What is Terrace Farming? Advantages and Disadvantages of Terracing

For thousands of years, humans have reshaped steep, challenging landscapes into productive farmland using one of the oldest and most widespread engineering feats: terracing. From the iconic rice terraces of Asia to the ancient vineyards of the Mediterranean, these stepped fields are a testament to human ingenuity in overcoming geographical limitations.

What Exactly Are Terraces?

Terraces transform steep, challenging slopes into productive farmland through a simple yet powerful design. Picture cutting a hillside into giant steps: each level features a relatively flat surface for growing crops, supported by a near-vertical wall called a riser, built from materials like stones, packed earth, grass, or trees.

These risers can range from mere inches to several feet high. This reshaping of the land serves crucial purposes.

• Firstly, it dramatically increases the amount of land suitable for farming in hilly regions.
• Secondly, it slows down rainwater rushing downhill.
• Thirdly, it allows more water to soak into the soil instead of running off.
• Finally, and critically, it traps precious soil that would otherwise wash away.

This ancient technique, used for over 5000 years across diverse regions like the Andes, the Himalayas, and the Mediterranean, is a testament to human ingenuity in adapting to difficult landscapes.

The Significant Benefits of Well-Managed Terraces

When properly designed and maintained, terraces deliver substantial ecological and agricultural rewards.

1. Taming Water Runoff and Boosting Conservation: One of their primary strengths is water management. Terraces significantly reduce the volume of water running off the land.

Research shows a global average reduction of 41.9% compared to natural slopes. Some specific examples are even more impressive: level terraces in semi-arid China achieved 86.7% less runoff, bench terraces in India reduced it by over 80%, and paddy terraces in Vietnam cut runoff by 75%.

In Southern China’s red-soil hills, reductions reached a remarkable 99.9%. This happens because terraces shorten the distance water flows, create a rougher surface that slows water down, and often include ridges that act like small dams.

Consequently, soil moisture increases significantly – studies show an average boost of 12.9%, with some terraced soils holding 5 to 6 times more water than sloping fields. This stored water is vital for crops, especially during dry periods.

2. Halting Soil Erosion and Saving Precious Dirt: Furthermore, terraces are champions at preventing soil erosion, a major global environmental problem. By slowing runoff, they drastically reduce the amount of soil washed away, with a global average sediment reduction of 52%.

Real-world impacts are clear: in China’s Wangjiaqiao watershed, terraces lowered soil loss from 18.5 to 13.2 tonnes per hectare per year, increased trapped sediment from 7.7 to 12.4 tonnes, and reduced the proportion of eroded soil reaching rivers.

Examples like broad embankment terraces (75.4% reduction) and level terraces in China (87.7% reduction) highlight their effectiveness. Well-maintained terraces typically keep erosion rates very low, often below 1 tonne per hectare per year.

Importantly, when terraced land covers more than 40% of a region’s steep slopes, overall soil erosion can drop by 43% to 70%. This protection comes from the combined effect of slower water, more plant growth whose roots hold soil, and the physical trapping of sediment moving downhill.

3. Boosting Crop Yields and Food Security: Moreover, terraces directly enhance food production. They create stable, moist, fertile land where only steep slopes existed before, increasing the area suitable for cultivation by 20% to 40%. More importantly, they boost crop yields by an average of 44.8%.

For instance, maize yields on fertile terraced fields in Tanzania were 270% higher than on bare slopes. Terraced soils often build up higher levels of organic matter and nutrients because less is lost to erosion.

Reforesting or planting trees on terraces significantly increases soil carbon storage; in China, terraces boosted soil carbon sequestration by 32.4% compared to sloping land. Beyond agriculture, terraces shape breathtaking cultural landscapes.

Five iconic ancient systems – like China’s Hani Terraces, Peru’s Machu Picchu, and the Philippines’ Rice Terraces – are recognized as Globally Important Agricultural Heritage Systems. These sites attract tourists, generating vital income; at China’s Longji Terraces, tourism provides 70.8% of local household income.

