Sea-level rise impact models and environmental conservation: A review of models and their applications

Abstract

Conservation managers and policy makers need tools to identify coastal habitats and human communities that are vulnerable to sea-level rise. Coastal impact models can help determine the vulnerability of areas and populations to changes in sea level. Model outputs may be used to guide decisions about the location and design of future protected areas and development, and to prioritize adaptation of existing protected area investments. This paper reviews state-of-the-art coastal impact models that determine sea-level rise vulnerability and provides guidance to help managers and policy makers determine the appropriateness of various models at local, regional, and global scales. There are a variety of models, each with strengths and weaknesses, that are suited for different management objectives. We find important trade-offs exist regarding the cost and capacity needed to run and interpret the models, the range of impacts they cover, and regarding the spatial scale that each operates which may overstate impacts at one end and underestimate impacts at the other. Understanding these differences is critical for managers and policy makers to make informed decisions about which model to use and how to interpret and apply the results.

Introduction

Sea-level rise has been identified as a major threat to coastal habitats and communities worldwide [1]. Sea-level rise projections based on the use of General Circulation Models (GCMs) for the end of the 21st century (relative to 1980–1999) range from 0.18 to 0.59 m, although this is not an upper bound as the Greenland and West Antarctic ice sheet contributions are uncertain [2]. The IPCC has recognized that sea-level rise by 2100 may be 0.10–0.20 m higher than predicted based on uncertainties of ice sheet melt and glacier dynamics. Scientists suggest that a 1–5 m rise in sea level by 2100 is more realistic when taking into account thermal expansion of ocean water, melting of ocean glaciers, ice sheet disintegration, and an acceleration of sea-level rise in the 20th century [3], [4], [5], [6], [7], [8], [9].

Sea-level rise has both biophysical and socioeconomic impacts, threatening coastal landscapes, their ecosystem services, and coastal populations [10], [11]. The primary biophysical impacts of sea-level rise include inundation and displacement of wetlands and low-lying lands [12], increased coastal erosion [13], [14], increased coastal flooding [12], [15], and saltwater intrusion into estuaries, deltas, and aquifers [16], [17]. Ecosystems may adapt naturally to sea-level rise in coastal areas with limited human influence because habitats may have room to migrate landward or accrete vertically in response to rising seas; however, densely populated coastal areas are characterized by infrastructure that is less mobile and more vulnerable. Socioeconomic impacts of sea-level rise may include: direct loss of economic, ecological, cultural, and subsistence values through loss of land, infrastructure, and coastal habitats; increased flood risk of people, land, and infrastructure; and other impacts related to changes in water quality, salinity, and biological activity [17], [18].

Development planning, land-use, and conservation agencies need reliable scientific tools to conduct vulnerability assessments that identify which coastal areas are threatened by sea-level rise. Coastal impact models provide a useful mechanism for predicting environmental responses to changes in sea level and the impacts of alternative management policies on future ecosystem behavior [19], [20]. Such tools enable planners and practitioners to proactively plan for sea-level rise, take immediate actions to ensure the security of coastal communities, and work towards the persistence of ecosystem services by reserving lands less vulnerable to sea-level rise for coastal communities and critical coastal habitats.