Location and General Description
The Bolivian Yungas are restricted to west-central Bolivia and extreme southeastern Peru (Olson et al. 2000). The northern, southern, western and eastern boundaries of this ecoregion terminate approximately at the 130 and 170 south latitudes and 690 and 630 west longitudes, respectively (Anon. 1980). The high humidity of the Yungas are from water droplets and rain deposited by northern trade winds (Stattersfield et al. 1998). The topography is complex, ranging from 400 to well over 3500 m asl, with most of the higher peaks accounted for by outlying Andean ridgetops (Stattersfield et al. 1998).
This ecoregion forms a transition along Andean slope between Amazonian and highland Puna habitat (Mee 1999, Olson et al. 2000). The habitat is tropical and subtropical moist broadleaf forest (Olson et al. 2000), including montane cloud forest, and other types of evergreen forest (Stattersfield et al. 1998). Trees are often lined with various epiphytes, including bromeliads, orchids and tree-ferns; Chusquea bamboo characterizes the region (Schulenberg et al. 1998, Whitney 1994, Mee 1999).
The number of endemic species in this ecoregion is high, with 35 range-restricted species and endemics (Stattersfield et al. 1998), including diademed tapaculo (Scytalopus schulenbergi) (Whitney 1994), and green-capped tanager (Tangara meyerdeschauenseei) (Schulenberg and Binford 1985). Additionally, expeditions undertaken just to study such rare and strongly endemic populations, such as the southern helmeted curassow (Pauxi unicornis) (Mee 1999). Althought birds and plants represent the strongest endemics, others include mammals such as the little known brocket deer, (Mazama chunyi) (Tarifa 1996).
Although this ecoregion is strong in montane endemism, other more wide-ranging, lowland dwelling Neotropical mammals are also likely, including species such as lowland tapir (Tapirus terrestris) (Bodmer & Brooks 1997) and jaguar (Panthera onca) (Tarifa 1996). Andean, andean slope, and xeric habitat specialists are also apparently present, such as the spectacled bear (Tremarctos ornatus), Geoffroy’s cat (Felis geoffroyi) and pacarana (Dinomys branickii) (Tarifa 1996).
Fortunately, most protected areas in this ecoregion are difficult to cultivate due to difficult access, steepness of terrain, and very high rainfall (Mee 1999, Herzog pers. comm.). There are a number of relatively large protected areas covering this ecoregion in both Peru (e.g., Tambopata-Candamo Reserved Zone - 14,800 km2) and Bolivia (e.g., Maididi NP 19,000 km2, Carrasco NP – 13,000 km2, Isiboror Sécure NP – 11,000 km2, Amboro NP - 1800 km2, Bellavista Protection Forest Reserve – 900 km2) which equate to over 60,000 km2 of protected area (Stattersfield et al. 1998). The distribution of these protected areas within the Yungas is fairly well covered in light of petroleum concessions and habitat alteration (see above).
Types and Severity of Threats
Although Bolivia has a decent and growing National Parks (NP) system, threats in the form of habitat loss and general degradation due to human activities persist outside protected regions (Mee 1999). This ecoregion is threatened because it is easier for local agrarianists to burn this habitat than true montane forest for growing cash crops (Collar et al. 1992). In some cases crops and logging have increased due to more intensified road-building efforts (Dinerstein et al. 1995). Extensive forest clearance in the Bolivian Andean foothills to cultivate crops has endangered over 70 species of birds, especially in the Departments of La Paz and Cochabamba (Collar et al. 1992). Additionally, certain game species from this ecoregion are threatened by over-harvest for protein and/or the wild bird trade (Mee 1999).
Justification of Ecoregion Delineation
The delineation’s for the Bolivian Yungas were derived from Instituto Geográfico Nacional (1987) for the Peruvian portion and Ribera (1994) for the Bolivian portion. Border areas were done by blending existing information and by expert opinion where matches could not be made. The linework follows the aforementioned authors, whose divisions were lumped to maintain out broader scale assessment. From Ribera (1994), the following vegetation classifications were lumped under yungas: mountain rim yungas (Ceja de Monte en Yungas), humid montane yunga forests (Bosque húmedo montañoso de Yungas), and subandian pluvial forests (Bosque pluvial subandino). Within this linework all areas of secondary and anthropogenic vegetation were included. From Instituto Geográfico Nacional (1987), linework originated from their high elevation forests (Yungas) classification. The line separating these from the Peruvian yungas was derived from significant changes in species distributions and is unique for many endemic species (Stattersfield et al. 1998).
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Prepared by: Dr. Daniel Brooks
Reviewed by: In process