One of the great things about living in an early voting state when so many people are running for president is the chance not just to hear the candidates but to hear big ideas on big issues, sometimes with the input of big local players. With upwards of 20 Democratic presidential candidates in the race, all have to find ways to distinguish themselves. So, some have been offering up detailed policy proposals on topics from college affordability to gun control, the mental health crisis to immigration.

On Monday, former Texas U.S. Rep. Beto O'Rourke held a roundtable on the climate-change crisis and discussed his $5 trillion, 10-year plan to address it. It aims for net-zero emissions on federal lands by 2050. Declaring we have 10 years left to act before it's too late, O'Rourke said, "This is nothing short of a fight for our future. Cities will be uninhabitable."

His plan calls, among other things, for the federal government to encourage conservation through market incentives and increased funding of the federal crop insurance program. It would have the impact on climate factor into every federal government procurement.

The people around the tables with him included Des Moines City Councilman Josh Mandelbaum; Tim Gannon, the 2018 nominee for Iowa agriculture secretary; Makenzie Heddens of the American Wind Energy Association and Chaz Allen of the Iowa Utilities Association.

The downside to presenting specific policy proposals is that a candidate has to sometimes go against the sacred cows of particular voting constituencies. Even though climate change affects Democrats and Republicans equally, as O'Rourke noted, it can cost votes in rural Iowa to talk about, say, big agriculture's contribution to the problem.

He had good Iowa talking points, praising our wind energy program, which panelists credited with creating good jobs and replacing coal. He challenged his audience to rely on American innovation to do the right thing, saying, "I want that wealth to be created here." And he urged putting farmers "in the driver's seat, instead of dictating to them."

He also had the perfect local illustration of the damage caused by changing climate patterns, drawing on his visit to Pacific Junction, which was underwater after the Missouri River overflowed. He noted that residents are considering leaving the southwest Iowa town. "Residents lost almost everything," he said. "Soybean fields are lakes."

Soybean fields, however, may be contributing to the problem. Crop monocultures such as the corn/soybean rotations, which dominate the Iowa agricultural landscape, replace natural grasses and prairies. A study by South Dakota State University in 2013 found that such conversion was happening at a rate comparable to deforestation in Brazil, Malaysia and Indonesia. It said 2 million acres of grassland (1.3 million net) were lost in the five years up to 2011 in North and South Dakota, Minnesota, Iowa and Nebraska because of conversion to corn and soybean cultivation. (The net figure includes some conversion back to grassland.) The researchers compared it to deforestation rates in Brazil, Malaysia, and Indonesia.

"This trend may have a significant impact on global climate change, and subsequently, our ability to secure our food supply long-term," wrote Tom Philpott in Mother Jones.

According to researchers at the University of Tennessee and Bard College, converting some of those corn fields into cow pasture could reduce greenhouse gas emissions from agriculture by up to 36 percent. But, said the 2013 Mother Jones piece, "Turns out, farmers in the Midwest are doing just the opposite. Inspired by high (at the time) crop prices driven up by the federal corn-ethanol program – as well as by federally subsidized crop insurance that mitigates their risk – farmers are expanding the vast carpet of corn and soy that covers the Midwest rather than retracting it."

A 2013 U.S. Department of Agriculture report on Climate Change and agriculture released during the Obama administration predicted that by mid-century, when temperatures are expected to rise by 1 to 3 degrees centigrade, and precipitation extremes intensify, corn and soybean yields will decline significantly. But are agribusinesses paying attention?

I asked O'Rourke about the connection between climate change and corn/soybean cultivation. "I agree that monocultures are part of the problem," he said. "I would love more rotation with small grains."

Cover crops, which are better for the soil, might not interest big agriculture, he observed, but the government still shouldn't mandate. "Give them a goal, incentive and a profit to make and I'm confident they'll do the right thing," he said.

Is he really confident, or playing it safe?

Contact: rbasu@dmreg.com Follow her on Twitter @rekhabasu and at Facebook.com/rekha.basu1106. Her book, "Finding Her Voice: A collection of Des Moines Register columns about women's struggles and triumphs in the Midwest," is available at ShopDMRegister.com/FindingHerVoice.