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The Alto Madidi region is in the sub-Andean belt, consisting of a series of parallel ridges to 800-2000 m and valleys at 300-500 m, with a generally north-westerly orientation (Map 71). The ridges are anticlines composed of Ordovician, Devonian, Carboniferous and Cretaceous sandstones and mudstones; the valleys are synclines with Tertiary sediments, conglomerates and rocks (Oblitas and Brockmann 1978). East of the Andes lie Quaternary sediments of the Andean piedmont (at 200-300 m) and the extensive Beni-Chaco plain (at 130-200 m).
The most conspicuous geomorphological feature in the region is the Madidi-Quiquebey syncline, between the Serranía del Tutumo (also known as the Serranía del Tigre) and the serranías of Chepite and Eslabón. The southern end of this broad valley is drained by the Tuichi River, which joins the Beni River upstream from Rurrenabaque. The Alto Madidi River flows north-westerly to the termination of the Serranía del Tutumo, where it makes a broad arc to flow eastward across the alluvial plain of the Beni, eventually uniting with the Beni River.
Soils in the region vary depending upon geomorphology. Steep-sided mountain ridges have shallow soils with numerous sandstone outcrops; these soils are susceptible to erosion and vary from strongly acidic to neutral. Lower hills with Tertiary substratum have deeper soils and are only moderately acidic. Valleys, abandoned terraces and the alluvial plains are characterized by deep soils that vary from heavy clays to sandy loams and are strongly to slightly acidic (R. Lara, pers. comm.).
The climate is humid to very humid with the mean precipitation estimated at over 2000 mm per year. Prevailing winds are from the north, causing north-eastern slopes to have the most rainfall; there is a marked rain shadow to the south-west near Apolo. The mean annual temperature is estimated to be 26°C. There is a dry season coinciding with the austral winter, but the southerly cold fronts characteristic of other parts of lowland Bolivia have little impact in the Madidi-Apolo region.
The vegetation in the Madidi region has been described by Foster (1991); the following account includes additional observations along the Tuichi River and adjacent areas. The plant communities are largely correlated with altitude and topography.
The highest western mountain ranges have extensive cloud forest on north-eastern faces; fern brakes and meadows can be observed on some ridgetops. The steep-sided mountains have slippery clay soils, and with the high rainfall there are numerous landslides; their vegetation is a patchwork of communities in different successional stages.
Montane humid forest occurs on the ridge slopes and intergrades into a lowland forest with Amazonian affinities; similar forest types are found on abandoned river terraces in the piedmont. The floristic diversity of this lowland forest is considerable, with 204 species of 2.5 cm or more dbh per 0.1 ha (Foster and Gentry 1991).
Floodplain forest and plant communities in various successional stages occur along the rivers; presumably large areas of swamp forest associated with river meanders exist downstream along the Madidi and Heath rivers.
The alluvial plains north-east of the Andean foothills support vegetation that is similar in structure and physiography to the widespread and extensive savannas of the Beni lowlands. These grasslands are a complex mosaic of plant communities resulting from the interaction of edaphic conditions (including duration and degree of inundation) and fire. The forests occur as patches and along rivers, adding to the diversity of habitat types (see Data Sheet for Llanos de Mojos, CPD Site SA24). Savanna complexes are found near the town of Ixiamas and along the Heath River on the Peruvian border. In addition, the region has a variety of riverine and non-riverine lakes and permanent marshes which support aquatic vegetation.
A "dry ridgetop forest" community occurs below the cloud level; although less diverse, there is little overlap in floristic composition between this forest type and the more widespread premontane forest communities. Dry forest and well-drained savanna occur on the downwind side of the south-western ridges near the town of Apolo. This area appears similar to much of the La Paz Yungas where cloud forest, humid forest, dry forest and montane savanna exist within relatively short distances of one another.
Preliminary data indicate that the Madidi-Apolo region is diverse and interesting, probably with more than 5000 species of vascular plants. Podocarpus and Prumnopitys (Podocarpaceae) have been found at elevations as low as 1400 m; also common are typical cloud-forest elements such as Cyathea (Cyatheaceae); Clusia (Guttiferae); Schefflera, Dendropanax (Araliaceae); Hedyosmum (Chloranthaceae); and Clethra (Clethraceae), as well as numerous species of Melastomataceae and Rubiaceae. Epiphytic mosses, orchids and ferns are particularly abundant.
