|Biological Monitoring: Signals from the Environment (GTZ, 1991)|
|Concept for a biological monitoring study:|
|2. Study area: the central Andean plateau|
The major source of livelihood of the population of the Altiplano is agriculture. Productivity is constrained by a number of natural factors, above all:
- extreme climatic conditions (dryness and cold, frosts)
Figure 4: The mosaic of agricultural land use on the Bolivian Altiplano near Huaraco (north of Oruro). Dry farming predominates in thc scmihumid part ot the Altiplano, with long fallow periods during which the fields are pastured.
Figure 5: Pastureland on the alluvial plain of the Rio Desaguadero south of´ Huaraco on the Bolivian Altiplano.
- infertile soils (poor nutrient availability, low humus content, risk of salinization) - the susceptibility of vegetation-poor areas to soil erosion.
The population has adapted to conditions on the Altiplano by developing a mixed and highly diverse system of crop and livestock raising (Fig. 4). At higher elevations, the lower rainfall, greater aridity and lower temperatures cause extensive livestock raising to gain in importance over the growing of crops.
In addition to indigenous crops, especially tubers and Andean orache, several European crops are also grown (RUTHSATZ 1983). Livestock is grazed on mountain slopes at elevations of up to above 4500 m above sea level. During the winter dry season, the "hard-cushion bogs", which are to some extent artificially irrigated, and alluvial plains represent the most favorable pasturelands (Fig. 5). The intensive grazing practiced in these ecosystems, which are relatively unproductive in any case, can lead to serious damage by erosion (ELLENBERG 1984; MILLONES 1982; WENNERGREN 1975).
The food produced in the Andes is barely sufficient to meet the nutritional needs of the farmers and shepherds themselves. A few products make their way to local markets, but with the exception of wool (alpaca, lame and sheep), the agricultural products of the Altiplano are of virtually no importance for export.
Besides the above-mentioned natural constraints on agricultural production, other negative factors are an inadequate network of roads and a lack of capital for purchase of fertilizers and pesticides. The only exceptions are areas in the immediate vicinity of larger cities, and the climatically more favorable area around Lake Titicaca.
While production of barley, potatoes and dried beans increased sufficiently between 1963 and 1972 to keep pace with population growth, the supply of the indigenous crops of oca, quinoa and papalisa has significantly worsened (WENNERGREN 1975). Bolivia's population is expanding so swiftly, however, that much higher growth rates are needed in the agricultural sector. Iligh priority must be assigned to conserving soil fertility, which is being jeopardized by European farming methods that aggravate the ongoing erosion, by overgrazing and possibly, an aspect which remains to be investigated, by the influence of environmental contaminants.