As the world warms, access to fresh water will become less and less obvious which is bad in itself, but as it turns out now, water shortages could contribute to even more warming through a positive feedback loop.

0.4 petagrams of carbon

As plants take up CO2 from the atmosphere, it should come as a no surprise that global agriculture is a large carbon sink. And since irrigation increases agricultural productivity, it seems logical that it has an effect on global carbon uptake. Now scientists from the University of Wisconsin-Madison have made it truly interesting and put a number to the impact of irrigation on global carbon uptake.

According to the results published in the journal Global Biogeochimical Cycles, irrigation increases agricultural productivity by a quantity that amounts to about 0.4 petagrams of carbon which is roughly the equivalent of the total agricultural productivity of the United States.

Sometimes less is more

As most people have personally experienced by watering their plants at home, increasing the amount of water does not necessarily mean better growth. There are diminishing returns. The study also showed this, but obviously on a much greater scale. It found that adding even a small amount of water to a dry area might have a bigger impact on productivity than adding a larger amount in a wetter region.

Agricultural management

Globally irrigation is currently practically optimised for maximum productivity. This might seem like good news, but sadly it also means that agricultural productivity is hard to increase through this manner even as food demands are still on the rise.

If the study has done anything, it has yielded extensive spatially-explicit maps of the influence of irrigation on carbon accumulation. These may prove vital in quantifying how organisational decisions in irrigated landscapes may impact regional and global carbon balance and climate.

© Jorn van Dooren | www.bitsofscience.org