Montane forests at 400-700 m are highly diverse in species of Sapotaceae and Lauraceae; a species of Ampelocera (Ulmaceae) is common, as are Poulsenia, Clarisia and Pseudolmedia (Moraceae). Also well represented are Leguminosae (particularly Inga), Meliaceae, Myrsinaceae, Rubiaceae, Melastomataceae and Guttiferae. As at the higher elevations, epiphytes are abundant and diverse - particularly orchids and ferns.
The premontane forest has numerous interesting plants not previously known to occur in Bolivia (Foster, Gentry and Beck 1991). These include Wettinia and Wendlandiella (Palmae), Anthodiscus (Caryocaraceae), Pterygota (Sterculiaceae) and Huberodendron (Bombacaceae). The predominant family is Moraceae; also well represented are Annonaceae, Araceae, Bignoniaceae, Euphorbiaceae, Leguminosae, Melastomataceae, Myristicaceae, Palmae and Rubiaceae.
On the dry ridgetops two generic novelties for Bolivia were discovered - Lecointea (Leguminosae) and Caryodendron (Euphorbiaceae). One of the most common species is an undescribed taxon in the Malvales; lack of good flowering material has impeded its determination as either a Reevesia (Sterculiaceae) or an undescribed genus in Malvaceae.
Montane forests near Apolo apparently are similar in composition to "yungas" forests in the adjacent Province of Larecaja, where dozens of endemic species have been described (Rusby 1893-1896, 1907). Fortunately, unlike that region, much of the vegetation near Apolo remains relatively undisturbed. Montane savanna near Apolo seems to have some affinity to the "cerrado" of Brazil, as evidenced by Dilodendron bipinnatum (Sapindaceae), a species previously thought to be restricted to the Brazilian Shield region.
Humid savannas near Ixiamas have species new for Bolivia (as yet unidentified) in the Burmanniaceae, Eriocaulaceae and Xyridaceae, and Schizaea incurvata - a fern known in northern South America, with a single report from Peru. Intriguing as well is the apparent lack of floristic similarity of the Ixiamas pampas to other nearby savannas in the Beni (S. Beck, pers. comm.) or to the Heath pampas in Peru (A. Gentry, pers. comm.).
The Amerindian residents of the region have much knowledge about the native plants and their uses. The Alto Madidi is sparsely populated, and utilization of plant products has been largely restricted to local needs, such as construction timber (many tree species), palm thatch, fibres from tree bark (Annonaceae, Lecythidaceae, Tiliaceae), and medicinal plants. Many trees with edible fruits are used as a means to increase hunting success.
Economically, palms are very diverse, and many have oil-rich fruits or seeds with potential as non-timber forest products (Moraes 1993). Until the 1960s the region was a major centre of quinine-bark production (Cinchona officinalis). Currently there is a great deal of logging activity centred on Swietenia macrophylla (Meliaceae), with secondary interest in Cedrela odorata (Meliaceae) and Amburana cearensis (Leguminosae). Many other valuable timber species occur in the region but have not been exploited commercially.
Social and environmental values
The Alto Madidi is home to two groups of indigenous peoples. The Tacana reside near Ixiamas and Tumupasa in the piedmont of the Serranía del Tutumo. Lowland Quechua are found in several small settlements along the Tuichi River and near Apolo. Both peoples have a long history of commerce and interaction dating at least from Spanish settlement of Apolo in the 17th century. These groups are subsistence agriculturists, who depend extensively on the forest to provide a substantial part of their diet (R.M. Ruiz, pers. comm.). Although no detailed ethnobotanical studies have been made, anecdotal information indicates that the Tacana practise silviculture in the forests surrounding their villages to promote the growth of desirable fruit-bearing trees.
The Tuichi watershed is probably important for several endemic species of fishes restricted to the Beni River watershed (J. Sarmiento, pers. comm.). The Tuichi River is the only major tributary free of heavy-metal pollution. Much of the Beni watershed is polluted by effluent from La Paz (Boopi River-La Paz River) or by mercury pollution from gold-mining activities along the Tipuani-Mapiri River.
The fauna of Alto Madidi is comparable to the flora for diversity and interest (cf. Pearman 1993), and is similar in composition to adjacent areas of Peru. Bird diversity in the less than 100,000 km² of south-western Amazonia that includes this region is thought to be one of the highest on the continent, with c. 10% endemism (Parker 1991). Large mammals are unusually abundant, particularly tapirs and spider monkeys (Emmons 1991). Several endangered species are known to occur in the region, among them spectacled bears (Tremarctos ornatus) and short-eared dogs (Atelocynus microtis).
