with the proliferation of coastal defences. This is an adaptation option (sensu IPCC 2014) that has been adopted worldwide to protect the growing coastal population and its property, transport infrastructure, industry and commerce, as well as valuable amenity and recreational areas (for review, see chapters in Burcharth et al. 2007, Zanuttigh et al. 2014). In this review, we discuss current evidence and thinking on biodiversity and ecosystem responses to global drivers of change, with a focus on recent rapid climate change and its interaction with regional and local impacts due to 'ocean sprawl'-the proliferation of artificial structures in the sea. We consider how efforts to combat climate change, such as mitigation via offshore renewables ('green' energies to reduce CO 2 emissions), and adaptation via sea defences are leading to a proliferation of artificial structures, resulting in changes in the proportion of hard versus soft coastal habitats, the distribution of species, assemblage composition, and community structure. We also discuss the role of coastal development, including ports and other transport infrastructure as well as offshore structures (e.g., oil and gas platforms), in altering coastal and marine ecosystem structure and functioning. Finally, we undertake a critical review of the current 'state of the art' in the emerging field of 'green engineering', which combines environmentally conscious attitudes, values, and principles with science, technology, and engineering practice, all directed towards improving local and global environmental quality. Our scope is the global coastline extending vertically to the uppermost extent of tidal influence, with particular emphasis on open coasts and offshore structures that have seen the most research. This is in contrast to the freshwater tidal reaches of estuaries, which have received little attention (but see Francis & Hoggart 2008, 2009, Hoggart et al. 2012). Many of the case studies and examples are drawn from temperate systems in developed countries, reflecting the experience of the authors and the distribution of published research. Two themes permeate our review: firstly, how ecosystem services are at risk from modification of the coast by artificial structures; secondly, the interaction between the provision of new 'hard' substratum as a societal adaptation response, resulting in altered habitat connectivity and changes in the distribution of species and composition of assemblages. We conclude by identifying current knowledge gaps and future research needs. Burgeoning coastal human populations The diversity of coastal habitats includes rocky shores, sandy and muddy beaches, barriers, spits and sand dunes, estuaries and lagoons, deltas, wetlands, and coral reefs. These individually and K27072_C004.indd 190 6/15/16 12:57 PM 191 OCEAN SPRAWL collectively provide a disproportionately greater number of ecosystem services (see Millennium Ecosystem Assessment [MEA] 2005 for a discussion of provisioning, regulating, supporting, and cultural services) to human ...