Consequences of lake and river ice loss on cultural ecosystem services
By Lesley Knoll
It’s springtime; birds are on the move and it is the time of year when lake ice-outs spread northward in Minnesota. Local and worldwide ice records were collected before we had weather stations and they provide an independent set of human observations. These records help us to see that over the past century, lakes around the Northern Hemisphere have earlier ice break-up, later ice formation, and shorter seasons of ice cover. Some areas also experience increased frequency in freeze-thaw events.
Minnesota lakes are not immune and long-term ice cover trends here mirror those worldwide. Winter is important to us in our state where the season is long and outdoor activities can be key to our well-being. Part of our love for winter is connected to lake ice and the cultural, social, and economic benefits we receive from it. In our study, we looked at consequences of ice loss on these benefits ranging from recreation, social relations, spiritual connections, to capturing the frozen landscape on your phone’s camera.
We used a quantitative approach to explore a winter warming effect on a wide range of ice-related uses. We showed that warmer winter air temperatures, but not cooler winter air temperatures, delayed the opening date of a winter ice road in Canada and led to cancellations of spiritual ceremonies in Europe and Japan, an outdoor ice skating race in Sweden, and ice fishing tournaments in Minnesota.
Minnesota is home to numerous winter ice fishing tournaments. In some years, there can be close to 100 fishing tournaments scattered across the state drawing in many participants and tourism dollars. We examined ice fishing tournaments in Minnesota in cooler vs warmer winters from 2005 - 2016. We found that that warmer air temperatures – about 25 F or warmer – during the winter were related with more canceled fishing tournaments in the central part of the state. We did not see this same relationship in the northern part of the state where it tends to be a bit cooler during the winter. Ice fishing cancellations will have economic consequences and influence the social network of northern communities. There is often a very social aspect to ice fishing and this story in Minnesota is a small part of a bigger story where lakes around the world are experiencing similar changes over the past century.
Our best example of climate change affecting cultural uses of lake ice is for Lake Suwa in Japan. For this lake there are ice records from 1443 to now. The record was updated by generations of Shinto priests to document the formation of an ice ridge. For the Shinto, the appearance of the ridge is a message from their deity and the ridge signifies the footsteps of one god crossing the lake to visit another god. These historical records go back centuries before the industrial revolution when large amounts of carbon were emitted into the atmosphere. For the first 250 years of record-keeping, there were only three years where Lake Suwa did not freeze. Since 1989, the lake has failed to freeze 21 times. These records show us that something as simple as lake ice can be used to document long-term changes in the climate.
Documented declines in ice cover are predicted to continue moving northward as air temperatures warm. Recent work shows nearly 15,000 lakes along southern limit of ice-covered lakes are already experience intermittent ice-free years. Our research findings help us understand how these losses might affect northern communities around the world.