George W. Bush's environmental policies during his presidency weren't that succesfull to begin with. On his presidential campaign he promised tu reduce carbon dioxide emissions by a considerable amount and a year after he won, he backed down on that promise claiming that carbon dioxide was not a pollutant under the Clean Air Act and that restricting it, it would cause energy prices to go up.
In 2001, he got out of the Kyoto Protocol, a treaty that required nations to reduced their greenhouse emissions and even the administration views on global warming were really controversial. They acknowledged it but they claim that it was because of natural causes instead of man made.
On the other hand, under Barack Obama's presidency, the largest marine reserve in the world was established, but to be fair, it was started by Bush's administration, albeit in a much smaller scale. He rejected the Keystone XL oil pipeline, voted against Bush's CLean Skies act, raised the fuel efficiency standards and invested in green energy during the Great Recession.
Hope this helps!
