What does 'moderate' impact mean?

The giant forest trees in the Bukit Timah and Central Catchment nature reserves. PHOTO: CHUA EE KIAM

Last week, an environment assessment report said the effect of soil testing works on animals and plants in the Central Catchment Nature Reserve could be kept to "moderate" levels if measures to reduce impact are strictly implemented.

What does "moderate" mean? The roughly 1,000-page report, seen by The Sunday Times, said a moderate impact "falls somewhere in the range from a threshold below which the impact is minor, up to a level that might be just short of breaching a legal limit".

Assistant Professor Chian Siau Chen of the civil and environmental engineering department at the National University of Singapore said there are usually five categories under the Environmental Impact Assessment (EIA) framework: Major, moderate, minor, negligible and beneficial.

"Moderate usually refers to moderately adverse changes to the ecosystem which may exceed the range of natural variation," he said, adding that potential for recovery without intervention is good, although a low level of impact may remain.

But Ms Natalia Huang, principal ecologist at consultancy Ecology Matters, pointed out that there is no standard description for such terms in Singapore. How the terms are used could vary, she said.

"Ideally, impacts to very sensitive environments such as the freshwater streams in the Central Catchment Nature Reserve should be negligible to minor, although some moderate impacts are often unavoidable, " she said.

Ms Huang called for the EIA report to be put online, as is standard practice in other countries. It is now available for public viewing at the Land Transport Authority's Hampshire Road premises, and by appointment only, until March 4.

Audrey Tan

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A version of this article appeared in the print edition of The Sunday Times on February 14, 2016, with the headline What does 'moderate' impact mean?. Subscribe