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examBoard: Cambridge
examType: IGCSE
lessonTitle: Terracing Techniques
Soil erosion is one of the most serious environmental challenges facing agriculture worldwide. When valuable topsoil is washed or blown away, it doesn't just disappear – it takes with it nutrients, organic matter and the very foundation of food production. Terracing is one of humanity's oldest and most effective solutions to this problem.
Key Definitions:
According to the Food and Agriculture Organization (FAO), about 33% of the world's soil is moderately to highly degraded due to erosion, salinization, compaction and chemical pollution. Without protective measures like terracing, we could lose most of our topsoil within 60 years!
Terracing transforms steep slopes into a series of steps or platforms that slow down water flow, giving it time to soak into the soil rather than washing away downhill. Think of it as turning a dangerous water slide into a gentle staircase for rainwater.
Terraces physically interrupt the flow of water down slopes, reducing its velocity and erosive power. The flat areas collect water, soil and nutrients that would otherwise be lost, while the raised edges act as barriers against runoff.
Beyond erosion control, terraces create level growing areas on otherwise unusable steep land, improve water infiltration and can help manage irrigation more efficiently. They can transform marginal land into productive farmland.
Different landscapes, climates and agricultural needs have led to the development of various terracing methods. Each type has specific advantages for particular situations.
Flat platforms with vertical or near-vertical walls, resembling steps. Best for steep slopes (15-60%). Requires significant labour but creates completely flat farming surfaces.
Wide, gently sloped channels with low ridges. Suitable for moderate slopes (2-8%). Allows for mechanised farming and is less labour-intensive to construct.
Ditches that follow land contours with ridges on the downhill side. Good for areas with heavy rainfall as they direct excess water to protected outlets.
Perhaps the most visually stunning form of terracing, rice paddies are specifically designed to hold standing water for rice cultivation. The terraces are built with clay-lined beds and precise levelling to maintain water at the perfect depth for rice growth.
Often called the "Eighth Wonder of the World," these 2,000-year-old terraces were carved into the mountains of Ifugao by hand. They follow the natural contours of the hills and mountains and are still in use today. If placed end to end, they would stretch approximately 22,000 kilometres! The ingenious irrigation system draws water from mountaintop forests, which is then channelled through bamboo pipes and stone canals to each terrace.
Common throughout Spain, Italy, Greece and other Mediterranean countries, these terraces typically use stone walls to hold back soil on steep slopes. They're particularly important for growing olives, grapes and citrus fruits in regions with seasonal rainfall and risk of summer drought.
Specially designed to optimise sun exposure for grapes, these terraces often face south or southwest. The stone walls absorb heat during the day and release it at night, creating a beneficial microclimate for wine production.
Built to allow olive trees to access deep soil while preventing erosion during winter rains. The terraces help retain precious water in this drought-prone region and make harvesting easier on otherwise difficult terrain.
Creating effective terraces requires careful planning and regular maintenance. The process involves several key considerations:
The Loess Plateau Watershed Rehabilitation Project is one of the world's largest and most successful soil conservation initiatives. Since 1994, this massive terracing project has transformed nearly 4 million hectares of highly erodible land. Before terracing, the region lost up to 3,000 tonnes of topsoil per square kilometre annually. The project has reduced sediment flow into the Yellow River by over 100 million tonnes each year while doubling farmers' incomes. Satellite images show a dramatic greening of the once barren landscape.
While terracing is an ancient technique, modern science and technology have introduced innovations that make it more effective and easier to implement:
When considering terracing as a soil conservation method, several factors must be evaluated to determine if it's the right approach:
Slope gradient, rainfall patterns, soil type and existing vegetation all influence terrace design and potential effectiveness.
Construction costs, maintenance requirements, potential yield increases and land value improvements must be weighed against other conservation options.
Local knowledge, available labour, community support and cultural practices can determine the success of terracing projects.
Following the devastating impacts of soil erosion that threatened food security, Rwanda implemented an ambitious terracing programme covering over 100,000 hectares. The radical terraces increased potato yields from 6 to 20 tonnes per hectare, maize from 1.6 to 4.5 tonnes and wheat from 1 to 3 tonnes. Beyond productivity, the terraces reduced landslides in high-risk areas and created over 15,000 jobs. Rwanda's programme demonstrates how well-designed terracing can address multiple environmental and social challenges simultaneously.
As climate change brings more extreme weather events and growing populations increase pressure on agricultural land, terracing remains a vital tool for sustainable land management. By combining traditional knowledge with modern science, terracing techniques continue to evolve, offering solutions for soil conservation that work with nature rather than against it.
Whether it's the ancient rice terraces of Asia, the vineyard steps of Europe, or new projects in Africa and South America, terracing demonstrates how human ingenuity can transform challenging landscapes into productive, sustainable agricultural systems while protecting our most precious resource – soil.
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