Glob. Biogeochem. Cycles doi:10.1029/2009GB003481 (in the press)
Farming on river-fed floodplains cuts their carbon storage, suggests a new study. These floodplains are highly productive ecosystems covering more than 1.3 per cent of the Earth's surface, but little is known about the quantities of carbon cycling through them.
In 2004, Georg Lair of the University of Natural Resources and Applied Life Sciences in Vienna and colleagues measured the organic carbon content of floodplain soils surrounding the Danube River in Austria. They found that the youngest soils — those less than 100 years old — sequester more than 100 grams of carbon per square metre each year. As undisturbed floodplains are regularly replenished by fresh, nutrient-rich sediments, they could maintain this high carbon uptake for centuries, the authors suggest. In intensively farmed floodplains, however, young soils take up much less carbon annually, making croplands significantly weaker carbon sinks than uncultivated ground.
Over 70 per cent of European floodplains and 46 per cent of North American floodplains have already been converted to cropland. The researchers warn that uncultivated plains should be preserved if we are to make the most of these carbon sinks.