The koala’s population size has declined about 30% over the last 18-24 years due to climate change and a severe decline in inland regions most exposed to recent drought.
The conservation status of the koala has been contested, in part because of uncertainty about relevant population parameters and marked variation in population trends across its large range.
The koala’s total geographic range and overall distribution has contracted significantly due to loss of large areas of habitat since European settlement. This decline was primarily due to disease, bushfires, and widespread habitat destruction in the early decades of the 20th century. In Queensland, extent of occurrence and area of occupancy have contracted by about 30%.
In 2012, the overall rate of decline in population size over the last 18-24 years, or three generations, was estimated at about 28% by the Threatened Species Scientific Committee. This rate is substantially influenced by a severe decline in inland regions most exposed to recent drought.
A separate expert elicitation process involving independent estimates from 15 koala experts of population size in every bioregion inhabited by koalas concluded that the koala population size reduction or projected reduction over three generations is a mean of 29%, albeit with substantial variation amongst experts in estimation of this rate.
Climate change is expected to lead to an increased rate of population reduction over the next 20-30 years, and the impacts of other threats will magnify over this period.
• Image | ©️ Nathan Rupert, Some Rights Reserved, (CC BY-NC-ND 2.0)
• Sources | (Gordon, Hrdina, & Patterson, 2006; McAlpine, et al., 2012; Melzer, Carrick, Menkhorst, Lunney, & John, 2000; The Senate Environment and Communications References Committee, 2011; Threatened Species Scientific Committee, 2012; Woinarski & Burbidge, 2020)