Beni savanna

• Category: Grassland, Tundra, and Human Biomes.
• Geographic Location: South America.
• Summary: This large, flood-prone tropical savanna in the lowlands of Bolivia constitutes a unique and exceptionally adaptive cultural landscape, with high levels of species and ecosystem biodiversity.

The Beni savanna occupies a large area in the warm tropical floodplains of the Mamoré and Beni Rivers in eastern Bolivia; it constitutes the largest area of flooding savannas in the Amazon drainage basin. It is surpassed in size only by the Llanos del Orinoco in Venezuela and the Pantanal of Mato Grosso in Brazil, which belong to the Orinoco and La Plata River basins, respectively.

Most of this region is flooded each year by overflowing rivers during the rainy season. The flooding extends roughly from December to June. By contrast, the other months are characterized by a marked shortage of rainfall, leading to a long dry season, which has its greatest intensity in the relatively cooler months of the year. The marked seasonal rhythm imposed by the annual flooding and drought is the main factor that influences the functioning of ecosystems in the Beni, the traditional patterns of human settlements, and the use of landscape and natural resources.

Overall, the Beni has a flat topography, forming an extensive alluvial plain. This plain has a characteristic microrelief pattern with altitude differences of just a few feet (meters) or less between different landforms. In this sense, the Beni has four main land units that are closely related to the intensity and duration of floods: not-flooded areas (upland or altura), scarcely flooded areas (wetland or semialtura), seasonally flooded areas (low and depressional lands, or bajura estacional), and permanently flooded areas (swamps, marshes, and lakes, or bajura permanente).

The Beni generally has nutrient-poor soils, particularly in the more distant, vast plains of the major river channels, which are seasonally flooded both by rainwater and by overflow from rivers and streams in the secondary river system, carrying mostly clear or black nutrient-poor waters. By contrast, the recent alluvial plains close to major rivers have richer soils because they are inundated by white water carrying considerable amounts of suspended sediment and average to moderate concentrations of dissolved mineral salts. This spatial pattern of soil fertility explains the preferential location of traditional human settlements on the banks of the rivers, where growing crops is possible and where transport through the river is easy with canoes and boats. In addition, the banks are topographically higher than the surrounding savanna plains and thus are affected only by floods of low intensity and duration.

Human Populations and Activities

The Beni savanna was originally populated by several indigenous groups, mostly belonging to the Arawak, Movima, Moseten, and Yurakare linguistic families. The largest populations today are the Mojeño and Baure (Arawak), Movima, Tsimane (Moseten), and Yurakare. The first three are the more numerous groups; they still have a traditional ethnic economy based on small farming and ranching, supplemented by fishing, hunting, and gathering in the savannas, forests, and rivers. By contrast, Yurakare and Moseten are eminently fishers, hunters, and gatherers—seminomads who practice cultivation only on a very small scale.

After the Spanish colonization and the later republic, mixing peoples and races created a significant Creole population. Creole and indigenous people—mostly Mojeño, Baure, and Movima—burn the savanna annually during the dry season so that after burning, the new grass will provide softer, more palatable forage for livestock. Since the introduction of cattle in the Beni by Jesuit and Franciscan missionaries during the seventeenth century, the savanna has undergone a long process of co-adaptation to fire and grazing. Thus, the Beni is now a remarkable cultural landscape where high levels of biodiversity remain, together with traditional patterns of adaptive human practices and use of natural resources.

Despite the creation of an extensive state-protected area that is also Indian territory, officially called Isiboro-Secure Indian Territory and National Park (TIPNIS), this area was threatened by the imminent construction of a new highway between Bolivia and Brazil that would have crossed the park's core area. This development would mean deforestation, loss of critical ecosystems and agricultural frontier, and expansion of the coca monoculture, as well as acculturation and loss of indigenous groups. However, after a sixty-five-day march by environmentalists and Indigenous people garnered international attention, the country's governments revisited the idea and nixed the highway, despite having already begun construction. While the victory offered hope to groups, development threats continue to loom over the region.

Global warming is already forcing changes upon the habitat selection of various species in the Beni savanna. Field studies have revealed, for example, that a number of species have been migrating upslope into the Andes foothills to the west of the savanna, most likely in order to maintain their optimal temperature and moisture conditions.

An area of traditional practice that may have worldwide import as solutions to global warming are sought is the ancient use of pyrolysis or biochar to enrich local soils. Simply put, causing organic matter—wood, grain husks, plant stalks, animal remains—to smolder or carbonize in a low-oxygen trench enclosure was a means of manufacturing a charcoal-like soil enricher. To Portuguese settlers, this native practice was called terra preta do indio; deposits of it are still in use as an extra-fertile soil in many areas of South America. Researchers have in recent years suggested biochar can contribute to carbon sequestration efforts on a global scale, as the process is readily measurable and verifiable—and thus able to be traded as a carbon emissions footprint-reducer commodity.

Bibliography

Hanagarth, Werner, and Stephan G. Beck. "Biogeographie der Beni-Savannen (Bolivien)." Geographische Rundschau, vol. 4, no. 11, 1996, pp. 662-69.

Lima, Ana Rosa De, and Alexandra Ellerbeck. "Nixed Bolivian Highway Offers Environmental Lessons to Big Brazil Bank." Mongabay, 24 Aug. 2016, news.mongabay.com/2016/08/nixed-bolivian-highway-offers-environmental-lessons-to-big-brazil-bank/. Accessed 28 Oct. 2024.

"Main Initiatives in the Beni Biosphere Reserve, Bolivia." UNESCO, 2 July 2024, www.unesco.org/en/amazon-biosphere-reserves-project/beni. Accessed 28 Oct. 2024.

Navarro, Gonzalo, and Mabel Maldonado. Geografía Ecológica de Bolivia: Vegetación y Ambientes Acuáticos. Editorial Centro de Ecología Simón I. Patiño, 2002.

Pouilly, Marc, et al., editors. Diversidad Biológica en la Llanura de Inundación del Río Mamoré. Editorial Centro de Ecología Simón I. Patiño, 2004.

Thomas, Evert. "New Light on the Floristic Composition and Diversity of Indigenous Territory and National Park Isiboro-Sécure, Bolivia." Biodiversity and Conservation, vol. 18, no. 7, 2009, pp. 1847-78.