Devaluation of hydrological role of cloud forests

18 December 2007

WOTRO researcher Friso Holwerda pleas for a re-evaluation of the idea that the Mexican broad-leaved cloud forests produce higher water yields than other forest types due to contributions by fog interception. He suggests that the pine belt above the cloud forest zone may prove hydrologically more important although this is to be confirmed by further study.
Holwerdas research programme focussed mainly on gaining hydrological information on montane cloud forests. Based on his research, Holwerda estimates the overall contribution of water via fog interception at a mere 50 mm per year or less than 2% of the annual rainfall. Also, he finds relatively high cloud forest water use (‘transpiration’) compared to findings for cloud forests under wetter and cloudier conditions elsewhere in the tropics. 
Forests provide important environmental and hydrological services, such as production of oxygen and prevention of erosion. To promote the conservation of forests, the Mexican government started in 2003 one of the world’s largest Payment for Environmental Services (PES) in which the national or local government pay owners of forests, provided they keep these forests in an optimum state to maintain a stable supply of good-quality water to downstream communities. For this PES programme, montane cloud forests are valued the most on the basis of their high biodiversity and generally high water yields.