Melbourne learned to diversify its urban forest - then quietly forgot the lesson

Walk down almost any street in inner Melbourne and you’ll pass them, the leafy canopies the city has spent decades growing and now counts among its green credentials. The City of Melbourne looks after more than 80,000 trees and plants thousands more every year. But that growing canopy hides a quiet vulnerability: more than a third of those trees belong to a single botanical family. The story of how Melbourne got there, briefly fixed it, and is now slipping back is written in its own planting records.

Melbourne has spent two decades replanting its forest.

Start with what’s going right. Since the mid-2000s the City of Melbourne has put thousands of new trees in the ground every year, steadily renewing an ageing canopy.

Source: Author’s analysis of City of Melbourne (2025), Trees with species and dimensions (Urban Forest). Excludes 26,521 trees with unknown planting dates.

More than a third of Melbourne’s trees come from a single family - the concentration reveal

But that growing canopy rests on a narrow base over a third of the city’s trees belong to one family, Myrtaceae, well beyond the share urban-forest guidelines consider safe.

Source: Author’s analysis of City of Melbourne (2025), Trees with species and dimensions (Urban Forest). Benchmark: City of Melbourne Urban Forest Strategy 2012–2032.

The family we over-planted is also one of the oldest and the slowest to replace — the mature backbone

Those trees are old, too: nearly three-quarters of Myrtaceae are mature, behind only Melbourne’s heritage planes and elms. You can’t swap out a mature canopy quickly, so the imbalance is locked in and it’s the younger, more diverse native plantings coming through now that will have to shift it.

Source: Author’s analysis of City of Melbourne (2025), Trees with species and dimensions (Urban Forest).

Melbourne diversified its new plantings then drifted back toward the gum tree — diversified, then slipping back

For years, new plantings stayed heavily Myrtaceae and deepened the imbalance. Around 2017 the city changed tack and fell well below the resilience threshold before the share quietly crept back up again.

Source: Author’s analysis of City of Melbourne (2025), Trees with species and dimensions (Urban Forest). Benchmark: City of Melbourne Urban Forest Strategy 2012–2032.

The city’s leafiest pockets lean hardest on the same few trees — where the risk concentrates

And the imbalance isn’t even across the city some of the most tree-dense precincts are also the most Myrtaceae-heavy, leaving them especially exposed.