Underground mining magnifies drought impacts in an adjacent protected raised bog

Stable and high water levels are crucial for wetland ecosystems, impacting their state, vegetation and conservation. To make informed conservation decisions, it is essential to consider the full range of ecosystem-level threats associated with artificially lowered water levels. This becomes particularly challenging when dealing with diffuse and indirect impacts, such as ombrotrophic bogs near underground mining activities that extract groundwater. In this study, we monitored water tables using automatic pressure loggers over an 11-year period in a protected hemiboreal bog and in drained peatland surrounding it in northeastern Estonia. The bog is located within the groundwater cone of depression caused by an adjacent oil-shale mine, approximately 60-70 m deep. By comparing monitoring points along the bog-drained forest gradient and analysing time series data, we were able to distinguish the influences of climate and mining activities on water levels in the bog. Our findings indicate that mining activities have clear effects on deeper bedrock aquifers and the bog itself, exacerbating the impacts of recent drought events. The dynamics of the hydraulic heads at different monitoring points reveal local infiltration 'windows' within the bog, likely resulting from underlying fracture zones in the bedrock. Considering the escalating intensity of climate change, mires' vulnerability to these combined impacts is expected to increase. Therefore, adopting a precautionary and forward-thinking conservation strategy is crucial when addressing ongoing or future drainage and mining activities near protected wetlands.