Yes, the “and” in the title is deliberate. The world is on the verge of a crisis that is endangering both human water security and freshwater biodiversity. That crisis is the rapid disappearance and degradation of one of the most endangered global habitats – freshwater ecosystems.
Around 3% of the world’s water is fresh, and 99% of this supply is either frozen in glaciers and pack ice or found underground in aquifers. Freshwater ecosystems, which comprise ponds, lakes, streams, rivers and wetlands, account for the remaining 1% of the world’s freshwater sources. Lakes and rivers are the main sources for human water consumption, but contain just 0.26% of total global reserves. Other important human uses of freshwater ecosystems include inland capture fisheries, which contribute about12% of all fish consumed, irrigated agriculture, which supplies about 40% of the world’s food crops, and hydropower, which provides nearly 20% of global electricity production. Excessive nutrient loading of water bodies is also a leading cause of water pollution worldwide. Human-induced biological invasion is another major threat to freshwater habitats worldwide.
Although freshwater ecosystems occupy only 0.8% of the Earth’s surface, they account for 100,000 to 126,000 (6-7%) of the estimated 1.8 million species globally. Thus, as the various human uses put pressure on scarce freshwater habitats worldwide, their biodiversity invariably will decline. This process is exacerbated by global environmental threats, such as climate change, nitrogen deposition and shifts in precipitation. Already, freshwater ecosystems are experiencing declines in biodiversity far greater than those in the most affected terrestrial ecosystems.
Loss of freshwater biodiversity has its most direct impact on inland fisheries. Fisheries landings from inland waters have increased fourfold, about 3% annually, since 1950. Such fisheries are especially critical in the developing world; for example, tropical rivers and inland fisheries are estimated globally to yield US$5.6 billion annually. Yet, overfishing of inland fisheries is endangering food webs and the structure of freshwater ecosystems. Freshwater biodiversity may also be linked to water quality. Biodiversity appears to enhance the purity of water by removing or dissolving nutrients, chemical pollutants, pathogens and faecal matter. Clean water and human water security may therefore depend on freshwater biodiversity, which in turn may be important for the healthy functioning of freshwater ecosystems.
A recent study by Charles Vörösmarty and colleagues in Nature illustrates how the global water crisis and freshwater biodiversity declines are linked. The authors find that freshwater ecosystems will remain under threat well into the future due to the escalating trends in species extinction, human population increases, climate change, water use and development pressures. Nearly 80% (4.8 billion) of the world’s population (for 2000) lives in areas where either human water security or biodiversity shows high incidence threat. However, there is a stark contrast between the developed and developing regions of the world. Much of the developed world faces the challenge of reducing freshwater biodiversity threats while maintaining established water services. In contrast, the accelerating pressures on freshwater ecosystems in developing countries indicate that they are facing a dual threat to both future human water security and biodiversity.
What is urgently needed is a new global strategy for integrated management of freshwater ecosystems, to combat both biodiversity loss and enhance human water security. Such a strategy must contain five areas of policy priorities. I label these priorities as the five “i’s” of integrated freshwater ecosystem management:
- identify the freshwater ecosystems globally that are at most risk yet potentially have the most importance in terms of biodiversity conservation;
- information on the potential links between freshwater biodiversity and other ecosystem goods and services, especially water quality;
- integrate consideration of biodiversity conservation and other ecosystem services in water management decisions;
- incentive mechanisms for improved water and freshwater biodiversity conservation, controlling pollution and eutrophication and managing inland fisheries sustainably; and
- investments in reducing water poverty globally, especially in improving access to clean water and sanitation for populations in developing countries.
Most freshwater ecosystems globally are undergoing such rapid and substantial change that both human water security and freshwater biodiversity are under threat in many regions. The conventional view that these systems should be primarily managed for satisfying human water security is a luxury that the world can no longer afford.
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