Large rivers of the tropics, many of which have extensive floodplains and deltas, are important in the delivery of nutrients and sediments to marine environments, and in providing ecosystem services associated with their high biological productivity.
These ecosystem functions entail biogeochemical processes that will be influenced by climate change. The most important changes are likely to involve:
- aquatic thermal regimes, with implications for thermal optima of plants and animals,
- rates of microbially mediated biogeochemical transformations,
- density stratification of water bodies and dissolved oxygen depletion,
- hydrological regimes of discharge, which determine the ecological structure and function of rivers. It also determines the extent and seasonality of aquatic environments and freshwater-seawater gradients where rivers meet oceans. In turn, affecting the distribution of marine, brackish and freshwater environments, and the biogeochemical processing as river water approaches the coastal zone.
In all cases, climate change affects biogeochemical processes in concert with other drivers such as:
- land use changes,
- dams and other hydrological alterations and
- water withdrawals.
As an adaptation option to climate change, that will contribute substantially to the protection of valuable river assets, effective management must be place-based focusing on local watershed scales that are most relevant to management scales.
The first priority should be enhancing environmental monitoring of changes and river responses coupled with the development of local scenario-building exercises that take land use and water use into account.
Protection of a greater number of rivers and riparian corridors is essential, as is conjunctive groundwater/surface water management. This will require collaborations among multiple partners in the respective river basins and wise land use planning to minimize additional development in watersheds with valued rivers.
Ensuring environmental flows by purchasing or leasing water rights and altering reservoir release patterns will be needed for many rivers.
Implementing restoration projects proactively can be used to protect existing resources so that expensive reactive restoration to repair damage associated with a changing climate is minimized.
Special attention should be given to diversifying and replicating habitats of special importance and to monitoring populations at high risk or of special value, so that management interventions can occur if the risks to habitats or species increase significantly over time.
Future research should strive to improve detection of current trends and projection of future changes
in catchment and river hydrology, with greater attention to climate feedbacks and human interaction.
Cover Image, Dry River Bed | Shever