It’s not the carbon per unit of energy, where natural gas excels, but in the leaks from wells and pipes, where the methane has 84 times the anthropogenic climate change impact of CO₂ in the decades following release.

The leaks are so bad in some places that it is killing trees in cities:

Natural gas leaks from underground pipelines are killing trees in densely populated urban environments, a new study suggests, adding to concerns over such leaks fueling climate change and explosion hazards.

The study, which took place in Chelsea, Massachusetts, a low-income immigrant community near Boston, also highlights the many interrelated environmental challenges in a city that faces high levels of air pollution, soaring summer temperatures and is now beset by one of the highest coronavirus infection rates in the nation.

Dead or dying trees were 30 times more likely to have been exposed to methane in the soil surrounding their roots than healthy trees, according to the study published last month in the journal Environmental Pollution.

“I was pretty blown away by that result,” said Madeleine Scammell, an environmental health professor at Boston University’s School of Public Health who co-authored the study. “If these trees were humans, we would be talking about what to do to stop this immediately.”

The study measured soil concentrations of methane and oxygen at four points around the trunks of 84 dead or dying trees and 97 healthy trees. For trees that had elevated levels of methane in the surrounding soil, the highest concentrations were found in the dirt between the tree and the street, suggesting that the gas had leaked from natural gas pipelines, which are typically buried beneath roadways.

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Stephen Leahy of the Northeast Gas Association, a natural gas utility group, said he had not reviewed the current study in detail but noted that “there are multiple factors that could be involved in tree damage, from disease to age to road traffic to methane.”

Methane, the primary component of natural gas, is approximately 84 times more potent in warming the atmosphere than carbon dioxide over a 20 year period, making plugging even small gas leaks important when trying to tackle climate change.

A recent study found so much methane escaping or intentionally vented from wells in the Permian basin of Texas and New Mexico that the climate impact associated with burning natural gas from the region was likely greater, over a 20-year period, than burning coal.

Gas, and particularly fracked gas replacing coal is not a bridge fuel, it’s toxic waste.