4. Providing Habitats and Protecting Biodiversity: Additionally, by creating varied micro-environments, terraces support greater plant and animal diversity. Studies in Japan found 189 plant species from 81 families thriving in terraced areas, with biomass typically 32% to 70% higher than on similar non-terraced slopes.

The Risks and Downsides of Terraces

Despite their impressive benefits, terraces are not foolproof solutions. Poor design, inadequate maintenance, or abandonment can lead to serious environmental problems.

1. Disrupting Natural Water Cycles: One significant risk involves water cycles. While terraces excel at storing water locally, large-scale projects can reduce the total water flowing into downstream rivers and aquifers over a wider region.

For example, extensive terracing and planting in China’s Loess Plateau contributed to a 56% decrease in available freshwater in the Yellow River basin over nearly 50 years.

This happens because more water is held in the soil or used by plants on the terraces themselves; in semi-arid areas, up to one-third of terrace water can be lost through evaporation.

2. Accelerating Erosion Through Poor Design: Furthermore, poorly designed or managed terraces can ironically worsen erosion instead of preventing it. Research shows that badly managed terraces can suffer 1 to 5 times more runoff and soil loss than well-maintained ones.

If the flat surfaces of the terraces aren’t perfectly level or lack proper drainage channels, rainwater concentrates and flows faster during storms, carving deep gullies into the terrace beds themselves.

This risk is higher if farmers keep the soil bare. The vertical riser walls are another vulnerability. Bare, steep risers are easily damaged by heavy rain and flowing water, leading to rills and gullies.

Water soaking into the riser adds weight and pressure, making collapses and landslides much more likely. Studies in Spain found a clear link between bigger landslides and taller terrace walls.

3. Deteriorating Soil Quality (Especially New Terraces):  Additionally, building new terraces involves major soil disturbance. Fertile topsoil is often scraped away or buried, exposing poor-quality subsoil on the planting surface. This results in low fertility for the first 5 to 10 years, with disappointing crop yields initially.

The disturbance also releases stored soil carbon and nitrogen. Another growing concern is pollution, especially on terraces used for high-value crops like grapes or citrus fruits. Intensive farming often involves heavy fertilizer and pesticide use.

Because terraces are so effective at letting water soak in, these chemicals have more time to seep deep into the ground, potentially contaminating groundwater and building up heavy metals like copper (from fungicides) in the soil over decades.

4. The Peril of Abandonment: Perhaps the most critical threat is abandonment. Driven by people moving away from rural areas, low farm profits, and high upkeep costs, terraces are being abandoned worldwide, especially in Europe and high mountain regions.

The consequences are severe. Without maintenance, drainage channels clog, risers crumble, and vegetation management stops. Consequently, runoff on abandoned terraces increases dramatically (typically 20% to 40% of rainfall becomes runoff), and soil erosion skyrockets – often 3 to 10 times higher than on maintained terraces, and sometimes 100 times worse than natural slopes.

This leads to massive wall collapses, destructive landslides, and deep gullies. In the Mediterranean, over half of all abandoned terraces suffer from serious gully erosion and landslides.

Once collapsed, rebuilding is usually too expensive, leading to permanent loss of fertile land and the cultural landscape itself. For instance, 62% of ancient terraces in Peru’s Colca Valley are abandoned, mostly in high-altitude areas.

Gaps in Our Knowledge About Terraces

1. Lack of Comparative Studies: While much is known, significant gaps in research limit our full understanding of terraces. One major shortcoming is the lack of comparative studies. Most research focuses on single sites or specific terrace types.

We urgently need systematic comparisons across different designs (like level vs. sloped terraces), construction materials (stone walls vs. earth banks), land uses (rice vs. forests vs. orchards), and varying climates and soil types.

For example, forest terraces might be best for reducing runoff in southeast China, while crop terraces excel in the southwest, but comprehensive data is scarce. Current research also shows an imbalance: studies on level or sloping terraces dominate (over 4000 publications), while terraces built with stone walls or used for orchards receive far less attention.

2. Inadequate Evaluation Methods: Moreover, evaluating the total value terraces provide is challenging. Current methods to put a price on benefits like water regulation, soil conservation, carbon storage, biodiversity, and cultural heritage are often complex and limited.

