If Texas were its own country, it would be the 48th most populous in the world, right between North Korea and Ghana. In terms of landmass, at 268,000 square miles it would be the 40th-biggest. But when it comes to environmental impact, Texas is on par with some of the largest, most industrialized nations on the planet.

Were the Lonestar State to secede from the union it would be the world's eighth-largest emitter of the greenhouse gas carbon dioxide, just behind Canada, with 630 million metric tons spewed into the atmosphere in 2005, according to new figures released this week by the U.S. government's Energy Information Administration. That's actually a reduction of 40 million metric tons since 2003, when Texas was the globe's seventh-largest CO₂ contributor. But even though the state is improving, Texas still outpaces the combined emissions of California and Pennsylvania, the states with the second- and third-highest CO₂ outputs.

Considering its role in the U.S. economy, it's no surprise Texas ranks as it does. As the nation's leading producer of energy, and with more cattle and oil refineries than any other state, it is essentially America's power plant, gas pump and beef basket. Yes, all those cows play a part. While many environmentalists focus on the methane (another greenhouse gas) produced by cows, the raising of cattle also contributes to CO₂ emissions (the burning of fuel to transport cattle and meat, etc.). A study released last summer by Japanese scientists showed that production of just 1 kilogram of beef results in more CO₂ emissions than going for a three-hour drive while leaving all the lights on at home. Texas also has the largest petrochemical industry in the country, which churns out a host of consumer products, everything from makeup to motor oil.

But it's not just industry and agriculture that give Texas such an outsize carbon footprint. Texans epitomize America's penchant for overconsumption, so much so that they've even coined their own phrase for superlarge portions: Texas-sized. The state's 23.5 million residents use nearly 3,000 more kilowatt-hours of electricity every year than the average American and a higher percentage of them drive large, gas-guzzling vehicles. Of the 20 million registered vehicles in Texas, one in four is a pickup truck. Of the 245 million vehicles registered in the United States, only 16 percent are pickups, according to the Alliance of Automobile Manufacturers. Last year light trucks made up 61 percent of all new vehicles (both personal and commercial) sold in Texas, compared to just over half of total vehicle sales in the country.

Nearly a third of Texas's carbon emissions come from transportation. With so much wide-open space, Texas hasn't needed the kind of urban planning that promotes density. Rather, it is a state of far-flung towns and cities, connected by highways and with practically no mass transit. Air quality has suffered as a result; by some estimates more than half of all Texans live in areas where the air is unsafe to breathe, as defined by the EPA's Clean Air Act.

Even in the reddest of Red States, one would think that such a health hazard would cause Texas to get serious about air pollution. But it is one of only 15 states without a climate action plan in place or even under consideration. This at a time when some of the most aggressive state plans have taken shape under Republican governors, according to national climate protection groups. In 2006, California Gov. Arnold Schwarzenegger muscled through the most ambitious carbon cap-and-trade plan of any state in the country, aimed at reducing statewide CO₂ emissions to 1990 levels by 2020. Last summer Florida's GOP Gov. Charlie Crist signed executive orders to slash the state's greenhouse-gas emissions to 20 percent of 1990 levels by 2050. In Minnesota, Gov. Tim Pawlenty last year signed a law requiring state utilities to generate a quarter of their power from renewable sources by 2025, and in Connecticut, Gov. Jodi Rell's Energy Vision initiative calls for 20 percent of all energy used and sold in the state to come from clean or renewable sources by 2020.

But to many Texans, environmental activism looks too much like big government threatening the state's business interests. Under Republican Gov. Rick Perry, Texas has dug in its heels when it comes to enacting any state initiatives aimed at cutting emissions or promoting efficiency. Perry publicly doubts that global warming is a manmade problem—something his predecessor George W. Bush has acknowledged—and pokes fun at those who do. Last year Perry remarked that Al Gore's mouth is the country's leading source of carbon dioxide, not Texas.

"The problem is that big oil companies run the show," says Luke Metzger, director of Environment Texas, a statewide environmental advocacy group. Last year the Texas Association of Manufacturers and Houston-based Exxon Mobil successfully lobbied against a bill that would have provided incentives to homeowners and businesses to install solar panels. The Republican-held state legislature even voted down a bill that would have allowed cities to increase their sales tax in order to fund the construction of light rail systems, for fear of appearing to be seen as raising taxes. When a Democratic state senator from Austin proposed a bill that would have merely set up a task force to study climate change, it was defeated thanks to fierce opposition from the business community, including the Texas Oil and Gas Association and Texas Automobile Dealers Association.

When Dallas-based power company TXU Corp. announced plans to build 11 new coal-fired power plants in 2006, to go along with the 18 the state already had, Gov. Perry fast-tracked the permitting process, limiting the time frame for public comment. That summer a coalition of more than 40 Texas cities and other local governments intervened at the permitting level and stirred up public opposition to the power plants. When New York-based private equity firm KKR bought out TXU for $45 billion last February, it scrapped plans for all but three of the plants. The fight is the subject of a new documentary by Robert Redford, "Fighting Goliath: Texas Coal Wars."

"The most important thing that came out of that is that Texans are finally understanding this problem and are starting to demand that something happen," says former Dallas mayor Laura Miller, who chaired the coalition until her term ended last year. The coalition is currently in an active lawsuit opposing the construction of the remaining three plants.

"People are starting to realize how vulnerable Texas is to the effects of global warming," adds Jim Marston, the regional director of the Texas office of the Environmental Defense Fund. "We have the longest coastline, which is highly susceptible to tropical storms and hurricanes in the Gulf, and an agricultural area in the western part of the state that is very close to the desert and could be seriously crippled by drought."

Marston says that Texans are also eager to take advantage of green business opportunities. "The business community here sees that a lot of green investment is flowing into California because they've created a market for it, but Texas actually has more potential than any other state to profit from green technologies." With so much flat, windswept land and plenty of sunshine, Texas has more potential for wind and solar energy than any other state, according to Environment Texas. And investment is starting to pick up. In 2007, for the third year in a row, Texas was the nation's leader in the amount of wind capacity added to the electric grid, as nearly $3 billion of wind-powered generators were installed in Texas. Also last year a group of businesses pledged to invest more than $10 billion in renewable energy projects in the state. Legendary Texas oilman T. Boone Pickens is planning to invest billions of his own money to build the world's largest wind-energy farm in the Texas panhandle, with construction slated to begin in 2010.

And in the absence of any leadership from the state capitol to address carbon emissions, the city of Austin has taken the reins. Its Climate Protection Plan, unveiled last February by Democratic Mayor Will Wynn, is seen by environmentalists as the country's most aggressive municipal initiative aimed at reducing greenhouse gases. The plan calls for 100 percent of all city facilities to be powered completely by renewable energy by 2012, and to make all new single-family homes zero-net-energy-capable by 2015, which means they'll have to be at least 65 percent more efficient and, with solar panels on the roof, able to generate as much energy as they consume over the course of a year.

As state legislators gear up for next year's session, a Republican-led coalition is forming with the hope of finally pushing through carbon-related legislation. West Texas cattle rancher and staunch GOP state Rep. Warren Chisum has gained the support of 55 members of the state House and Senate as part of the House Carbon Caucus he formed after last year's session. "It's disappointing to me that Texas doesn't have a state plan right now," says Chisum, who says he wants to approach the issue not from an ideological standpoint but from a practical one. "We've wasted a lot of time debating this issue. I simply see this as an issue of good state government. Rather than wait for something to come down the pike from the federal government, we should go ahead and enact something for ourselves, and not let a bunch of federal bureaucrats stuff something down our throats." Spoken like a true Texan.