Tropical savannas (or expansive grasslands) of northern Australia cover roughly the top third of the country and are home to some cute and quirky critters: the Long-tailed Planigale, the Northern Quoll, the Gouldian Finch, and so many more.
The natural beauty of this landscape gives the appearance of untouched wilderness. It is sparsely populated and largely un-surveyed. Consequently, northern Australia’s savannas were assumed to be in tip top condition until fairly recently (the last 40 years) when observations of some local wildlife got fewer and fewer and monitoring in Kakadu National Park found sharp declines in mammals.
And quite serious declines at that. In a decade of monitoring within this world heritage area, scientists found that Kakadu had lost 90 % of their mammal abundance and diversity.
What was worse? No one could pinpoint exactly why it was happening.
Unlike the waves of extinction that initially travelled from southern Australia into the central deserts following European settlement which were generally well-documented and understood to be a result of altered land use and introduced animals, northern Australia’s savannas still appeared to be so wild and rugged… and untouched… yet its fauna was disappearing without a trace.
The landscape was getting quiet.
Research attempting to explain this rapid and severe decline was first published in 2011 and by 2019, extensive research had been undertaken to untangle the mystery and identify the threats that faced our wildlife.
I will of course provide links to some of the pivotal papers published on this topic at the end of the article. Until then, we will talk about what caused the disappearance of our northern fauna and some of the incredible work being done on the ground to turn this story around!
Scientific research, land management and observation have now identified several main threats to the wildlife of tropical savannas: fire, feral grazers and feral cats as well as the combinative and interactive effects of these threats.
Fire was a natural part of savanna ecosystems for more than 60,000 years as Indigenous groups who once walked the country, lit small patchy fires often as they went: flushing game, creating paths, protecting sites, for many reasons.
These fires “burn cool” as they trickle through the landscape and selectively burn drier vegetation, maintaining a lot of the ground cover vegetation and canopy so that wildlife have somewhere to shelter. Ultimately, this creates a “mosaic” pattern of burnt and unburnt areas in the landscape which act as a series of natural firebreaks.
As dry lightning storms tear over the land in the build up to the monsoonal wet season (the late dry season), fires begin in the parched grasslands that quickly cover huge areas of country if not checked. When indigenous people moved off country to work on towns, missions and stations in the late 1950s and 60s, and stopped their traditional burning practices, out-of-control wildfires were left to travel unchecked through the landscape.
Hot, vast, fast.
Without a mosaic of firebreaks, these fires wreak havoc.
The savanna fauna is well-adapted to the Indigenous style of “right way fire” and thrives under these conditions.
By mimicking this in the form of a landscape-scale prescribed burning program in the early dry season (immediately after the monsoon), scientific monitoring has found that the abundance and diversity of animals in savannas can begin to return.
Which is incredible.
The take away is that maintaining habitat by burning in the “right way” (to mimic traditional indigenous burning practices) is critical for maintaining wildlife in the landscape.
Not only does it provide them with a place to live, feeding and breeding resources, but dense ground cover also shelters and protects wildlife from predation – especially from feral cats who seem to have learnt that a late dry season wildfire scar is a smorgasbord: an easy place to get a bite to eat with plenty of animals left with nowhere to hide.
In Australia, feral grazers include large hoofed animals: cattle, horses, donkeys and even buffalo in some areas that weren’t designed for these delicate landscapes. Introduced for agriculture, their hard hooves can trample out sensitive areas of land (especially waterways and wetlands) and their large appetites can dramatically change the structure of the habitat: after all they aren’t fussy eaters and remove lots of plant life.
The change to, and removal of ground cover by grazing animals has a similar impact to that of late dry season wildfire which removes ground cover and canopy, leaving animals with no shelter and no resources.
By creating large paddocks and mustering to “destock” or remove cattle and other introduced herbivores from areas of country, parts of the landscape can flourish with plant life returning to its natural balance.
Scientific monitoring has found that destocking is especially important once an area is burnt. This is because grazing in “cool burnt” areas on the fresh green grass that sprouts back has a similar “defoliating” impact as hot late season fires would.
So how can we protect our precious fauna of northern Australia’s tropical savannas?
Well, the research says that when we get the fire regimes right, and remove as many feral herbivores as we can – that’s when the landscape comes back to life!
A link to the paper that first documented declines in mammals is here.
And, a link to long-term monitoring data from Mornington Wildlife Sanctuary in the central Kimberley, north-Western Australia showing the benefits of “right way fire” and destocking is here.
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