World Ocean Observer - Freshwater

Water: Elixir of Life, on Land and in the Sea

Tundi Agardy, PhD.

Water makes life possible - no other element is so universally required by living things. The bulk of our bodies is water, and all life on earth depends on it, either for drinking, nurturing eggs and young, or providing living space. Even ocean creatures rely on freshwater; all water is inexorably linked. This essential connection between freshwater and seawater underpins the great array of life in the sea.


Freshwater ecosystems are diverse and valuable in their own right. The number of species supported by freshwater systems far exceeds that which would be expected given the small amount of space they occupy on the planet. For instance, inland wetlands occupy less than 1% of the Earth's surface, yet support 40% of known fish species1. In fact, it has been estimated that a quarter or more of all vertebrate species live in or near inland waters. Endemism - that is, existence of species that exist nowhere else in the world - is generally high in rivers, streams, and lakes, since physical barriers set the stage for speciation.

Rivers and streams deliver freshwater and other nutrients to estuaries, and to all coastal seas. But the link between rivers and oceans also has a cost - whatever degradation is occurring in freshwater ecosystems inevitably impacts marine life as well. As pressures on aquatic systems mount around the world in response to growing needs for drinking water, irrigation, and energy needs, less and less water is able to reach the world's coasts -- changing the very nature of marine ecosystems, making estuaries more saline and diminishing the extent of ecologically important brackish waters. And as poor land use practices lead to pollution and erosion, run-off and other non-point discharges create a toxic brew of coastal seas downstream. Disappearing coastal wetlands only exacerbate the problem, as the ecosystem service of water filtration that these critical habitats provide are being lost.

Yet, significant hope lies in the multi-stakeholder and international efforts to better manage watersheds, as is occurring in many of the world's great river systems. So, too, does hope lie in the greater awakening of the public to the crucial role that healthy freshwater systems play in supporting the world ocean.

Freshwater as a Resource


Freshwater is one of the most important provisioning services the planet's ecosystems provide mankind. Drinking water is necessary to sustain life, of course, but so too is water needed to provide sanitation, irrigate crops, tend livestock, sustain freshwater aquaculture, support industry, and generate electricity. Contemporary withdrawal uses 25% of the continental run-off to which the majority of the population has access each year2. However, only 15% of the global population lives in relative water abundance, and that figure will drop as population pressures mount and water-overuse threatens renewable water sources.

Demand for potable water is on the rise as the world population approaches 7 billion; clean and sanitary water supplies are increasingly in short supply and are leading to serious conflict in many parts of the world. The World Bank estimates that one quarter of the world's low income population lacks adequate access to freshwater (20 liters of dependable water per day), while 1.1 billion people do not have access to clean drinking water3. The annual health burden on the global population caused by inadequate water, sanitation, and hygiene is 1.7 million premature deaths and loss of more than 50 million years of life4.

Water quality is less important an issue for agriculture, within limits. Contaminated water supplies used to irrigate food crops can cause serious disease outbreaks, and farm animals can fall prey to water-borne diseases. Conversely, water quantity is the main issue for other uses of freshwater, such as for energy generation or transport, although sediment pollution does impact hydropower operations.

As freshwater supplies dwindle and water wars erupt in arid hot-spots around the globe, desalination of seawater is increasingly looked to as an alternative source of water. However, desalination has significant environmental, as well as substantial economic, costs. A recent report suggests that desalination capacity will increase 61% worldwide between 2006 and 2010 and a total of 140% by 2015. Most of the growth in capacity will occur in the Middle East and northern Africa, but capacity will also increase in China, India, Australia, Spain, the U.S., and even the U.K.5

Reports analyzing desalination at the global scale, throughout the U.S., and in California suggest that the operations may contribute significantly to greenhouse gas emissions and may have dramatic ecological impacts due to the release of large quantities of brine laced with water treatment chemicals6. A recent report by the National Academy of Sciences (US) urges caution in the development of new desalination facilities, and outlines key avenues of research that should be undertaken before desalination is scaled up to meet our ever-increasing water needs.

Freshwater Ecosystems and Their Condition

Surprisingly, the extent and distribution of freshwater ecosystems or inland waters is unevenly or even poorly known at the global and regional scales, partly due to difficulties in delineating and mapping habitats with variable boundaries due to fluctuations in water levels. In some cases, such as the extent and location of wetlands, there is no comprehensive documentation, even at the regional or national levels. On the whole, the larger wetlands and lakes and inland seas have been mapped along with the major rivers, however for many parts of the world the smaller, immensely valuable wetlands are not well mapped or delineated, despite the importance of the services they provide for human wellbeing7.

