Forests and Water - upstream/downstream linkages

Upstream/downstream linkages

Are watersheds appropriate management units? There is a need to rethink scale of
intervention, upstream–downstream linkages, temporal and spatial processes, biophysical
and socio-economic linkages, and political issues.

Porto Cervo International Conference, Working Group 3

Until about 25 years ago, most upland regions did not attract much mainstream social concern. Remote and relatively inaccessible, they were generally perceived as difficult, unyielding and unprofitable environments. Science and policy tended to misunderstand the complexity of ecological, socio-economic and political linkages to “developed” downstream areas.

Since the Rio de Janeiro Summit, awareness of the socio-economic importance of upland and mountain areas has increased, as has concern for upstream/downstream linkages. Four factors have driven this process:

• increasing shortages of freshwater in lowland areas, leading to recognition of the importance of uplands and mountains as “water towers” - at both the national and international levels;
• increasing environmental degradation in the uplands, which threatens lowland socio-economic interests;
• expanding international markets in “marginal” upland and mountain areas - for mining, agriculture, tourism, etc.; and
• political instability in the post-Cold War global order, causing many low-intensity international, civil and ethnic conflicts, most of which involve guerrilla warfare in rugged upland and mountain areas with poor access.

In response to these concerns, the International Year of Mountains 2002 and the International Year of Freshwater 2003 contributed to raising the international community’s commitment to socio-economic development of upland people, and upstream/downstream socio-economic linkages.

Sustainable development in upland areas and a proper understanding of upstream/downstream social linkages cannot be achieved without understanding first the complexity of upstream/downstream ecological systems.

Slope instability drives major upstream/downstream systems such as the Yellow River/Yangtze systems on the Tibetan plateau, the Andes Amazon system, and the Himalaya Ganges/Brahmaputra system. In these systems, over large geological timeframes, gravity, intense rainfall and high seismic activity have been producing massive sediment transfers from mountains and accumulations that form riverine floodplains.

The river basin is the most satisfactory unit for studying upstream/downstream ecological linkages but scale, variation over time, and the great range and diversity of landscape units must be taken into account. This complexity makes generalizations impossible: put simply, measurements and conclusions from work in watersheds with drainage basins greater than 20 000 km² do not necessarily apply to smaller land units. Failure to take this into account has been a chief cause of the misrepresentation and misunderstanding that led to inappropriate policies in the past.

Assessing the impacts of human activities on these geophysical processes is even more complicated, and it is sometimes impossible to disentangle upstream from downstream factors. Although external geophysical forces are governed primarily by gravity (mass transfer) - making them highland impacts on the lowlands - human impacts can originate in the highlands or the lowlands. Socio-economic upstream/downstream linkages are complex, interactive and entropic processes.