Washington: A study by researchers at the Texas A and M University, US, has suggested that the assumption that encroaching woody plants slurp up water and drain nearby rivers in a particular area, is not true, and clearing these plants might make drought worse.
The assumption is the driving force behind efforts from Texas to South Africa to clear shrubs from drought-prone land.
Hydrologist Bradford Wilcox and his colleague Yun Huang examined water levels going back to 1925 for four of Texas`s biggest rivers near the parched Edwards Plateau in the west of the state.
What they found shocked them.
"Rivers on the Edwards Plateau not only are not disappearing, but they are increasing in flow," said Wilcox. "By a lot. I mean, it`s doubled. That`s really big," he added.
The landscapes that Wilcox is describing are karst savannahs that are fed by groundwater and the occasional rain storm.
A century ago, the Edwards Plateau was heavily populated by massive herds of cows, goats and sheep.
However, as Texas developed, the number of herds diminished and left wastelands of eroded soil and rock.
These ``degraded`` landscapes slowly recovered and, eventually, aggressive woody shrubs such as juniper and mesquite blanketed what had once been prairie.
Such plants today are demonized as greedy water drinkers, and ranchers are asking for government help in removing them.
Yet, when Wilcox examined water records, he found an increase in water flows that he attributes to increased land cover by woody plants.
Rain patterns in the area haven`t changed drastically and there has been little urbanization.
"I can`t really think of any other plausible explanation," Wilcox said. "The obvious no-brainer is that it has had this massive change in land cover. There`s more vegetation, there`s more cover, there`s more protection. And so it allows more water to enter into the soil," he added.
These results might cause land managers to look for other solutions to mitigate drought.