Mind the sustainability gap Joern Fischer 1 , Adrian D. Manning 1 , Will Steffen 1 , Deborah B. Rose 1 , Katherine Daniell 1 , Adam Felton 1 , Stephen Garnett 2 , Ben Gilna 1 , Rob Heinsohn 1 , David B. Lindenmayer 1 , Ben MacDonald 1 , Frank Mills 1 , Barry Newell 1 , Julian Reid 1 , Libby Robin 1 , Kate Sherren 1 and Alan Wade 1 1 The Fenner School of Environment and Society, The Australian National University, Canberra, ACT 0200, Australia 2 Institute of Advanced Studies, Charles Darwin University, Darwin NT 0909, Australia Despite increasing efforts to reach sustainability, key global biophysical indicators such as climate change and biodiversity loss continue to deteriorate rather than improve. Ongoing failure to move towards sustainability calls into question the focus of current research and policy. We recommend two strategies for progress. First, sustainability must be conceptualized as a hierarchy of considerations, with the biophysical limits of the Earth setting the ultimate boundaries within which social and economic goals must be achieved. Second, transdisci- plinary research programs must confront key normative questions facing modern consumer societies. The huma- nities should have a key role in such programs. Assisted by these strategies, ambitious targets that realistically reflect the biophysical limits of the life-support system of the Earth must be set and relentlessly worked towards. Introduction Despite increasing efforts at all levels of society to create a sustainable future, global-scale indicators show that humanity is moving away from sustainability rather than towards it [1–3]. Several high-profile reports have recently emphasized the potential risk of existing trends to the long-term viability of ecological, social and economic sys- tems [2–4]. Here, we argue that the widening gap between our current trajectory and meaningful sustainability tar- gets calls for a new model of sustainability – one that is built on a hierarchical conceptualization of ecological, social and economic considerations, and addresses key ethical and normative dilemmas of modern consumer life styles. We propose tangible actions for academics, natural resource managers and policy makers that can help to close the sustainability gap. For the first time in human history, our activities are so pervasively modifying our own life-support system that the ability of the Earth to provide conditions suitable for our species to thrive can no longer be taken for granted [2]. Nearly 50% of land has been transformed by direct human action, with negative consequences for biodiversity, nutri- ent cycling and soil structure. Approximately 75% of fish- eries worldwide are fully exploited, overexploited or depleted, and some might never recover [5]. More nitrogen is now fixed into reactive forms by fertilizer production and fossil fuel combustion than is fixed naturally in all terrestrial systems [6]. The Earth is in the midst of its sixth great extinction event, but the first caused by the activities of just one biological species (Homo sapiens). The global climate is changing beyond known patterns of natural variability, with potentially serious consequences for the well being of humans and other biota [2,3,7]. Although there have been regional-scale improvements in some indicators of poverty, food supplies and the environment [2], these are overshadowed by the ongoing deterioration of key biophysical indicators at the global scale [2,3]. For example, rates of biodiversity loss and global warming continue to increase rather than decrease [3]. The growing ‘sustainability gap’ between what needs to be done and what is actually being done calls into question current approaches to sustainability research, policy and management. Current approaches to sustainability Sustainability has been defined in many different ways. Examples of definitions include: ‘sustainable develop- ment is development that meets the needs of the present without compromising the ability of future generations to meet their own needs’ [8]; the ‘triple bottom line’, in which environmental, social and financial outcomes are taken into account [9]; a systems perspective where sustainability exists when no elements of the system are overloaded [10]; and an ecosystem perspective, which considers sustainability to be ‘the capacity to create, test, and maintain adaptive capability’ [11]. Although sus- tainability is a relevant concept at many scales, our main concern in this paper is the global scale. Specifi- cally, we are concerned that current actions might be insufficient to safeguard human well being and the adaptive capability of ecosystems over the next decades and centuries. Two sets of action are widely accepted as being vital to tackling the sustainability challenge: (i) integration across academic disciplines; and (ii) integration of academic insights with societal action. Integration across academic disciplines has drawn strongly on the biophysical and social sciences, particularly ecology and economics [12]. Integration of research with societal action increasingly occurs through participatory methods, such as scenario planning [2], and novel policy and management tools, such as markets for ecosystem services [13]. Yet despite pro- gress on both fronts, humanity continues to move away from sustainability [2,3]. Forum TRENDS in Ecology and Evolution Vol.22 No.12 Corresponding author: Fischer, J. (joern.fischer@anu.edu.au). Available online 7 November 2007. www.sciencedirect.com 0169-5347/$ – see front matter ß 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.tree.2007.08.016