Tourism dates from at least the early 20th century when the Mulford biological expedition passed through Rurrenabaque and Ixiamas on its way to Manaus (Rusby 1922). Currently there are two ecotourism companies in Rurrenabaque that specialize in river trips up the Tuichi River. Salt licks along the Tuichi have been identified by C. Munn (Wildlife Conservation International), and the potential for showing macaws and other impressive animals is likely to increase ecotourism.
As in so much of Latin America, the Madidi-Apolo region is undergoing profound changes in land use; here the impetus is timber exploitation and colonization. These two factors will have a particularly synergistic and potentially destructive effect in northern La Paz. Comparison of satellite images from 1985 and 1990 revealed that 3697 km² of lowland and montane forests had been cleared in La Paz Department (11.7% of the total forested area), with an annual rate of deforestation of 91.3 km² (CUMAT 1992).
Bolivia is one of the world's largest producers of mahogany (Swietenia macrophylla), but over-exploitation and deforestation in Santa Cruz and the Beni have forced searchers to more remote regions of the country. Mahogany tends to be found in relatively dense stands (1-3 trees per ha) that are widely dispersed over a large geographic area. Timber companies typically build extensive road networks, log the mahogany populations and then abandon the forest (Synnott and Cassells 1991; cf. Rice, Gullison and Howard 1995).
The creation of roads in Bolivia is inevitably followed by colonization. This is particularly true in the Department of La Paz, where soil depletion and expanding populations in the Yungas and Alto Beni provide a constant stream of migrants to the newly opened lands of the frontier. Currently, the southern (i.e. Rurrenabaque-Ixiamas) portion of the La Paz-Pando highway is heavily settled, and it is inevitable that colonization will expand as new roads are made. Unlike the indigenous peoples of Iturralde Province, the colonists are market-oriented agriculturists with strong commercial contacts in the city of La Paz. They usually clear and cultivate five to ten times as much land per year as do the subsistence indigenous farmers.
Multinational oil corporations have been awarded long-term concessions along the Madre de Dios River and in the front ranges of the Andes. It is yet unclear whether there are sufficient petroleum reserves to justify extraction. Due to the region's remoteness, it is unlikely that any potential extraction will occur prior to the year 2000. Pipeline construction would necessitate extensive road building; the oil companies have expressed an interest in working with Bolivian agencies to minimize deforestation.
Madidi was recognized in 1990 as the most diverse humid forest ecosystem in Bolivia by Conservation International's Rapid Assessment Program (Parker and Bailey 1991). Since then the Global Environment Facility (GEF) (World Bank) has designated the Alto Madidi as one of nine priority conservation areas in Bolivia.
In 1992, the Bolivian Government contracted a team of biologists and anthropologists to recommend boundaries for a National Park. They recommended establishment of an 18,000 km² reserve (CDC 1992). The proposed Madidi National Park, which has strong support from the indigenous people in the area, would encompass most of the region's vegetation types. The proposed park is adjacent to Peruvian protected areas (Santuario Nacional Pampas del Heath, Zona Reservada Tambopata Candamo - see CPD Site SA10), as well as other designated protected areas in Bolivia (Pilón Lajas NP, Manuripi-Heath NP). The Madidi park would unite these reserves into a very large preserved region.
Opposition to the park has been expressed by colonist unions and the forest industry. Lumber companies have short-term concessions within the proposed park boundaries and are demanding that these pre-existing concessions be honoured. The actual boundaries for the park, as well as permitted activities within the area, would be determined by Presidential decree. It is approaching four years since the formal proposal was made by the Environmental Secretariat of the Bolivian Government to create a National Park in the region. Definitive action was taken in December 1995 to grant this important area formal status as a National Park.
The recent legal formalization of the status and boundaries of the NP included creation of a participatory commission where the local inhabitants are directly involved in the park's management. This approach should provide a forum where land-use conflicts can be equitably dealt with. Although all of Iturralde Province was declared a Forest Reserve and is legally off-limits to agriculture, colonization is proceeding at a very rapid rate. The areas surrounding the park will continue to face substantial pressure from timber companies and colonists. At present, there is no integrated management programme being implemented in the region or developed. Thus, the long-term prospects for conservation of biological diversity in the whole region remain in doubt.
Map 71. Madidi-Apolo Region, Bolivia (CPD Site SA36), showing Madidi National Park (as proposed)
CDC (1992). Propuesta del Parque Nacional Madidi. Report by the Centro de Datos para la Conservación de Bolivia (CDC), Instituto de Ecología, Museo Nacional de Historia Natural, La Paz.
