An estimated 50% of the world’s wetlands, ranging from the fast-disappearing mangrove swamps in East Asia to the environmentally challenged Jamaica Bay marshes in the heart of New York, have disappeared in the last 100 years. Many of those that remain have been fragmented with dams, sluices and canals.
Mostly the wetlands have receded under the pressure from growing populations and cities. But sometimes they have been deliberately eradicated as in Iraq, where the former regime drained most of the vast extent of marshlands that stood between the Euphrates and Tigris rivers since the dawn of history and turned much of its population into refugees.
Admittedly, the idea of ‘reclaiming’ the Iraqi marshes and using the water for irrigation was originally a British plan, but that was before scientists knew about the complex interaction between water, land and climate and the key role of the wetlands in protecting a diversity of birds, fishes and plants. Now the draining of the Iraqi marshes is seen by the United Nations, the European Parliament and by many non-governmental organisations as a tragic and probably irreversible assault on culture and environment.
Patrick Denny, a wetlands scientist, has spent much of his career in Uganda, the second country in the world after Canada to grant official protection to its extensive wetlands by constitutional law. He says a good wetland acts as both a sponge and a filter.
‘It holds water, and allows a river to be released more slowly,’ he said. ‘It keeps the rivers flowing. In the dry season it keeps the streams trickling. It gives time for the water to recharge the aquifer and keeps the water table up.’
Without this sponge function, rivers flow faster and carry off valuable nutrients, soil and organic matter from up-stream. Not only is this an economic waste, but the nutrients can damage lakes and kill fish by promoting an explosive growth of algae and reducing the oxygen at deeper levels – a process known as eutrophication.
The effects of neglecting wetlands can be seen in the world’s largest tropical lake, Lake Victoria, which is bordered by Uganda, Tanzania and Kenya, and is a source of livelihood, food and employment for more than 30 million people.
The once-astonishing diversity of fish species in the lake has been sadly depleted not only by the introduction of aggressive non-native species, but also because of the run-off of pollution and silt from the catchment.
Protection of the lake’s environment was one of the reasons that prompted the Ugandan government to adopt a national wetlands policy and enshrine it in the constitution.
Swamps occupy about 13% of Uganda’s territory, and used to cover a much greater area, including the land around the capital, Kampala. But a frustrated wetland is always a potential flood, and the urban sprawl and industries that surround Kampala are prone to frequent inundation as nature reasserts its rights.
The ensuing pollution and water stagnation clearly are sources of disease, but Prof. Denny said this is the result of a poorly managed environment and human pressure.
‘The classic word is that wetlands are wastelands,’ he said. ‘I can think of nothing further from the truth. If water and wetlands systems are well managed, then health issues are not as serious as one might believe.
‘Disease usually comes from poorly managed systems in which human beings themselves have changed the balance of nature. In a naturally functioning system with good biological diversity, you are not likely to have many mosquitoes because of the amount of fish, insects and birds that eat the larvae.’
Prof. Denny, who teaches mid-career water professionals at the UNESCO-IHE Institute for Water Education at Delft, the Netherlands, said wetlands act as a natural purification system if they are allowed to do their job.
Seeded with fast-growing papyrus, which has many economic applications, the marshes not only filter out the impurities but recycle nutrients as well. This produces food for the invertebrates, which in turn provide nourishment for fish and birds.
‘If you have more diversity, there is a greater chance that the people who live in those systems can have a sustainable way of life,’ he said. Riparian people can ensure a better supply of fish by helping nature through digging ponds called ‘fingerponds’ at the fringes of the wetlands where fish collect. The ponds remain flooded in the dry season: the fish are fed on domestic waste and can grow fat.
Even industrialised countries, which have exported their dam- and canal-building technologies into the developed world, are starting to undo some of the hard engineering of rivers and lakes and allow water to occupy natural flood plains with beneficial effects for the people, the environment, for biological diversity and for the underground aquifers.
It is even possible to create small artificial wetlands to treat the sewage output of a village or clean the effluent from conventional sewage plants, which in Africa frequently fail to function because of electricity cuts and poor maintenance.
Such artificial swamps are odour-free, Prof. Denny said, and the water that comes out of the end is clean, although enough nutrients can be left in to keep fishes happy and to use in agriculture.
In New York’s Jamaica Bay, which has had every conceivable pollutant dumped into it over decades, and is partly bisected by the runway at John F Kennedy airport, the cleanliness of the water is a source of wonder to environmental scientists. Despite such resilience, the 10,000 acres of wetlands, forests and beaches have shrunk by about half their original size because of a combination of man-made and natural causes.
Engineers have belatedly come to appreciate that the once-neglected bay, like the disappearing mangrove swamps of Asia, may play an important role in calming the energy of the sea and protecting the mainland as climate change brings with it the threat of rising ocean levels. From New York to Venice, and Indonesia to Uganda, environmentalists are increasingly finding out that bogs and swamps are not insalubrious wastelands, but waterlogged wealth and friends of nature and of mankind. – Third World Network Features
About the writer: Barry James writes for the UNESCO Courier. The above article appeared in UNESCO-IHE (Institute for Water Education) Update (January 2004).
