Peruvian geographer Javier Pulgar Vidal (1987) divides Peru into eight “natural regions” based on climate, altitude, and indigenous land use (Figure 6.2). With some alterations, these zones apply to the rest of the Central Andes. After reviewing this modern classification, we will note some of the natural and cultural factors that have caused change in the
Figure 6.2. Cross'section of the Central Andes showing the major environmental zones according to Pulgar Vidal (1987). (Adapted from Richardson 1994).
Andean environment over the span of human occupation and briefly sample some of the major issues in the study of prehistoric human-environment interaction in this region.
Pulgar Vidal (1987) uses Quechua folk terminology to label his “natural regions.” Though these regions are organized from west to east and largely along the altitudinal gradient that so strongly affects local climate and environment in this tropical region, there are important latitudinal (north-south) gradients as well. For instance, coastal aridity increases to the south from the Ecuadorian-Peruvian border to the Atacama Desert of northern Chile, while the average impact of El Nino events decreases along the same trend. The high elevation puna zone (see below) of central and southern Peru grades north into the moister paramo of Ecuador and south into the more arid Salt Puna and Dry Puna of northern Chile and adjacent regions.
Pulgar Vidal’s (1987) first zone, chala, runs from the Pacific shore up the western slopes to about 500masl. Though a desert in Peru and Chile, this coastal zone is covered with dense fog or garua in the austral winter. The presence of a desert on a tropical coast results from two factors: the rain shadow of the high Andes and the cold Humboldt or Peru Current that flows from Antarctica north as far as the Illescas Peninsula in northern Peru. Above 200 masl and up to 1,000masl in places, the garua permits a xerophytic plant community known as lomas that provided some plant foods, fuel, and faunal resources for early inhabitants of the western slopes. The desert becomes more extreme as one moves south, while to the north (into Ecuador) the coastal zone receives more precipitation but garua does not form. The chala is broken by river valleys that run perpendicular to the coastline; some have year-round flow while others are ephemeral. From the earliest occupation, the valleys have provided people with water and plant and animal resources. Irrigation and, with it, intensive farming of the fertile valley floors began at least 4,400 years ago in some coastal valleys and probably as early as 6,100 years ago in quebradas of the western slopes (Burger 1992; Dillehay et al. 2005; Grieder et al. 1988; Quilter et al. 1991; Shady Solis et al. 2001). Finally, thanks largely to nutrient upwelling in the Humboldt Current, the Pacific Ocean off Peru and Chile constitutes one of the world’s richest fisheries. Even the first inhabitants of the region made extensive use of marine resources as much as 13,000 years ago (Sandweiss et al. 1998, 1999; see also Chapter 10), and fishing has remained important through the present.
The next zone is the yunga, present on the western slopes overlooking the Pacific Ocean from 500 up to 2,300 masl, and on the eastern slopes overlooking the Amazon basin from 2,300 down to 1,000 masl (Pulgar Vidal 1987). Cut by deeply incised river valleys and dry quebradas, the western or maritime yunga consists of parched hillsides and mountain slopes where only lomas plants grow (at the lower elevations) during the winter. Under normal circumstances, agriculture is possible only in the valleys. The eastern or fluvial yunga consists of forested slopes, deep valleys, and lateral quebradas. This zone receives more regular and abundant precipitation than the maritime yunga and offers forest products as well as potential for agriculture. Most indigenous Andean crops grow in irrigated regions of both the chala and the yunga zones.
Moving up, the quechua zone lies between 2,300 and 3,500 masl and includes some of the most productive land in the Central Andes. Here the terrain rises in smooth steps above rich valleys. Rainfall is seasonal and both rain fed and irrigation agriculture is possible. In later prehistory, terracing became an important means of increasing the amount of arable land in the quechua zone and above. The quechua zone is the upper limit of maize cultivation, and many other Andean crops grow well here. Average annual temperature ranges between 11° and 16° C, with maximum temperatures as high as 29° C and minimums as low as -4° C. Though there are some seasonal differences, diurnal variation is much more striking and significant, as geographer Carl Troll (1958) pointed out half a century ago. In the higher reaches of the quechua zone, warm days can alternate with nights below freezing. Here, and in higher elevation zones, Andean people have long taken advantage of this cycle to make freeze-dried potatoes known as chuno and dried camelid (llama, alpaca, and relatives) meat called charqui (jerky in American supermarkets and convenience stores). These are storable staples with a long shelf life.
It is in the quechua zone (Pulgar Vidal 1987) that one reaches an important potential barrier for human habitation: the effects of decreasing oxygen saturation with altitude. Looking at biological studies of the effects of altitude on human health and reproduction, both Richardson (1992) and Aldenderfer (1998) have suggested that the initial colonization of the Andes above about 2,850 masl may have required a multi-generational period of gradual adaptation to altitude.
Pulgar Vidal (1987) defines the region from 3,500 to 4,000 masl on both the eastern and western sides of the Central Andes as suni or jalca. This is a steeper terrain than the quechua zone, with high relief and narrow, rocky quebradas. Only limited areas are suitable for agriculture. The climate is cool, with average annual temperatures between 7° and 10° C and a maximum-minimum range of 20° to -16° C. Many high altitude Andean crops grow here, including the chenopods quinua and canihua, the lupin tarhui, the fava bean or haba, and tubers such as oca and olluco.
The highest permanently habitable zone is the puna, from 4,000 to 4,800masl (Pulgar Vidal 1987). This is a relatively low relief, high altitude grassland that appears as north-south strips including the altiplano of southern Peru and Bolivia around Lake Titicaca. The puna is a cold region, with average annual temperature between 0° and 7° C. Like the quechua and suni zones, however, there is strong diurnal variation, and days can be quite warm. The potato (Solanum tuberosum) is the most important of the few indigenous domesticates that grow in the puna zone. Other important crops in the puna zone include canihua (Chenopodium pallidicaule), which grows to 4,400 masl, and quinoa (Chenopo-dium quinoa), which grows in the puna zone in Ecuador but only to about 4,000 masl in Peru, Bolivia, and northern Chile (National Research Council 1989). However, this region is the home of the Andean camelids, the wild guanaco (Lama guanicoe) and vicuna (Lama
Vicugna) and the domestic llama (Lama glama) and alpaca (Lama paces). These animals were an important source of meat and wool for Andean peoples, and domesticated llamas also served as beasts of burden (though with a very limited maximum load, about 25 kg or one sack of potatoes).
The janca zone runs from 4,800 masl to the top of the Andean peaks (Pulgar Vidal 1987). Though visited by prehistoric people (e. g., Reinhard 2005), the low temperatures and lack of oxygen make this a poor place for habitation. Still, the glaciers and snowcapped peaks of the janca are the origin of the rivers that water the Central Andes.
On the eastern slopes of the Central Andes, below the yunga lies the rupa-rupa or high jungle zone from 400 to 1,000 masl (Pulgar Vidal 1987; it is called ceja de selva or eyebrow of the jungle in Peruvian Spanish). This is a warm, humid, well-vegetated region of broken terrain cut by valleys and quebradas. Average annual temperature ranges from 22° to 25° C and it never freezes. Both farming and herding can be practiced here.
The final zone is the Amazonian jungle or emagua. This hot, wet environment has many peculiarities of importance for understanding human adaptations, but it lies outside the scope of this chapter (see Chapter 12 in this volume).
World History