CUMAT (1992). Desbosque de la Amazonía boliviana. Centro de Investigaciones de la Capacidad de Uso Mayor de la Tierra (CUMAT), La Paz.
Emmons, L.H. (1991). Mammals of Alto Madidi. In Parker III, T.A. and Bailey, B. (eds), A biological assessment of the Alto Madidi region and adjacent areas of Northwest Bolivia, May 18-June 15, 1990. RAP (Rapid Assessment Program) Working Papers 1, Conservation International (CI), Washington, D.C. Pp. 23-25.
Foster, R.B. (1991). Plant communities of Alto Madidi, Bajo Tuichi, and the foothill ridges. In Parker III, T.A. and Bailey, B. (eds), A biological assessment of the Alto Madidi region and adjacent areas of Northwest Bolivia, May 18-June 15, 1990. RAP Working Pap. 1, CI, Washington, D.C. Pp. 15-19.
Foster, R.B. and Gentry, A.H. (1991). Plant diversity. In Parker III, T.A. and Bailey, B. (eds), A biological assessment of the Alto Madidi region and adjacent areas of Northwest Bolivia, May 18-June 15, 1990. RAP Working Pap. 1, CI, Washington, D.C. Pp. 20-21.
Foster, R.B., Gentry, A.H. and Beck, S. (1991). Plant list: Alto Madidi, Bajo Tuichi, and the foothill ridges. In Parker III, T.A. and Bailey, B. (eds), A biological assessment of the Alto Madidi region and adjacent areas of Northwest Bolivia, May 18-June 15, 1990. RAP Working Pap. 1, CI, Washington, D.C. Pp. 75-92.
Moraes-R., M. (1993). Diversity and uses of Bolivian palms. I. Southern area of Iturralde Province, Dept. La Paz. International Foundation for Science D/1585-1. 8 pp.
Oblitas-G., J. and Brockmann-H., C.E. (1978). Mapa geológico de Bolivia. Servicio Geológico de Bolivia (GEOBOL) and Yacimientos Petrolíferos Fiscales de Bolivia (YPFB), La Paz.
Parker III, T.A. (1991). Birds of Alto Madidi. In Parker III, T.A. and Bailey, B. (eds), A biological assessment of the Alto Madidi region and adjacent areas of Northwest Bolivia, May 18-June 15, 1990. RAP Working Pap. 1, CI, Washington, D.C. Pp. 21-23.
Parker III, T.A. and Bailey, B. (eds) (1991). A biological assessment of the Alto Madidi region and adjacent areas of Northwest Bolivia, May 18-June 15, 1990. RAP Working Pap. 1, Conservation International, Washington, D.C. 108 pp.
Pearman, M. (1993). The avifauna of the Río Machariapo dry forest, northern La Paz Department, Bolivia: a preliminary investigation. Bird Conserv. Internat. 3: 105- 117.
Rice, R.E., Gullison, T. and Howard, A.F. (1995). Ecology, economics and the unsustainable harvest of tropical timbers: the case of mahogany in the Chimanes Forest, Bolivia. In MacBryde, O.H. (ed.), Measuring and Monitoring Forest Biological Diversity: The International Network of Biodiversity Plots. International Symposium, May 23-25, 1995. Smithsonian Institution / Man and the Biosphere Biodiversity Program, Washington, D.C. P. 92.
Rusby, H.H. (1893-1896). On the collections of Mr. Miguel Bang in Bolivia, I-III. Mem. Torrey Bot. Club 3: 1-67, 4: 203-274, 6: 1-130.
Rusby, H.H. (1907). An enumeration of the plants collected by Miguel Bang, IV. Bull. New York Bot. Gard. 4: 309-470.
Rusby, H.H. (1922). Report of work on the Mulford Biological exploration of 1921-1922. Mem. New York Bot. Gard. 29: 101-112.
Synnott, T.J. and Cassells, D.S. (1991). Evaluation report on Project PD 34/88 rev.1 (F), Conservation, management, utilization and sustained use of the Chimanes region, Department of Beni, Bolivia. International Tropical Timber Council, Tokyo.
This Data Sheet was written by Dr Timothy J. Killeen (Museo de Historia Natural Noel
Kempff Mercado, Casilla 2489, Av. Irala 565, Casilla 2489, Santa Cruz, Bolivia and
Missouri Botanical Garden. P.O. Box 299, St. Louis, MO 63166-0299, U.S.A., or Casilla
8854, La Paz, Bolivia).
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