How to improve land productivity on slopes:
The rehabilitation of crop terraces

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Region South America
Capital Lima
Surface area 1,285,216 km2
Population 28,380,000 inhab.
Population density 22 inhab./km2
Infant mortality rate (per thousand births) 33
Fertility rate (births per woman) 2.9
Population growth rate (per annum) 1.5 %
Life expectancy (female-male) 72 – 67 years
Average temperatures (min./max.) 16.7 / 22.1 ºC
Forest area 51 %


The Colca Valley is situated in an Andean valley in the mid-western part of Caylloma Province in the Department of Arequipa. Its altitude ranges from 2,200 metres to 4,500 metres above sea level, the limit for livestock farming. Large mountains dominate the valley, characterized by a deep canyon more than 100 km in length and carved by the Colca River.
Well before the Inca period, the local population farmed the lands through terracing so as to benefit from the specific characteristics of different altitudes; however, this technique has been more or less abandoned since the colonial era. The remaining terraces are poorly maintained and rarely irrigated. The Peruvian NGO, DESCO, have undertaken to restore the terraces and the irrigation canals while raising awareness on their usefulness. The results speak for themselves, land productivity and crop production has increased, erosion and water loss has been reduced and the managed landscape attracts tourism.

Ecosystem levels and altitude

The Colca Valley was initially inhabited by the Collahuas who, even before the period of the Incas, developed a production system based on terraces and irrigation schemes. By terrace farming, the local population benefited from the characteristics specific to the different altitudes. Beyond 3,800 metres, Camelidae (alpacas, llamas and vicuñas) are bred. Mixed livestock and agriculture are found below this altitude and in the past, the valley sustained a population of 60,000 inhabitants solely due to its resources (crops and livestock). However, as a result of the colonial period, the technique has been abandoned and the population has been reduced to 6,000 inhabitants.
From an ecological viewpoint, the zone is rich in varied species with up to fifteen ecosystems identified by scientists. However, from a productive viewpoint, three main systems are identified: the high Andean zone at over 3,800 m altitude is restricted to Camelidae breeding; the inter-Andean valley, between 3,000 m and 3,800 m with mixed livestock and cropping systems and the low Andean zone, ideal for fruit production.

1. The rehabilitation of terraces permit both the farming
of sloping lands and the prevention of erosion.
© UNEPs Success Stories photo archive

badCauses and effects in the drop of land productivity

Land productivity has greatly diminished in the Colca Valley since the colonial era. According to official estimations, 30% of arable land has been lost due to the degradation of terraces and the lack of maintenance of the irrigation systems. Poor land management has also contributed to a drop in soil fertility. In fact, farmers have forgotten the agricultural practices of their ancestors, which consisted of enriching the soil with mulch and compost, as well as crop rotation and mixed cropping techniques or polyculture. Short-term agricultural production, that takes full advantage of immediate returns, was preferred to the detriment of sustainable development that exhausted resources and damaged the land. Tree logging for firewood is another well-known cause of desertification.
The mountainous zones are characterized by dramatic water shortages, steep slopes and serious climatic limitations on agriculture (frosts, low atmospheric humidity). Average annual rainfall is 350 mm, of which 60% is concentrated between January and March with only one harvest a year. Small land properties are common and on average, each family possesses 1.2 hectares, split up into several smaller plots distributed among different ecological zones. In general, farmers cultivate between eight and sixteen different crop varieties, maize, beans, potatoes, barley and quinoa being the more common among them. The traditional techniques adopted to overcome environmental difficulties consisted essentially of terraces, irrigation networks and the beneficial effects of the microclimate present at varying altitudinal levels.

2. Agriculture on mountainous regions is rendered difficul
t by its steep slopes and the risks of erosion. Here the men
plough the flat fields thanks to the construction of terraces.
© UNEPs Success Stories photo archive

goodPossible solutions

DESCO, a Peruvian NGO based in Lima and founded in 1965, implemented its project in the district of Lari in the Colca Valley located between an altitude of 3,200 m and 4,500 m. The project aims to restore the terraces, improve irrigation structures and introduce agro-forestry practices in the region. The expected results include the improvement of agricultural productivity and renewed ecological awareness among local farmers. Thus, local traditional knowledge should be re-evaluated and complemented by means of modern techniques and sustainable agricultural systems such as agro-forestry and reforestation.

