Coastal erosion occurs along many of the world’s shorelines, but is of particular concern to small islands. In response, island shorelines are often armoured through engineered structures such as seawalls, rip-raps, dikes or similar. Such hard protection is rarely successful in island contexts; rather than stop erosion, hard protection often simply redistributes and sometimes exacerbates shoreline erosion, and fails to protect property, land and food production. Such hard-protection structures frequently collapse shortly after construction. Why then does hard protection remain widespread? We argue that diffusion, specifically learning and emulation, helps explain the spread of hard protection. Island communities learn from the apparent effectiveness of hard protection in some contexts, and consider it an appropriate and accepted response to coastal erosion, regardless of its actual consequences (emulation). Case studies from the Pacific (Fiji, Federated States of Micronesia) and Indian Ocean (Maldives, Mauritius) show that both mechanisms are at work in small island states (SIDS) and may be mutually reinforcing. The case studies underline the role of the specific context in the understanding of not only why a specific adaptation measure is introduced, but also how it may change and evolve over time—and accordingly, when and how communities can move to more effective and sustainable alternatives to hard protection.

海岸侵蚀发生在世界上许多海岸线上，但小岛屿尤其值得关注。作为回应，岛屿海岸线通常通过海堤、激石、堤坝等工程结构进行防护。这种硬保护在岛屿环境中很少成功；硬性保护并没有阻止侵蚀，往往只是重新分配，有时甚至加剧了海岸线侵蚀，无法保护财产、土地和粮食生产。这种硬保护结构经常在施工后不久就倒塌。为什么硬保护仍然普遍存在？我们认为扩散，特别是学习和模仿，有助于解释硬保护的扩散。岛屿社区学习从硬保护在某些情况下的明显有效性，并认为这是对海岸侵蚀的适当和可接受的反应，无论其实际后果如何（效仿）。来自太平洋（斐济、密克罗尼西亚联邦）和印度洋（马尔代夫、毛里求斯）的案例研究表明，这两种机制都在小岛屿国家 (SIDS) 中发挥作用，并且可能相互加强。案例研究强调了特定背景的作用，不仅可以理解引入特定适应措施的原因，还可以理解它如何随时间变化和演变——以及相应地，社区何时以及如何转向更有效和可持续的替代方案到硬保护。