Increased pH and dieback of lichen

Increased pH and dieback of lichen

Lecanora conizaeoides is an epiphytic lichen adapted to very acidic conditions, and a reduction in atmospheric SO₂ in western and central Europe has coincided with a dramatic decline in its distribution. Hauck et al. study lichen diversity and bark chemistry in northern Germany and compare the results with comparable data collected 13–15 years previously. Neither competitors nor parasites that might have benefitted from the reduction in SO₂ are likely to account for the decline in L. conizaeoides cover on trees, and the results instead suggest that an increase of only 0.4 in bark pH is responsible.