pantanal has not
been assessed adequately. In spite of general and specific concerns, however,
developing sustainable use practices appears to be the best way to promote
conservation of subtropical and tropical wetlands globally (Crisman et
al. 1996).
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A solid legal framework for the protection of
the Pantanal has been developing at the federal and state level in Brazil,
but enforcement of such statutes is critical if effective conservation
will become reality. Enforcement is most effective when done as much as
possible by the people interacting with the wetland daily, rather than
state or federal officials having little vested interest in the resource.
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Of the triad of prerequisites required for effective
conservation and management of any ecosystem (ecological understanding,
sound legal/policy framework, effective enforcement), detailed understanding
of the ecological structure and function of the system forms the base for
the other two. Unfortunately, such an ecological base is lacking for the
Pantanal. Most investigations on the Pantanal (Por 1995) have focused on
structural elements (geology, hydrology, biota), and until the late 1980's,
little attention was paid to functional aspects of the ecosystem. There
is a critical need to take an ecosystem approach to understanding the Pantanal,
both whole and subbasin. Such an approach should include a detailed assessment
of ecosystem functional processes and delineation of zones of human/watershed
interaction (ecotones) with the Pantanal.
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Traditionally, there has been a strong north-south
linkage between tropical and temperate scientists. The Pantanal is no
exception. Although the Everglades of Florida has been the focal point
for experience transfer in wetland management, this is but one model ecosystem.
There is critical need for an east-west dialogue within the tropics regarding
management of large wetland ecosystems. Development of a pantropical perspective
on wetlands including such important systems as the Okavango, Kafue, and
inner delta of the Niger in Africa, Tonle Sap in Cambodia and the Llanos
of Venezuela, among others, will assist conservation efforts in all and
will draw attention to critical needs in wetland management throughout
the tropics.
Given the immense size of the Pantanal (140,000
km2) compared to other large wetlands of the subtropics and
tropics, the Everglades (historically 10,520km2) and Okavango
(approximately 16,800 km2) for example, hinders direct comparison
because of pronounced differences in circumference-to-area ratios. The
smaller the ecosystem, the greater the likelihood that human interactions
within ecotonal zones will influence a greater percentage of total wetland
area.
Future interwetland comparisons must also consider
the influence of rivers and roads for extending ecotonal zones of human
influence into the ecosystem. To date, there is a paucity of investigations
delineating the innermost boundary of human impact in wetlands.
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Representatives from approximately 34 nations
attended the Second World Conference on Preservation and Sustainable Development
in the Pantanal held in Washington, D.C. during September 1999. These people
participated in the conference not only for their love of the Pantanal,
but also to obtain a "take home message" that would assist them in developing
conservation and management strategies for their own wetland ecosystems.
Perhaps the most important message would be that humans are both part of
a wetland's ecology and the key element in the long-term solution of ecosystem
management. The important caveat to this message, however, is that no management
strategy can be effective until a baseline understanding of the structure
and function of the entire ecosytem is achieved.