Spending millions of taxpayer dollars to replenish Hawaii’s vegetation and native forests may seem extravagant except for the alternative: public consumption reliant on declining sources for absorbing rainwater and replenishing groundwater. The alternative would be to take the salt out of ocean water at enormous expense, which is why Gov. Neil Abercrombie is asking legislators to save the forests. The response should not be delayed.

Half of Hawaii’s forests have been lost, as feral pigs and goats worsened the situation by eating vegetation, allowing alien plants to consume more water and increase runoff, according to a study by the state Department of Land and Natural Resources.

Climate change has added to the problem: Statewide winter rainfall has been 12 percent lower in the past 20 years than previously.

"Temperatures are steadily rising while cloud cover lessens," explains University of Hawaii geography professor Tom Giambelluca, "meaning more water is evaporating."

He pointed out that forests play an important role in intercepting water from clouds and reducing direct runoff.

Groundwater levels around Pearl Harbor, which supplies 60 percent of Oahu’s water, have dropped by half since 1990.

"Without vegetation and forest cover," the study points out, "most of our islands’ rainfall would quickly run off unused into the ocean.

Instead, the forest buffers the impact of heavy rains. Rainfall collects on the leaves, branches and understory, allowing it to drop slowly into the ground."

From there, the water is tapped by wells and tunnels to supply nearly all of Hawaii’s drinking water.

About $11 million per year in the decade ahead would be the cost to double the amount of protected watershed, partly by fencing off areas from invasive animals and replanting native species. The report makes a solid argument for accepting the cost, as only 10 percent of the state’s priority watershed areas is now protected. Abercrombie says he hopes to double that percentage in a decade.

The reduction of native forests has caused extensive water loss across landscapes. The alternative cost of a desalination plant to provide 5 million gallons a day projected for Oahu’s Ewa district would be $40 million to build and more than $5.4 million a year to operate, according to the DLNR study. Obviously, that should not be regarded as an alternative.

Abercrombie expects legislative approval on this issue, pointing out in a news release that Sen. Donovan Dela Cruz, chairman of the Senate Water, Land and Housing Committee, has said it "makes economic sense for agriculture, environment and our future drinking source."

While doubters may question the effectiveness of Abercrombie’s proposal and the expenditure, especially in tough fiscal times, the proactive attempt is worthwhile. The importance of watersheds cannot be ignored, and the availability of precious water cannot be taken for granted.