Large numbers of ducks that were initially driven out of the Central Valley in California but are now returning, are having a positive effect on rice growing there.
Alterra researcher Dr Jan Willem van Groenigen examined the effect of the birds together with Linda van Diepen, a student at the time. The ducks eat the seeds of weeds and break up the remaining stalks of the rice plants, which helps them to decompose more quickly therefore increasing the rate of nitrogen uptake by the soil. This in turn helps the rice plants to grow more quickly. The irony is that the ducks were first driven away as the marshes in the Central Valley were dried out to make way for rice cultivation. The ducks now return in the winter when the farmers flood their fields. The results were published in Agriculture Ecosystems & Environment.