Soil Degradation and Desertification in Bolivia: Causes, Impacts, and Conservation Strategies
Land Degradation Worldwide
The degradation of land globally is a critical issue, stemming from the deterioration of vital resources. UNESCO-UNEP has emphasized the severity of this problem, leading to the 1977 United Nations Conference in Nairobi, which focused on the world’s soil health.
Currently, 1,701 million hectares (Mha) of cultivated land worldwide are at risk of joining the 3,190 Mha of potentially arable land already lost. Water erosion impacts 1,093.7 Mha (22% of the total surface area), wind erosion affects 11%, chemical degradation 5%, and physical degradation 2%. In Latin America, FAO estimates that 600 million hectares are affected by land degradation.
Developed countries with humid climates often face soil contamination as their primary concern, while countries with sub-humid to arid climates struggle with erosion.
Erosion in Bolivia: Introduction
Bolivia’s diverse landscape, ranging from hyper-arid to arid zones, presents a variety of challenges and opportunities for land use. The erosion process in Bolivia is exacerbated by rugged topography and a dry to dry sub-humid climate, with increasingly frequent droughts in recent decades.
These conditions make the land highly susceptible to degradation from water and wind erosion. Studies indicate an annual loss of approximately 1,800,000 tons of topsoil from Bolivia’s 1,500,000 hectares of agricultural land due to erosion, gradually diminishing its productive capacity.
Landholders, often impoverished, lack awareness of this problem, leading to a decline in living conditions with serious consequences for future generations. According to the National Program to Combat Desertification and Drought (PRONALDES-1996), erosion affects 100% of the land in the departments of Oruro, Potosi, Chuquisaca, and Tarija, 32% of La Paz, 33% of Santa Cruz (Chaco), and 46% of Cochabamba.
The arid condition is defined by a water balance deficit, with rainfall 5 to 20 times lower than potential evapotranspiration. In semi-arid regions, rainfall is 1.5 to 5 times lower, and in dry sub-humid areas, it is 0.65 to 1.5 times lower.
The region affected by erosion in Bolivia encompasses approximately 450,000 km2 (41% of the total land area), home to 77% of the population (approximately 6,370,000 inhabitants). This erosion leads to the loss of productive soils, vegetation cover degradation, biodiversity loss, increased poverty, and technological, legal, and institutional deficiencies, significantly impacting the quality of life in the affected regions.
Causes of Soil Degradation in Bolivia
The primary causes of land degradation in Bolivia are water and wind erosion, resulting in:
- Topsoil loss
- Changes in the ground surface
- Sedimentation of lowlands, reservoirs, and lakes
- Flooding in riverbeds or drainage areas
- Erosion of riverbanks
- Sediment coating of productive areas, forests, or rangelands
Deterioration of Soil Materials Due to Erosion:
Water Erosion: Characterized by soil loss, modification of the soil surface, and sedimentation of lowlands, reservoirs, and lakes.
Wind Erosion: Characterized by soil loss, modification of the soil surface, and sediment coating of productive areas, forests, and/or rangelands.
Deteriorating Soil Conditions Inherent in Bolivia:
Chemical Deterioration: Characterized by nutrient loss, pollution, salinization, deterioration of soil fertility, and flooding.
Physical Impairment: Characterized by crusting or sealing of topsoil, compaction by machinery or animals, increased salinity (mainly chlorides and carbonates), and deterioration due to hydrological saturation and flooding.
Biodeterioration: Characterized by an imbalance of microbiological activity in the topsoil and drastic changes in the natural soil system.
Description of the Region Affected by Erosion in Bolivia
To facilitate study and description, the region affected by erosion in Bolivia is divided into 5 physiographic provinces, each with distinct characteristics related to erosion problems.
Desertification in Bolivia
The Convention on Desertification, opened in Paris in June 1994, defines desertification as: “Land degradation in arid, semi-arid, and dry sub-humid areas resulting from various factors, including climatic variations and human activities.” This definition highlights the complex interplay of social, economic, physical, biological, and climatic factors contributing to desertification.
Main Factors Affecting the Process of Desertification in Bolivia
According to the Preliminary Map of Land Desertification in Bolivia (1996), pressure on natural resources has intensified since the colonial era, particularly in densely populated areas like the highlands and valleys. This pressure, driven by a mining-based economy, has led to the consolidation of human settlements in specific geographic locations, impacting the resilience of ecosystems and contributing to desertification in Bolivia.
