RIO DE JANEIRO, Oct 9 (Tierramérica) - The potential negative effects of hydroelectric dams have strengthened opposition against the Brazilian government's plan to build two on the Madeira River, the largest tributary of the Amazon and which starts in the Bolivian Andes.

"The Jirau dam would flood an area greater than the project plans, due to the sedimentation that could elevate the Madeira riverbed by six meters," Glenn Switkes, of the International Rivers Network, told Tierramérica.

The Madeira carries half the sediment that ends up in the Amazon River, he said, corroborating the fears of the report released Oct. 3 by the Bolivian Forum of Environment and Development, about changes that could hurt fish populations and the water quality of Bolivian rivers.

The authorization for both dams lacks complementary studies about sedimentation, and public hearings have yet to be held, so the debate will be extended into next year, predicts Switkes.

BUENOS AIRES, Oct 9 (Tierramérica) - Residents of the city of Palpalá, in the northwestern Argentine province of Jujuy, are protesting the operations of Sulfhaar, a sulfuric acid factory that already has approval from government authorities.

Sulfhaar set up shop in August in Alto La Torre, a neighborhood where there are already 15 factories challenged by local residents, including silver and lead foundries, paper mills and a borax plant.

"They moved in without asking permission, even though since 1990 an ordinance bans new contaminating factories," Orlando Conejo Vargas, of the Organized Residents of Palpalá, told Tierramérica.

"We live half a block away from the factories, and at night we hang damp cloths in the doorways to prevent the odor and the pollution from entering," he said. Palpalá is 15 km from the provincial capital and is home to 45,000 people.

GUATEMALA CITY, Oct 9 (Tierramérica) - The United States has forgiven 24 million dollars of Guatemala's bilateral debt, with the condition that it be used to preserve tropical forests over the next 15 years.

The U.S. ambassador to Guatemala, James Dirham, explained to Tierramérica that the funds "will help conserve Guatemala's cloud forests, tropical jungles and mangroves, which are home to hundreds of species of birds, and (especially) aquatic birds that migrate" between the two countries.

The resources will be earmarked for preserving, among other areas, the western high plains volcanic chain, where there are 885 animal species, 100 medicinal plant species and a forest of conifers. And also the eastern region of Cuchumatanes, with its 13,000 hectares of rich biodiversity.

The Oct. 2 agreement is the 10th one like it to be signed by the United States and is the largest debt-for-nature exchange granted by Washington.