The allure of clear lakes

How much is water quality worth to society? It’s a hard question to answer, at least without undertaking expensive surveys. Now researchers have turned to the enormous cache of public photos on Flickr to find out how much people value lakes with clear water. The team found that people visited clearer lakes more frequently and were willing to travel farther to reach them.

To come to this conclusion, the researchers searched Flickr, a photo-sharing website, for geotagged pictures snapped at or near lakes in Minnesota and Iowa from 2005-12. Some lakes in the region were so clear that the depth visibility exceeded 10 meters, while others had water clarity of less than half a meter. The team came up with 41,852 photos and calculated the number of unique visitors per lake per day.

Many of the Flickr users listed their hometown on their public user profiles, so the researchers also could figure out how far each person had driven to reach the lake. The team chose to focus on visitors from 12 states in the Midwest, since tourists from more far-flung states and countries had probably flown to their destination. Overall, the analysis included 6,438 trips.

People were more likely to visit bigger lakes with clearer water, the researchers report in Frontiers in Ecology and the Environment. For every additional meter of water clarity, visitors drove nearly an hour longer to get to and from the lake, spending about $22 more in travel costs. Lakes with boat ramps also were more popular.

The study authors estimate that improving a lake’s clarity by one meter would bump up the average number of visits by 1,389 per year. The overall number of lake visits in a region might not increase, since the number of people travelling to the murkier lakes could drop. But if people opted to visit a lake rather than, say, a pool, the total number of visits could rise. Roberta Kwok | 5 February 2015

Source: Keeler, B.L. et al. 2015. Recreational demand for clean water: evidence from geotagged photographs by visitors to lakes. Frontiers in Ecology & the Environment doi: 10.1890/140124.

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