Cation responses to global changes alter ecological processes in ombrotrophic systems

•Ombrotrophic bogs, which store large amounts of carbon as peat, receive all their mineral nutrition through deposition. This limited nutrient input means they are particularly sensitive to local and global changes that displace vital cations.
•We review how acid deposition drives cation displacement (i.e. sodium, magnesium, potassium and calcium) in ombrotrophic bogs. We then synthesise the literature across scales of ecological organisation on the role of cation availability in shaping plant stoichiometry and function, community dynamics and ecosystem function.
•Acid deposition from industrialisation drives declines in cation concentrations in peat, and although recovery is underway, cations remain depleted in acid‐affected areas. Cation depletion could cause decreased Sphagnum spp. growth and decreased plant diversity. There is higher uncertainty in how cations contribute to ecosystem processes. Future trends will likely be dictated by climate change‐driven increases in marine deposition, which will increase cation concentrations in maritime bogs and alter ecological processes across scales.
•Synthesis . There is limited yet compelling evidence that cation availability is a key determinant of ecological processes across scales. We propose a research agenda to understand how past and future changes in cation availability may alter carbon cycling in bogs and explore potential management.