Freshwater ecosystems provide many ecosystem services to support mankind and maintain human well-being. In addition to freshwater for drinking, bathing, cleaning, etc., inland water systems provide provisioning services in the form of food substances, especially fish; materials such as timber, fiber and fuel, including peat; energy from hydro-electric facilities; and novel products from biodiversity. Within river basins, inland waters provide many hydrological functions and support public good functions that are "free of charge" and extremely expensive to replace8. Additional ecosystem services provided by inland waters include: biological regulation; biodiversity habitat; nutrient cycling and soil fertility; local atmospheric and climatic regulation; waste processing and detoxification; bank stabilization; and support vectors of human infectious diseases. In addition, freshwater ecosystems have significant aesthetic, artistic, educational, cultural and spiritual values, and provide invaluable local opportunities for recreation and, increasingly, tourism.

Biodiversity in freshwater ecosystems is largely unknown and undervalued, much like marine biodiversity. But unlike the patterns of life in the sea, which are widespread, freshwater ecosystems are living labs in speciation, and demonstrate notably high levels of endemism. This means that each freshwater body threatened by overuse, pollution, landscape changes, or removal of water, threatens an uncommon and sometimes unique set of living beings. According to a newly released study done by the World Wildlife Fund (WWF) and The Nature Conservancy (TNC), parts of major rivers such as the Amazon, Congo, Ganges, Yangtze, and the rivers and streams of the Southeastern United States are outstanding for rich fish populations and high numbers of species found nowhere else. In addition, several smaller systems that had not been identified in previous global assessments, such as Congo's Malebo Pool, the Amazon's western piedmont, and Cuba and Hispaniola, were determined to have high numbers of fish species unique to those ecosystems9.

As water demand is increasing, pollution from industry, urban centers, and agricultural runoff is limiting the amount of water available for domestic use and food production. Water quality degradation is most severe in areas where water is scarce because the dilution effect is inversely related to the amount of water in circulation. Toxic substances (e.g. chemical pollution from urban domestic and industrial sources and from herbicides & pesticides) are a serious and increasing threat as land use in watersheds changes. The regulation capacity of inland waters has often been used for waste disposal or remediation, but not always within the capacity of the system to assimilate such materials indefinitely. Eutrophication and pollution have degraded both habitats and services, and contribute to the reduction in human wellbeing10.

Major trade-offs have occurred between various sorts of ecosystem services provided by inland waters, leading to substantial adverse changes in habitats and species, and services, such as freshwater and food supply. Such trade-offs occur because utilizing freshwater systems for energy generation, for example, can diminish the ability of these ecosystems to support biodiversity. Such trade-offs are clearly shown in the case of river fragmentation (i.e. modification of a river through dams, reservoirs, interbasin transfers, and irrigation consumption).

It is true that these changes have improved transportation, provided flood control and hydropower, and boosted agricultural output by making more land and irrigation water available. At the same time, physical changes in the hydrological cycle disconnect rivers from their floodplains and inland water systems and slow water velocity in riverine systems, converting them to a chain of connected reservoirs. This, in turn, impacts the migratory patterns of fish species and the composition of riparian habitat, opens up paths for exotic species, changes coastal ecosystems, and contributes to an overall loss of freshwater biodiversity and inland fishery resources.

Irrigation has similarly led to increased food production in drylands, but this in many cases is unsustainable without extensive public capital investment as waterlogging, pollution, especially eutrophication and salinization, degrade the system and other services. Changes in natural flow regimes have caused a decline in biodiversity and services provided by inland water systems, and those provided by coastal systems.

Threats to freshwater diversity are thus numerous and widespread. In the WWF/TNC study described above, agriculture, industry, drinking and livestock were found to place freshwater ecosystems in 55 (out of a total of 426) ecoregions under high stress, threatening the species and habitats they support11. This represents more than 10 percent of the world's ecoregions, which are defined by a large area encompassing one or more ecoregions that contains a distinct assemblage of natural communities and freshwater species. And, damage is already widespread: more than half the area in another 59 ecoregions has already been converted from natural habitats to cropland and urban areas.

In the United States, news outlets recently reported a looming water supply crisis in the western states, escalated by human-caused climate change that already has altered the region's river flows, snow pack and air temperatures12. Since 1960, thermoelectric, self-supplied industrial, and irrigation water withdrawals increased, reaching a peak in 1980. Demand for municipal and rural use has grown steadily over the past few decades, with municipal demand increasing more rapidly. Total water withdrawals declined about 10% between 1980 and 1985, and then grew slightly from 1985-2000, equaling about 345 billion gallons per day in 200013. Water conservation and an unprecedented water recycling program are key to the 20 year, $1.5 billion water supply strategy introduced by Los Angeles Mayor Antonio Villaraigosa. While dry seasons and the effects of climate change threaten Los Angeles' future water supply, population growth is expected to increase water demand in the city 15 percent by 203014.

