The paper presents the findings from a 15-year study of trees in the Hubbard Brook Experimental Forest in New Hampshire. In 1999, 40 tonnes of calcium pellets were dispersed by helicopter over a 12-hectare section of the forest in which the trees showed declining growth rates and a high rate of unexpected deaths. Previous soil analysis had showed that it had half the normal level of calcium.
Researchers from the University of California, Berkeley and Syracuse University found that trees in the calcium-treated site grew more healthily, producing 21 per cent more wood and 11 per cent more leaves, when compared to trees that grew in a nearby control site.
‘It’s generally accepted that acid rain harms trees, but the value of our study is that it proves the causal link between the chronic loss of soil calcium caused by decades of acid rain and its impact on tree growth,’ said John Battles of UC Berkeley, who led the study. ‘The temporal and spatial scope of the study – 15 years and entire watersheds – is unique and makes the results convincing.’
This story was published in the November 2013 edition of Geographical Magazine