PRACTITIONER’S PERSPECTIVE Letting giants be – rethinking active fire management of old-growth eucalypt forest in the Australian tropics David Y. P. Tng 1 *, Steve Goosem 2 , Greg J. Jordan 1 and David M. J. S. Bowman 1 1 School of Plant Science, University of Tasmania, Private Bag 55, Hobart, TAS 7001, Australia; and 2 Wet Tropics Management Authority, Cairns, Qld 4870, Australia Key-words: alternative stable states, fire ecology, fire management, forest–savanna bound- aries, giant eucalypt forest, landscape ecology, old-growth forest, plant functional traits, pre- scribed burning, Wet Tropics Introduction Tall old-growth forests are of global social-economic, polit- ical and ecological significance. These forests contribute sig- nificantly to the global carbon budget and are of high conservation value given sustained logging and clearing over the past two centuries (Tng et al. 2012a). In Australia, these old-growth forests extend from tropical to temperate regions of Australia in areas where rainfall exceeds 1000 mm per year, being characterized by emergent eucalypt trees attaining statures of 30 m to more than 80 m, with canopy and understorey layers consisting of mesophytic broad-leaved trees and treelets, sclerophyllous shrubs and graminoids (Fig. 1). These forests support some of the tallest flowering plants in the world, are important habitats for a unique suite of flora and fauna, and are important forest cover for metropolitan water catchments – values that make giant eucalypt forests a focal point of scientific study and ecotourism (Tng et al. 2012a). Until recently, these eucalypt forests were extensively exploited as a timber resource, but now, most remaining old-growth stands have been set aside for conservation. In some regions containing giant eucalypt forest, native forestry activities either have ceased or are based on short- rotation harvests of regrowth forests, meaning that the trees can never achieve their potential size. Regeneration typically occurs after landscape fires, and fire is also used to initiate regeneration of temperate eucalypts after logging and to reduce fuel loads (Attiwill et al., in press). In tem- perate regions, fire management of the remaining stands of old-growth giant eucalypt forest is largely based upon fire suppression and fuel reduction burning in surrounding open forests, as fires in giant eucalypt forests are extremely difficult to control because these forests are only flammable under dangerous fire weather conditions (Bowman et al. 2013). In subtropical and tropical forests, fuel reduction burning is used to reduce fire hazard within the giant forests as well as in adjacent open forests and savannas. What constitutes the most appropriate and ecologically sustainable fire management practices of these giant forests remains a controversial issue among scientists, land managers and conservationists. Here, we outline recent advances in landscape ecology theory, palaeoecolo- gy and functional biology research on a giant eucalypt forest type in the Wet Tropics region of northeast Austra- lia to explore options to achieve sustainable management of these systems. Given the ecological similarity between Australia’s giant eucalypt forests and other old-growth forests in the Northern Hemisphere (Tng et al. 2012a), the insights gleaned herein have implications for a wide range of old-growth forests. Further, the expansion of rain forest into surrounding savannas has implications for the management of savannas and grasslands, where there remains debate as to whether increased woody biomass should be managed using fire or allowed to accumulate (Bond & Parr 2010). Giant eucalypt forests in the Wet Tropics Eucalyptus grandis W.Hill ex Maiden is native to the east coast of Australia, extending from the middle of New South Wales (latitude approximately 33°S) to north Queensland (latitude 16°S). The most northern outlier populations are located in the Wet Tropics bioregion of Australia where E. grandis forests reach a height of over 60 m and form a narrow but distinct band at rain forest– savanna boundaries that does not exceed 4 km in width (Harrington & Sanderson 1994; Tng et al. 2012b; Fig. 1). The understorey of the forests forms a spectrum from dense tropical rain forest to an open layer of flammable perennial grasses with scattered shrubs. Over the last 50 years, it has been demonstrated that the aerial extent of rain forest understoreys is increasing in E. grandis forest throughout the Wet Tropics region, at the expense of grass understoreys (Harrington & Sanderson 1994; *Correspondence author. E-mail: david.tng@utas.edu.au © 2014 The Authors. Journal of Applied Ecology © 2014 British Ecological Society Journal of Applied Ecology 2014, 51, 555–559 doi: 10.1111/1365-2664.12233