by Gerry T. Estrera
“Everyone agrees water is basic for life,” notes veteran journalist Juan L. Mercado. “When cisterns go dry, disease and death rates surge. That ushers in economic decay — and political instability. Water riots can be ugly. And no one has yet invented a substitute for water.”
At that time, in 1952, the Bureau of Coast and Geodetic Surveys reported that forests covered 8.6% of the province of Cebu. Twenty years later, unchecked logging and slash-and-burn farming (locally known as “kaingin”) razed natural forests to only four square kilometers scattered in three adjoining watersheds.
Today, Cebu has no forest cover to speak of. This must be the reason why the province is often hit by water shortage. Will Davao follow suit?
“Without vegetative cover, especially the trees, the land’s water absorption capacity is greatly reduced,” contends Ines Basaen who, at the time she spoke those words, was the national coordinator of the International Labor Organization’s community-based environment impact assessment for indigenous people’s project.
In an article she wrote for the Philippine Center for Investigative Journalism, Joy Hofer quoted Diosmedes Demit — who joined the “Fast for the Forests” — who said, “If the forest perishes, so will the life of people. The trees are our source of life. Without trees, there will be no water. If there is no water, there will be no life.”
Is it really true? Do trees really produce water?
“You ask an interesting question,” Dr. Patrick B. Durst, senior forestry officer with the regional office of the UN Food and Agriculture Organization (FAO) in Bangkok, Thailand, said. “As with so many things related to forests and trees, the answer is not simple — certainly not as simple as many people would like to present it.”
Dr. Durst, who is married to a Filipina and has helped coordinate FAO’s forestry programs for more than two decades now, said that trees are not a source of water “in the narrow sense.”
“In fact, as living organisms, trees are substantial consumers of water, particularly when growing healthily,” said the American forester who started his international career in 1978 as a US Peace Corps Volunteer in Bohol. “That is why, for example, people sometimes plant fast-growing trees to help drain swamps; the trees consume water and draw down the water level.
“Conversely,” he continued, “water tables sometimes rise when trees are cleared from an area. Famous watershed studies at the Coweeta Hydrological Laboratory in North Carolina, conducted since 1934, show very clearly that there was a scope for increased water yield by reducing forest vegetation.”
Water use by trees is also at the heart of the argument of many against the use of eucalyptus trees. In 1990, an estimated 10 million hectares, or approximately one-quarter of tropical forest plantations, were planted with eucalyptus. More than half of these were located in tropical Asia, including the Philippines.
“As a fast-growing species, eucalyptus uses a lot of water and may contribute to a lowering of water tables,” Dr. Durst argued. “The same is true of most fast-growing tree species. It seems, not illogically, that you need a lot of water to produce a lot of wood quickly.”
So, what role do trees play in “producing” water?
Clearly, trees must be good for something it comes to watershed management, or else foresters and water management specialists wouldn’t make so much fuss about trees.
Here’s Dr. Durst again: “The answer is that trees (and more importantly healthy forests) are very important. The main benefit they provide is helping to intercept precipitation and facilitate its infiltration into the soil and ground water storage areas.”
According to the FAO forestry expert, the trees also help reduce erosion of soil by “breaking the fall” (that is, the impact) of rainfall that might otherwise dislodge soil particles upon harsh impact.
First, tree (leaves, branches, etc.) intercept rainfall. But more importantly, healthy forests’ ground cover — organic litter, twigs, small plants and fallen leaves, among others — help trap water and hold it until it has an opportunity to soak into the ground soil.
In addition, roots whether alive or decaying, provide additional pore space above that of normal soil texture for water to infiltrate into the ground. This is the reason why local springs and streams maintain a healthy flow when surrounded by protected micro-watersheds.
Dr. Durst urged foresters — and environmentalists, too! — to be honest about the “relative benefits” of forests and other land cover for watershed protection. He added that healthy grasslands can be just as effective, or more so, in preventing soil erosion and aiding water infiltration.
“We cannot talk of providing sustainable water to the people unless we protect the sources of the commodity — the watersheds,” Elisea Gozun, former head of the Department of Environment and Natural Resources (DENR), once pointed out.
In the 1950s, the Philippines had as much as 9,600 cubic meters of clean water per person, according to Dr. Rafael D. Guerrero, former head of the Philippine Council for Aquatic and Marine Research and Development. Four decades later, Filipinos must make do with little more than a third for that volume – 3,300 cubic meters per capita.
“Water isn’t just a commodity. It is a source of life,” says Sandra Postel, director of the Massachusetts-based Global Water Policy Project. Ideally, a person should have at least 50 liters of water each day to meet basic needs – for drinking, food preparation, cooking and cleaning up, washing and personal hygiene, laundry, house cleaning.
