The first three months of 2016 saw a plunge in the US’ coal production that may be without precedent. The US Energy Information Administration, which has figures going back to the 1970s, shows only a single quarterly drop of similar magnitude—and that one came during a workers’ strike back in the early 1980s. Excepting periods of labor problems, US coal production has not been this low since the EIA started tracking it.

Part of the problem is temporary. The winter was unusually mild, which lowers energy use in general. As a result, many of the coal-burning electrical plants had large stockpiles of coal on hand; they burned through these reserves rather than ordering new coal.

But most of the issues are systemic. Coal is now being undercut by renewables and natural gas, which are displacing some of the demand. Utilities are responding to those low prices by adding new renewable and gas capacity. That additional capacity comes at a time when the US’ electricity demand has been growing at an unexpectedly slow pace. Combined, these factors have resulted in less use of existing coal plants. New environmental regulations are also forcing the oldest and least efficient plants to shut down early. Most of these are also coal.