Miranda Gibson is today sitting on a small platform 60 metres high in a Eucalyptus regnans beneath Mt Mueller in central Tasmania. She has been on the platform for more than four weeks and intends to stay until the tree is cut down or governments keep their word that the tree, its wildlife and the mountainside forest in which it sits are protected.

Just over the ridge from Miranda are the Styx River and its Valley of the Giants, named after the kings and queens of the eucalypts, which tower up to 100 metres high - that is, as high as a soccer field is long.

In 2010, Tasmania's logging industry was facing bankruptcy. It publicly sought out the environment movement for talks aimed at a mutually beneficial outcome: money to help loggers exit the industry and protection of contentious forest such as the Valley of the Giants and nearby Weld and Florentine valleys.

An agreement was struck. While not involved in negotiations, I had urged federal ministers to help out. On August 7 last year, the Prime Minister, Julia Gillard, flew to Hobart to join the Tasmanian Premier, Lara Giddings, in signing an agreement which would deliver $277 million of taxpayers' money to the loggers and regional Tasmania in return for ''immediate'' protection of 430,000 hectares (less than half) of Tasmania's state forest areas.

The money is flowing - up to $70 million so far, including to Forestry Tasmania, the state's public forests manager, which has a history of indebtedness (selling a public resource it got for free); and to Gunns Ltd, once the state's major logger. The agreement guarantees Malaysian logging juggernaut Ta Ann 265,000 cubic metres of wood each year until at least 2027. An announcement on which logging contracts will get payouts (of amounts up to $3 million) to get out of the industry is due any day.

However, in the high-conservation-value forests agreed for ''immediate'' protection, logging has continued apace. This includes clear-felling and firebombing of forests that the International Union for Conservation of Nature considers worthy of World Heritage status.

I am not just a backer of brave Miranda Gibson. I think Tasmania's glory days are ahead of us. The combination of our fantastic food and wine industries with high-quality manufacturing of fabrics, garments and sustainable furniture with the rapidly growing global demand for ecologically sound tourism give Tasmania huge prospects. As with Malcolm Fraser's decision to stop whaling in 1978, Julia Gillard has a lot to gain if she stops logging the world's tallest flowering forests in Tasmania, and Victoria, now.

With those signatures last year, the authority of Prime Minister and Premier was required to put the rogue Forestry Tasmania out of high conservation value forests. But the rogue has continued, initiating the logging of 10 square kilometres. On Friday the federal minister for the environment signed up to logging of another 10 square kilometres or so this summer - at great cost to the public purse. It will extend new logging roads into a pristine rainforest and tall eucalypt area in an obvious prelude to longer-term destruction.

I have repeatedly raised this issue with federal ministers including the Prime Minister. In November she countered my concern by writing to me with this reassurance: ''In accordance with the [agreement], 430,000 hectares of native forest ... has been placed in informal reserves by the Tasmanian Government.''

But when we met at The Lodge on December 9 it became clear that extensive logging had been authorised in these same reserves. I told the Prime Minister that, while I would be available to discuss any matter, I would not be at our regular meetings - weekly when Parliament is sitting - until her government's commitments to protect the 430,000 hectares of forests were honoured.

I take the biosphere seriously. We depend upon it for everything, including life. It is being destroyed at the greatest rate in human history. Some commentators think that requiring ministers to keep publicly signed agreements is less important than keeping tea drinking arrangements. I don't.

My relationship with Julia Gillard is a good one and I have found her, with this exception, someone who does what she says she will do. It is not difficult for the Prime Minister to ensure Forestry Tasmania does what most Australians want it to do - get out of these forests and let Miranda Gibson have her next cup of tea with her friends down on the ground.

She has invited the Prime Minister to join her.

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