Forests in Taiwan jeopardized by acid rain: EPA

The nation's forest ecosystems have been jeopardized because the amount of acid rainfall they receive now exceeds their ability to recover, the Environmental Protection Administration (EPA) said yesterday.

The EPA released a newly completed study on acid rain, suggesting that six crucial forest ecosystems have been jeopardized by excessive acid rainfall at three to 10 times higher than their tolerance.

Taking the forest in Fushan, Ilan County, as an example, EPA officials said that it now receives more than 10 times its "acid critical load," and a forest in Shanping, Kaohsiung County, receives more than eight times its critical load.

The "acid critical load" refers to the maximum amount of acid deposits that a region can receive without damage to its ecosystems.

Project investigator Lin Neng-huei (林能暉), an atmospheric sciences professor at National Central University, said that acid critical loads can be categorized into five levels of sensitivity based on indicators showing the ecological impact of acid rain, with the first level being the most vulnerable.

Ecosystems that can tolerate acidic pollution have high critical loads, while sensitive ecosystems have low critical loads. The sensitivity level depends on the acid-rain neutralizing capacity of the water, rocks and soil.

"However, five out of the six forests investigated could be classified as the second level, which shows their relatively high vulnerability," Lin said at a press conference yesterday.

Lin said that when the environment fails to neutralize the acid being deposited, ecological damage inevitably occurs.

Two common air pollutants in acid rain are sulphur dioxide and nitrogen oxide. When these substances are released into the atmosphere, they can be carried over long distances by prevailing winds before returning to earth as acid rain.

"The EPA will seriously monitor acid rainfall in different regions in order to understand the possible negative impact being made on ecological systems," said Ho Soon-ching (何舜琴), director-general of the Bureau of Air Quality Protection and Noise Control.

Ho said that Taiwan has set up many regulations to limit the use of inferior fuels for automobiles in a bid to effectively prevent air pollution. However, foreign pollutants traveling long distances from China, which has experienced rapid industrialization, contributes to more than 50 percent of air pollutants in this country.

EPA statistics show that the pH level of rainwater is about 4.9 in Taipei, 4.6 in Chungli and 4.8 in Kaohsiung. The lower the pH level of rainwater, the more acidic it is. According to the EPA, the normal pH of rainwater should fall between 5 and 6.

Lin said that a research network including scientists in the US, Japan, China, Hong Kong and Taiwan has been established to exchange critical data about pollutants causing acid rain in the Pacific region. Taiwanese researchers are calling for more countries to take part in the network in order to monitor the regional distribution of pollutants and prevent local ecological damage.