Kellie Falbo is tackling climate change one step at a time. That means lowering carbon emissions by driving a biodiesel vehicle, keeping a vegetable garden, and composting with worms.

Sure, those efforts by themselves won’t make much difference globally. But sitting in the Happy Lucky Tea House, which is proudly “serving up world change” (according to the awning outside), she sees a constellation of small steps here in the heart of Colorado’s Larimer County that can ripple outward to address an overwhelming challenge.

About 30 miles southeast, in neighboring Weld County, Steve Wells looks out over a very different picture.

More than 600 oil and gas wells dot the flat grasslands that extend to the horizon of his 35,000-acre ranch. Many of them involve hydraulic fracturing – the controversial drilling practice that Larimer County's largest city, Fort Collins, tried to ban a few years back.

He gets angry when he talks about the activists who would like to ban fracking but who have never come to talk to him or bothered to see that the water hasn’t been damaged and that wildlife is thriving. The income from those wells has made an enormous financial difference for Wells, whose grandfather started the ranch in 1888, allowing him to contribute to local charities, such as a local food bank and a women’s shelter.

As for man-made climate change? He doesn’t believe it is happening.

When it comes to global warming, the border between Weld and Larimer Counties might as well be a fault line.

They are two quintessentially Colorado counties – Weld stretching eastward from the shadow of the Rockies onto the wide and empty skirts of the high plains, while Larimer gathers up the cities that cluster against the foot of the Rockies north of Denver.

But their different character speaks to a broader divide nationwide. Weld voted for Mitt Romney in 2012; Larimer voted for President Obama. Larimer life rotates around Fort Collins, a college town as home of the local state university; Weld considered seceding from the state in 2013.

They are blue and red America in miniature, and their different approaches to climate change mirror the rift within America itself.

Polls show that the partisan divide is wider on climate change than any other issue. In 2001, the gap between Republicans and Democrats on whether climate change is real and human-caused was 17 percentage points. This year, the gap stands at 41 points. Just 43 percent of Republicans now believe climate change is human-caused, compared with 53 percent back then.

What has happened? How has public opinion become more fractured even as scientists have moved toward consensus?

Views of science play a role, as does the willingness to take an economic hit to affect the global temperature a degree or two. But Colorado shows how the divide on climate has become as tribal as politics itself.

Amanda Paulson/The Christian Science Monitor The community solar farm in Fort Collins is just one example of the way that city in Northern Colorado is taking a lead on climate change solutions. The city has reduced per capita greenhouse gas emissions by 18 percent since 2005, and has a plan to be carbon neutral by 2050.

In Larimer, the Kellie Falbos look on climate change with a mounting sense of moral urgency, determined to save what they see as a planet in crisis. While in Weld, the Steve Wellses sigh at the headlong expansion of the federal government – from healthcare to Western land rights – and worry that climate change is just the next Trojan horse.

It’s not that there are no Americans in the middle. Far from it, actually, and there are efforts here and elsewhere to knit together the vast middle into a political force. Yet for the Americans driving the climate conversation, the issue has become a badge of belonging – a statement on which worldview they accept – as much as a matter of policy.

“If they understand the science or believe in the science, I don’t think that’s super necessarily important,” says Jack Zhou, a Duke University PhD who has surveyed climate attitudes. “The facts of the matter matter a little less and some of the identity measures matter a little bit more.”

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On his ranch near Greeley, Mr. Wells sits inside his “office,” an enormous warehouse filled with hunting trophies, flags, eagle images, rodeo posters, and mementos: a 1927 green beer-delivery truck, a guitar signed by rock star and Second Amendment crusader Ted Nugent, and a ’92 Harley Davidson low-rider in a glass case.

His understanding of the climate and of climate science comes from the numerous articles he reads every day, sifting through them “to search for the truth.”

What strikes him as convincing? Articles about emissions from Mt. St. Helens influencing climate more than humans (a claim opposed by most scientists), and ones detailing NASA data showing the Antarctic ice cap is growing (a paradox that scientists acknowledge, though most say it is insignificant in terms of broad warming trends).

The articles fit into a broader pattern of partisan distrust. He recounts what he sees as a litany of Democratic failures and distortions on energy and the environment.

“Jimmy Carter said we’d be out of oil by the year 2000 and we were headed for an ice age, and that didn’t pan out,” Wells says. “Then it was acid rain. Then we started the global warming thing, and now we’ve started on climate change. You need to follow the money to figure out the truth. If you look at Al Gore’s net worth since he got out of office versus now, he’s made a lot of money with this so-called energy issue.”

