Written March 2019
The following photos were taken on several walks through the Sydney region where fires had recently burnt through. Most represent the work of arsonists who incinerated a large section of the Royal National Park in January 2018. It is important not to romanticise wildfires, especially those with human origin. Arson is a serious threat to biodiversity. So, for that matter is climate change. Too frequent burning can result in the loss species and can promote the colonisation of weeds that can permanently alter ecosystem dynamics.
Having said that, fire is in fact necessary for the continued diversity of many plant Australian plant communities. It initiates flowering in many Australian plant species, including many ground orchids and the grasstrees (of the genus Xanthorrhoea; pictured below). It triggers seed germination in many genera including Acacia, and many Proteaceae (Banksia, Grevillea, Hakea and their relatives). And it creates physical space for many herbs and subshrubs such as Pimelea linifolia [1], and Patersonia sericea.
Fire also brings different colours, patterns and form to the landscape. In their undisturbed state, sclerophyll communities such as heathlands and eucalypt forests tend to be a combination of subdued tones: dull greens, greys, olive. But fire can create a sharp, binary combination of charred black with regrowth that is intensely pale or lime green. It also can affect not just tone but textural diversity. These communities can go from quite subtle and diverse in texture to being initially quite monocultural, with a particular location dominated by the resprouting or reseeding of a single species (as above with Melaleuca armillaris, or below with Allocasuarina distyla, or in the third image dominated by Acacia suaveolens). Highest biodiversity and visual diversity tends to occur at the intermediate stage between initial regrowth and the ‘climax’ community which again tends to be dominated by fewer species.
Spatially, fire opens a landscape, like X-ray vision. this is most notable in dense scrub or tall heath, where suddenly vast areas are now open at eye level – save for the ‘bones’ of branches – where you were previously hard-pressed to see more than a couple of metres.
[1] Morrison, D.A. 2002. Effects of fire intensity on plant species composition of sandstone communities in the Sydney region. Austral Ecology 27(4): 433–441.