In the heart of the South American continent Bolivia is situated, the country often referred to as the Tibet of South America. The comparison is telling that Bolivia’s landscape is a mosaic of high mountain peaks, low land valleys, and extensive forest. However today’s landscape in the high Andes of Bolivia is dominated by open grasslands, bushy steppes – tholares – and the huge salt pans. In the lower-lying valleys – the valles – where most of the Bolivian population is concentrated, flat areas are subject to intensive agriculture, while the shrub-covered mountain slopes are used as a pastures. With the exception of planted Eucalyptus and Pinus, trees are mostly absent in these regions.
Small patches of native high – elevation prime forest are however found occasionally. These forest patches, dominated by species of the genus Polylepis occur at altitudes of up to 4 200 meters in the Eastern Cordillera and up to 5,200 meters on volcanoes near the Chilean border, making themselves the highest woody plant formation on earth. Until a few decades ago, researchers believed that the occurrence of such small isolated forest patches was caused by specific microclimatic conditions which restrict tree growth to the sheltered ravines, boulder slopes and rock faces. Recent ecological, biogeographic, and phytosociological evidence has shown, however, that these patches are remains of widespread forests which have been almost entirely wiped out as a result of human impact.
The two main factors directly effect the shrinking of Polylepis forests are overgrazing and the use of the fire. Significant part of the Bolivian highlands is burnt annually to enhance the growth of pasture grasses or frequently for no apparent reason. These fires frequently do not kill adult trees and therefore have been disregarded as a threat to the forests. They do, however, damage seedlings and prevent forest regeneration. Grazing animals have a similar though usually not as through effect on forest. Since Polylepis resprouts readily after being cut, timber extraction does not lead to the disappearance of the forest unless it is conducted on a commercial basis or in patches of forest that are already severely degraded.
The forests began disappearing during the time of the pre - Incas, long before the arrival of the conquistadors in 1531. Hunter - gatherers and pastoral nomads were setting fires to clear the land for easier hunting and increased grazing, thus pushing the woodlands to places inaccessible or unsuitable for use. Ultimately these societies gave way to permanent agricultural communities and highly developed cultures, such as the Inca, which appreciated the importance of forests as sources of fire wood and watershed protection. Although the Inca terraced high mountain slopes, potentially removing Polylepis, they also strictly protected trees and forests by laws that threatened to severely punish anyone who disrespected the land. The conquistadors changed all that. They disrupted the entire social system, practiced unsustainable land-use methods and over harvested for the sake of mining.
Polylepis forests, before introduction of sheep and cattle by conquistadors, had covered vast areas extending from Venezuela to Argentina and thus perpetuating productive microhabitats in otherwise exposed and severe highland conditions. Thanks to the tree’s ability to live in harsh places that man cannot easily access, patches do still thrive, although at a surprisingly low amount. In Bolivia, only 10 % of the original cover remains today, mostly in the Western Cordillera. What is further surprising, that these statistics have not resulted in Polylepis being listed as endangered. The patches that are still present are doing well, but again this is attributed to their relative inaccessibility.
Contained within these isolated patches is a wealth of unique flora and fauna. Polylepis forests are made up of 20 evergreen tree species belonging to the rose family. Those natural forests have up to 270 species of higher plants. Large, undisturbed forests also support a variety of mammals such as pumas (Puma concolor), Andean deer (Hippocamelus antisiensis), and Mountain viscachas (Lagostomus viscaccia). Up to 25 bird species, many of which are threatened endemics, occur exclusively in Polylepis woodlands. Examples include the Giant Conebill (Oreomanes fraserii), the White-browed Tit-Spinetail (Leptasthenura xenothorax), the Royal Cinclodes (Cinclodes aricomae) and the Ash-breasted Tit-Tyrant (Anairetes alpinus). For the Andean people, Polylepis forests also represent an important natural resource. A study done in Bolivia revealed that 91 % of the plant species are sustainably used for natural medicines, food, and for construction and ritual purposes.
Possibly more important than the decline of biodiversity is the loss of ecosystem functions provided by natural forests. Reduced water catchment’s capacity and increased soil erosion are probably the most important consequences of forest destruction. Without trees to slow run-off, absorb excess water and hold the soil together, massive amounts of fertile topsoil have been lost to erosion. The aggregated effect of unsustainable land-use practices, of which forest destruction is only single component, is an overall decrease in agricultural productivity in degraded areas. This condition forces inhabitants to use their land ever more intensively which then leads to even greater depletion of resources. In addition this vicious circle is coupled with a growing human population, what makes Bolivia one of the least densely populated countries in South America.
The traditional approach of preserving Polylepis forests in Bolivia with the establishing national parks or restricted-access forests would not be appropriate approach. Most forest remnants are simply too small and too important resource for local people. It would be not feasible to displace indigenous inhabitants from areas they have been traditionally using for many centuries. In most cases, conservation of Polylepis forests will only be possible in co-operation with local people. Involvement and awareness of the ecological importance of the forests among villagers are required to arouse their interested in Polylepis protection.
Current unsustainable land-use practices need to be converted to sustainable through implementation the spatial separation of land with different uses. Traditional and modern techniques such irrigation, terracing, agroforestry, intercropping would reduce soil erosion and increase land recuperating. Many communities are willing to adopt those novel land-use techniques but at least some traditional components should be contain in changes in order to make it easier for the people to accept them.
Conservation of Andean ecosystems must be pursued concurrently with the problems of the community as a whole. Health, nutrition and education are the main needs. Solving the problem of unsustainable wood consumption is another key to successful conservation Polylepis forests together with endangered species which live within them. One example of such attempt is the Polylepis Project looking for the cooperation with three local villages in order to protect the forests and develop alternatives for fuelwood and timber. As part of the project reafforestation with native tree species has been initiated.
Additional source of income for indigenous people might also be helpful. Such a profit might be fetched by development of local ecotourism. Nature lovers would travel far to see pristine Polylepis forests with abundance of endangered species. If this ecosystem is provided with the necessary conservation activates, villagers may eventually be able to host and show visitors the fruits of their labors and gaining some income at the same time.
At present, aid organization, Bolivia’s government and international organization must revise their strategies to favor long-term development over short-term profit and to give preference to implement real solution rather than simply treating symptoms.
Michael Kessler (1998): Land use, economy and the conservation of biodiversity of high-Andean forests in Bolivia. In: W. Barthlott and M. Winiger (eds.): Biodiversity. A Challenge for Development Research and Policy. Springer, Berlin, pp. 339–351.