Addressing transboundary conservation challenges through marine spatial prioritization

The Adriatic and Ionian Region (AIR) is an important area for both strategic maritime development and biodiversity conservation in the European Union (EU). However, given that both EU and non-EU countries border the sea, multiple legal and regulatory frameworks operate at different scales which can hinder the coordinated long-term sustainable development of the region. Transboundary marine (or maritime) spatial planning can help overcome these challenges by building consensus on planning objectives and making the trade-offs between biodiversity conservation and its influence on economically important sectors more explicit. We approach this challenge by developing and testing four spatial prioritization strategies, using the decision-support tool Marxan, which meets targets for biodiversity conservation whilst minimizing impacts to users. We evaluate these strategies in terms of how priority areas shift under different scales of target-setting (e.g. regional versus country-level). We also examine the trade-off between cost-efficiency and how equally solutions represent countries and maritime industries (N = 14) operating in the region using the Protection Equality metric. We show that there are negligible differences in where priority conservation areas are located when we set targets for biodiversity at the regional versus country scale. Conversely, the prospective impacts on industries, when considered as costs to be minimized, are highly divergent across scenarios and bias the placement of protection towards industries located in isolation or with few other industries. We conclude by making several recommendations to underpin future MSP efforts in the region, including the identification of: 1) areas of national significance, 2) transboundary areas requiring cooperation between countries, and 3) areas where impacts on maritime industries require careful consideration of the trade-off between biodiversity conservation and socio-economic objectives. This article is protected by copyright. All rights reserved.