South Australian Biodiversity Under Threat from Ongoing Drought Crisis

A recent Guardian Australia article has spotlighted the devastating ecological impacts of South Australia's ongoing dry conditions, featuring insights from three members of the Environment Institute, Dr Stefan Caddy-Retalic, Dr Jess Marsh, and Dr Katja Hogendoorn. Together, their insights paint a confronting picture of how prolonged drought and rising temperatures are pushing South Australia's ecosystems to the edge.

Parts of the state, including the Adelaide Plains, the Fleurieu, Yorke and Eyre Peninsulas, and the upper South East, have recorded the lowest rainfall on record over the past 14 months. Trees are shedding limbs, waterways are turning to dust, and many once-resilient species are reaching a breaking point.

Dr Stefan Caddy-Retalic says tree species across the Adelaide Hills are visibly under stress. Messmate stringybarks, wattles and other eucalypts are showing signs like dead branches, leaf scorching, and regrowth sprouting at the base, a survival response to extreme conditions. Coastal shrubs, including coast daisy bush and coast beard-heath, are also suffering.

The effects of lower rainfall, increasing heat, and development that disturbs tree roots are making it harder for these ecosystems to bounce back. As Adelaide’s climate shifts from warm Mediterranean to semi-arid, even some native trees, along with familiar introduced species like jacarandas and oaks, are struggling to adapt. This also impacts birds, mammals and insects that rely on trees for food, shelter and habitat.

Dr Jess Marsh is worried about what comes next for Kangaroo Island’s critically endangered assassin spider. The species is only known from one patch of habitat, and its survival depends on cool, moist vegetation along creek lines. But those habitats are drying out fast, following years of bushfire damage and fungal dieback in native plants.

“I’m really concerned for that whole population,” Dr Marsh says. “They need complex vegetation and healthy eucalypts. It’s getting hotter and drier, and species like the KI assassin spider are on a knife edge. We are going to lose species.”

Native bees are also under threat. Dr Katja Hogendoorn, who studies both native and introduced bees, says Greater Adelaide is home to around 150 native bee species. All of them rely on flowers for nectar, which they need to fly and reproduce.

“If a bee cannot find nectar, it cannot fly, it cannot produce offspring,” she says. The 2019 drought led to species like the blue-banded bee disappearing from urban gardens. Dr Hogendoorn expects another decline this season. And it won’t just be bees that vanish. She expressed how the issue affects all flying insects, and a reduction in flying insects leads to less birds who rely on them. 

With some of South Australia's most important ecosystems now under serious pressure, the message from researchers is clear, our natural systems are in trouble. Without urgent action to reduce emissions, protect habitat and support species resilience, we risk losing more than individual species but the intricate ecological networks that sustain life.