The NSW government has committed to combating Sydney's heat island effect by planting 5 million trees over the next 12 years, in a bid to offset the cracking pace of development.

NSW Premier Gladys Berejiklian said the government would spend $38.7 million over the next four years on its "Five Million Trees" initiative, as part of its plan to boost Sydney's existing tree canopy from 16 per cent to 40 per cent by 2030.

NSW Premier Gladys Berejiklian committed $37.5 million to planting five million trees across Sydney over the next 12 years. Credit:Louise Kennerley

While Ms Berejiklian trumpeted the policy as a first for any Australian state government, dozens of councils across the country have also implemented canopy policies and targets.

"No other state government that I know of anywhere in Australia has ever talked about tree canopy," she said.