The Lari terrace rehabilitation project began in 1992 (picture 1.). In 1998, a surface area of 1,050 hectares of terraces was restored. However, certain terraces are so badly damaged and difficult to irrigate that they are beyond repair.

bladTerrace rehabilitation

A terrace may be defined as an area for cultivation whose slopes have been levelled or raised and stabilized by a small wall made of stones (pictures 1. and 3.). The advantages of terraces go beyond their capacity to transform slopes into arable land; they are also effective in the control of erosion and improve water management, they maintain soil humidity and reduce the risk of frosts. They enable farmers to better utilize the microclimatic and ecological characteristics at different altitudes. On the whole, terrace cropping transforms the agricultural potential of land otherwise limited to tree planting, into irrigated farming land (picture 2.).
In order to restore Andean terraces, three elements are required; the stone wall, the terrace itself and the access route or pathway.

3. A terrace may be defined as an area for cultivation
whose slopes have been levelled or raised and stabilized,
usually with stone walls.
© UNEPs Success Stories photo archive

Agro-forestry is strongly recommended on the terraces. It involves farming a combination of annual crops such as cereals and perennials such as fruit trees. This type of production system generates both economic and ecological benefits since local farmers diversify their produce while enriching the land. A technique used to maintain the terraces involves planting woody species close to the walls to act as both support and as windshields (See Ecuador case study).
The recommended tree species are capuli (Prunus sp.), cypress (Cupresus macrocarpa) and pine (Pinus sp.) noted for their physical properties and their ability to recycle nutrients.


The effectiveness of the project can best be measured by using crop productivity as an indicator. Productivity has increased by 29% between 1990 (before the project) and 1998 (after the project) in the region chosen by DESCO. Crops showing greater productivity are quinoa (80%), potatoes (51.6%) and sweet peas (33%).
The results can thus be summarized as follows:

the methods and know-how to construct terraces as well as water and soil conservation practices, have been reintroduced.

  • 317 hectares of terraces have been restored and 101 hectares of arable land has been reclaimed, benefiting 364 families.
  • the irrigation canals have been repaired0 and improved, whose flow is now 30 to 50 litres/second on average.
  • the network of irrigation canals has been optimized allowing wider distribution.
  • 41,000 trees of local species have been planted in the framework of agro-forestry.
  • productivity has increased for the principal crops (quinoa, maïze, potatoes).
  • the role of women has been encouraged and reinforced during community meetings.
  • the notion of terraces to attract tourists has been promoted.

This case study was proposed by Mr Francisco Brzovic and José Torrico within the framework of the United Nations Environment Programme ‘Saving the Drylands’ award.
For more information, please contact the following person:

Mrs Elizabeth Migongo-Bake.
PO Box 30552

Tel. (+254) 2 623252/61
Fax (+254) 2 624249



The teacher explains the terrace cropping system in class.


What do you think of the case study? Do you live in a mountainous region?
Do you face similar problems to those faced by the inhabitants of the Colca Valley in Peru?


Locate Colca Valley in Peru.
Is your country on the same continent as Peru? Does your region encounter the same problems as those found in Colca Valley in Peru? Are their problems similar to yours?
What are the differences?
What are the similarities?


Draw the terraced crops on the mountains with the local farmers that work and grow plants there. Paste your picture to your notebook.


Outdoors, on a heap or mound of earth, construct mini-terraces by flattening the earth at different levels, which is stabilized with stones and small branches. With your classmates, start a competition to construct the best mini-terraces.


Tick the correct answers from the following:

In Peru, terraces are used to:

• construct steps.
• act as a windbreak.
• reduce noise levels.
• combat erosion.
• enlarge the agricultural
land area.
• farm in mountainous
• raise goats.

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