§ Mr. Alex Carlile
To ask the Secretary of State for Scotland if he will make a statement regarding the recent finding of a committee of the Forestry Commission on a link between conifer trees and river acidification.
§ Sir Hector Monro
[holding answer 7 December]: None of the Forestry Commission's committees has made a recent finding of this kind.
An expert workshop jointly sponsored by the Forestry Commission and the Department of the Environment concluded in June 1990 that the primary cause of surface water acidification was the deposition of airborne sulphur and nitrogen pollutants, but that there was also an association between trees and acidification resulting from the effectiveness of trees in scavenging these airborne pollutants. Whether the latter phenomenon would result in increased surface water acidification depended, however, on the sensitivity of the geology and soil in any given catchment area.
The members of the Forestry Commission's north Scotland regional advisory committee recently considered this and other scientific evidence presented to them in the course of considering planting grant applications over which objections had been raised on environmental 788W grounds. They advised the commissioners that, in their opinion, there was sufficient doubt about the effect that tree planting on the specific sites concerned would have on surface water acidification as to prevent their recommending that the applications should be approved at this stage. In the light of this advice, the Forestry Commissioners have decided to delay taking a decision on these applications pending further monitoring of the sensitivity of the sites to further acid inputs from the atmosphere.