The human race -- you -- has become the dominant force of change on the planet. What you eat, how much you drive and even whether you pick up after your dog affects the ecosystem in your neighborhood and around the Earth.

Now, what would it take to get you to change?

An in-depth survey of 3,000 households in Ramsey and Anoka counties is providing environmental researchers at the University of Minnesota insight into just that question.

It turns out that most people really do care about their impact on the environment. But what really drives them to change is knowing how they rank on their own personal pollution scores, and how they compare to their neighbors.

After that comes the simple, American can-do attitude.

"We expect that attitudes will drive 10 or 20 percent of the carbon emissions," said Larry Baker, a senior fellow at the university's Water Resources Center and one of the scientists who conducted the Twin Cities Household Ecosystem Project. "If we could reduce energy use by 20 percent, that would be a huge benefit."

Few families of four leave a smaller footprint than the household of Sarah Hobbie, an ecology professor who is involved in the project.

Hobbie's family lives in a cozy St. Paul bungalow with four -- count them, four -- programmable thermostats. Either she or her husband walks their son to his nearby school in the morning and then bikes the rest of the way to campus, even in winter. The other drives their daughter to her school.

Three of four in their home are vegetarians (their 4-year-old son eats turkey sandwiches), and they drive a Toyota Corolla.

Their carbon footprint is well below the survey's average. But still, air travel was killing them. Of the estimated 6,279 kilograms of carbon that make up their annual footprint, 30 percent was because of the monthly trips she and her husband, also an ecology professor, were taking for work.

"That had a pretty big impact on me," she said. Now she travels perhaps once every two months and tries to confer with colleagues by Skype or video.

"We all want to move in that direction," she said.

But Hobbie and her fellow environmental researchers are not the norm. Despite the fact that in this country cars, refrigerators, homes and furnaces have become vastly more efficient, "we have been unsuccessful in reducing energy or carbon dioxide emissions for 40 years," Baker said.

"The problem is, we consume more of everything."

Cars, lawns and values

So in 2008 the research team set out to find out what would motivate people to change. They sent a 23-page survey to 3,000 households in Ramsey and Anoka counties to find out about their lives and attitudes. They asked about thermostat settings, number of children, cars, bedrooms, miles driven to work, lawn size and fertilizer use -- even whether there were vegetarians in the house.

They used the results to estimate each household's consumption of carbon, nitrogen and phosphorus.

Carbon is important, they say, because it is the leading cause of climate change. Nitrogen and phosphorus are nutrients that create massive algae blooms in lakes and streams, depleting the water of oxygen for other plants and wildlife.

They also asked the families about their beliefs -- like whether a lawn made lush from nitrogen fertilizer is a moral imperative.

"It's conscience," said Kristen Nelson, an environmental sociologist involved in the research. "It has to do with principles of life. Lawns are embedded in that."

Most importantly for the carbon analysis, they obtained home energy records for two-thirds of the households, a mother lode of data.

From that mass of information they created a "household flux calculator" designed to estimate the flow of the three pollutants into and out of each household.

A sweater makes a difference

Some findings were fairly predictable. For most families, cost and convenience are more important than concern about the environment. People in the suburbs tend to use more fertilizer than those in the urban core. People with bigger houses and bigger families had a bigger carbon footprint, as did people who drove farther to work.

But they also found some surprises. Vegetarian households "fluxed" 13 percent less nitrogen because nitrogen is used to grow the corn and other feed for livestock. A fifth of the households contributed three-fourths of the air travel emissions and 40 percent of the motor vehicle emissions.

Small changes, they found, can make a big difference. For instance, dropping the thermostat 3 degrees centigrade reduced carbon consumption by 3 percent. "Just putting on that sweater makes a significant difference," said Nelson.

And since Minnesota banned phosphorus in detergent last year, pet waste is now a leading contributor of the phosphorus that leaches into lakes and streams.

In the end, the researchers hope to find out how best to influence social norms and change behavior.

What they know so far is that, "it's not because of the environment" that people change their habits, said Liza Pryor, a project leader at the Science Museum of Minnesota, a partner in the project. "[It's] because there is some kind of status in scoring better."

They did find, however, that their data have some impact in the real world. Last year Baker gave one of his many community talks about the project at Mark Grimes' church in Golden Valley. Beforehand, he had some in the audience fill out a shorthand version of the survey, and they compared results during the presentation.

"We found out that we were fairly green," Grimes said. He and his wife keep the thermostat at 55 degrees at night, and he just had new windows and doors installed in their house. But there was one resident who was embarrassed by a carbon score that was off the charts.

"They had four teenage kids who just sat in the shower," Grimes said.

Josephine Marcotty • 612-673-7394