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Erosion is the primary cause of land degradation in the world. It not only reduces arable surfaces and soil fertility, more particularly in uplands, but also leads to the pollution of downstream waters, silting of weirs and irrigated perimeters. Being sensitive to often brutal threshold effects, erosion varies significantly during rapid transitions from one cultivation system to another. Such is the case in northern Laos where population growth, grouping of villages and land reform led within less than ten years a very noticeable reduction of fallow periods.
The currently on-going program in the Luang Prabang area aims at:
- Improving farmers' revenues through innovative and environmental friendly cultivation practices;
- Provide decision-makers with agricultural erosion projection tools within the scope of realistic scenarios of changed land use and climatic changes;
- Strengthen the research capacity in this field in Lao PDR;
- Train Lao and European students on integrated watershed studies;
- Deepen knowledge on interactions between cultivation systems and soil and water degradation.
These objectives meet those of the regional program carried out jointly by IRD and the International Water Management Institute (IWMI) in the Lao PDR, Vietnam, Thailand, the Philippines and Indonesia, with the Lao PDR being the focal point.
The Houay Pano watershed, situated 10 km from Luang Prabang, covers 65 hectares. It is cultivated by 32 families by slash and burn with a fallow period reduced to two-three years. Under study since 1999, it is equipped with an automatic meteorological station, seven rain gauges, nine threshold meters with automatic liquid level recorders and sampling devices. Three innovative cultivation practices are tested: improved fallow with legumes, cultivation of pineapple in curbed stairs accompanied with improved fallow, and sowing under living cover (system recommended by Cirad).
This program mobilises six scientists from NAFRI (Laos) and six from IRD assigned to Vientiane, grouping skills in agronomy, human geography, hydrology and soil science in order to study such themes as: economic and social constraints, conflicts in use, dynamics of cultivation systems, hydric and agricultural erosions at different scales, water quality, sequestration and erosion of carbon.
These works also benefit from the collaboration by colleagues from CIRAD of the Lao PDR and other French institutions like CEA and the Federative Institute of Research “Environment and Management of Regional Space” which includes the laboratories of CNRS, INRA, CEMAGREF and INAPG. This program relies on advanced isotopic geochemical and geophysical techniques.
These studies are financially supported by IRD, IWMI, the Institute of Universe Sciences , the Ministry of Research and the French Fund for World Environment. Linked to the Nabong Faculty of Agriculture (the Lao PDR) and “Physical, chemical and biological function of continental biosphere” DEA (INRA, Pierre and Marie Curie University and INAPG), this program annually welcomes four or five Lao students and four or five French students. With IRD colleagues from the same Research Unit, this program also organizes national and regional training courses with support from the Ministry of Foreign Affairs.
It is expected that the field of intervention of this program will expand spatially to the scale of large watersheds equipped with a hydropower dam (example in the Lao PDR the Nam Ngum), with the objective of linking soil conservation in basins upstream to dams with water silting and quality in pondage.
Members of the IRD team based in Vientiane participating to the project:
Alain Pierret: apierret@gmail.com
Emmanuel Bourdon: bourdon@irdlaos.org
Christian Hartmann: christian.hartmann@ird.fr
Jean Luc Maeght : maeght@ird.fr
Jean Pierre Thiebaux : thiebauxird@laopdr.com
Yann Le Troquer : Yann.letroquer@ird.fr
Contact :
Responsable du projet MSEC:
Christian Valentin
Directeur adjoint
Bioemco - Biogéochimie et Ecologie des Milieux Continentaux
UMR211 - Institut de Recherche pour le Développement
32, av. H. Varagnat, 93143 Bondy cedex, FRANCE
Tel. +33 (0)1 48 02 55 31, Fax +33 (0)1 48 47 55 34
http://www.biologie.ens.fr/bioemco/
http://msec.iwmi.org, http://www.fire.upmc.fr/
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