A $45 million intervention package to protect the threatened koala population has been announced by the New South Wales Government.

Key points: 25,000 hectares of forest across NSW set aside for koala reserves

25,000 hectares of forest across NSW set aside for koala reserves Koala population in NSW has declined by more than 25 per cent in 20 years

Koala population in NSW has declined by more than 25 per cent in 20 years Fixing road kill hotspots, opening a koala hospital among NSW government measures

Thousands of hectares of land will be set aside for koalas, which have fallen in population by about 26 per cent over the past two decades in NSW.

Almost 25,000 hectares of state forest in the mid-north coast will become a koala habitat.

A new koala hospital will also open at Port Stephens to care for sick and injured koalas, under the new measures to protect the iconic Australian species.

The reserves will be a place for koalas to breed freely, NSW Premier Gladys Berejikilian said at an announcement at Taronga Zoo.

"We know that there are around 36,000 koalas left in the state, but we don't know that for sure," Ms Berejikilian said.

"It would be such a shame if this nationally iconic marsupial did not have its future secured."

The Government's goal is to stabilise and eventually increase the population of koalas.

Gladys Berejikilian announced the new measures at Taronga Zoo. ( ABC News: Jean Kennedy )

More than 20,000 hectares of state forest on the Central Coast, Southern Highlands, North Coast, Hawkesbury and Hunter with koala habitat will be used as new koala reserves.

Over 4,000 hectares of native forest on the Mid North Coast will also be transferred to the National Parks Estate.

About $20 million from the NSW Environmental Trust will be used to purchase land with prime koala habitat that can be permanently reserved as national parks.

Environment Minister Gabrielle Upton said the strategy was a comprehensive policy which involved fixing road kill hotspots, introducing more vaccines, conducting more research, and engaging local communities.

The actions to conserve koalas were informed by a 2016 review of the state's decline of koala populations, led by the state's chief scientist Professor Mary O'Kane.

The NSW Government's proposed koala strategy across the state. ( Supplied: NSW Government )

Professor Rebecca Johnson, the director of science at the Australia Museum, was also involved in the review.

Dr Johnson said the strategy was exciting as it "embeds science as policy".

"It's an excellent first step … the most important thing is trees for them to live in, and leaves for them to eat," Dr Johnson said.

"Koala conservation is complicated — they have a very coastal distribution, they have a very specific diet, of largely, entirely eucalyptus leaves.

"They've suffered the impacts of urbanisation when land is cleared for developments or housing."

Other actions in the Government's strategy include creating a network of koala and wildlife hospitals and establishing a single wildlife rescue call number.

The strategies will be implemented and monitored over three years, and reviewed in 2021.