Small streams are disappearing not only because of water withdrawls or overdrafts, but also from mining and damming. However, because there is no widely accepted way to classify streams for ecological monitoring, no national dataset exists for reporting on their gains or losses . Thus many freshwater ecosystems in the U.S., and the biodiversity and other ecosystem services they provide, are at risk from physical alteration, freshwater overdraft, alien species invasions, chemical pollution, sedimentation, and climate change impacts that affect recharge and source water15.

Prospects for the future of freshwater ecosystems and their noteworthy biodiversity are dim. In the next few decades, some 3 billion people will live in countries classified as water stressed16. As competition for freshwater resources increases around the world, freshwater habitats and species are among the most imperiled.

Changing freshwater ecosystem conditions and the health of the oceans

Freshwater finds its way to oceans via streams, rivers, runoff, and rain, bringing with it compounds much-needed by life in the sea and at its margins. But in addition to nutrients, freshwater also brings with it things that the oceans don't need, in the form of pollutants.

Oceans are unfortunate in being downstream, of everything. All our chemical inputs, unused fertilizers, debris, eroded silt and topsoil, untreated sewage, medicines -- from our farms, our suburbs, our cities, and our factories -- eventually make their way to the world ocean. As a result, coastal seas are now described as the most chemically altered environments on earth17. It should not be surprising, given the world ocean is downstream of every watershed, and all forms of pollutants reach the seas via river inputs, atmospheric deposition, and run-off. Expanding dead zones result, endangering fisheries, biodiversity, and human health.

The indirect degradation of oceans is an increasing problem, despite government regulations on pollutants. This is partly due to the fact that the Earth's most vital organs: riparian and coastal wetlands, seagrass beds, and mangrove forests that are its lungs, liver and kidneys acting to filter out toxins before they reach the open sea, continue to be destroyed.

This is a story not easily told, which is why this may be the biggest sleeper issue of all. How much easier to portray the plight of the great whales, or to document the decline in fisheries, or to show a coastline sullied by unsustainable development. Pollution is difficult to see, even harder to trace, sometimes ephemeral, but with long-lasting impacts. Eutrophication - the over-fertilization of nearshore waters caused by too many nutrients from fertilizers, sewage, animal waste, food processing residues - threatens to disrupt the ecological balance of coastal areas around the world. At the same time, toxins enter the marine system and reside there for long periods - until they are actively removed by mitigation (or until they enter the human food chain, leaving the marine environment to reside in our own tissues).

Non -point source pollution underlies ever-expanding "dead zones" - areas of low or no oxygen, needed to support most marine life. In the Gulf of Mexico dead zone, less than a third of the states in the 31 state watershed contribute the vast majority of the nitrogen and phosphorus delivered to the Gulf, primarily through non-point source pollution from rural run-off. Alexander concludes that nutrient reductions in the Gulf may be most efficiently achieved by managing nutrients in watersheds drained by large rivers.18 Corn and soybean cultivation is the largest contributor of nitrogen to the Gulf; while animal waste combined with crops cultivation contribute most of the phosphorus.

Riparian buffers have long mitigated the effects of run-off, preventing polluted freshwaters from reaching coastal systems. But as a new study in Nature points out, small stream systems may be even more important in removing pollutants and preventing eutrophication of coastal seas. Patrick Mulholland and co-authors found that nitrate was filtered from stream water by tiny organisms such as algae, fungi and bacteria. This in and of itself was not news; however, the researchers discovered that entire stream networks are important in removing pollution from stream water, not just individual streams. However, the important role that even small streams have in removing and/or transforming nitrates (and therefore preventing eutrophication downstream, and in estuaries and oceans) can quickly be overcome by too many nitrates entering the water. Thus, there are thresholds to the ability of freshwater ecosystems to provide the important ecosystem service of maintaining water quality.

Thus freshwater ecosystems and marine ecosystems downstream are threatened by both pollutant loading and the loss of stream habitat as development continues to transform the landscape. But the situation is not hopeless. Realization is growing, and market-based mechanisms to enable better watershed management are cropping up (see next section). And perhaps the one bright light in the current worldwide economic downturn is that use of fertilizers is expected to plummet as the cost of fertilizer shoots up. The consequences for both freshwater ecosystems and marine ecosystems will be positive, as has been shown to happen in the past. When the dissolution of the Soviet Union ended state subsidies of fertilizer, and fertilizer use fell dramatically. In Cuba, for instance, coral reef health improved as fertilizer use diminished. If the end result is a forced movement to more sustainable agriculture and better opportunities for small scale growers that practice sustainable methods, this may indeed be the silver lining in the dark economic clouds that currently blanket the world.

