Saving the World’s Rivers: What Must Be Done?

C. A. Sullivan, D. Dudgeon et al.*
Thursday, December 8, 2011

Flying across any continent today confirms that the world’s rivers are dominant features in the landscape, and are places where humans and animals gather to reap the many benefits and services they provide. Rivers of all sizes all over the world have underpinned the process of human development. As we progress into the twenty-first century, this development process must now be reassessed. Across the world, we have mismanaged and in some places almost destroyed the core ecological fabric on which river health – and indeed our own survival – depends. Human-caused stressors now endanger the biodiversity of 65% of the world’s river habitats, putting thousands of aquatic wildlife species at risk.

One of the most comprehensive studies of global rivers to date has examined human stressors on all the major rivers of the world. This study, published in September 2010 in the journal Nature, evaluated the state of the world’s rivers by taking into account the major “ecological insults” we impose upon them. The 23 threat factors used in this analysis all have well-documented impacts on human water security and aquatic biodiversity. These were grouped according to their effects on river ecological health and biodiversity, and on human water security. Each of these threats was weighted separately, which is important since the effects of a factor such as nitrogen pollution on fish, for example, are not the same as its consequences for human water security.

Using geo-referenced global databases jointly developed by the team, the combined impact of these multiple threat factors can be displayed graphically, demonstrating global conditions across the 99 million km2 of major river basins included in the study.

Our study found that vast areas across both the developed and developing world arrive at similarly acute levels of imposed threat to their freshwater resources. Sources of degradation in many of the developing world’s most threatened rivers bear striking similarities to those of rivers in similar condition in wealthy countries. However, the highly engineered solutions practiced by industrialized nations, which typically emphasize treatment of the symptoms rather than protection of resources, not only often prove too costly for poorer nations, but also appear to do little to secure healthy river systems.

The reliance of wealthy nations on costly technological remedies to overcome their water problems and deliver water services does little to abate the underlying threats, producing a false sense of security in industrialized nations, while perilous water insecurity in the developing world still remains a major global problem. In addition, lack of comparable investments to conserve biodiversity, regardless of national wealth, help to explain accelerating global declines in freshwater species.

The state of the Amazon

So far, the huge scale of the Amazon has helped it to resist the pressures from human development, although these are clearly beginning to encroach, as illustrated by the higher level of Human Water Security threat within the basin. The severity of these pressures is clearly demonstrated in the coastal areas of several of the riparian countries, where areas of high human population densities are also those where freshwater biodiversity is most threatened. With over 100 dams planned for the Amazon basin, it is clear that the reasonably healthy state of the river will not last long, unless more stringent measures are taken to reduce such high human pressure.

The situation in Venezuela also provides a useful illustration, where the Grand Savanah in the south of the country faces little threat to human water security, and also to biodiversity. In contrast to this, the coastal plain of that country, which represents a continuous ribbon of development, reflects high levels of threat to both humans and biodiversity. In the Orinoco basin, for example, urbanisation, canalization of rivers, oil exploitation, conversion of wetlands and loss of river habitats are all bringing about degraded river conditions ranking among the worst in the world. This highlights the need for more effective environmental governance in the face of rapid development and industrialisation.

Threats across the Indian sub-continent

Most people in the Indian sub-continent face a high level of water security threat. While this has been mitigated to some extent by infrastructure in the Indus, Ganges and other river basins, high levels of threats to humans remain. Unfortunately however, these efforts to improve human conditions though the development of dams and large irrigation schemes have created high levels of biodiversity threat in most rivers of the region. In Sri Lanka and Bangladesh, in contrast to India and Pakistan, the level of human water security threat is higher than the threat to biodiversity. This situation reflects the relatively lower levels of river fragmentation and land conversion in those countries.

The case of Rwanda

One of the smallest, most densely populated countries in Africa, is Rwanda. There is no doubt that human population density is a major factor impacting on the world’s rivers. As demonstrated in the three main rivers systems in Rwanda, this takes the form of overcrowding and degradation of riparian areas, mismanagement of solid waste, uncontrolled runoff, and lack of strong legislation to regulate all forms of water pollution. The Kagera (originating in Burundi), is one of the most important rivers in Rwanda. It is the largest tributary to Lake Victoria, flowing along the border between Rwanda and Tanzania. Our analysis has shown that human wellbeing is threatened in this river basin by the lack of water and sanitation services. In addition to the severe health impact this has, especially on children, the deterioration in water quality directly impacts on river health and freshwater biodiversity. Fortunately, the Kagera River also flows along the edge of the Kagera national park, which affords some protection, and this is evident from the lower threat intensity for biodiversity in the eastern part of Rwanda.

In the case of the Razizi River, hydropower dams have caused downstream impacts on the river and its biodiversity. Since more hydropower projects are planned for the region, government officials should take action to ensure that all possible aspects of their construction and operation are fully examined before any decision is made on their implementation. Deteriorating river health also characterizes the Kagitumba River, which flows through some heavily populated areas. As in many other parts of the country, impacts from agriculture, mining and deforestation have affected this river and its biodiversity. To make matters worse, across Rwanda and in other parts of sub-Saharan Africa, anticipated increases in large-scale irrigated agriculture associated with ‘land-grabs’ by outside investors, is likely to exacerbate drainage-basin degradation, raising concern over the future of river health across the region.

