Almost a decade after Norway signed a $1-billion deal with Indonesia to help protect its tropical forests, the first payment for reduced emissions will be made after deforestation rates fell, environmentalists and government officials said.

Indonesia imposed a moratorium on forest-clearing under the 2010 climate deal, with payments linked to the Southeast Asian nation's progress on lowering planet-warming emissions from felling trees, which release carbon when they rot or are burned.

Indonesian Environment and Forestry Minister Siti Nurbaya Bakar and Norwegian Climate and Environment Minister Ola Elvestuen agreed the first payments would be made after deforestation rates dropped in 2017, according to a statement issued on Saturday by the Norwegian embassy in Jakarta.

No details were provided on the payment amount, although green groups estimate the figure to be about $20 million.

"It is a big deal because it reflects the fact that Indonesia has turned (a corner), and that is great news for all of us," said Oyvind Eggen, director of the Oslo-based Rainforest Foundation Norway.

"We want to see from Indonesia that this is a trend and not a one-year event," he told the Thomson Reuters Foundation.

Home to the world's third-largest tropical forests, Indonesia is also the biggest producer of palm oil.

Environmentalists blame much of the forest destruction on land clearance for oil-palm plantations.

Deforestation and forest fires continue to blight many parts of the country, while revisions to the forest-cutting moratorium have lacked transparency, environmental campaigners say.

By November 2016, Indonesia's forest moratorium covered an area of more than 66 million hectares (163 million acres).

Image: World Resources Institute

In an attempt to tackle its annual haze from fires on deforested land, Indonesia switched its focus from containment to prevention after a particularly bad outbreak in 2015 that cost the country $16 billion and left more than 500,000 people suffering respiratory ailments.

"The fires in 2015 were one of the key reasons we are moving now," said forest expert Eggen on the climate deal's progress.

There had been a shift in political will and greater transparency from Indonesia over the last four years, he noted.

Indonesia confirmed on Saturday that carbon emissions from deforestation declined in 2017. Once independently verified, payments for about 4.8 million tonnes of avoided emissions will be made, the Norwegian embassy statement said.

New measures introduced by the Indonesian government, including a ban on destroying primary forests and peatlands, and limiting palm oil expansion were critical, said Norwegian minister Elvestuen.

Future pay-outs under the $1 billion deal would be made when further deforestation progress was proven, Eggen said.

He urged Jakarta to strengthen and extend its moratorium to include secondary forests - areas that have been cleared but where woody vegetation has again taken over.

Re-evaluation of forestry concessions with a high deforestation risk, a more transparent approach, and protecting the interests of indigenous people were also key, Eggen said.

"The commitment is there - but now it depends clearly on whether Indonesia continues to reduce deforestation," he added.