Lisa Jackson is stepping down from her post as the administrator of the Environmental Protection Agency after a four-year term.

"I will leave the EPA confident the ship is sailing in the right direction, and ready in my own life for new challenges, time with my family and new opportunities to make a difference," she said in a statement announcing her departure.

Kevin Wolf / AP

This file photo shows Environmental Protection Agency Administrator Lisa Jackson during an interview with The Associated Press at EPA Headquarters in Washington. Jackson, The Obama administration's chief environmental watchdog, is stepping down after a nearly four-year tenure marked by high-profile brawls over global warming pollution, the Keystone XL oil pipeline, new controls on coal-fired plants and several other hot-button issues that affect the nation's economy and people's health.

Jackson, 50, is expected to depart the E.P.A. early next year. She is the first African-American to head the agency.

Her tenure at the helm of the E.P.A. was marked by clashes with some in the GOP and the energy industry who said environmental regulations limited job creation and hurt new innovation. The administration abandoned an attempt early in President Barack Obama's first term to pass cap-and-trade legislation to address global climate change. That legislation failed to pass the Senate, and the E.P.A. moved instead on a series of regulatory efforts including successful implementation of emissions standards for new cars and small trucks.

"I want to thank President Obama for the honor he bestowed on me and the confidence he placed in me four years ago this month when he announced my nomination as Administrator of the Environmental Protection Agency," she said in her statement, which indicated she will leave the cabinet after the State of the Union address. "At the time I spoke about the need to address climate change, but also said: 'There is much more on the agenda: air pollution, toxic chemicals and children’s health issues, redevelopment and waste-site cleanup issues, and justice for the communities who bear disproportionate risk.'"

Saying that Jackson has been "an important part of my team," Obama praised those efforts in a statement.

"Under her leadership, the EPA has taken sensible and important steps to protect the air we breathe and the water we drink, including implementing the first national standard for harmful mercury pollution, taking important action to combat climate change under the Clean Air Act and playing a key role in establishing historic fuel economy standards that will save the average American family thousands of dollars at the pump, while also slashing carbon pollution."

In an interview with the New York Times, Jackson said she intends to "decompress" and do public speaking engagements but does not yet have plans for a new job.