MINI REVIEW Peace parks and transboundary initiatives: implications for marine conservation and spatial planning Peter Mackelworth Blue World Institute of Marine Research and Conservation, Ka ˇ stel 24, Veli Lo ˇ sinj, Croatia Keywords Marine conservation; marine protected areas; marine spatial planning; peace park; transboundary conservation initiatives; transboundary protected areas. Correspondence Peter Mackelworth, Ka ˇ stel 24, Veli Lo ˇ sinj, Croatia, HR51551. Tel: +385 51 604 666; Fax: +385 51 604 668. E-mail: peter.mackelworth@blue-world Received 15 July 2011 Accepted 13 Jan 2012 Editor Ashwini Chhatre doi: 10.1111/j.1755-263X.2012.00223.x Abstract Increasing use of the marine environment makes the development of spatial planning desirable. However, ambiguity and connectivity in the marine system has the potential to create conflict between neighboring States, particularly in contested border regions with overlapping ecosystems and migratory species. Interest in the concept of transboundary conservation is expanding in the ma- rine system. Increasingly, there is a strategic move toward attempting to com- bine conservation issues with resolving conflicts between States by promoting these initiatives as peace parks. Although this strategy has the potential to pro- vide solutions there are risks involved. A review of nine marine transboundary initiatives provides insights into hazards and best practices that may inform future conservation and spatial planning in this system. Results suggest that, like most conservation, long-term sustainability of projects is based on trans- parency, the availability of appropriate funding, and governmental will. While the branding of marine transboundary conservation initiatives as peace parks may help to provide initial political impetus to projects, maintaining govern- mental interest is a significant long-term issue. This review aims to stimulate the debate on strategies for developing marine transboundary conservation for the future, bearing in mind the potential for conflict in these regions. Introduction The definition of maritime boundaries has been a drawn- out affair, full of conflict even before the arguments over the concept of “the free sea” (Grotius 1609) and “the closed sea” (Selden 1635) were adopted by con- testing States for control of maritime trade. Compromise led to the development of customary international law based on the territorial and high seas system which was later codified by the UN Conventions on the Law of the Sea. However, the realization that a wealth of resources lay hidden within and below the waters has led adja- cent States to claim wider ribbons of the marine envi- ronment, with the increasing definition of continental shelves and exclusive economic zones (EEZs), and vari- ations therein. The sectoral and fragmented governance regime for the high seas and the area beyond national jurisdiction (ABNJ) allows competent States and orga- nizations to appropriate a greater share of the natural resources (Hart 2008). If these regions are to be equi- tably and sustainably used, a balance needs to be found between the common heritage principle and the open access regime (Balgos et al. 2008; Molenaar & Oude Elferink 2009). While the governance of the high seas and the ABNJ are ongoing international debates, re- source conservation and disputes between neighboring States is generally considered a domestic issue, and the focus of this review. Ideally, coastal States will create ma- rine spatial plans (MSPs) to manage their maritime space (Pomeroy 2009; Agardy 2010). As MSPs develop, neigh- boring States will need to coordinate management where ecosystems extend and migratory species roam across in- ternational boundaries to effectively control these shared common regional resources (Brunner 2003). Does this in- creasing appropriation of the marine environment hin- der conservation? Or is there an opportunity to advance 90 Conservation Letters 5 (2012) 90–98 Copyright and Photocopying: c  2012 Wiley Periodicals, Inc.