Threats to the Cordillera Rice Terraces in a Period of Rapid Climate Change

Published on December 13, 2008

Deep into the Cordillera rice terraces are soil dwellers that dig their way through in a disrupted ecology. These lowly but destructive creatures endanger the nurturing ground that sustains the rich rice biodiversity of the Cordillera granary.

BY MARY CARLING
Center for Developments Program in the Cordillera
Northern Dispatch
Posted by Bulatlat

Deep into the Cordillera rice terraces are soil dwellers that dig their way through in a disrupted ecology. These lowly but destructive creatures endanger the nurturing ground that sustains the rich rice biodiversity of the Cordillera granary.

In the recent years, keepers of the rice terraces were astounded by “giant earthworms” that have invaded their paddies. Measuring 42 centimeters, these earthworms aggressively burrow into the soil, making numerous holes that allow water to run into the inundated terraces. This infestation has not only been affecting the growth of crops, it is also causing erosion of the terrace walls.

Earthworms have been beneficial to farmers because they are tillers of fertile topsoil. They play an important role in the ecosystem. In these days, however, the earthworms are destructive, a pestering problem for farmers that one has lamented, “What used to be a blessing is now a curse.”

This dramatic development in the rice terraces has generated a lot of interest among farmers, agricultural technicians and non-government organizations (NGOs), so that in November this year, the Montañosa Resource and Development Center (MRDC) organized a conference in Sagada to tackle the plight of farmers.

Why do giant earthworms suddenly appear in the rice terraces?

According to a preliminary study conducted by MRDC, farmers in Ifugao say that the first year of infestation occurred when the people started logging the forests to support a flourishing woodcarving industry. Banawe folk recall that in the1970s, these worms were there but it was only in the 1990s that their presence has become destructive to farming.

In some parts of Mountain Province, Kalinga, Abra and Benguet, farmers discovered these earthworms between the years 2000 and 2006. Farmers in Mountain Province attribute the upsurge in the number of giant earthworms to the erratic weather patterns. The MRDC pointed out that earthworms are forest dwellers that were forced to seek refuge in the rice terraces when their habitat was disturbed by human encroachment.

A study made by Dr. Xiaoming Zou, one of the world’s foremost experts on earthworm ecology, revealed that changes in land use alter the role earthworm play in the balance of their ecosystems. He said that as forests vanish, native earthworms disappear and exotic earthworms overpopulate.

Of the many species of exotic earthworms, the Pontoscolex corethrurus is found in the Philippines. Another species, Pheretima elongata, is found in the Ifugao rice terraces.

Controlling the giant earthworm

As farmers find solutions to control the earthworm population, Charlotte Camfili, an agriculturist of MRDC, cited that earthworm predators like the striped shrew rat, could have controlled the infestation. But this particular rat is one of the vanishing species of the Cordillera biodiversity.

In combating this giant earthworm infestation, farmers relied on their traditional knowledge. Applying organic pesticides has been their first weapon in defending their rice terraces from these “natural enemies”. In Tubo, Abra, when the giant earthworms attacked their rice paddies in 2005, the farmers effectively annihilated them with the bark of a poisonous tree species from the forest.

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