What effect is acid rain having in Britain?
We know that the increase in acidity of some fresh waters is linked to acid rain. Areas worst affected are those where the rocks are already naturally acidic and the soils are thin. Where the rocks are calcium rich such as chalk and limestone, the acidity is neutralised as it enters and passes through the soil. Some forest soils have become more acidic. Partly that is due to the dead needles falling down and partly because the trees trap atmospheric moisture – and with it its acidic component – which works its way down to the forest floor. It appears that conifer forests can act as giant sieves, filtering pollution out of the air and transferring it to the soil so that streams in forests growing on thin, acidic soils might become more acidic than similar water courses in grasslands. So far trees in Britain have largely been unaffected by the very acidic rain which has denuded many forests in Central Europe.
