Interior Secretary Ken Salazar will step down from his position in March, the department announced Wednesday.

The 57-year-old Salazar, who resigned his Senate seat in 2009 to take the helm of the federal agency that oversees millions of acres of public lands, will return to Colorado to spend time with his family. His departure has been rumored for months, although there was considerable speculation in recent weeks that he might stay on in the position. The Denver Post, which first reported Salazar’s intentions Wednesday, noted that he and his wife are the primary caregivers to a 5-year-old autistic granddaughter.

Salazar’s decision makes him the latest departure from President Barack Obama’s energy and environment team. EPA Administrator Lisa P. Jackson announced last month that she is leaving after the State of the Union address.

Former North Dakota Democratic Sen. Byron L. Dorgan is considered a strong candidate to replace Salazar. Interior’s Deputy Secretary David Hayes — who held the same position in the Bill Clinton administration — also is considered a possible replacement. Dorgan declined to comment when reached by email Wednesday. Another possibility is outgoing Washington Democratic Gov. Christine Gregoire, whose name has also been recently tossed around as a replacement for EPA’s Jackson and as a potential successor to Energy Secretary Steven Chu should he leave the Cabinet. The departure of a Latino from the Cabinet is likely to increase the pressure on Obama to diversify his second term team of advisers.

Salazar “helped usher in a new era of conservation for our nation’s land, water and wildlife,” Obama said in a written statement. The president also praised Salazar’s efforts to resolve disputes between the federal government and American Indian tribes, and said the secretary ensured that decisions on energy production “are driven by the best science and promote the highest safety standards.”

During his four-year tenure, Salazar oversaw the response to the worst environmental disaster in United States history after a drilling rig exploded and sank in the Gulf of Mexico in 2010. It took months before the leaking well deep beneath the ocean could be plugged.

Salazar also led the reorganization of Interior’s offshore drilling program, which had been criticized for years for being too cozy with the industry it regulated.

Interior’s response to the spill — which included a temporary moratorium on drilling — was criticized as heavy-handed by Republican lawmakers, who later blocked a Salazar initiative to designate some Bureau of Land Management properties as “wild lands” — a category that critics feared would limit activities on public lands.

Interior’s efforts to force greater disclosure of the chemicals used in hydraulic fracturing to produce oil and gas on public lands have also sparked criticism by industry and lawmakers.

In his announcement, Salazar touted the department’s efforts to promote conservation and renewable energy development on public lands.

As part of Obama’s Great Outdoors program, Interior established 10 national wildlife refuges and seven national parks since 2009. During the same period, the department authorized 34 large-scale solar, wind and geothermal projects on public lands. If constructed, the projects could produce more than 10,000 megawatts of energy — enough to power more than 3 million homes.

“Today, the largest solar energy projects in the world are under construction on America’s public lands in the West, and we’ve issued the first leases for offshore wind in the Atlantic,” said Salazar in a statement. “I am proud of the renewable energy revolution that we have launched.”

Interior’s renewable push also has irked some environmentalists, who have challenged some projects in court under the Endangered Species Act. Environmentalists also have criticized Interior’s tentative approval last year of limited offshore drilling in Alaska’s Arctic seas. Interior is currently under pressure from green groups to declare a moratorium on Arctic drilling activity, following the accidental grounding of a Shell Oil Co. drilling rig off Alaska’s coast during a Dec. 31 storm.

Niels Lesniewski contributed to this report.