It seems like a safe bet to say that planting trees is a good thing: who could argue with that? Well, not so fast. A teak plantation in Northern Laos, typifying the type of plantation landscape studied in the Huay Pano catchment. Photo by Guillaume Lacombe/IWMI.
Scientists from the CGIAR Research Program on Integrated Systems for the Humid Tropics and the French Institut de Recherche pour le Développement worked with colleagues from Lao PDR, and Vietnam to confirm that growing trees in a plantation—in this case, a teak plantation—actually increases water runoff, erosion, and downstream silting when compared to naturally re-growing forest areas.
The researchers compared different land-use situations in two upland agricultural areas exposed to the same monsoonal climate. In the Houay Pano catchment of northern Laos they looked at what happened when local people gave up rice-based shifting cultivation and started cultivating teak trees in plantations. In the Dong Cao catchment of northeastern Vietnam, they looked at land that had gradually reverted to natural forest after being used for annual crops and fodder, or mixed-trees plantations.
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The original paper entitled "Contradictory hydrological impacts of afforestation in the humid tropics evidenced by long-term field monitoring and simulation modelling" can be downloaded here: