North Sumatra’s (BPS 2010b, c). Since most agricultural activi- ties occur on the flat coastal and alluvial plains, the integrity and sustainability of the water ecosystem services provided by the inland and upland forests is of paramount importance to the millions of people they support in these lowland regions. Te forest’s ability to capture and hold water is vital, since it slows and regulates its release. Te area where orangutans occur over- laps with 44 large water catchment areas and is thus very im- portant to guarantee proper functioning of ecosystem services related to water (Map 24).
“Up to 45% of the largest cities in the world depend to some extent
on forested water catchment areas for their water supply.” (Dudley and Stolton 2005)
Residents in both Aceh and North Sumatra have reported ma- jor reductions in river discharge over recent decades, which they attribute to the logging of upstream forests, negatively affecting freshwater fisheries and agricultural water resources. Te same communities also report significantly reduced rice yields during the same period. One study reports that in 2000 approximately 50 percent of the streams in Aceh had less than 50% of the water flow in the springtime compared to 1990. Approximately 20% of the flows are reported to have been completely dry throughout the year. For North Sumatra the situation is comparable: on aver- age 80% of the rivers contain less than 50% of the usual water flow compared to 10 years ago and approximately 15% of the riv- ers had completely fallen dry (LMU 2000). Water shortages can have direct impacts on agriculture, as in 1998 when over 5,000 ha