From southern Europe to the east coast of the United States, debate is raging over how vulnerable the eucalyptus tree is to fire and whether it's doing more harm than good.

Portugal, Greece, Spain, Chile, California and now Hawaii have all battled wildfires this year as high temperatures and strong winds have whipped small sparks into violent infernos. But fire needs fuel, and what these places also have in common is an invasive species — Australia's eucalyptus tree.

Exotic souvenir from the south In the early 1800s, the eucalyptus tree was an exotic specimen from the new southern land, and aristocrats, collectors and botanists alike were eager to plant them in gardens around London and Paris.

"All of these things combine to make eucalypt forests particularly flammable parts of the landscape in those environments they've been introduced to," Dr Curran said.

Environmental groups in Portugal have long campaigned against the use of eucalyptus trees in plantations, fearing poor management could increase the fire risk.

"For many Californians, eucalypts are a valued part of the natural landscape, while for others they are a nightmare that fuelled the disastrous 1991 Oakland Hills fire," a study into their impacts on the state read.