New modeling shows where to focus conservation efforts for Australia's endangered alpine ash Sadie Harley Scientific Editor Andrew Zinin Chief Editor An alpine ash forest is a sight to behold. Alpine ash (Eucalyptus delegatensis) is a tall eucalypt species that grows in the cool, wet mountains of southeastern Australia. These forests store large amounts of carbon in their wood and soils.

They help regulate water flows into major rivers and dams and provide habitat for a wide range of birds, mammals and insects. Mainland alpine ash forests are now formally listed as endangered. This is because bushfires are becoming more frequent and severe due to climate change, which threatens to wipe out some of these forests.

In our new study, we examined how alpine ash forests would change under different climate scenarios and found that difficult choices likely lie ahead. Is it still possible to protect this unique species? We think so.

From the ashes Alpine ash is what ecologists call an "obligate seeder." This refers to plants that, after a major disturbance such as a bushfire, can regenerate only from seed. If a mature forest burns, many adult trees die. However, the heat from the flames opens their seed capsules high in the canopy, releasing a flush of seed that allows the forest to regenerate.

But this strategy works only if there is enough time between fires for young trees to mature and start to reproduce. In recent decades, increasingly hot and dry conditions have sparked larger fires, including the devastating "Black Summer" fires of 2019–20. As a result, some regions have burned repeatedly within a matter of years.

When fire returns before the new generation of trees can produce seed of their own, alpine ash forests can fail to regenerate and may be replaced by other vegetation. This process, known as "immaturity risk," is a major reason alpine ash is now considered an endangered species. In response, forest managers are increasingly turning to aerial resowing.

Helicopters or planes are used to drop seed over burned areas where young trees were killed before they could produce seed. The goal is to protect patches of alpine ash forest that could otherwise be replaced by other species and turn into shrublands or grasslands. Research has shown this active management approach helps protect smaller pockets of alpine ash affected by repeated severe fires.

But it is still unclear how effective aerial sowing can be at a landscape scale. What we did In our study, we used a powerful computer model to simulate these ecosystems over the next century and examined the forest changes that happened along the way. We focused on the Australian Alps, the country's highest mountain range, which stretches across southeastern Australia.

We then tested how alpine ash forests would fare under different climate scenarios. This allowed us to consider three main questions: - What drives alpine ash decline in mainland Australia, and how much loss can we expect? - In a warmer climate, how important is the reproductive age—meaning when the trees first produce seed—to the species' survival?

- How effective is aerial resowing after fires in protecting alpine ash at a landscape scale?