Forum Forestier Lémanique The World Conservation Union Interaction between forest and water: common beliefs being challenged Virpi Stucki, Programme Officer, Forest Conservation Programme, IUCN Gland IUCN Photo Library © Jim Thorsell

Forum Forestier Lémanique The World Conservation Union Forests and hydrological functioning – public perception Roots Canopy Forest floor Increase infiltration Stabilise soils Reduce erosion Affect cloud formation and rainfall Improve water quality

Forum Forestier Lémanique The World Conservation Union Forests and hydrological functioning – public perception – cont. The importance of the Alpine region for water supply is widely recognized Yet, from the hydrological point of view, the mountain regions are stated to present « the blackest of black boxes in the hydrological cycle » (Klemes, 1988)

Forum Forestier Lémanique The World Conservation Union The links between forests and water have recently been questioned Extreme climatic events on the increase In 2005… Floods in India July-August Hurricane Stan October Hurricane Wilma October

Forum Forestier Lémanique The World Conservation Union Extreme climatic events on the increase

Forum Forestier Lémanique The World Conservation Union The links between forests and water have recently been questioned – cont. Down with trees Jul 28th 2005 From The Economist Planting trees can exacerbate drought and fail to tackle climate change Logging does not raise flood risk By Richard Black Environment Correspondent, BBC News website October

Forum Forestier Lémanique The World Conservation Union PUMPS OR SPONGES? Forests and water quantity

Forum Forestier Lémanique The World Conservation Union Source: « Water for Work » programme in South Africa Cloud forest in Costa Rica Source: Forests and water quantity – cont.

Forum Forestier Lémanique The World Conservation Union Whether forests increase or decrease the overall annual runoff depends on a number of variables, such as: the age of the forest topograhpy species composition soil properties meteorological conditions forest location within the watershed Forests and water quantity – cont.

Forum Forestier Lémanique The World Conservation Union Riparian buffer zones Source: Sukhomajri in India Forests and water quality

Forum Forestier Lémanique The World Conservation Union Studies show that: Buffer zones typically remove 50-90% of pesticides and nutrients However, sometimes results are contradictory to expectations Forests and water quality – cont.

Forum Forestier Lémanique The World Conservation Union Forests and floods Soil wetness is a crucial factor for runoff response Source: Scott et al. (2004)

Forum Forestier Lémanique The World Conservation Union Forests and floods – cont. Scientific experience shows that: Reforestation reduces small to medium storm events but cannot prevent extreme events Studies show that the economic losses of cumulative small- and medium size storm events are as big as those of the rare extreme events (Munich Re, 2006)

Forum Forestier Lémanique The World Conservation Union The importance of scale « Myths » about land-use impacts on hydrological conditions are often based on the extrapolation of effects observed at smaller scales to large ones (FAO, 2000)

Forum Forestier Lémanique The World Conservation Union Source: Source: “The severe floods in Eastern India and Bangladesh are not the result of a natural disaster, but of a ruthless exploitation of wood which has been practiced over centuries in the forests of the Himalayas“. Basler Zeitung, The importance of scale

Forum Forestier Lémanique The World Conservation Union Measurability of land-use effects by basin size (FAO, 2000) Quantity Quality The importance of scale – cont.

Forum Forestier Lémanique The World Conservation Union Conclusions No single explanation for the water-forest relationship does not mean that there is no relationship The multifunctional nature of forests in a landscape should be recognized Scientists should avoid overstating research findings Simplistic messages should not be replaced with equally simplistic ones Transferring costs of public policy based on such uncertainty to upland rural poor should be avoided Underlying assumptions and uncertainties of such findings should be made explicit

Forum Forestier Lémanique The World Conservation Union Permanent pasture Protected Primary Forest Degraded Forest Lands Permanent pasture Plantations Secondary forest Permanent pasture Intensive agricultural land Degraded Primary Forest

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