Fire crews will investigate whether an out-of-control bushfire in Tasmania's north was deliberately lit.

The fire near Nunamara, east of Launceston has been downgraded to an advice alert, after being at watch and act level much of the day.

Crews are battling about 74 bushfires across the state, with 50 of those uncontrolled.

Fifteen fires are under advice level alerts.

John Hazelwood from the Tasmania Fire Service (TFS) said the Nunamara fire looked to be an act of arson.

"It's one of quite a number of fires that were lit on the same day and there is no natural cause that we can possibly put them down to at this point," he said.

"So we will investigate and prosecute if it's deemed to be deliberate and we can find the person who lit them."

A total fire ban remains in place across Tasmania until midnight on Tuesday, and another 16 areas have bushfire advice level warnings

Extra resources considered if TFS asks: Treasurer

The Tasmanian Government would provide more resources for the state's firefighters if needed, Treasurer Peter Gutwein said.

In the past fortnight up to 80 fires have been burning around the state, and currently more than 50 are uncontrolled.

While no homes have been lost, nor people injured, more than 45,000 hectares of land has been burnt.

Treasurer Peter Gutwein said the impact to the state's economy was ''challenging, but manageable".

The fire service is yet to ask for extra resources, but Mr Gutwein said he was ready to consider any request.

"These are unprecedented circumstances, it is difficult and obviously the Government will do what it needs to do, should the fire service require additional resources," he said.

NSW and ACT emergency services agencies are already sending 140 people to help Tasmanian firefighters.

Threat to World Heritage wilderness

A Tasmanian conservationist wants the current state bushfires recognised as the worst threat to Tasmania's pristine wilderness in several decades.

About 11,000 hectares of World Heritage Area has already been burnt.

Stands of Australia's only winter-deciduous tree are now in the path of the fire.

Fires have destroyed this part of Tasmania's World Heritage Area. ( Supplied: Dan Broun )

Conservationist Geoff Law said many species in the area were irreplaceable.

"Pencil pine, king billy pine, cushion plants, potentially areas of deciduous beech, these are places which are either burning or in the firing line from blazes burning out of control not far from the boundaries of these national parks," he said.

The Fire Service said wilderness values were taken into account as part of their firefighting efforts, and some interstate reinforcements would be deployed to World Heritage Areas.

The Wilderness Society's Tasmanian spokesman, Vica Bayley, said the fire fallout would be felt in the environment.

"The consequences of the fires burning into incredibly remote alpine bio-sensitive ecosystems is the near-permanent destruction of those ecosystems," he said.

"I mean these are incredibly ancient and incredibly fragile areas and landscapes and it would take centuries, if not millennia, for these ecosystems to recover."