from https://en.wikipedia.org/wiki/Eucalyptus#Adaptation_to_fire https://en.wikipedia.org/wiki/Eucalyptus#Adaptation_to_fire: "Eucalyptus oil is highly flammab

from https://en.wikipedia.org/wiki/Eucalyptus#Adaptation_to_fire https://en.wikipedia.org/wiki/Eucalyptus#Adaptation_to_fire: "Eucalyptus oil is highly flammable; ignited trees have been known to explode. Bushfires can travel easily through the oil-rich air of the tree crowns... ...In seasonally dry climates oaks are often fire-resistant, particularly in open grasslands, as a grass fire is insufficient to ignite the scattered trees. In contrast, a eucalyptus forest tends to promote fire because of the volatile and highly combustible oils produced by the leaves, as well as the production of large amounts of litter high in phenolics, preventing its breakdown by fungi and thus accumulating as large amounts of dry, combustible fuel." So yes, part of it is that it secretes oils that are highly flammable. Another part is that it tends to accumulate dead leaves etc at the base, which aren't broken down as fast as that of most trees. The Eucalyptus has evolved to expect periodic fires - it's flammable because stoking fires is adventageous to it. The problem is that now, due to climate change, the fires are more frequent and more intense, and because habitats are so small, there's nowhere else for the koalas to go when one part of the forest burns.