Nitrogen isotopes in remote lake sediments reveal effectiveness of nitrogen mitigation

Since the pre-industrial era, human activities have drastically increased reactive nitrogen (Nr) deposition in lakes, altering nitrogen (N) cycles. To trace its continental-scale footprints, we synthesized dated sediment δ15N records from 51 remote lakes across North America, Europe, and East Asia. Results reveal that the accelerated declines in δ15N (indicating increased Nr deposition) occurred earlier in North American and European lakes (~1950 CE), coinciding with the Great Acceleration, while similar changes in East Asian lakes appeared around 1985 CE, paralleling China’s rapid socioeconomic development. δ15N in North American lakes reversed around 2005 CE (~10%), and earlier in European lakes (~1995 CE) with more pronounced (~40%) increases. Meanwhile, East Asian lakes showed no reversal (only a slowdown in the δ15N decline). These regional differences match the timing and implementation of N emission policies, underscoring the need for region-specific and multi-N species (e.g., NHx and NOy) mitigation strategies to protect lake ecosystems. Enhanced deposition of anthropogenic nitrogen in North American and European lakes emerged during the Great Acceleration (post-1950), while shifts in East Asian lakes appeared after the 1980s, based on isotopic analysis of sediment cores from 51 lakes across East Asia, North America, and Europe.