The era of fossil fuels is drawing to a close, but the futures of those who have worked in coal and oil don't have to be dark, the wife of Democratic Party candidate Bernie Sanders said Monday.

"We do not want to invest any more money in fossil fuels," Jane Sanders said in an interview before speaking to about 120 Democrats and a few self-avowed conservative Republicans at a town hall at the Wolcott Galleria in Casper. On Saturday, the Natrona County Democratic Party will hold its caucus at the Casper Events Center.

"Climate change is real, it's man-made, and we need to address it," Sanders said. "It's a crisis. It's our obligation to leave our planet healthy and habitable for our children, grandchildren and future generations."

This doesn't boil down to just politics, because energy producers worldwide are making other choices for the raw materials they use, she said. "That's why coal is declining in price. That's why they're laying off workers long before coal has been regulated, or the industry has moved to sustainables (energy sources)."

The nation needs to invest in renewable sources including solar, wind, geothermal, biomass, Sanders said.

But that does not mean ignoring the pain of those who have been losing jobs at the mines, including the nearly 500 people who were laid off at the North Antelope Rochelle and Black Thunder mines last week, she said.

The government should ensure miners' benefits and pensions are protected, as well as investing in training for the new energy industry, Sanders said. "It's not their fault that climate change is a problem. It's not their fault that the price of the fossil fuels are going down. They shouldn't be living in limbo and hoping to keep a job."

She made similar points during the town hall.

But Shawn Johnson pressed her on the subject. Johnson is a Casper city councilman and billed himself as "the conservative Republican in the wolf's den," but wanted more information before he voted -- to which Sanders said, "good," and the crowd applauded.

Hillary Clinton, Johnson said, recently remarked she wanted to put the coal industry out of business. So he wondered how Bernie Sanders would regard the fossil fuel industry that underpins Wyoming's economy.

"People can't wait for new training or new manufacturing jobs to be created," Johnson said. "This is happening right now, and it's a crisis in Wyoming right now. Taking out fossil fuels can't happen by turning off the light switch, and that is essentially what is happening."

So why should Wyomingites vote for a Democrat, he asked.

Sanders responded the national and global economies already are moving away from fossil fuels with falling prices.

She didn't minimize the pain of lost jobs, adding retraining takes time. Her husband has pushed for the extension of unemployment benefits, she said. "His bill protects the pension and benefits, and doesn't let the coal companies take that away from the workers."

The question, she posed to Johnson, isn't "why would you vote for a Democrat," but "why can we vote for Bernie."

After the town hall, Johnson agreed global economic powers drive energy prices and thought Sanders' response was reasonable.

But he remained wary of what he perceives as a Democratic mentality that the nation can just turn off the fossil fuels industries like a switch, he said.

"To me, it's a progressive thing," Johnson said. "You can't just shut off coal, you can't just shut off oil. You've got to ease into it, otherwise you will have things like what we see in Wyoming happening."