Under Labor’s system the factions choose who is in the ministry, which is ratified by caucus, and the prime minister allocates the portfolios.
While some have interpreted the shift from education as a demotion, environment and water remain in Cabinet.
Prime Minister Anthony Albanese said Ms Plibersek would have a particular focus on the Murray-Darling Basin.
“I spoke to Tanya about it. She's very happy to take up the issue of environment and water,” Mr Albanese said.
“My view is that Tanya will be outstanding in that area, but also particularly in the area of the Murray-Darling Basin Plan, as well; it's very important that that actually gets delivered. Tanya is someone who can get things done.”
Labor has been consistent in saying the plan should be completed in full, but water looms as a controversial issue for the new government, with irrigators and communities in key basin states, including Victoria, wanting to head off the use of water buybacks as a mechanism to achieve an additional 450Gl of water for South Australia.
“She's an experienced former minister, as well as a former shadow minister,” Mr Albanese said.
“And that will be an area, as well as implementing the policies that we have on things like our rangers program, our urban rivers program, our plan to deal with the Murray-Darling Basin but our plan on a range of other environmental programs as well, in particular the Great Barrier Reef.
“We made very significant announcements during the election campaign about all of those policy areas.”
On social media Ms Plibersek said she was delighted to be appointed.
“I look forward to the challenge,’’ she said.
“Australia is lucky to be home to the most beautiful natural environments in the world, which we need to protect and preserve for future generations. Let’s get to work.”
The issue of the stalled Shepparton Bypass project will fall to Ballarat MP Catherine King, who was confirmed as Minister for Infrastructure as well as Regional Development and Local Government.
Ms King will sit in Cabinet as the senior minister, but Kristy McBain, considered a rising star in Labor ranks, has been appointed Regional Development, Local Government and Territories Minister and will take on some of the portfolio responsibilities.
The agriculture portfolio remains in Cabinet, with Queensland Senator Murray Watt the new minister.