President Barack Obama’s recent conservation efforts and his pledges to slow global climate change could leave behind a commitment to sustainability and environmental efficiency, but President-elect Donald Trump has promised to overturn Obama’s environmental legacy.

Near the end of his eight-year term in office, President Obama displayed a passion for conservation and environmentally friendly advancements. The fuel efficiency standards Obama set in place in August aimed to cut carbon emissions by increasing America’s use of solar energy, wind power and energy-efficient vehicles, according to Daily Signal.

On Sept. 15, Obama formally created the Northeast Canyons and Seamounts Marine National Monument, a fishing-free zone dedicated as marine reserve off the coast of New England. The reserve encompasses nearly 5,000 square miles of the Atlantic Ocean, making this the largest marine reserve on the planet, according to the New York Times. The reserve is home to many unique species of fish and deep-sea corals, as well as whales, dolphins and turtles.

The creation of the marine reserve included the immediate banning of drilling and exploration for oil and gas, while red crab and lobster businesses would be allowed to continue for next seven years before these industries cease within the boundaries of the Northeast Canyons and Seamounts Marine National Monument.

Obama has designated 22 other national monuments during his presidency, according to National Geographic.

Obama said his concern for the environment stems from both fond childhood memories of body-surfing in Hawaii and a desire to share similar moments in nature with his children and future grandchildren.

“Dangerous changes in our climate [are] caused mainly by human activity; dead zones in our ocean caused mainly by pollution that we create here on land; unsustainable fishing practices; unprotected marine areas in which rare species and entire ecosystems are at risk,” Obama told New York Times. “All those things are happening now.”

Some environmentalists were upset with Obama, spewing backlash and critique of the president’s attempts at environmental consciousness. Obama committed to turning the U.S. into a leader in the pursuit to mitigate the effects of climate change, yet he gave the green light to industries in fracking and drilling for oil, as actor Mark Ruffalo (“The Avengers,” “Begin Again”) pointed out at a climate change rally on October 26, according to The Huffington Post.

It appears the controversial pipeline in Standing Rock, North Dakota was but the beginning of a series of land snatching to boost drilling and fracking as Trump takes office in January. Trump received support from many oil and gas executives, and had begun to create a transition team of lobbyists for fossil fuel companies and critiques of the global climate change crisis, according to Washington Post.

Trump apparently believes that global climate change is a “hoax”, according to AP Politics, and has been reported stating that he believes a 2-3 degree temperature increase could be a good thing.

During his campaign, Trump promised that he would reverse President Obama’s commitment to environmental care at the Paris Climate Summit in 2015. Trump cannot formally pull out of the pact to which the U.S., along with scores of other countries, agreed last year, according to The Atlantic. Yet Trump could delay climate change research by withholding funding and refuse to recognize the pledges and commitments Obama made on behalf of the U.S.

Obama’s environmental legacy will include an attempt to set the U.S. as a world leader for environmental efficiency and sustainability at the 2015 Paris Climate Summit, as well as the designation of the largest marine reserve on the planet. Yet what Obama has called his proudest legacy, Trump has promised to reverse.

As Obama’s term comes to a close, many environmentalist activist groups are rolling up their sleeves and preparing to fight in order to maintain the size of the national monuments, to support actions taken to slow climate change, and “to defend America’s bedrock environmental progress,” said Environmental Defense Fund (EDF) President Fred Krupp on the EDF website.