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The colour of water

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This week’s Nature (subscription) is all about a very special fluid – water. Fresh water, to be precise.

Globally, irrigation accounts for most freshwater use (in some countries up to 80%). But in rich countries in particular, electricity production also places an intolerably high burden on freshwater supplies. In a commentary, Mike Hightower and Suzanne A. Pierce lay out strategies, such as using waste water, sea water or brackish groundwater for cooling, for economizing water usage by power generation.

It has become customary to blame climate change for all kinds of things, from violent conflict in Darfur to the unseasonal mosquito which last week plagued me in my bedroom.

The global water crisis is no exception, no matter whether it signifies flood or drought. Let’s for now just take a look at the latter. Is global warming really worsening the problem of water scarcity?

One might think no. Every physicist will tell you that you’ve got to get more precipitation in a warming world. As temperatures increase, so does evaporation of ocean water which generates clouds and rainfall.

However, the extra energy in the atmosphere has the effect of changing the distribution of rainfall over land. The crux is that in a wetter world many places may actually face longer dry spells between heavier rain events.

Existing climate models are too coarse to resolve the processes which lead to rainfall, so where, and how soon, precipitation will change is still rather uncertain. For my feature article, I spoke with scientists about what they think might be the effects of more extreme patterns of rainfall on soil moisture, land degradation and agriculture – and about possible adaptation strategies.

In a second feature, Emma Marris investigates what plant breeders, agronomists and geneticists have to offer when it comes to produce more crop per drop in dry regions. The wide-spread feeling that biotechnology is at best a mixed blessing for the developing world has not gone away, she found.

As so often when it comes to climate change (and not just that), Africa is in the centre of concerns. Imported science and technology can help; but one wonders if western experts and funding agencies are always right in forcing strategies on societies which they don’t really understand, just because these strategies work at home.

For a totally non-scientific, but altogether enlightening, insight into an agricultural sub-Saharan society (long before climate change had appeared on the horizon) it’s worth checking out Chinua Achebe’s classic novel Things fall apart.

Quirin Schiermeier


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