The National Arboretum Canberra is indeed “a big hit”, and Sally Pryor’s article (Canberra Times, April 14, p10) is a welcome celebration of its appeal to both Canberrans and visitors. However, some of the article’s commentary focused on “... what about the trees?” appears to misunderstand elements of the Arboretum’s genesis and history. These concerns are not new; a decade ago, I defended the arboretum in the face of a Canberra Times front page report in March 2008 claiming that it was “Cactus”, and a “hospice for trees”. As a member of the Arboretum Jury in 2004-5, and chair of the tree selection committee advising the Arboretum Board and ACT Government for much of the subsequent five years, I am again happy to defend both the design and tree choice, without pretending that either were perfect.
The competition jury of seven experts and community leaders was chaired by Sandy Hollway, who also chaired the Bushfire Recovery Task Force, and informed by a variety of technical and professional advice. It chose the winning design of a “100 Forests, 100 Gardens” because of its aesthetic appeal, reinterpretation of the Griffin Plan, and vision that the forests of ‘rare, threatened or endangered species’ could contribute to both awareness of the threats to tree species and to their conservation. The winning design also required substantially less water use than some of the other four finalists.
Monoculture forest blocks were used the basis of the design so that visitors could, as the trees grew, immerse themselves in the look, feel and smell of each individual species. The late Dr Ken Eldridge explained that rationale with insight, clarity and passion in a video screened at the Arboretum Visitor Centre.
While there is research that demonstrates various advantages of mixed species plantings, there is also ample evidence, including in Canberra – for example in the Cork Oaks or Himalayan Cedars at the Arboretum, or in Charles Weston’s use of circular plantings in Westbourne Woods and Weston Park – that well-managed monocultures can be both attractive and enduring. Mixed species plantings would look quite different - the Southern Tablelands Ecosystem Park forest at the Arboretum (Forest 20) provides a good example of the comparison. Rather like the Griffins’ design of Canberra, arboretum monocultures or polycultures are more a matter of taste than of right or wrong.
The tree selection committee’s role was to nominate suitable candidate species for the architects’ consideration. The primary criteria we used were the species’ conservation status (rare, threatened or endangered); as much evidence as we could find from historical records and the lengthy experience of expert committee members about the likelihood of the species surviving and growing well on the (rather difficult, as your article notes) site; limiting the proportion of forests requiring irrigation in the long term to no more that 10%; ensuring all continents and many tree genera were represented; and non-weediness. Over time, the difficulties of securing planting material of some of our suggested rare, threatened or endangered species led to the inclusion of ‘iconic’ species, such as bunya pine.
There was plenty of relevant experience among the tree selection committee’s members and advisors. Some – like the late Robert Boden, and John Gray –had long and distinguished careers working with trees in Canberra, including directly with Lindsay Pryor in his explorations of which native and exotic trees were adapted to Canberra’s challenging climate. Others, like the late Ken Eldridge, and John Turnbull and Mark Richardson, could draw on a wealth of international experience in comparable environments.
A few of the plantings we proposed– most notably, Wollemi Pine – were always going to be experimental; and a few previously uncultivated species, such as Buchan Blue Wattle, turned out to be unpredictable. Jon Stanhope, whose vision and ongoing support for the Arboretum made it possible, reasonably suggests we could have made some different choices.
But as the article notes, all but a handful of species and less than 1% of the trees are ailing across the 100 Forests. That seems overwhelmingly positive, and suggests the species choices were not too misguided. Over time, more of the forests will need to be thinned, as some have been already. As well as benefitting the forests, thinning will create opportunities for creative use of the wood from thinned trees, as beautifully exemplified by Ashley Eriksmoen’s piece Circuit, currently on display in the Visitor Centre.
The bigger issues for Canberra’s trees are, as some critics of the Arboretum pointed out when it was being developed, those for the urban trees in our parks, streets and gardens. We’ve come to take them somewhat for granted, and we’re not investing enough in maintaining them or preparing for climate change. The ACT Government’s recent Living Infrastructure Information Paper is a timely contribution to the discussion that we need to have, and decisions we need to make, about investing in the next generation of urban trees to both mitigate and survive climate change. Rather as the ACT Government did in establishing the Arboretum after the 2003 bushfires, we also need now to invest in creating and realising a vision for the trees across the rest of our city over the century ahead. Canberra Tree Week, starting on 30 April, offers us opportunities to continue that important conversation.
Peter Kanowski is Professor of Forestry in the Fenner School of Environment and Society, ANU. He was a member of the Arboretum Competition Jury and Chair of the Arboretum Tree Selection Advisory Committee.
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