Alpine habitat may be more susceptible to bushfire

Griffith University researchers have revealed new findings about how Australia’s most biologically diverse alpine habitat is responding to climate change and bushfires.

Capturing the dynamics of climate change and vegetation of 455 square kilometres of Australia’s highest area surrounding Mount Kosciuszko, researchers assessed vegetation cover through a timeseries of Landsat satellite data.

The success of this study indicates the methodology could be replicated to monitor similar climate induced changes in alpine areas worldwide.

Dr Brodie Verrall.

Griffith Centre for Planetary Health and Food Security Fellow Dr Brodie Verrall said the alpine area was mapped to observe and analyse the changes resulting from the warming climate between 1990 to 2000, 2010, and 2020.

“Ultimately, warmer temperatures, longer growing seasons, declining snow cover and variable precipitation regimes have resulted in the rapid expansion of the woody vegetation,” Dr Verrall said.

“The changes are likely to have broad ranging consequences for fire risk management, carbon sequestration, water supply and biodiversity.

“It is extremely important to understand what is happening in these alpine areas so we can prepare and predict how the warming climate and associated bushfires will impact these unique ecosystems in the future.

“A key surprising discovery is that subalpine woodlands are more resilient to bushfires than previously thought and they are expanding, however the results also showed this is increasing the amount of biomass which could exacerbate future fires.

“We found the cover of woody vegetation is increasing in the alpine, and we know the intervals between fire events are shortening and the severity of bushfires is increasing.

“Ultimately, these changes could strengthen feedback between shrubs and fire by increasing fire frequency and severity.

“While the subalpine woodlands we assessed seem resilient to one severe bush fire, other research from Victoria has highlighted tracts which have burned multiple times in recent decades are not recovering.”

The study found shrublines were advancing upslope, indicating new climatic habitat was becoming available with climate change and this was the first documented example of this phenomenon in the southern hemisphere.

This process may lead to the decline of relatively diverse alpine grasslands that currently occupied higher elevation areas.

The study found a slight treeline recession as a response to wildfire which stunted the expansion of subalpine woodland cover and suppressed the upslope advancement of shrublines.

Dr Patrick Norman in the field around Mount Kosciuszko.

“Wildfire may play an important role in regulating the encroachment of woody vegetation into alpine areas in the future, which would be an entirely new ecological process for this unique area,” Dr Verrell said.

“These events are likely to negatively impact some vegetation communities and species less tolerant to fire like those cold loving plant species remaining in the area from after the last ice age.

“There is also potential for a positive feedback loop to form as higher temperatures and altered precipitation regimes increase the frequency and severity of wildfires, which may be amplified by increasing fuel loads and dryness from the proliferation and advance of woody vegetation in alpine areas.

“It was assumed subalpine vegetation would expand upwards into cooler alpine areas as the temperature rises but our data showed the snow gums expanded within the subalpine into the once treeless patches of the subalpine heathlands after the 2003 fires.”

The research ‘The impact of climate change and wildfire on decadal alpine vegetation dynamics’ has been published in Australian Journal of Botany.