Thomas L. Crisman
 
 

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. 

 

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