It’s not surprising to find such skepticism in Weld County, which is solidly Republican. Action to reduce greenhouse gas emissions here can seem like a direct shot at a major source of its prosperity: Weld County has more oil and gas wells than any other Colorado county by a wide margin.

In a county with 63 people per square mile, no one is waiting for Google to move in. Ranching and farming and drilling are pretty much all Weld County has got.

That, and an independent streak. In 2013, some of its county commissioners proposed a plan to secede from Colorado and – along with several other rural counties – form a new state.

Not everyone in Weld County has oil-well income. The county is also home to some major manufacturing tied to solar and wind energy – renewable sources that are broadly popular in red and blue America alike.

But for residents like Roni Sylvester, owner of a Weld County farmhouse, climate change elicits only one response.

“I think it’s a complete and total hoax,” she says.

In one study he conducted, Mr. Zhou of Duke tested whether Republicans might show more support for curbing emissions if the rationale was couched in conservative ideals such as national security or safeguarding the economy. Instead, opposition to climate action actually hardened. It was seen as a liberal issue, period.

Ms. Sylvester has a website devoted to property-rights issues and is deeply angry about the many ways she sees environmental regulations infringing on those rights: through the Endangered Species Act, the creation of national monuments, and climate change.

To her, it’s the “climate activists” who have the science wrong and the “climate realists” like herself who are holding the line on bad policies, such as cap and trade, in which carbon emissions are limited but allowances can be traded among businesses.

“I see things like cap and trade as only a means to further enrich those who are trying to implement it,” she says. “The flip side is that I’m 1000 percent for research, and I really, really encourage and want research. But I want scientific, untainted by politics, research.”

“First you say you can’t farm there, ‘You might hurt the sage grouse, which needs tall grass, and the piping plover needs short grass,’ and then you deny [farmers] the opportunity to generate income and support their family, then you come along and say, ‘Oh, you can’t frack there either,’ and it's always based on emotion instead of solid science.”

Amanda Paulson/The Christian Science Monitor Roni Sylvester stands in front of several of the gas wells drilled on the 200-acre farm where she and her husband live in LaSalle, Colo. The farm has been in her husband's family for four generations. Ms. Sylvester is a property-rights advocate who believes that climate change is a hoax, and is bothered by the many inroads into property rights that she says are caused by environmental legislation and activists.

What seems most solid to Bill Jerke, who has lived his whole life on a 160-acre farm just south of Greeley, is that costs will go up if the climate activists get their way. Climate change is happening, he says, but wouldn’t it be better to adapt?

“If we were to change our industrialized habits to the tune of being able to make a major impact, it would destroy civilization to a degree,” says Mr. Jerke, who heads a local group that educates people about the benefits of the oil and gas industry. “I happen to like A/C and being able to move around. I’m not going to turn all that off because someone thinks they might be able to change global warming to the tune of a degree or two over a century.”

His view is telling. Even among Americans who believe in climate change, the willingness to pay to address it is all over the map.

“I think people might have a nominal, ‘Yeah, I want a cleaner environment,’ ” says Zhou. “But then when you push them on that or give them tradeoffs, then the environment does not fare well.”

About 42 percent say they wouldn’t pay even a dollar a month, according to a September poll conducted by the Energy Policy Institute at the University of Chicago and The Associated Press-NORC Center for Public Affairs Research. But 57 percent of respondents say they’d pay some monthly fee to curb emissions (often $20 or $50).

• • •

Those are the people that Falbo wants to reach.

She founded a nonprofit to promote sustainable living, saying she saw a need for education about the individual actions people can take to live more sustainably.

“The people who hear about climate change and choose to ignore it – if we can reach 10 percent of those people who think they don’t make a difference, and show they can, that will have impact,” Falbo says. “It gets discouraging, but I’m hopeful.”

Raised to love the outdoors during her youth in Oregon, Falbo’s lifelong environmental ethic has guided her toward climate activism.

“It was always ingrained in me that you’ve got to take care of the Earth, and she’ll take care of you,” she says.

That is Larimer County talk.

Cross the county line from Weld County, and it’s not like you’ve entered Massachusetts. Larimer isn’t liberal in the way that, say, Boulder County, to its south, is. This is farm country, too.

But at the heart of Larimer County is Fort Collins, home of Colorado State University, and the city feels like a college town, from the funky cafes along Linden Street to the backpack-toting Millennials who use the county as their trailhead into the Rockies.

Oil and gas development is here, it just isn’t nearly as important.

