Global anthropogenic emissions of greenhouse gases and hazardous air pollutants have produced broad yet regionally disparate changes in climatic conditions and pollutant deposition in the Canadian boreal zone (the boreal). Adapting boreal resource management to atmospheric change requires a holistic understanding and awareness of the ongoing and future responses of terrestrial and freshwater ecosystems in this vast, heterogeneous landscape. To integrate existing knowledge of and generate new insights from the broad-scale impacts of atmospheric change, we first describe historical and present trends (∼1980–2015) in temperature, precipitation, deposition of hazardous air pollutants, and atmospheric-mediated natural disturbance regimes in this region. We then examine their associations with ecosystem condition and productivity, biological diversity, soil and water, and the carbon budget. These associations vary considerably among ecozones and likely undergo further changes under the emerging risks of atmospheric change. We highlight the urgent need to establish long-term, boreal-wide monitoring for many key components of freshwater ecosystems to better understand and project the influences of atmospheric change on boreal water resources. We also formulate three divergent future scenarios of boreal ecosystems in 2050. Our scenario analysis reveals multiple undesirable changes in boreal ecosystem structure and functioning with more variable atmospheric conditions and frequent land disturbances, while continuing business-as-usual management of natural resources. It is possible, though challenging, to reduce unwanted consequences to ecosystems through management regimes focussed on socio-ecological sustainability and developing resilient infrastructure and adaptive resource-management strategies. We emphasize the need for proactive actions and improved foresight for all sectors of society to collaborate, innovate, and invest in anticipation of impending global atmospheric change, without which the boreal zone will face a dim future.

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Northern temperate lakes are being affected by global environmental changes (Bedford et al., 2020;Richardson et al., 2018).An increase in temperature and changes in precipitation patterns and atmospheric nitrogen deposition are leading to fundamental alterations in land-aquatic hydrological and biogeochemical linkages (Creed et al., 2018). These environmental changes can be best studied in lakes, as lakes integrate atmospheric, terrestrial, and aquatic processes (Williamson et al., 2009). An important signal of alterations is an increase in the frequency and duration of phytoplankton blooms (Ho et al., 2019;Winter et al., 2011) as well as changes in