What can be done?

Our study revealed that there are very few places in the world where rivers can be described as healthy. Even regions distant from human populations have been impacted by human actions, for example through atmospheric deposition of pollutants.

Overcoming this global crisis of water insecurity for both humans and biodiversity requires deliberate prevention of impairment rather than simply offsetting threats once they arise. It is more cost effective to ensure that river systems are not impaired in the first place. This could be accomplished through better land use planning and management, better irrigation techniques and emphasis on protecting ecosystems and all the life forms within them.

In the few areas of the world where  threats to both human water security and biodiversity are low, the best strategy for any future development would be to ensure that natural capital is protected, and ecosystems remain intact.  Across the developed world existing human water security infrastructure will require continuous upgrading  to protect biodiversity while retaining existing human water services. In developing countries, it is vital that we ensure that the establishment of human water security is not achieved at a cost to freshwater biodiversity. This challenge will require both technical innovation and political commitment, possibly best met through an approach known as “Integrated Water Resource Management” (IWRM). IWRM should be promoted even at the international scale (despite the manifest difficulties of establishing the management authorities that would be required for this). Local communities should also be encouraged and enabled to become more involved in river basin management processes. Almost all the world’s major rivers run through more than one country, and river basin commissions and international water legislation should be established and strengthened in all parts of the world, with an emphasis on transparency and public participation.

Within the public arena, efforts should be made to promote greater understanding of how individual actions affect river health. Farmers should be encouraged to leave buffer strips along riverbanks, and wetlands should be protected and preserved rather than drained for agricultural use. River connectivity should be re-established, and wetland and floodplain conversion avoided, so that the river and its floodplain remain linked. In many places, impacts of bad practice are exacerbated by the effect of atmospheric pollution, carrying mercury and other pollutants across continents, transporting them from power station smoke-stacks in countries where environmental regulations are weak. This highlights the need for improved water and environmental governance, not just globally, but at all scales.

At the more local scale, detailed habitat monitoring and species inventories are needed, and there is much scope for benefits to be gained from the establishment of conservation corridors which include river systems. Ecosystem services provided in river basins must be identified and publicized widely, and their values quantified and captured in decision-making processes. Clearly, the value of the world’s rivers is immeasurable, but unfortunately, recognizing the monetary worth of the resources provided by rivers is too often the necessary push humans need to take action to better preserve and manage these valuable systems. However, it must be recognized that monetary interests of some stakeholders may be incompatible with those of others, and thus non-monetary metrics are also needed to support decision-making. The time has come to recognize that the increasingly scarce resources associated with healthy river systems will increase in value over time, not decrease.

Land management and land-use planning is also vital, and local governments in particular have a key role to play here. Recognizing and rewarding the value of good practice in agriculture and land management can be achieved through a system of payments for ecosystem services, and such approaches can provide the win-win situation of supporting regional development through payments for better environmental stewardship. When considering water infrastructure, options that would do the least harm to riverine health and biodiversity should be prioritized. Given the extent, prevalence and intensity of deterioration of the world’s rivers, we must have zero tolerance for further ecosystem degradation, even if the monetary costs are high.

Those involved in managing a nation’s water resources should be provided with training on how infrastructure developments can impact river systems, and financial resources must be made available to enable them to implement best practices. Within the decision processes associated with river development, much more emphasis must be placed on ecological values, and a systems approach should be taken to ensure a holistic assessment is made.

There is no doubt that a radical change is needed in the way humans interact with rivers. In most of the world’s rivers, similar threats and stressors are operating, and human impacts are negatively influencing river ecosystems and their biodiversity. We must treat the causes, and not just the symptoms of this degradation. Urbanization, industrial and agricultural development, and river habitat modification have all reached a pandemic level, and the interaction of multiple stressors often causes unintended consequences within river basins. These problems can be addressed by streamlining institutions involved in water management, supporting the development of integrated datasets, putting in place more effective legislative frameworks, and providing adequate funds for implementation and enforcement.

Ultimately, if these measures can be achieved, it may just be possible to refocus the development trajectory so that a more balanced relationship between humans and global river ecosystems can be found, before it is too late.

More information: 

*The full list of authors includes S. E. Bunn, P. M. Davies, M. O. Gessner, S. Glidden, P. Green, P. B. McIntyre, A. Prusevich, C. Reidy Liermann, C. J. Vorosmarty. Coming from a range of countries, institutions and disciplines, they have all worked for many years on issues relating to river health and development, and as a result have a truly global perspective on this vitally important issue. This article is based on “Global threats to human water security and river biodiversity,” Vörösmarty et al, 2010, Nature, vol. 467, no. 7315. Learn more about the study here:

The research outlined here was supported by funding from the NSF Division of Earth Sciences, the Global Water System Project (Bonn), DIVERSITAS-freshwater BIODIVERSITY (Paris), the Australian Agency for International Development and the institutions where the authors are based.