Tree-sitter Miranda Gibson is undecided whether she'll return to the 60-metre high platform that was her home for 15 months.

A bushfire has forced Ms Gibson to end her record-breaking protest in southern Tasmania after close to 450 days.

The anti-logging activist has lived atop a eucalypt in the Tyenna Valley northwest of Hobart since December 2011.

She says her campaign will continue - for the short term at least - on the ground.

"I'll be assessing the situation as it goes in terms of the fire risk and in terms of the campaign and what I can effectively achieve on the ground or in the tree," she told AAP on Thursday.

"As time goes on I'll be able to make a decision about how I approach that."

An emotional Ms Gibson abseiled to the ground to be embraced by former Greens leader Bob Brown.

Police had warned her support crew that a bushfire only a few kilometres away posed a risk with more hot weather on the way for the island state.

"Any change of wind could bring it this way quite rapidly, quicker than I'd have time to escape," Ms Gibson said.

"That was basically the reason for having to make this hard decision but obviously I have to prioritise safety and not put myself or anyone else at risk."

The 31-year-old attracted international attention with her campaign to protect a forest that has now been nominated for a World Heritage listing.

She used cutting edge technology to blog, Skype and Facebook the world as spokesperson for the green group Still Wild Still Threatened.

Environmentalists say her tree-sit was Australia's longest, beating the 208 days Manfred Stephens set in north Queensland in 1995.

She says there were highlights like reaching her one-year anniversary and watching wedge-tailed eagles soar by.

There were tough times as well.

"Over winter obviously (there were) difficult weather conditions to get through and the isolation, missing my friends and family, was always a consideration," she said.

"They're the challenges I was willing to sacrifice and to accept in order to do this for the forest."

Current Greens leader Christine Milne sent her congratulations and Dr Brown described her as and "Australian par excellence".

"Miranda's tree, when she got up there, was going to be a bowl of woodchips," he said.

"Now it's going to be World Heritage, all because of Miranda."

Ms Gibson, a trained teacher, says she it will take time adjusting to terra firma, but she has no regrets.

"It's been so long since I've been to the ground so obviously it's a big day for me and an emotional day," she said.

"I have no regrets at all about doing it and I'm really proud that I've made this stance.

"I believe that through this we are going to see protection for these forests."