A vulnerable global heritage
ANDREW L. HAMILTON
argues that the extreme vulnerability
freshwater biodiversity demands a re-think
of the human values,
socio-economic systems that threaten it
The freshwater in the world's lakes and rivers makes up a tiny fraction (about 1 part in 10,000) of all the water on Earth. Yet this tiny fraction has provided the 'spark' or 'stuff of life' that allowed the evolution and proliferation of different species to flourish over millennia in geographically isolated and protected freshwater ecosystems. Indeed, lakes and rivers can be viewed as 'hotbeds' of evolution that have left humanity with an astonishingly rich, but at the same time very fragile, biodiversity heritage.
It is now clear that freshwater species are more vulnerable to extinction than their marine counterparts. Indeed, the extreme vulnerability of freshwater biodiversity parallels that of the native flora and fauna of oceanic islands. Both systems are surrounded by protective barriers which have enabled the forces of evolution to create countless species adapted to their unique natural surroundings.
Unfortunately, when these barriers are removed or weakened, these same life forms are frequently unable to cope with the changed conditions. The result is possible extinction.
Freshwater ecosystems are intimately linked to human activities. Throughout history, people have built their communities along the shores of lakes and rivers. From ancient times, cultures and civilizations have evolved and adapted to the annual cycle of renewal of the world's great river systems. But the human stresses now placed on freshwater ecosystems around the world are increasingly complex and increasingly pervasive.
In many cases, the capacity of these systems to assimilate human wastes has been surpassed, along with their capacity to support living freshwater resources in a sustainable manner. An unmistakable result of the cumulative impact of human-related activities is the dramatic loss of freshwater biodiversity.
It is discouraging, though not surprising, that for species after species it is those that live all or part of their lives in freshwater that are most vulnerable to human intervention. Many freshwater fish, amphibians, mussels, crayfish and dragonflies are threatened or endangered, while many others are already extinct.
The reasons that freshwater species are so vulnerable to human intervention are various. Some are obvious. Habitat destruction, invasive alien species, overexploitation and pollution are powerful threats to the biodiversity of freshwater ecosystems.
People often tend to live, work, consume and release their wastes near inland water. They dam, divert, channel, impound, reclaim and regulate rivers and lakes for a variety of purposes such as energy production, industry and agriculture until they bear little or no resemblance to the original ecosystems within which the life forms evolved. The life forms inhabiting these confined ecosystems often have nowhere to go, and the result is their elimination.
Even raindrops may contain traces of potent, man-made chemicals that can have an impact on biota and humans thousands of miles from the sources of pollution. Watersheds funnel such stresses - which include man-made chemicals, invasive alien species and sediments - into streams, rivers and lakes.
Understanding biodiversity loss
If we are to understand and try to address the causes of biodiversity loss we have to recognize that these biophysical stresses are a result of certain human values, decisions and socio-economic systems. For example, growing international trade and other pressures associated with globalization are breaking down barriers of every kind. The barriers that once protected watersheds and their ecosystems are not immune to such stresses. Global access to resources, and humanity's inexhaustible demand for consumer goods, fuel the worldwide conversion of resources (and habitats) into commodities for a global market place.
The ever-increasing demand for human food, for example, is generating a boom in freshwater aquaculture as landings of wild-caught fish decline. The impact of aquaculture on the biodiversity of freshwater ecosystems is likely eventually to compare with the impact of agriculture on the biodiversity of terrestrial ecosystems.
Global trade will increase the introduction of invasive alien species, and once a species has invaded a habitat, the results can last forever - as with extinctions. Because they reproduce and spread, often with devastating effects on native species, their impact can be greater and longer lasting than chemical pollutants. For example, unique and endemic fish species are endangered or already extinct as a result of the intentional introduction of the Nile Perch into Lake Victoria in Africa. Many species of freshwater mussels in the North American Great Lakes are rapidly disappearing because of the introduction of the zebra mussel over a decade ago. A detailed analysis of the way in which alien species have invaded North America's Great Lakes clearly demonstrates the role of international trade.
The rapid development of biotechnology also carries risks, even if it promises to enhance human welfare. We have to recognize that genetically engineered organisms, once released into the environment, may well behave like other invasive alien species.
The release of modified or alien species - unintentional or otherwise - habitat destruction and pollution will all doubtless play a role.
The only hope of slowing, or perhaps even reversing, the rate of loss of freshwater biodiversity is to give the issue high priority. It is not enough for freshwater experts to appreciate the vulnerability of these rich and diverse ecosystems. The public and politicians must be made sufficiently concerned to want to take action. The Convention on Biological Diversity specifically recognizes the extreme vulnerability of small oceanic islands. Unfortunately, the equally vulnerable freshwater biota is not given similar recognition, even though scientists have long recognized its vulnerability.
The need to change
Fundamental changes in the way we interact with freshwater ecosystems are needed. A good start would be to take more of an 'ecosystems approach' to conservation, protection, sustainable use and equitable sharing of freshwater biodiversity.
An important feature of such an approach would be to pay much greater attention to lakes and rivers as integral parts of basin ecosystems, in which the watershed, and especially the land uses in the watershed, can have significant effects on the ecosystem.
Perhaps most important, and certainly most difficult, is the compelling need to understand the socio-economic factors driving the loss of biodiversity. This may well mean a more interdisciplinary approach to help us understand the links between global macroeconomics and ecology. It is particularly important that we improve our understanding of how the current rules of the global 'monopoly game' impinge on global biodiversity.
We have to begin to document clear examples of market failures leading to loss of biodiversity, as well as being prepared to raise serious questions and offer constructive solutions that could help turn market failures into important lessons for the future.
Local communities are in the front line of efforts to save biodiversity and we should not overlook the potential for local initiatives to make a difference. In the long run, the rules of global economics will need to be altered - perhaps drastically - to encourage informed and responsible decisions about the uses of the planet's biodiversity and its many life-support functions.
The challenge is to encourage ground rules that make it possible - particularly for indigenous communities - to conserve, protect and use the biodiversity of local freshwater ecosystems in a sustainable manner.
Andrew L. Hamilton is Head of the Science Division, Commission for Environmental Cooperation, Montreal, Quebec, Canada