So what emerges is a green tinge tempered by heartland pragmatism, with more carrots than sticks behind greenhouse-gas reductions.

Fort Collins has developed policies that have curbed per-capita emissions 18 percent since 2005. By 2050, the city aims to be carbon neutral. Voters even supported a five-year ban on fracking, but the state Supreme Court recently ruled it unconstitutional.

For many climate-change believers, concern about global warming has been growing in recent years as they’ve soaked up scientific reports about a melting Arctic.

Jackie Kozak Thiel, for one, has made climate change a personal priority for years. But fresh urgency came recently when she became a mother.

For her, and many others, that makes climate change action a moral calling.

“The intergenerational equity piece of sustainability has new meaning when you’re looking at someone you love so much, who will be your age when you meet these [carbon] goals,” says Ms. Kozak Thiel, who is Fort Collins’s chief sustainability officer. “That’s the city we want to deliver to her. And casting the compassionate net beyond your own blood, that’s the future you want to deliver to all young people.”

• • •

Back in Weld County, that idea resonates with Greeley Mayor Tom Norton, a Republican.

For more than a decade, he served in Colorado’s legislature, even spending time as president of the state senate, and he remembers thinking that legislators talking about climate change in the early 1990s were “completely nuts.”

But now, he says, “my opinion has changed.”

“We need to think as long term as we can imagine, and be very thoughtful about what we leave for our children,” he adds.

He’s hardly become a liberal climate crusader. A lot of his fellow Republicans’ concerns about big government crushing small business still ring true to him.

Climate change, he says, is “something we need to deal with, and yes, we need to pay attention to it, but I’m such a property-rights and economic person that I think we have to pay a lot more attention to the cost to the general public of what we’re saying we need to do, and regulating people out of business is not the way to solve the problem.”

But he thinks it's time for politicians and others to start thinking about sustainability measures that make sense.

That puts him in America’s murky middle on climate change – believing in the problem but not energized about the most aggressive prescriptions.

“People toward the extremes are yelling louder,” says Jon Krosnick, a Stanford University political scientist who studies climate attitudes. “And also the Congress has become much more polarized in this way.”

That dynamic is fed not just by politics, but also by the public’s limited bandwidth.

“The science and technology around climate change is pretty difficult to understand,” says Professor Krosnick. “And it’s hard enough in the political arena to get people to think about the things that are happening that affect them today.”

But there is opportunity for common ground.

Amanda Paulson/The Christian Science Monitor Bill Jerke, standing on the Weld County farm that has been in his family since 1945. Mr. Jerke, who directs a local group that educates people about the benefits of oil and gas, isn't concerned about climate change as an issue.

In Weld County, Carl Erickson is running for commissioner as a Democrat. He holds drastically different opinions about energy, fracking, and climate change than many of his neighbors do.

So he focuses on things they can agree on – the importance of oil and gas companies becoming more responsible with their well siting and technology, for instance, which he’s beginning to see some companies do, or focusing on issues of air quality and water, things most people in a rural area can agree are important.

“There are the polarized groups that are going further away, but there’s a vast majority in the center that are starting to actually listen and think and that’s the group we really have to [engage],” Mr. Erickson says.

Meanwhile in Larimer County, George Wallace sees the issue from a global as well as local perspective.

A retired natural-resources professor, Mr. Wallace is now an organic-farm owner surrounded by conservative neighbors. Mostly, he doesn’t engage on political issues with them, outside of some lighthearted teasing.

But he laments the degree to which America has become isolated into what he calls “tribal information sources,” leaving less civility, discourse, and willingness to engage respectfully. Still, he’s determined not to give up.

“We live well, and it’s real easy to say, ‘Don’t worry about it’ – not to attempt personal lifestyle changes very much,” he says. “But I know [we’ll] be faced with enormous challenges. Water’s going to be one of them, and food. I can’t help but look at it beyond just my own family. Worldwide we’ll have some huge challenges.”

So, like Falbo, Wallace looks for small ways he and his wife can help: serving actively in civic groups, driving a Toyota Prius when they go to town, not using commercial fertilizer or pesticides, which require energy to produce.

And he looks for ways to build bridges.

The partner with whom he trains park rangers on mules and horses in the backcountry is far to the right. So Wallace manages to find small areas of overlap where they can talk about issues like climate change.

“One way we can talk about it is the forests,” he says. “I take the things that are right in front of us, forest health and snowpack and runoff, and we can talk about that.”

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He adds: “You’ve got to use the connections you have with people.”

• Staff writer Zack Colman contributed to this report.