Australia’s vast, unprecedented wildfires are going to have a devastating effect on the biodiversity of the country. To fully understand why this is the case, you need to know something about where species occur and why.
Australia is a land of lizards. Karin and I see them everywhere we walk and frequently encounter them in gardens. Reptiles are the most diverse group of vertebrates in Australia, with more than 1000 described species. Of these, over half are lizards. One family alone, the skinks (Scincidae) accounts for almost 440 species, with species new to science being described every year. Some of these lizards are physically extremely impressive, particularly the dragons (Agamidae – about 90 species) and the monitors or goannas (Varanidae – 30 species). We encountered lace monitors (Varanus varius) over Christmas at Port Macquarie, in coastal bushland and (very dry) rainforest at Sea Acres National Park (see photos above and below):
Spot the goanna:
Growing up to two metres in length, they seem to arrogantly swagger through the bush as though they own it; which of course they sort of do – they were here millions of years before people arrived. Smaller but still impressive are the Eastern water dragons (Intellagama lesueurii) – here’s male and female checking one another out:
Much smaller but more charming are the various skinks that seem to inhabit every garden and green space in the city; this one seems to be the Eastern water skink (Eulamprus quoyii):
And here’s where we get to the main point of this post. All of the lizards I mentioned above are endemic to Australia, it’s the only place on Earth where they naturally occur. But they are all widespread species found across a huge area in the east of the country, from Queensland to Victoria, a linear distance of over 2,000 km. This is unusual for species in Australia, and indeed in the rest of the world; most organisms naturally occur over a much smaller area. To see what I mean, look at the image below from Steve Wilson & Gerry Swan’s book A Complete Guide to Reptiles of Australia:
The maps adjacent to each species description illustrate the distribution of these organisms. The garden skink and the grass skink live in suitable habitat over vast areas. But the other two species are much more restricted in their ranges, which are so small that they need to be highlighted with arrows. The elongate sunskink (Lampropholus elongata) for instance is found only “in the vicinity of Grundy Fire Tower and “The Flags”” at 1180-1455 m in the Great Dividing Range. This is more typical of species distributions in Australia: most are restricted, and some are extremely restricted. This is true of other reptiles, plants, birds, insects and fungi, in fact all major groups, not just the lizards. Such a skewed distribution of species occurrences, with many rare and localised, and a few common and widespread, is natural; it’s an outcome of the processes of natural selection and evolution. But it’s been exacerbated by habitat loss across the world, including Australia. According to the Wilderness Society of Australia, the country “has lost 25% of rainforest, 45% of open forest, 32% of woodland forest and 30% of mallee forest in 200 years”.
But even these figures do not reflect the full scale of the loss: I’ve seen estimates that more than 90% of the temperate rainforest exemplified by Sea Acres National Park has been destroyed. Given what I’ve said about the limited distribution of many species, that must mean that locally endemic species have gone extinct in the past. The huge extent of some of the Australian bushfires, individually covering tens of thousands of hectares and collectively around 6 million hectares, means that most or all of a species’ population could be wiped out. To give just one example, a small marsupial mammal, the Kangaroo Island dunnart (Sminthopsis aitkeni), is found only on Kangaroo Island. Indeed, it’s restricted to the western part of the island, where a large bushfire has been raging out of control in recent days. We will only know whether this species has survived, and in what numbers, once ecologists are able to survey the area once the danger is over.
However even for widespread species the fires can have a massive effect on their genetic diversity, which is an important component of biodiversity. When we lose individuals from a population we lose genetic variants too. A recent assessment by ecologists at the University of Sydney has suggested that almost half a billion reptiles, mammals and birds have been killed so far by the fires. Losses of trees and other flowering plants, as well as insects, spiders and so forth, will be much, much greater of course.
This destruction of biodiversity has a human impact too. On television news reports we’ve heard farmers and fire fighters describing the emotional trauma of seeing animals on fire and hearing the screams of koalas as they burn in the tree tops. All of this biodiversity serves to ensure that Australian ecosystems function effectively and sustainably now and in the future. Ecosystems which are crucial for reducing the future effects of climate change, for ensuring supplies of fresh water, supporting agriculturally-important pollinators and predators of pests, and bringing in billions of tourist dollars. All in all these fires are a tragedy for Australian biodiversity, as well as for the human population of this fabulous country.