Keeping bodies of water clean has obvious local benefits for those who want to access or use them, but sometimes, the cost of cleaning can outweigh those benefits. At least, that's what previous studies found when comparing benefit-cost analyses of cleaning local bodies of water.
But a new study has calculated the global benefits and found that they are vastly higher than the local benefits and costs.
"It was initiated by the lead author John Downing, who's a lake scientist, who has done research on methane emissions from eutrophying lakes," said Steve Newbold, a University of Wyoming environmental ecologist and co-author of the study. "It occurred to him that the climate impacts of those emissions, if those are not accounted for in benefit-cost analysis, that could be an important category of benefits that are not usually recorded."
Eutrophying, or eutrophication, are terms for when a body of water becomes progressively more enriched with minerals and nutrients. Agricultural runoff has increased eutrophication as fertilizer nutrients like phosphorus and nitrogen find their way into waterways. This can lead to an explosion of algae growth known as a harmful algal bloom.
"The fertilizer that makes plants grow better on land also makes algae grow better in lakes. And when those algae bloom, they turn the lake green, and when that algae decays and is decomposed, it can take a lot of oxygen out of the water column and that harms the fish and other aquatic species in there," said Newbold. "Part of that process involves emitting methane into the atmosphere."
Methane is a particularly potent greenhouse gas because it traps significantly more heat than carbon dioxide (CO2). Less methane in the atmosphere can help slow global warming.
"Greenhouse gases, like methane and CO2, get well mixed in the atmosphere, and no matter where they're emitted, they contribute to global warming more or less the same. And that just increases the global average temperature, whether they're emitted in your local lake or someone else's local lake on the other side of the globe," said Newbold.
This means that the benefits of keeping the local pond clean of excess nutrients are enjoyed globally, creating a value of up to trillions of dollars.
In a featured case study, the authors found that preventing algal blooms in Lake Erie provided a global value 10 times greater than the local value that came from beach use or sport fishing. They estimated that the global social cost of eutrophication-driven methane emissions from lakes between 2015 and 2050 could be as much as $81 million.
"Our hope is that now we've put this potential category of benefits on the radar screen of the economists and federal government agencies who do these benefit-cost analyses for a living," said Newbold. "When those folks do their regulatory impact analyses that are required for large regulations, this could be one additional category of benefits that is not left off of the bottom line of water quality regulations."
Have a question about this story? Contact the reporter, Ivy Engel, at iengel@uwyo.edu.