Biological and Physical Factors:
a) Water Erosion: Occurs at the highest rates in the Andean and Sub-Andean regions, which are home to the largest population in Bolivia.
b) Wind Erosion: More prevalent in areas with rainfall below 400 mm/year.
c) Salinity and Sodification: Resulting from irrigation practices in some highland and valley areas, leading to the accumulation of toxic elements like boron and sodium. An estimated 30-40% of irrigated land in the study region faces salinization problems.
d) Drought: Exacerbates desertification, with particularly severe droughts recorded in 1952, 1983, and 1992, impacting arid, semi-arid, and dry sub-humid areas. Recent droughts have been linked to global warming and cooling phases (El Niño phenomenon), causing significant weather changes, floods, and droughts.
e) Mining, Industrial, and Urban Areas: Contribute to land desertification through soil and water contamination. In Potosi, Oruro, and La Paz, toxic liquid waste from mining activities severely damages agriculture, livestock, and forestry. Untreated industrial and urban wastewater further pollutes rivers and adjacent lands, particularly around departmental capitals and major population centers.
f) Loss of Vegetation Cover: Caused by intensive agriculture, grazing, browsing, firewood and construction material extraction, deforestation for agriculture (chaqueo), and forest burning. Negative impacts are evident in the valleys of Chuquisaca, Tarija, Cochabamba, and Potosi, and the highland areas of La Paz and Oruro.
g) Human Settlements: Driven by limited access to basic resources, particularly water, leading to the gradual occupation of productive land and the creation of towns and cities, along with supporting infrastructure. This expansion negatively impacts the extent of productive agricultural land.
Socioeconomic Factors:
a) Poverty: Significantly contributes to desertification by hindering access to healthcare, education, sanitation, energy, and housing, and exacerbating the economic hardship of rural populations, leading to negative environmental impacts.
b) Population Pressure: In valleys and some highland areas, leading to the utilization of marginal lands for agriculture, resulting in shifting cultivation and contributing to the desertification process.
c) Land Tenure: Land fragmentation, often into micro or small plots, due to limited economic alternatives and inheritance practices, contributes to the deterioration of soil quality, particularly in rural areas where land scarcity is prevalent.
Soil and Water Conservation
1. Objectives
- Define concepts of soil and water conservation.
- Understand land use capacity issues.
- Learn about mechanical and agronomic conservation practices for mitigating soil and water erosion.
- Gain an overview of major conservation practices recommended for hillsides.
- Describe the importance of soil and water conservation as a practical system.
2. Concept of Soil and Water Conservation
Soil and water conservation involves the rational use and management of natural resources, incorporating mechanical and agronomic practices to recover, maintain, or increase production capacity and enhance water infiltration in soils.
3. Concept of Land Use
Land use refers to the sustainable utilization of land without causing erosion or compromising its long-term productivity.
4. Outline of Land Use (Shang Modified 1977 & Michaelsen 1971)
This scheme emphasizes maximizing land use capacity. Intensive crop production (grains, potatoes, vegetables, etc.) is recommended for less steep land with deeper soils. Crops, pastures, orchards, and forestry are recommended for steeper slopes with shallower soils unsuitable for intensive agriculture.
The scheme, used by FAO technicians, considers soil depth and slope as key factors in determining land use intensity and recommending appropriate conservation practices. However, it’s essential to consider the technical and financial capacity to implement these practices and adapt them to specific field conditions.
5. Soil and Water Conservation Practices
Numerous practices have been developed to conserve soil and water, adapted to various agro-ecological and socioeconomic conditions. These practices are broadly categorized as mechanical practices and agronomic measures.
5.1. Mechanical Practices and Measures for Modifying Erosive Factors:
These practices aim to reduce erosion by modifying factors that contribute to it:
- Vegetation Cover: Protects the soil surface from raindrop impact and runoff.
- Physical Works: Reduce surface runoff and increase water infiltration.
- Slope Length Reduction: Dividing slopes into narrower strips reduces runoff velocity.
- Slope Reduction: Constructing physical structures to reduce runoff velocity and promote sediment accumulation.
6. Major Recommended Practices for Hillside Land Conservation
6.1. Mechanical Practices:
These involve structural works to control water movement, including:
- Dead or Stone Barriers
- Infiltration and Deviation Structures
- Waterways
- Individual Terraces
- Clean-Tilled Narrow Terraces
- Bench Terraces
- Gully Reclamation Dykes
6.2. Agronomic Measures:
These involve land management practices to rehabilitate, maintain, and increase soil productivity and regulate water movement:
- Living Barriers
- Contour Cultivation or Contour and Slope Furrowing
- Conservation Tillage
- Organic Amendments
- Agroforestry Practices
- Crop Rotation
- Strip Cropping
- Mixed Cropping
7. Soil and Water Conservation as a Practical System
Effective soil and water conservation requires integrating appropriate practices within the farming system to control erosion, conserve water, and improve soil productivity. This integrated approach forms a comprehensive soil and water management and conservation system.
A conservation system should combine mechanical works and agronomic measures. Mechanical practices protect the plot, control erosion, and improve water use, while agronomic measures focus on rehabilitating, preserving, and enhancing soil productivity. Farmers should be guided in selecting and implementing a practical system that aligns with their cropping system and considers both agro-ecological and socio-economic conditions.