“Eucalypts evolved to burn their neighbours”

Australia will feel the effects of climate warming faster than any other country,
having already experienced a 1.9°C rise in average daily winter temperatures compared to baseline 1961–1990 averages for the same period (Bureau of Meteorology).

In fact, CSIRO climate projections to the end of this century (2090) indicate a rise of 3°C or more unless we drastically change behaviour.

Australia’s hugely reduced tree cover from about 40% in 1788 to just 16% today explains one of the reasons we are already 10 years further advanced in climate warming than the rest of the world.

Assuming that every country succeeds in bringing carbon back into balance by 2050, we gardeners can play a major part by planting the right trees that will survive temperatures up to 3°C warmer than today. Whilst that amount sounds insignificant, the increase is actually the difference between the average annual temperature of Sydney compared to Melbourne today.

Another reason for Australia’s much higher temperatures is because 80% of Australia’s forests contain eucalypts. Being flammable, they outcompete other trees that are not able to regenerate (as either seeds or by resprouting) when the next rains come.

“The forests are beautiful. You get away from the stress, smell the smells, see the birds. But then they catch on fire.” David Bowman, fire ecologist, University of Tasmania.

So we gardeners need to heed the warning and choose trees for planting that are both not flammable and have proven climate adaptability.

Safer gardens

Flammability is an incredibly complex issue that Lesley Corbett tackles in his book Safer Gardens. Not only is there no uniform agreement by scientists on different continents about testing, our Tasmanian and Victorian researchers often disagree, and the same tree can be regarded as flammable in one state and safe in another. However there are some general rules that everyone agrees on:

• Deciduous trees are much less flammable than evergreens, particularly eucalypts and wattles. Fires become really dangerous after soil moisture is depleted, and dry leaf and falling bark litter fuel the flames. Oaks and poplars are notable fire suppressors.
• Evergreens, particularly natives from our high rainfall rainforests with dark green leaves, are rarely flammable (excluding pines and eucalypts). Olives and evergreen Cork and Holm Oaks are flammable but not as threatening as eucalypts.

High risk plants

Natives

• Acacias in general
• Angophera costata
• Banksia integrifolia
• Cortaderia jubata
• Corymbia ficifolia/maculata (formerly eucalyptus)
• Cupressus macrocarpa/sempervirens (Monterey and Italian Cypress)
• Eucalyptus camaldulensis/globulus/regnans
• Grasses
• Grevillea robusta
• Kunzea ericoides
• Xanthorrhoea (Grass trees)

Non natives (almost all Mediterranean)

• Laurus nobilis (Bay Tree)
• Miscanthus sinensis (all grasses)
• Myrtus communis (common myrtle)
• Olea europaea (olive, i.e. high oil content)
• Pinus species (halepensis/pinea/radiata)
• Quercus ilex/suber (Holm and Cork Oaks)
• Rosmarinus officinalis (rosemary)