Scientists treated New Hampshire watershed for acid rain; nitrogen later surged
A long-term study in New Hampshire found that adding calcium-rich minerals to a forest to combat acid rain led to an unexpected surge in nitrogen runoff into streams. The findings challenge existing models of how forest ecosystems process nutrients.
Why it matters
It provides critical insights into the unintended consequences of environmental restoration efforts and ecosystem management.
A large-scale effort to restore an American forest damaged by acid rain had an unexpected environmental effect when added nutrients caused a huge increase in nitrogen flowing into nearby streams. In October and November 1999, researchers spread about 45 short tons (40 metric tonnes) of a calcium-rich mineral over a 29-acre (11.8-hectare) catchment in New Hampshire. The treatment was meant to replace important soil nutrients that had been washed away by decades of industrial pollution. It worked at first, improving tree growth and leaf health over the next decade. But long-term monitoring later revealed a surprising change: by 2013, the treated valley was sending 30 times more inorganic nitrogen into its streams than nearby untreated forest catchments. The findings, published in the journal Proceedings of the National Academy of Sciences (PNAS), challenged long-standing ideas about how forest ecosystems handle nutrients.
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