Under drought conditions, tropical forests can be as efficient
at using water as desert ecosystems, researchers report. When
push comes to shove, all ecosystems have the same maximum rain-
use efficiency, a measure of total plant growth per unit of
precipitation. The finding indicates there's an upper limit to
ecosystems' productivity, said Travis E. Huxman, a plant
physiological ecologist at the University of Arizona in Tucson.
He and a team of researchers calculated the upper limit, which
they call RUEmax (maximum rain-use efficiency). Life depends on
the productivity of plants, Huxman pointed out, adding, "RUEmax
defines the limits of that production." However, the research
indicates that under drought conditions, high-productivity
systems like grasslands and forests grow even less than
expected. Most of the climate-change scenarios for the next
century predict an increase in extreme events, including more
droughts. Huxman said, "We originally expected drought to impact
grasslands to some degree, but this f