COPIOUS deposits of natural gas, along with even more bountiful beds of coal and plenty of wind power, have given the state of Wyoming billions in revenue. Now all three sources are provoking alarm as the bounty helps drive prices southward.

The plunge in natural-gas prices, in particular, is causing anxiety. Every fall of a dollar per million British thermal units (mBtu) costs Wyoming dear. It is especially damaging because energy production makes up roughly two-thirds of state and half of local-government revenue. A warm winter and a flood of new production from new shale deposits have pushed the benchmark natural-gas price down to $2.20 per mBtu. Four years ago, it was close to $9 per mBtu.

The low gas price, combined with proposed tighter federal regulations on carbon-dioxide emissions, threatens to dethrone Wyoming’s other cash cow, coal. For decades coal produced half of America’s electricity, and roughly half of it came from Wyoming’s Powder River Basin. Yet by the end of last year coal was providing less than 40% of America’s power, the lowest share since 1949. Even wind is in trouble: a valuable tax credit may soon end.

The problem is that Wyoming has no economic plan B. It exports more energy than any other state, yet it has the lowest industrial-diversity index in the nation. Manufacturing (much of it energy-related) accounts for only an estimated 7.5% of Wyoming’s gross state product.

Wyoming is not poor—at least, not yet. It has a Permanent Mineral Trust Fund worth $5.8 billion and a $1.4 billion “rainy day” fund as well. The state has been adroit at turning anything connected to minerals to its advantage. For years it has been the country’s leading recipient of federal mineral royalties (states get 48% of all royalties derived from federally owned mineral leases within their borders), with education the main beneficiary. Since 2002 Wyoming has built 62 new elementary and primary schools, quite a few of them funded with federal royalty money.

And Wyoming has been chipping away at its reputation as a carbonocracy. In 2007 it convinced the National Centre for Atmospheric Research to build a supercomputer centre in Cheyenne. In April Microsoft announced plans to build a $112m data centre, also in Cheyenne. The state is counting on its savings and political skills to keep it afloat until energy prices rise, assuming they do. Wyoming’s governor, Matt Mead, has ordered state agencies to plan for an 8% budget cut next July. That will hurt.