Australian communities – and the insurers that cover them – will be exposed to larger, more intense bushfires unless new solutions to climate change are found, fire and climate experts say.

Climate change, an accumulation of fuel stock and urban sprawl are expected to lead to more “megafires” – larger blazes that are much harder to control – over the next 40 years.

Fire seasons are starting earlier and lasting longer, and the risk of a blaze “morphing” into an uncontrollable force is expected to increase, Melbourne University senior lecturer Kevin Tolhurst said on the ABC’s “Four Corners” program on Monday.

“We’re looking at three factors converging,” he said. “One is climate change, one is over-accumulated fuels, particularly in fire-dependent forests, and the last is the rapid growth and development of human populations at what we call the ‘wildland/urban interface’.”

Kevin Hennessy, from CSIRO’s Climate Impact and Risk Group, said the risk of very high and extreme fire danger days could jump to a high of 70% by 2050. He says the increase in bushfire intensity is due to greenhouse gas emissions.

Macquarie University’s Professor Andy Pitman was more dire in his appraisal, citing a 100% increase in bushfire risk unless governments and business move to curb emissions and population growth.