Techniques like estimating the cost of building equivalent water storage or calculating lost fertilizer value have drawbacks, such as relying on imperfect comparisons or missing indirect benefits. Non-monetary evaluation methods are underused.

Existing tools also struggle to measure how these benefits change over time or how terraces affect water and sediment movement across entire landscapes, not just the immediate plot.

3. Ignoring the Negatives: Crucially, research has historically focused much more on the positive impacts of terraces. The significant potential downsides – particularly how they alter regional water availability, the pollution risks from intensive farming, and the devastating long-term effects of abandonment – are seriously understudied. A truly balanced picture requires dedicated research into these risks and their underlying mechanisms to develop effective solutions.

Building Sustainable Terraces for the Future

The research points towards clear solutions for maximizing terrace benefits while minimizing risks. Preventing problems starts with science-based design and construction. Sustainability must be prioritized over just making fields easier for machines.

Strict technical guidelines are needed, considering local soil type, depth, slope steepness, and rainfall patterns. Key elements include properly sizing the terraces (width, height), ensuring stable riser slopes, and incorporating effective drainage channels and protective ridges. Reducing the overall slope length and increasing terrace width generally improves water absorption and reduces erosion danger.

Moreover, maintaining dense plant cover on both the flat surfaces and the risers is absolutely essential. Plants shield the soil from pounding rain, slow runoff with their stems and leaves, anchor the soil with roots, and reduce water loss through evaporation.

In dry areas or on newly built terraces, covering the soil surface with rock fragments (“armouring”) can effectively prevent erosion until plants get established. Importantly, relying solely on terracing is risky.

Combining terraces with other structures like small earth dams, sediment traps, strips of dense grass, and well-designed waterways creates a much more robust system.

These complementary features work together to safely manage heavy runoff, trap sediment before it causes damage, and prevent water from concentrating and carving gullies. Fixing small rills immediately is also critical to stop them from growing into major problems.

Looking ahead, targeted research is vital. Comparative studies are urgently needed to understand how different terrace types perform in various environments. This will guide farmers and planners in choosing the best design for their specific location and needs.

Furthermore, research must move beyond looking at single effects. We need holistic studies that examine the overall impact of terraces on entire watersheds – how they affect water flow upstream and downstream, carbon storage over time, wildlife networks, and potential pollution pathways. Understanding how terrace type, vegetation cover, and management practices interact is key.

Finally, tackling the root causes of abandonment is critical. Research must explore effective models for long-term terrace upkeep, restoration techniques, and ways to make terrace farming economically viable for communities.

This includes setting clear management goals, developing fair payment schemes for farmers who maintain terraces and their environmental benefits, creating supportive laws, securing reliable funding for maintenance, and ensuring farmers have access to the latest knowledge.

Studies must directly link the survival of terraced landscapes to broader trends in rural economies, population shifts, and government policies. Only by addressing both the environmental engineering and the human dimensions can we ensure these ancient landscapes continue to provide food, protect the environment, and sustain communities for generations to come.

Conclusion

Terraces stand as one of humanity’s most enduring and widespread adaptations to difficult terrain, offering proven solutions for conserving soil, saving water, growing food, and preserving culture.

The evidence for their benefits is robust: 41.9% less runoff, 52% less erosion, 44.8% higher crop yields, 12.9% more soil moisture, alongside vital roles in tourism and biodiversity. However, the research delivers a crucial reality check: terraces are a powerful tool with inherent risks.

Poor design, neglect, or abandonment can trigger severe consequences: 1-5 times more erosion, disruption of regional water cycles (reducing downstream flows by over 50% in major basins), significant soil degradation, pollution, and catastrophic land instability leading to collapses and landslides.

The path forward demands respect for this complexity. Sustainable terracing requires precise, site-specific designs grounded in solid science, unwavering commitment to long-term maintenance, the integration of protective vegetation and complementary water control structures, and proactive strategies to keep terrace farming economically and socially viable.

Generally Asked Question

Why Is Terracing Used In Southeast Asian Agriculture?

1. Turn land less fertile. ❌
2. Turn land more leveled. ✅
3. Turn land more valuable. ❌
4. Turn rain less useful. ❌