Marine managers have long recognized that effective conservation of ocean areas and creatures requires delving into watershed management, for all the free-flowing waters of the earth either find their way into, or dramatically affect, ocean ecosystems. However, achieving this level of ecosystem-based management requires the spanning of disciplines and professions in a way that is not natural to our sectoralized science and management, and keeping the big picture, regional view very much in mind.

The Great Promise of Watershed Management


Regional cooperation to address issues of water use and allocation, as well as threats to freshwater systems originating from pollution, over-fishing, and changes in riparian landscapes, holds great promise for effectively manage river systems and watersheds, but the way regional ecosystem-based management provides a ray of hope for ocean management19.

There are good examples of watershed / waterbasin management frameworks and institutions already in existence around the world, from the Mekong River Commission (Vietnam, Thailand, Laos, Cambodia) to the International Commission for the Protection of the Danube River (Austria, Bosnia-Hercegovina, Czech Republic, Germany, Hungary, Moldova, Romania, Serbia, Slovakia, and Ukraine ), to the drought-parched Murray/Darling Basin in Australia (involving the states of South Australia, New South Wales)20. However, this large scale, top down, command and control form of management has its limitations, without effective local involvement at much smaller scales.

A telling example is provided by the Protection of Ecoservices Project undertaken by the City of New York to safeguard the city's drinking water supply. The City made an investment of $300,000 to facilitate sustainable farming practices in the New York City watershed, enlisting the help and entrepreneurial spirit of farmers in the Catskills Mountains to implement measures to preserve water quality. These measures included establishing riparian/stream buffers on private lands, reducing fertilizer/pesticide use, and conserving wetlands that naturally filter water flowing through them. This Payment for Ecosystem Services (PES, as such initiatives are called in the market-based conservation world) initiative really paid off - it saved the City literally billions of dollars in water treatment costs, and it rewarded farmers financially, allowing them to maintain their traditional, small scale farming livelihoods.

Such combinations of public sector management and private sector market-mechanisms may be the best hope we have for conserving freshwater biodiversity and services. And if we are to succeed at that, we will have come a long way in conserving marine ecosystems and services as well, for the lifeblood of seawater is, after all, freshwater -- pure, clean freshwater that is the elixir of life.

Endnotes and Further Reading

1 Millennium Ecosystem Assessment (MEA). 2005. Ecosystems and Human Well-Being. Ch. 20 Inland Water Systems. Island Press, Washington p561

2 Millennium Ecosystem Assessment (MEA). 2005 Ecosystems and Human Well-Being. . Ch. 7 Fresh Water. Island Press, Washington p 167

3 World Health Organization/UNICEF 2004. Meeting the MDG Drinking Water and Sanitation target: A Midterm Assessment of Progress. WHO Geneva

4 MEA (2005) p 195

5 Kristin, C. 2008. Environmental costs of desalination. Environmental Science &Technology 41(16) :4837

6 WWF. 2007. Making water: Option or distraction for a thirsty world? WWF Gland, Switzerland; National Research Council (US) 2008. Desalination: A National Perspective. National Academies Press, Washington, DC; Cooley, H., P.H. Gleick and G. Wolff. 2006. Desalination, with a grain of salt: A California perspective. Pacific Inst. Available at

7 Millennium Ecosystem Assessment (MEA). 2005. Ecosystems and Human Well-Being. Ch. 20 Inland Water Systems. Island Press, Washington p563-4

8 Ibid. p 561-563

9 See for more information and an online copy of the report

10 This and the following three paragraphs are adapted directly from Ch. 20, Inland Water Systems. In MEA. 2005. Ecosystems and Human Well-Being; pp 561-580


12 Tim P. Barnett, David W. Pierce, Hugo G. Hidalgo,Celine Bonfils,Benjamin D. Santer, Tapash Das,Govindasamy Bala, Andrew W. Wood, Toru Nozawa, Arthur A. Mirin, Daniel R. Cayan, Michael D. Dettinger.. 2008. Human-Induced Changes in the Hydrology of the Western United States. Science 319 (5866): 1080 - 1083

13 State of the Nation update by the Heinz Center, available at

14 , ENS-Newswire, May 15, 2008.

15 See index of landscape changes

16 See

17 Postel, S. and B. Richter. 1993. Rivers for Life: Managing Water for People and Nature. Island Press, Washington DC

18 MEA..2005. Ecosystems and Human Well-Being. Ch 19. Coastal systems and coastal communities. pp

19 Differences in Phosphorus and Nitrogen Delivery to the Gulf of Mexico from the Mississippi River Basin," by the U.S. Geological Survey, USGS, published in the journal "Environmental Science and Technology

20 See Agardy, T. 2008. Casting off the chains that bind us to ineffective marine management: the way forward. Ocean yearbook 22:1-24; also Kimball, L. 2001. International Ocean Governance. IUCN, Gland Switzerland. See;;