EPOW - Ecology Picture of the Week

Sky Afire

Northern Territory, Australia

Explanation:  On a cross-country journey through northern Australia in September of 2011, we entered the desert/grassland fringe in central Northern Territory ... to encounter an area on fire.  
  

Along Highway 66 in central Northern Territory, Australia,
we encountered ominous signs of extensive, active grassland fires.

This part of Australia stretches through the "Top End" northern portion of Northern Territory, where extensive wildfires burn annually.  Some fires are set deliberately as controlled burns to help reduce fuels and risk to loss of property and lives.  They are also burned to help control invasive plants, to keep the soil fertile and encourage regeneration, and even to meet commitments to Aboriginal communities.  

Indeed, Aboriginal people have used burning for a number of purposes, including encouraging the regrowth of wild food plants.  They would also set fires to flush out kangaroos that they would then hunt, much like some of the "beats" that local people in India would do to flush out game and predators from dense brush.  

Many signs along the highways remind travelers
to be particularly mindful of their use of fire.

Lightening is a major source of natural fire starts in the region.  

Many wildfires are also started by careless and indiscriminant use of campfires, tossed cigarettes, and other human activities.  Doubtless, a few fires may be set as deliberate acts of arson, as well.

One casualty of such fires is air quality.  Laboratory studies have shown that fast burning of grasses produces small (30-60 nm) smoke particles, whereas slow burning produces larger (60-210 nm) particles (Wardoyo et al. 2007).

The sky grew heavier as we drove on, the scent of burning
infiltrating our vehicle.

Much of the grassland savanna ecosystem here is fire-adapted, which means that fires occurred often prehistorically and the vegetation has adapted to withstand and even flourish with frequent, local, low-intensity ground fires set by lightening and then extinguished by the seasonal monsoonal rains.  It is the change now in the fire regime to intermittent, deliberate, high-intensity or extensive fires that is the challenge, particularly as recently-burned sites continue to reburn.  

Signs denote "fire protection zones" where burning without
a permit is prohibited.

  
This landscape will continue to be shaped by traditional use, invasive species, current social interests, economic forces, and, above all, shifting climate and increased aridity (Alexandra 2012).  Fires will continue to be part of the scene, and how they are managed will be an increasing challenge for ecosystems, their services, and local communities alike. 

Information:
     Alexandra, J.  2012.  Australia's landscapes in a changing climate -- caution, hope, inspiration, and transformation.  Crop and Pasture Science 63(3):215-231.
     Russell-Smith, J., A.C. Edwards, K.K. Sangha, C.P. Yates, and M.R. Gardener.  2019.  Challenges for prescribed fire management in Australia’s fire-prone rangelands – the example of the Northern Territory.  International Journal of Wildland Fire.  https://doi.org/10.1071/WF18127.
     Wardoyo, A., L.Morawska, Z. Ristovski, M. Jamriska, S. Carr, and G. Johnson.  2007.  Size distribution of particles emitted from grass fires in the Northern Territory, Australia. Atmospheric Environment. 41. 10.1016/j.atmosenv.2007.07.020. 
   

Acknowledgments:
     My appreciation to my Australian friend and colleague Deane Lewis who did the Herculean driving across the deserts of Queensland and Northern Territory.  Deane runs the wonderful and information-rich web site The Owl Pages.