The park is renowned for its floristic diversity and includes one of the areas of highest plant diversity within the south-west of Western Australia—an area itself identified as a global biodiversity hotspot.  The park contains 1748 recorded flora species, at least 75 of which are endemic, which means they occur nowhere else in the world.  Eighteen of these species have been listed as Threatened flora. More than 120 plants are listed as Priority species, meaning they are restricted in their distribution and may also meet the criteria to be listed as Threatened, however there haven’t been sufficient surveys to see how rare or threatened they are. The park is rich in species of the Proteaceae family (Banksia, Hakea including the spectacular Royal Hakea), the Myrtaceae family (such as Eucalyptus and Melaleuca), the Fabaceae family (pea, Acacia) and the Ericaceae family (heath).

There are several reasons for the outstanding species diversity and endemism of this area, including its long geologic and climatic stability, isolation, diversity of habitats and nutrient deficiency of the soils.  These factors have led to the persistence of ancient lineages and a high degree of speciation and specialisation in response to edaphic factors (the chemical and physical properties of soils).

One of the fascinating features of the mountain flora of the Fitzgerald River National Park is that some of the species also occur on the mountains of Stirling Range National Park, more than 100 kilometres to the west, but nowhere else.  This indicates that the populations of these species were previously connected, possibly once being more widespread in the south coast region. As the climate changed, they were left isolated on disjunct ranges, showing the highly important role the mountains play as refugia for flora species.   

The fascinating adaptations of some of these species, in particular those from the Proteaceae, has enabled them to survive in a nutrient poor landscape but also makes them vulnerable to the root pathogen, Phytophthora dieback (Phytophthora cinnamomi) which causes widespread death of susceptible species.  There is no way to eradicate Phytophthora dieback once it is introduced.  

I knew about Phytophthora dieback having studied it at university and working in the ecological field in WA for 20 years. The devastation that it can cause never really hit home until I had spent years working in the Stirling Range National Park, where the disease has spread throughout much of the park over many decades. The susceptible species of the Stirling Range, which were once common across the mountains, now occur only as scattered individuals and are close to extinction on many of the peaks.  There are few examples of extensive healthy Proteaceous shrublands left, and I had only seen what the healthy and diverse mountains should look like in small patches or in historical photographs.  

Luckily, the Fitzgerald River National Park was still largely free of Phytophthora dieback when the disease became recognised as one of the major threats to the biodiversity of this area and management measures were implemented to prevent its introduction and spread. Statutory protection for the core, central area of the national park was enacted under the Fitzgerald River National Park Management Plan in 1991, which included limiting access to this wilderness area to prevent the introduction and spread of Phytophthora dieback.  

The first time I visited the Fitzgerald River National Park it finally hit home what a healthy south coast Proteaceous landscape should look like.  All those Proteaceous thickets that were causing us such grief to walk through were a sign of a healthy and thriving landscape.   

Of course, there are other pressures beside Phytophthora dieback.  The drying and warming climate is taking its toll, causing drought events resulting in mass plant deaths through the park.  The warming and drying climate is also likely to change fire regimes, potentially leading to more frequent and higher severity fires.  While plant species in this region have adaptations that assist in recovery from fire, frequent and intense fires can cause population declines and potentially extinctions.

Two months after our trip into the wilderness area in late 2025, lightning strikes ignited fires in the remote and inaccessible central part of the park, very close to where we had been monitoring. The bushfire burnt intensely during its first week and took three and a half weeks before it was fully contained, with elevated and variable fire weather conditions hindering suppression efforts.

The fire ended up burning approximately 170,000 hectares, which included 145,800 hectares, or around 50 per cent, of the Fitzgerald River National Park.

It was hard to hear the stories and see the images of the size and severity of the fire, and to think of all the species impacted that were already so restricted.  Eleven Threatened flora species were impacted by the fire in some way, with four of these largely restricted to the area of the fire, meaning that almost all of their populations were affected.  Seventy-three priority flora species, of which 30 are endemic or near endemic to the park, occurred within the burnt area.  All known occurrences of the Eucalyptus acies Threatened Ecological Community fall within the fire boundary and are also likely to have been significantly impacted. Substantial areas of the Proteaceae dominated Kwongkan shrubland Threatened Ecological Community were also impacted by the fire. 

Some plants can resprout following a fire but there are numerous species within the Fitzgerald biosphere (particularly on the mountains) that are killed by fire and will instead have a flush of seedlings that germinate following fire.  There are also many plants that will respond to fire with a flush of flowering, and the fire will stimulate growth of a number of fire ephemeral species.  But there is a long way to go for recovery.  The young plants will have to survive drought, grazing by hungry herbivores, competition, disease and many more dangers before those incredibly diverse shrublands and heaths can reach maturity.  

We need to do everything we can to make sure that Phytophthora dieback is not one of those pressures.  So far, Phytophthora dieback has been excluded from the mountain tops in the wilderness areas.  Prior to the fire, spot infestations had been identified in several locations on the sandplain, but these infestations have so far been mostly contained.  However, the fire has impacted a huge area and made the spread of this disease a much higher risk.  From increased human access to increased water run-off, the scorched wilderness area is now much more vulnerable than ever.

On our trip in late 2025, we did eventually reach our Threatened flora population and completed our monitoring. It felt like an achievement just getting there, but we didn’t realise just how important it was at the time.  Now the fire has gone through, the data we gathered on the pre-fire populations will be very important in assessing the recovery of these threatened flora and communities after the fire.  

While the potential impacts that such a fire has on the ecology of the park are significant, we must remain optimistic.  If, there is good rainfall in the coming seasons, short interval fires are prevented, and Phytophthora dieback is managed to prevent its introduction into healthy habitat, in a few years the wilderness area will once more be back to hiding its rich biodiverse secrets behind swathes of colourful, spiky and impenetrable plants.

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