< Why scientists have pumped a potent greenhouse gas into streams on public lands

JUANA SUMMERS, HOST:

The biggest and most important ecological study in the United States is facing criticism because its work involves the deliberate release of the most potent known greenhouse gas. NPR's Nell Greenfieldboyce reports on why it's been doing this in national parks and forests and why some people say it should stop.

NELL GREENFIELDBOYCE, BYLINE: The gas is called sulfur hexafluoride. It's about 23,000 times more effective at trapping heat than carbon dioxide. And it persists in the atmosphere for thousands of years. The gas mostly gets used by the electric power industry, but for decades, scientists have sometimes used it, too.

BOB HALL: We always knew it was a greenhouse gas, but we always said, well, we're using just a tiny amount of it.

GREENFIELDBOYCE: Bob Hall is an ecologist at the University of Montana. He's bubbled this synthetic gas into streams to measure how quickly gases can move from the water into the atmosphere. That's important to know for understanding stuff like what role streams and rivers might play in climate change.

HALL: The beauty of sulfur hexafluoride is we only have to add it in very tiny quantities, and it's really, really easy to measure, and it's perfectly unreactive. We're not doing anything to the ecosystem by adding it. It's not reacting with anything. It's not poisoning anything.

GREENFIELDBOYCE: Recently, though, Hall stopped using this gas and switched to another one, in part because, to him, it just seemed ironic to release this powerful greenhouse gas when studying carbon dioxide and climate change. But sulfur hexafluoride is still used by one major ecology study. It's the National Ecological Observatory Network, aka NEON. NEON has been called the largest investment in ecological research in the United States ever. It will run for 30 years, making lots of different measurements at sites across the nation, in part to track the effects of climate change. Critics say a study like this shouldn't be releasing such a notorious gas when there's alternatives.

CHANDRA ROSENTHAL: They're doing these experiments on public lands like national parks and national forests, which this doesn't fit with the mission of these agencies at all.

GREENFIELDBOYCE: Chandra Rosenthal is with a watchdog group called Public Employees for Environmental Responsibility. She says so far, NEON has released about 108 pounds of the gas.

ROSENTHAL: That's equivalent to burning more than a million pounds of coal.

GREENFIELDBOYCE: Her group has obtained internal records like emails. They show that in 2019, a government scientist at Yellowstone National Park questioned why NEON was releasing sulfur hexafluoride there. That scientist's concerns were soon shared with officials who oversee other public lands where NEON was using this gas. And the documents show they were unhappy.

ROSENTHAL: But they haven't really had the authority to do anything about the fact that this stuff is being used.

GREENFIELDBOYCE: In response to the questions raised by those officials, NEON did consult with technical experts who felt that the study could use far less of this gas, that it wasn't actually necessary for the study to keep taking these measurements year after year. Kaelin Cawley works at Battelle, the nonprofit research organization that operates NEON. She says the plan is to phase out this gas.

KAELIN CAWLEY: We have discontinued it recently at several of our sites, but not all of them.

GREENFIELDBOYCE: Now, the amount of gas used in this study is really, really small compared to the vast amounts of greenhouse gases being released by power production and other sources. Still, Walter Dodds gets the concerns. He's a streams researcher at Kansas State University who served as one of NEON's advisers. He says the climate crisis is making people rethink all kinds of things.

WALTER DODDS: I think it may be, you know, an overreaction of sorts, but it's completely understandable as well. We all are worried about what our own footprints are.

GREENFIELDBOYCE: The National Science Foundation, which funds NEON, told NPR that it supports the current effort to minimize its use of this gas. But Public Employees for Environmental Responsibility is asking this agency to stop releasing it on public lands immediately. Nell Greenfieldboyce, NPR News.

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