Environmental and societal consequences of winter ice loss from lakes

Climate change is reducing winter ice cover on lakes; yet, the full societal and environmental consequences of this ice loss are poorly understood. The socioeconomic implications of declining ice include diminished access to ice-based cultural activities, safety concerns in traversing ice, changes in fisheries, increases in shoreline erosion, and declines in water storage. Longer ice-free seasons allow more time and capacity for water to warm, threatening water quality and biodiversity. Food webs likely will reorganize, with constrained availability of ice-associated and cold-water niches, and ice loss will affect the nature, magnitude, and timing of greenhouse gas emissions. Examining these rapidly emerging changes will generate more-complete models of lake dynamics, and transdisciplinary collaborations will facilitate translation to effective management and sustainability. Editor’s summary More than half a billion people live near lakes that freeze over in the winter. However, lakes are rapidly losing winter ice cover in response to warming, and the rate of loss has accelerated over the past 25 years. Hampton et al. reviewed the state of seasonal ice cover on lakes and discuss some of the consequences of its disappearance. Ice loss will affect culture, economy, water quality, fisheries, and biodiversity, as well as weather and climate. —Jesse Smith BACKGROUND Lakes are rapidly losing ice in response to climate change. Most of the world’s lakes freeze, with a median ice duration of 218 days. The rate of lake ice loss has markedly accelerated over the past 25 years, with ice melt in some regions across the Northern Hemisphere arriving 45 days per century earlier and with many lakes experiencing increased intermittency of ice cover during winter in addition to ice-free winters. Lake ice loss is expected to affect a substantial proportion of the world’s population, who rely on these lakes for diverse needs, including drinking water, fisheries, transportation, and more. Until recently, both logistical challenges as well as misconceptions of winter as a time of quiescence resulted in limited winter research. Conspicuous decreases in ice cover and advances in technology have spurred rapid growth in winter research on seasonally ice-covered lakes. This Review is structured around a central question that winter researchers are frequently asked: Why does it matter that lakes are losing winter ice? ADVANCES Changes in ice cover have critical consequences for water quality, fisheries and biodiversity, weather and climate, as well as important cultural and socioeconomic activities. Socioeconomic benefits of freshwater ice include recreation, cultural identity, ice fishing, and ice roads for winter transportation. Ice roads across lakes and rivers are extensively used in oil and gas exploration, and they offer connectedness for remote communities during winter. Although the full socioeconomic importance of lake ice has not been accounted, illustrative examples exist. For Sweden’s population of about 10.5 million people, ~$880 million US dollars are spent annually on ice fishing. Less easy to quantify is the extent to which interacting with lake ice contributes to cultural identity while shaping social cohesion and cultural heritage for the millions of people who live near a lake that seasonally freezes. Global data syntheses and models reveal further change. Shifts in ice quality, toward thinner and less stable white ice, have also contributed to increased fatal drowning events in areas of the world where ice was once safer for humans to traverse. Shorter ice duration has allowed lakes to warm faster, accelerating evaporative water loss globally and contributing to summer water quality issues, such as cyanobacteria blooms. Warmer water can favor invasive species and negatively affect cold-water fish and other organisms that are well adapted to ice-covered aquatic conditions. Ice seasonally creates a distinctive ecological niche space. Clear ice allows for high transmission of light that can fuel substantial algal growth, providing highly nutritious food for zooplankton grazers and their predators and generating food web effects that extend beyond winter. Ice provides a stable structure that effectively isolates lakes from the atmosphere and surrounding land, with several important implications: Ice cover can prevent shoreline erosion from wave action during the winter and reduce greenhouse gas emissions as well as evaporative water loss to the atmosphere. For lakes prone to creating lake-effect snow, ice cover prevents these extreme events from occurring in downwind communities. OUTLOOK Recent model projections predict complete loss of ice on thousands of lakes that historically experienced seasonal ice cover. Synthesis of historical ice records combined with global climate models suggests that up to 230,400 of the world’s 1.4 million lakes larger than 0.1 km2 will experience some years with no ice cover by 2080. Lakes at lower latitudes are vulnerable to losing 80% of ice days that are safe for humans to traverse. Anticipating the environmental and societal consequences of freshwater ice loss requires updated theory and models that consider the role of winter conditions and that incorporate data across the full annual cycle. Greater scientific and public understanding of the importance of lake ice for ecosystem health is key to supporting breakthrough science that informs sound stewardship of freshwater resources. Baikal seal pup on the ice of Lake Baikal. The Baikal seal (Pusa sibirica) is the world’s only exclusively freshwater pinniped, and it is well adapted to a lake that freezes for half the year. It gives birth and raises pups on lake ice and maintains open holes in the ice to fish under ice through the winter. PHOTO: CC BY-NC-SA 2.0 PACIFIC ENVIRONMENT