Bog Recovery in Northeastern Estonia after the Reduction of Atmospheric Pollutant Input

The restoration of wetland ecosystems is one of the flagships of modern conservation ecology, and the development of methodologies is vital to the enhancement of biodiversity. Bogs in northeastern Estonia have been under intensive pressure from alkaline fly ash pollution emitted by oil shale-heated power plants since the 1950s. In the vicinity of pollution sources, the input of alkaline fly ash has increased the ash content in mosses and raised the pH value of bog water, which had caused the replacement of Sphagnum mosses by other bryophytes and the invasion of eutrophic plants by the 1980s. The results of our study show that in recent decades, after the reduction in atmospheric input by power plants, the ash content in mosses has fallen, bog water pH is lower, and bog-specific plant species have begun to return to the bogs that were moderately polluted in recent decades. However, historically heavily polluted bogs show little signs of self-restoration, and their vegetation is still threatened by continuing degradation. Based on the wide gradient of pollution intensity, we suggested a list of indicators that can be used to evaluate bog degradation rates and restoration success.