Meet our tallest tree

It’s a 63 metre high Mountain Gum growing in Namadgi National Park west of Bendora Dam. With a circumference of almost 6.5 metres, it’s estimated the tree could be around 400 years old.

How did we find and measure it?

The ACT Government use a high tech remote sensing system to create three dimensional models of the ACT land area. Lidar, standing for light imaging detection and ranging, is a form of radar that can create accurate computer models of the city for town planning and to look at the distribution of vegetation to assist in strategic bushfire hazard reduction burns. The ANU’s Fenner School of Environment and Society analysed our Lidar data to create models of vegetation height and cover. As part of this process a Mountain Gum (Eucalyptus dalrympleana) was identified as the tallest tree in the ACT.

Lidar modelling shows the height of the ACT’s tallest tree relative to the surrounding trees.

Why is this tree so big?

The area where the tree is growing is quite open with relatively large spaces between it and other large trees. This is possibly the result of historical logging which commenced in the Brindabella’s in the 1930’s and ceased prior to the parks gazettal in 1984. The 2003 bushfires may have also killed some nearby trees meaning the Mountain Gum no longer had to compete for resources with other large trees.

Who came second?

The tallest trees in our urban areas are typically around 40 metres high. That’s slightly taller than the new light towers at Manuka Oval. But his tree dwarfs them all, growing arrow straight from the steep mountain side to 63 metres. The tallest trees in urban Canberra are the Ribbon Gums and Flooded Gums in the rainforest walk at the National Botanic Gardens, a stand of planted eucalypts near Clunies Ross Street in the ANU and some Eurabbie (Eucalyptus bicostata) in Telopea Park.

Who lives there?

Our Mountain Gum contains a number of hollows and supports numerous Mistletoe plants. These features are habitat resources for a range of fauna, some of the most charismatic being the Greater Glider (Petauroides volans), Yellow-bellied Glider (Petaurus australis) and Powerful Owl (Ninox strenua). These species are more common in the tall forests of Namadgi where their habitat needs are best met.

Why is it important?

Large trees provide more habitat resources for animals than smaller trees. Tree hollows, which are critical for many different animals such as parrots and possums, typically don’t start to develop hollows until they are at least 120 years old. Big old trees drop more branches, which become homes for ground dwelling mammals such as Antechinus and, most importantly, allow a greater diversity and abundance of insects to live in woodlands and forests. These insects play a critical role in a healthy ecosystem by pollinating plants, eating plants and providing food for other animals. Big trees also have more bark and support more mistletoe, both of which add significantly to their habitat values. The identification and protection of large trees is therefore an important part of conserving our biodiversity.

What’s being done to protect large trees?

The ACT Government recognises the importance of large trees and actively tries to keep or increase their number where possible. Large trees identified in the planning of new suburbs often form the basis for local parks and open spaces. Patches of native forest with unusually high numbers of large trees may be excluded from fuel reduction burns or prioritised in wildfire control where possible.

Large dead trees that have been removed from urban areas for safety reasons have been translocated to the Barrer Hill Restoration Project in the Molonglo River Reserve, where they have been enriched with carved hollows and artificial bark. The trees are being monitored to determine how effective translocated trees are at attracting local wildlife.