According to a primer prepared by the climatology and agrometeorology branch of PAGASA, ENSO occurs in the Pacific basin every two to nine years. It usually starts during the Northern winter (December to February) and exhibits phase-locking to annual cycles (El Niño and rainfall fluctuations associated with it tend to recur at the same time of the year). Once established, it lasts until the first half of the following year, although at times it stays longer (examples: 1939-1941, and 1989-1992 episodes). More importantly, El Niño events are often preceded and/or followed by La Niña.
According to PAGASA, the forthcoming La Niña would greatly affect the
country's eastern seaboard, particularly Cagayan Valley, Isabela, Southern Leyte, Leyte, Agusan del Sur and Norte, Davao Oriental, Samar, Aurora and the Bicol provinces.
Soil erosion would be a common sight during La Niña. "When land is The coming denuded of trees, scorched by burning, and deprived of its humus by intense heat, the earth soon erodes," explains Steve Musen, the director of the Davao-based Mindanao Baptist Rural Life Center (MBRLC) Foundation, Inc.
Scientists are still searching for the mechanisms that could trigger the warming (El Niño) or cooling (La Niña) of sea surface temperature in the equatorial Pacific. "Once the warming or cooling has started or continued for a certain period of time," PAGASA said, "there are already existing climate models that could somehow predict its duration."
How does La Niña affect the country's weather? According to PAGASA, "La Niña's effects could be manifested in above the normal rainfall conditions in major parts of the country, particularly along the eastern sections. This is mainly due to more intense northeast monsoon and tropical cyclone activities."
Musen said trees contribute to agriculture by controlling erosion, conserving water supplies and providing shade, shelter and wind barriers. "Trees are one of the nature's most efficient weapons of soil defense and are used to tie down steep hillsides, check the growth of big gullies, stabilize unsteady stream banks and screen cultivated fields from harmful winds," he said.
Without trees, floods are expected to happen. "Floods are among the most destructive calamities man has to cope with," PAGASA wrote in a brochure that explains the hows, whats, and hows of floods. "Even the most minor flooding poses some inconveniences."
A really big flood can result in millions even billions of pesos of damage to road and bridges, buildings and other economic infrastructure, in the loss of agricultural crops and livestock, loss of productivity in industry, commerce and trade - not to mention the incalculable loss of human life.
"With too much rain and floods, agriculture production especially in flood-prone areas will be adversely affected with physical and economic losses," Dr. Guerrero said. "Floods will wash away crops, hasten soil erosion and increase crop spoilage due to poor storage and distribution problems."
The PCAMRD chief admitted that Filipino farmers cannot do anything against the onslaught of La Niña except to prepare and plan for it. "Planting in flood-prone areas should be avoided to avert crop losses," he stressed. "Drainage and flood-control structure should be renovated beforehand."
For its part, the Department of Agriculture has been tasked with immediately conducting an information campaign among the country's farmers to advise them to change the type of crops they would be planting this season. Farmers, particularly those in eastern Luzon, should consider switching to crops suitable to the predicted high rainfall in the coming months.
The Philippine Council for Agriculture, Forestry and Natural Resources Research and Development recommends that farmers should build dikes and small farm reservoirs to prevent flooding during the La Niña.
Climate centers in Australia, Japan and the United States said the predicted La Niña phenomenon would continue for the next three to six months.