Proposed mining pose a great risk to unprotected 1000 year old stands of Huon pines in Tasmania

Huon pine (Lagarostrobos franklinii (Podocarpaceae)) is a slow growing conifer only found in high rainfall parts of western and southern Tasmania, Australia. The species is notable for being one of the longest lived trees in the world with individual trees reaching 2500 – 3000 years (Buckley, 1997) and one clonal stand thought to exceed 10,000 years (Anker et al., 2001). The species is the sole member of a basal podocarp genus that diverged around 50 mya from its closest relative, the New Zealand endemic silver pine (Manoao colensoii) (Biffin et al., 2011), and is an important part of Tasmania’s conifer rich palaeoendemic flora (Jordan et al., 2016). The species is restricted to fire protected high rainfall regions of western and southern Tasmania mostly in lowland riparian areas. Forests dominated by the species cover an area of around 10,500 ha with its original distribution considerably reduced by inundation for dam construction, fire, logging and mining since European settlement (Peterson, 1990). Extensive harvesting of its valuable rot resistant timber in the 19^th and 20^th centuries have left only approximately 10% of stands having avoided impacts of logging (Kerr and McDermott, 1999). These undisturbed stands, which can contain trees over 1000 years old, are now extremely rare, are restricted to the most remote and least accessible locations (Kerr and McDermott, 1999). Old trees of Huon pine have great conservation value contributing significantly to forest biodiversity with, for example, a single >1200 year old individual being found to harbour an epiphytic flora of 147 species (Jarman and Kantvilas, 1995).

In the last few years new effort has been made to refine mapping of the distribution of Huon pine including undisturbed stands by both the Tasmanian Government and citizen scientists. Current mapping is of limited accuracy and provides little information as to the age, size and density of pines within mapped areas. Undisturbed stands of ancient Huon pines have recently been documented lining the entire length of the Wilson River in the most northern part of the species range, from its confluence with Yellow Creek to where it flows into the Pieman impoundment, 15 km downstream (see map). A representative field survey of a small area of non-riparian Huon pine forest in the middle reaches of the Wilson River identified 14 Huon pines over 100 cm in diameter, including one tree 160 cm in diameter (McNamara and Gros, 2022). Given the slow growth rate of Huon pine (approximately 0.5 mm per year (Buckley, 1997)) these stands have likely established 1000-1600 years ago. The Wilson River ancient Huon pines, along with other notable undisturbed stands nearby including Harman River, where the oldest known Huon pine tree is found, and Yellow Creek (see Map), further establishes the area as having some of the most important undisturbed forests remaining of the species. The only area which may exceed it is the Denison River catchment protected in the Franklin-Gordon Wild Rivers National Park.

Despite their great age the Wilson River Huon pine stands are not protected and fall within an active mining exploration license area (see map). Recent mining exploration by a Perth, Western Australia, based mining company has discovered a potentially large tin deposit that they refer to as the ‘Big Wilson’ that is co-incident with the Wilson River stands. This find has been touted by the company as a big opportunity to grow their business. However, opening up this area for mining poses major risks to the ancient Huon pines either by direct disturbance, water quality impacts, timber poaching or an increase in the threat of fire.

Concerningly, any environmental impact assessment for a proposed mine will not have to consider the impact of mining on the stands because Huon pine is not a threatened species and forests of the species are not a recognized as a threatened vegetation community. To not have a legislated mechanism in place to protect ancient trees from development is a massive oversight by the Tasmanian Government. Around the world, old large trees like the ancient Wilson River Huon pines have been disproportionately lost to human disturbance (Lindenmayer et al., 2012) but, given their critical ecological role, the imperative to conserve them has gained momentum (Lindenmayer et al., 2014). Protection of ancient Huon pines in the Wilson River and nearby catchments is of great priority. The mining company should desist from developing the ‘Big Wilson’ and other ore bodies near unprotected ancient Huon pines. Instead, they should focus their activities where the intense impacts of mining, that continue long after mining ceases, will have less impact on Tasmania’s irreplaceable ancient trees.

References:

Anker, S.A. et al. (2001) ‘Holocene vegetation and paleoclimatic and paleomagnetic history from Lake Johnston, Tasmania’, Quaternary Research, 56(2), pp. 264–274.

Biffin, E., Conran, J.G. and Lowe, A.J. (2011) ‘Podocarp evolution: a molecular phylogenetic perspective’.

Buckley, B.M. (1997) ‘Climate variability in Tasmania based on dendroclimatic studies of Lagarostrobos franklinii’.

Jarman, S. and Kantvilas, G. (1995) ‘Epiphytes on an old Huon pine tree (Lagarostrobos franklinii) in Tasmanian rainforest’, New Zealand Journal of Botany, 33(1), pp. 65–78.

Jordan, G.J. et al. (2016) ‘Palaeoendemic plants provide evidence for persistence of open, well‐watered vegetation since the Cretaceous’, Global Ecology and Biogeography, 25(2), pp. 127–140.

McNamara, K. and Gros, C. (2022) A Study of Huon Pines within the Wilson River Catchment, northwest Tasmania. unpublished.

Kerr, G.J. and McDermott, H. (1999) The Huon Pine Story: The History of Harvest and Use of a Unique Timber. Mainsail Books.

Lindenmayer, D.B. et al. (2014) ‘New policies for old trees: averting a global crisis in a keystone ecological structure’, Conservation Letters, 7(1), pp. 61–69.

Lindenmayer, D.B., Laurance, W.F. and Franklin, J.F. (2012) ‘Global decline in large old trees’, Science, 338(6112), pp. 1305–1306.

Peterson, M.J. (1990) Distribution and conservation of Huon pine. Hobart, Tasmania: Forestry Commission.

James Worth, Conifer Specialist Group member