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Soil erosion: diagnosis and source
A NATURAL PHENOMENON: A MOUNTAIN ENVIRONMENT
TABLE 43
Agrarian structure in Ecuador 1954-1985: number of holdings and area occupied (expressed as percentages)
|
Size in ha |
1954 |
1974 |
1985 | |||
|
Number |
Area |
Number |
Area |
Number |
Area | |
|
0-20 |
90 |
17 |
85 |
19 |
83 |
20 |
|
20-100 |
8 |
18 |
12 |
34 |
15 |
44 |
|
> 100 |
2 |
64 |
2 |
48 |
1 |
35 |
The Sierra is an enormous mountain barrier, 100 to 120 kilometres wide, made up of two parallel ranges (the Cordilleras) with a depression between them formed by a succession of fault basins. The main landforms are as follows:
• In the intra-Andean zone there are two distinct tiers within watersheds. Below 2400 m the terrain is relatively flat (0 to 20% slope) with scattered shrubby xerophytic plant cover. The people live in small villages and grow irrigated crops: sugar cane, fruit trees and vegetables. Evidence of erosion can be seen everywhere - not only in the irrigated areas where there is insufficient control over water, but also in the areas poorly protected by the shrubby plant cover. However, most-of the Sierra landscapes lie on the second tier between 2400 and 3200 m, which has the following features:
• a tight network of ravines and cañones - evidence of active headward erosion where slopes are over 70%; there is very little agriculture, and only shallow soils;
• flat runon areas (less than 10% slope) where the large cattle ranches (haciendas) are found; the landforms between these areas and the ravines are much less regular (25 to 50% slopes), with a pronounced shrinking of small maize plots in the face of long-standing and very active erosion;
• either pediment-terraces or debris cones, rising up to the mountainous zone; on slopes of less than 25 % animal husbandry flourishes on large- or medium-sized farms (haciendas with hundreds of hectares, or fincas with tens of hectares); higher up, between 3000 and 3200 m, are the first escarpments, where the first wave of minifundios has been established, a development that has led to increased erosion.
• On the ranges or cordilleras, the Andean highlands start at 3200 m (De Noni and Viennot 1985), and it is here that minifundios have spread extensively in the last ten years. Potato, onion, broad bean, barley, quinoa, lupin, etc. are grown as high as 3800 m, where extensive sheep and goat-rearing takes over - and sometimes llamas, which can go as high as 4400 m. The ever-increasing inroads of agriculture in this environment is reflected in active degradation.
• Lastly, on the outer slopes, gradients are even steeper (over 70%). Erosion is localized and depends on soil instability, which increases as the natural vegetation and pastures are steadily replaced by tropical crops.
The Andes thus constitute an environment very prone to erosion (through the action of rain and humans), since there is a relationship between slope, speed of flow, volume of runoff and intensity of erosion.
AN HISTORICAL PHENOMENON: MINIFUNDIOS AND HACIENDAS
The Sierra is the region of the country with the greatest population pressure on land. As a general rule, heavy population densities, varying from 50 to over 200 per km² (Ambato region) (Delaunay 1989), characterize the minifundios. The distribution of farm units (number and area), based on Ministry of Agriculture censuses, is given in Table 43.
For all years, minifundios (0 to 20 ha) account for more than 80% of the farm units, but occupy only 20% of the arable land and are located mostly in places where it is hard to get a good return. The good flat land in the watershed is managed by the haciendas for extensive cattle ranching. This paradoxical situation is the outcome of an historical process with three key phases (De Noni 1986):
• the historical consequences of the Spanish conquest were dramatic, leading to a general decline in population (through war, disease, etc.); in practice, the indigenous people were treated as slave labour and were herded together on to huge estates, which then quickly developed into the large farms better known as haciendas;
• since the beginning of this century, Ecuador has seen a remarkable expansion in population, particularly in the rural sector; in 1586, the population of the whole country was about 150000; between 1780 and 1886, it doubled from 500000 to 1000000; and between 1886 (Estrada 1977) and 1989 it increased tenfold, reaching 10500000;
• in the face of the widespread discontent of a rapidly growing population, on 11 July 1964 the military government then in power passed an agrarian reform law with the aim of abolishing the virtual condition of servitude (huasipungo) to which the numerous labourers on the haciendas had been reduced since the conquest; the large landholders were to surrender their privileges and give up a part of their land; this is how the minifundio agrarian system developed, with the units being run by small peasant farmers who were now free landowners; in reality, however, the haciendas kept the best land for themselves, yielding only inhospitable land to the agrarian reform.