Repair and revitalisation of Australia's tropical estuaries and coastal wetlands: Opportunities and constraints for the reinstatement of lost function and productivity Marcus Sheaves a,c,1 , Justin Brookes b , Rob Coles c , Marnie Freckelton a , Paul Groves d , Ross Johnston a,c , Pia Winberg e a School of Marine and Tropical Biology, James Cook University, Townsville, Queensland 4815, Australia b School of Earth and Environmental Science, University of Adelaide, Adelaide 5005, Australia c TropWATER, James Cook University, Townsville, Queensland 4815, Australia d Great Barrier Reef Marine Park Authority, Townsville, Queensland 4815, Australia e Shoalhaven Marine and Freshwater Centre, University of Wollongong, Nowra, New South Wales 2541, Australia article info Article history: Received 15 August 2013 Received in revised form 28 January 2014 Accepted 29 January 2014 Available online 22 February 2014 Keywords: Tropical Estuary Wetland Ecosystem health Coastal fisheries Remediation abstract Tropical fisheries are in decline around world as a result of diverse anthropogenic threats. These threats are intimately linked to biodiversity and conservation values because of the heavy dependence of both fisheries and high value marine and coastal wetlands on coastal ecosystem health. Consequently, if the widespread degradation of coastal ecosystems can be halted and remediated, there are substantial benefits to fisheries output, ecosystem resilience, food security, livelihoods, recreation and the protection of ecological assets of national and global significance. The extent, intactness and quality of Australia's tropical coastal ecosystems has declined markedly since European settlement, due to the cumulative impact of many small encroachments and local barrier construction on the extent and productivity of coastal wetlands, mangroves and seagrass meadows. Additionally, coastal ecosystem dependent biota has been excluded from large areas of critical habitats. Despite these changes, coastal fisheries show no clear declines that could not be explained by changes in effort. This lack of detectable decline is probably partly attributable to the short history of available fisheries catch data. However, it is also likely that it reflects the offsetting of lost natural productivity by greatly increased anthropogenic nutrient loads; a substantial problem as governments are committed to large scale, long term efforts to reduce discharges of nutrients to coastal waters. This possibility underlines the importance of rejuvenating lost coastal productivity. Evaluation of past remediation efforts show that documented success is rare, due to a complex of factors including ineffective prioritisation, a lack of necessary knowledge and resources, and inefficient monitoring and evaluation. Past experiences from Australia's tropics and around the world, together with current ecological understanding, suggests some generally desirable characteristics to enhance the likelihood of successful remediation and repair actions. & 2014 Elsevier Ltd. All rights reserved. 1. Introduction Despite vigorous management of commercial and recreational fishing, coastal fisheries are in decline around Australia. School prawns landings are falling along Australia’s south-east coast under the influence of increasingly variable rainfall patterns [1], and the east coast penaeid prawn trawl fishery has been in slow decline in both total catch and fishing effort over the last 20 years [2]. Catches of a variety of species are declining in Western Australia due to multiple environmental stressors [3] and heavy fishing pressure [4]; large sciaenids and serranids in northern Australia are at risk from fishing efforts that target spawning aggregations [5,6]. These declines represent serious threats to Australia's food security and fisheries livelihoods. Coastal ecosystems (estuaries and coastal wetlands) are critical contributors to Australia's tropical fisheries, with estuary dependent species contributing 51% and 62% of total value of Queensland's and Northern Territory's commercial fisheries catches [7], and 73% and 76% by numbers of Queensland's [8] and Northern Territory's [9] recrea- tional fish catch. This dependence is much more extensive than usually recognised because the prey species of many commercial and recreational fish also have estuary dependent phases [10]. Threats to fisheries are intimately interlinked with threats to biodiversity and conservation values of coastal ecosystems Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/marpol Marine Policy http://dx.doi.org/10.1016/j.marpol.2014.01.024 0308-597X & 2014 Elsevier Ltd. All rights reserved. E-mail address: Marcus.sheaves@jcu.edu.au (M. Sheaves). 1 Tel.: þ61 7 4781 4144; fax: þ61 7 4725 1570. Marine Policy 47 (2014) 23–38