One gum tree can look very much like another. Maybe you know your River Red Gums, or can pick a Manna Gum out of a lineup, but for a lot of us the extraordinary diversity of gum trees – the eucalypts – remains hidden.

What makes gum trees special?

Eucalypts are of course one of the defining features of Australia’s environment. There are around 800 species across Australia and almost 300 in Victoria alone. Visit a forest or woodland anywhere in the state and you’ll almost certainly find eucalypts. They shape ecosystems and provide vital habitat for wildlife, plants and fungi. They provide food: their leaves, nectar, the nutrients in their wood. Insects making a home in their leaves, bark and branches are in turn food for other species.

But this ubiquity disguises the fact that many eucalypts are at risk of extinction. In Victoria, more than 70 species and sub-species are recognised as threatened. These include 27 that Trust for Nature has identified as priorities for conservation on private land.

The Lima Stringybark, one of Australia’s most endangered trees

Take, for instance, the Lima Stringybark. This endangered eucalypt has rough, brown bark, can grow up to 30 m tall, and grows in forested valleys. Lima Stringybarks are found only in a tiny area near Lima on Taungurung Country in the foothills of the Strathbogie Ranges.

Their habitat is now severely fragmented and degraded, and young trees are struggling to survive. There are thought to be fewer than 1,500 trees left in the world, most of them found along roadsides or on private land. None live in public conservation reserves.

One of the largest remaining populations is protected by Ben Petrides and his family through Trust for Nature.

“You definitely feel a sense of responsibility to ensure the tree is protected,” says Ben.

“It’s quite a privilege to have on our property a species that only a handful of people have seen in their lifetime.”

Growing up in Melbourne, Ben discovered the magic of the Strathbogie Ranges through school camps. In 2018, he and his family found the 100 ha property at Lima – 23 ha of which are protected under a conservation covenant.

“My wife Tess and I were looking at a property around the corner when the planets aligned. We drove up the driveway and saw the Strathbogie Ranges and fell in love. We’re conscious of protecting the area for future generations and having space for flora and fauna to prevail. We enjoy the birdlife and all the types of flora and fauna.”

Identifying gum trees

Ben’s property is home not just to Lima Stringybarks but seven other species of gum trees, including Broadleaved Peppermint, Red Stringybark, Red Box, Bundy, Eurabbie and Yellow Box.

How do you tell them apart?

“Birdwatchers talk about the vibe or the overall impression you get when you look at a bird,” says Shelagh Curmi, Conservation Program Manager for the Goulburn Broken catchment at Trust for Nature. “It’s the same with gum trees, you get a feel for what they look like.”

The boxes and peppermints are easier to distinguish by their bark, but when it comes to telling apart the Lima and Red Stringybarks it becomes much more difficult. Both have the reddish, stringy bark that gives the stringybarks their name. Their leaves, at least from the ground, look identical. And to make it more challenging, the different gums seem to like growing together.

The trick, it turns out, is that the Lima has flowers and gumnuts in groups of three, while the Red has groups of seven, nine or 11. The trouble is, those flowers and gumnuts can be ten metres or more up in the air. Cue stumbling around with binoculars tilted to the canopy, neck aching.

Over 95% of the Lima Stringybark’s remaining habitat is found on private land, and for that reason it’s one of 27 species of eucalypt identified as a priority for protection under Trust for Nature’s Statewide Conservation Plan. Others include species like the critically endangered Bellarine Yellow Gum, found only on Wadawurrung Country, or the endangered Warby Range Swamp-gum found in endangered spring soaks on Yorta Yorta Country.

Why tree diversity matters

“Recent research indicates that only a quarter of the evolutionary diversity of eucalypts in Victoria is protected in existing reserves on public land,” says Dr Doug Robinson, Chief Conservation Scientist at Trust for Nature.

“Protecting habitat on private land is critical to ensure that the other three-quarters of eucalypt diversity in Victoria is maintained and flourishing.”

This diversity has real benefits for nature. One group of eucalypts, including gums, boxes and ironbarks (a group belonging to the subgenus Symphomyrtus) tends to grow on more fertile soils and has more nutrients in their leaves. This in turn means these trees support a greater variety of insects and spiders, birds and tree-dwelling mammals. Some eucalypts are mainly pollinated by birds, others by insects, which turn shapes the communities of wildlife that live among them.

Threats to eucalypts

The threats facing eucalypts at risk of extinction are many. Small populations render them vulnerable. Grazing, weeds or lack of genetic diversity make it difficult for seeds to germinate and saplings to flourish. Land-clearing on private land and roadsides continues. Changing water flows and availability, a warming climate, and new pests and diseases are emerging threats.

“For these species with small populations and distributions, protection is the most important thing landholders can do to ensure their survival. By improving habitat through weeding and keeping stock away we can help young saplings get a roothold and preserve the genetics of these species,” says Doug.

It’s not just looking after species that is important, but individual trees. Big, old trees play a particularly vital role in ecosystems. The hollows that provide homes for many species like owls and gliders can take decades to centuries to form.

“Old trees are irreplaceable. They’re long-lived, keystone features of habitat and as conservation practitioners, we always need to think about how best to assist their survival and health. We can help ensure their health for another generation or two.”

So next time you encounter a gum tree, pause for a moment. Feel its bark, breathe in its scent, listen to the breeze in its leaves, and wonder at the variety of this extraordinary group of trees.