Thread by @Peters_Glen

1. In the 2019/20 season, forest fires have burned a globally unprecedented percentage of any continental forest biome:

21% of the Australian temperate broadleaf & mixed forest biome has so far been burned (red line at the top), usually ~2% (pink bar)

rdcu.be/b2cIM

2. The Gospers Mountain fire near Sydney has burned more than 510,000 ha (to January 2020) since ignition by lightning on 26 October 2019; it is the largest forest fire recorded in Australia

(nice hiking area, for those that have not been to the area)

3. Why have the fires been so devastating this year?

Fires in eucalypt forests propagate primarily through the litter layer, and its dryness effectively acts as the ‘on/off switch’ for forest fire activity.

In 2019, area exceeding critical flammability threshold was a record.

4. Naturally occurring firebreaks, such as moist gullies, swamps or south-facing slopes, that normally dissect the forest landscape have dried out during the current widespread drought, affecting the probability of mega forest fire events in a highly nonlinear way.

5. The extreme drought provided the preconditions for the unconstrained spread of fires over millions of hectares of forest, triggered by the arrival of hot dry windy weather conditions & ignitions in early September 2019

6. The resulting large sizes of the fire complexes may prove challenging for biota that require dispersal from unburned forest for their post-fire recovery.

7. Given the links between the record-breaking high temperatures and widespread prolonged extreme dryness in eastern Australia and climate change, these unprecedented fires may indicate that the more flammable future projected to eventuate under climate change.

/end