Mountain transformations

Mountain environments help to even out the rate of water flow between wet and dry seasons. But human activities, such as forest conversion, can disrupt normal flows and increase siltation, with costs to downstream users. Mining and fertilizer use can contaminate mountain water before it goes downstream. So in some places downstream users have begun to compensate upstream users to mitigate the negative impacts (for instance in Costa Rica).²⁶ Many of the commercial activities in mountains contribute to income generation and growth. But mountain people have not always benefited appropriately from the goods and services provided by mountain areas. The objective here is not to stop change in mountains; it is to manage resources in ways that provide sustainable livelihoods for mountain dwellers and provide the goods and services valued in lowland areas.

Deforestation in mountain areas has contributed to lasting changes in land productivity. Large areas of European mountain forests were cut and have not grown back because of changes in land use and soil loss. Some mountain areas in Africa have been stripped of vegetation by overgrazing and are no longer capable of supporting sustainable livelihoods. Land conversion (deforestation) and species depletion can often be spread over time spans longer than a normal human life, so impacts may not be immediately perceptible. Institutions need to be improved so that they can pick up these signals before it is too late. Some mountain attributes change over even longer periods, through gradual erosion or uplifting due to tectonic processes. Glacial retreat due to global warming is already occurring and over the next 50 to 100 years, nearly all mountain glaciers are likely to have melted, affecting downstream water flows. Some environmental fixes, such as restoring glaciers or reforesting in higher altitudes where trees grow slowly, may be impossible in any humanly relevant time span.