US: Nearly 80 per cent of world’s population — 4.8 billion people as calculated in 2000 — live in areas experiencing high level of threats to human water security or biodiversity. A study published in Nature is the first to consider factors affecting both human water security and biodiversity in its analysis of threats to global freshwater resources, such as pollution and the density of dams.
Vörösmarty, a civil engineer at the City University of New York and his colleagues carried out a computer-based assessment to quantify documented threats to human water security and freshwater biodiversity in global river systems. From this they produced a series of global maps showing the cumulative effect of the multiple threats. One of the maps illustrates areas where human water security is affected, together with the severity of the threats. Another charts the same areas and threats for biodiversity and a third map combines the two surveys.
The researchers found that regions of the world with intensive agriculture and dense human settlement, such as the United States and Europe, experience some of the highest levels of threats to both human water security and biodiversity.
In addition, the results show that local impacts are transported downstream, with more than 30 of the 47 largest rivers in the world, including the Nile, recording at least moderate threat levels at the river mouth. Only a small fraction of the world’s rivers are unaffected by humans, with remote parts of the Amazon that flow through dense rainforest showing the lowest levels of threats.
Vörösmarty estimates that, by 2015, around USD 800 billion will be required to cover the annual global investment in water infrastructure. He also noted that technological solutions that help to deal with threats to human water security, such as building dams, can harm biodiversity. But he added that there does not need to be a trade-off between providing people with water and protecting biodiversity. For example, preserving flood plains rather than constructing flood-control reservoirs would provide a cost-effective way to control floods while protecting biodiversity of wildlife that occupies such areas.
“If you want to manage water resources better, you have to jointly manage biodiversity protection and human water security,” he said.