FACTBOX: Presidential candidates on environment and energy

(Reuters) - President George W. Bush plans on Wednesday to call for halting the growth of greenhouse gas emissions by 2025. The three candidates vying to succeed him have made more ambitious proposals.

Here is what they are saying about environmental and energy issues:

* CLIMATE CHANGE

New York Sen. Hillary Clinton, Democrat - Cut U.S. greenhouse gas emissions to 80 percent below 1990 levels by 2050 through cap-and-trade system; require all publicly traded U.S. companies to file report on climate change risks with the Securities and Exchange Commission.

Illinois Sen. Barack Obama, Democrat - Cut carbon dioxide (CO2) emissions to 80 percent below 1990 levels by 2050; reduce emissions to 1990 levels by 2020; require fuel suppliers to cut carbon content by 10 percent by 2020.

Arizona Sen. John McCain, Republican - Favors cap-and-trade CO2 approach; sponsored legislation in 2007 to cut emissions by 30 percent by 2050.

* VEHICLE FUEL ECONOMY

Clinton - Boost corporate average fuel economy standards, or CAFE, to 55 miles per gallon by 2030, offer $20 billion in "green vehicle bonds" to help U.S. automakers meet standards, invest in plug-in hybrid technology.

Obama - Double fuel economy standards in 18 years, give automakers tax credits to retool plants and invest in advanced lightweight materials and new engines.