(CNN) -- The U.S. presidential race is under way, and environmental issues are taking a more prominent place in the candidates' campaigns than in the past. Along with the economy and the war in Iraq, climate change has become an integral part of each candidate's platform, a remarkable evolution from earlier U.S. presidential campaigns as recent as four years ago.
Democratic presidential candidates Barack Obama and Hillary Clinton shown in their January 31 debate.
The following is a breakdown on each candidate's platform on the environment. You can also learn more at CNN's Election Center 2008:
Would develop a new treaty to replace the Kyoto Protocol, which is set to expire in 2012.
Would focus on international attention to solve the problem of global deforestation.
Would focus the mission of the Department of Energy on moving toward energy independence with a new approach to solar, wind, biofuels, hydropower, geothermal and other sources of renewable energy.
Would place a market-based cap and trade system to reduce carbon pollution. ... In combination with efficiency, fuel economy standards and other proposals, she states the system will ensure the goal of reducing U.S. contribution to global warming below 1990 levels by 80 percent.
Would oppose drilling in the Arctic National Wildfire Refuge. Watch Clinton on the environment
Would commit to leading the fight against global deforestation.
Would support maintaining current moratoriums on new offshore oil and natural gas drilling.
Would support maintaining the protections of the Endangered Species Act.
Would support protecting the Arctic National Wildlife Refuge from oil and gas development by permanently designating it as wilderness.
Would implement an economy-wide cap-and-trade program to reduce greenhouse gas emissions to the level recommended by top scientists.
Would make the United States a leader in the global effort to combat climate change by leading anew international global warming partnership.
Would establish a National Low Carbon Fuel Standard (LCFS) to speed the introduction of low-carbon non-petroleum fuels.
Would create a Technology Transfer program within the Department of Energy dedicated to exporting climate-friendly technologies to developing countries.
Would offer incentives to maintain forests globally and manage them in a sustainable fashion.
Would develop domestic incentives that reward forest owners, farmers and ranchers when they plant trees, restore grasslands or undertake farming practices that capture carbon dioxide from the atmosphere.
Watch Obama on U.S. energy policy
When asked during a 2007 GOP primary debate if he believed global warming existed, Huckabee said, "Whether humans are responsible for the bulk of climate change is going to be left to the scientists, but it's all of our responsibility to leave this planet in better shape for the future generations than we found it."
Huckabee would pursue all avenues of alternative energy including wind, solar, clean coal and biodiesel.
Would propose greenhouse gas emissions be curtailed.
Would support drilling in Alaska's Arctic National Wildlife Refuge and increased offshore drilling.
Introduced the Climate Stewardship and Innovation Act of 2007 with Sen. Joseph Lieberman (I-Connecticut). The legislation is designed to significantly reduce the nation's greenhouse gases, accomplished through a combination of trading markets and the deployment of advanced technologies.
Would propose use of alternative energy sources, including nuclear.
Video: Watch GOP candidates talk about climate issues
States the key to sound environmental policy is respect for private property rights.
Believes the strict enforcement of property rights corrects environmental wrongs while increasing the cost of polluting.
Individuals, businesses, localities, and states must be free to negotiate environmental standards. • Voted against the drilling in the Arctic National Wildlife Refuge in 2001, but voted for new oil refineries in 2006. • Opposes the Kyoto Protocol. Voted in 2003 against speeding up forest thinning projects.
Click here to visit Ron Paul's campaign site
Romney stated during a 2007 GOP debate: "...Is global warming an issue for the world? Absolutely. Is it something we can deal with by becoming energy independent and energy secure? We sure can. But at the same time, we call it global warming, not America warming. So let's not put a burden on us alone and have the rest of the world skate by without having to participate in this effort. It's a global effort, but our independence is something we can do unilaterally."
Would support more drilling offshore and in the Arctic National Wildlife Refuge.
Would bring clean energy technology to market.
Would promote clean, efficient uses of existing fossil fuels
Video: Romney on the environment E-mail to a friend