IN FOCUS
2 Planning for an uncertain future

NEWS
10 Venice will succumb to sea-level rise, the question is when
11 Mexican wins Kalinga Prize
12 Laureates find new ways of looking at old problems
13 ICTP takes seismology course to epicentre of Haitian tragedy
13 A graduate diploma in nanoscience for Arab universities
14 Mission accomplished for Lady Amber

INTERVIEW
15 Madiodio Niasse on the risks associated with large-scale foreign land acquisitions

HORIZONS
17 Sandwatchers find a market for a weed
20 Striving for a better tomorrow in Mujib

IN BRIEF
24 Agenda
24 New Releases

Direct link A World of Science Vol 10 N°2 (PDF document)
See also archives for A World of Science.

Water too has a tipping point

In 2009, Rockström et al. proposed the concept of ‘planetary boundaries’, beyond which lay the point of no return, or tipping point. They estimate that humanity has already transgressed three out of nine boundaries, those for climate change (greenhouse gas levels), the rate of biodiversity loss and the global nitrogen cycle. Humanity may even have transgressed a fourth boundary, they suspect, the limit for freshwater use, or may be close to doing so. Current consumption is estimated at 2 600 km3 per year – and rising.

This study is cited in the Fourth World Water Development Report, Managing Water under Uncertainty and Risk, launched by UNESCO on 12 March on behalf of the 28 agencies comprising UN-Water. Rockström et al. suggest that the social cost of transgressing the planetary boundaries will depend upon how resilient and green our societies are. Going green will not alone ensure more water-friendly policies, however, as exemplified by the controversies over biofuels and large-scale foreign acquisitions of arable land. Above all, the report observes, we need to acknowledge the cross-cutting nature of water across the entire development spectrum. Food and energy production, industry, human and environmental health are all dependent on water, all essential for socio-economic development and all increasingly interdependent.

Forgetting that water flows over sectoral boundaries can be a costly mistake. The Mississippi Delta in the USA has been radically modified to supply agriculture and hydropower. By reducing risks to agriculture upstream, the scheme has amplified risks downstream, exacerbating the impact of Hurricane Katrina on New Orleans in 2005. Where is the link? The dam constructed on the river interrupts sediment transfer. Without the constant deposition of sediment, tidal and wave action is gradually eroding the delta on which New Orleans is built, causing the city to sink and thus to flood more easily. The pumping of groundwater, oil and natural gas in the delta has caused further subsidence.

This example illustrates a wider problem. The lack of interaction between sectors, as well as between users, decision-makers and managers, has allowed water resources to become seriously degraded around the world, threatening all the sectors that depend on water and thus compromising development. With climate change likely to make water resources less abundant in future, even as demand for water grows, humanity finds itself on an unsustainable development path.

At a time when humanity is facing an uncertain and perilous future, Managing Water under Uncertainty and Risk drives home the point that a ‘business-as-usual’ approach to water management is not an option. We must adapt our development planning and management to reflect the bigger picture. And we don’t have much time. Herein lies the key message of the report, extracts from which you will find overleaf. The Earth Summit in Rio in June should offer an ideal occasion to drive this message home.

Gretchen Kalonji
Assistant Director-General for Natural Sciences