Damming, sediment mining, water diversions and groundwater extraction inhibit efforts to meet UN Sustainable Development Goals by 2030, says report
The livelihoods of over three billion people living along the world’s largest river systems are under threat from a range of stressors, said a study published in journal One Earth on June 19, 2020.
Growing populations placed unexpected stresses on the world’s great rivers — hotspots of resources, agriculture, trade and energy production — in developing nations.
Rivers respond to changes in the environment through self-adjusting processes of erosion and sedimentation. A range of other stressors, however — including damming, sediment mining, water diversions and groundwater extraction — affected big rivers.
The construction of mega-dams for hydropower, flood control, irrigation and water supply increased manifold.
Around 3,700 dams are planned or are under construction and — if fully implemented — will decrease remaining free-flowing rivers by 21 per cent, according to the study.
Dams trapped sediment, altered river flow regimes and — in tropical regions — caused a substantial release of greenhouse gas methane as a result of vegetation decay.
Sand and gravel mining destroyed riverbeds across the world, as the demand for concrete and silica increased. This was linked to severe ecosystem degradation, illegal mining, organised crime and social injustice.
These stressors inhibited efforts to meet the United Nations’ Sustainable Development Goals by 2030.
Great rivers — including the Ganga, Mekong and Nile — were more vulnerable to human-induced activities and climate change, the study said.
The resiliency and health of the world’s largest river systems, their deltas and their vulnerability to extreme events was reviewed by the study’s co-authors, University of Illinois professor Jim Best and University of Southampton professor Stephen Darby.
The introduction of non-native species — such as fish, invertebrates and vegetation — can have almost immediate ecological effects and economic consequences, compounded by river interlinking, the study pointed out.
Pollution from industrial, domestic, and agricultural sources can pose a threat as well: Research revealed the extent of riverine antibiotic pollution introduced in river water through human and animal waste and leaks from wastewater treatment plants and chemical factories.
This antibiotic pollution is present worldwide and aided the development of antimicrobial resistance.
What is needed?
Timescales over which stressors exert an effect must be recognised and incorporated into management responses. The researchers stressed the need for governance at local levels internationally to confront these issues effectively.
Effective international institutions must provide a channel for scientific advice and help support and enable the capability of local, national and transnational river-management organisations. The effects of these stressors must be incorporated into planning as well, the study said.
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