While there has been a strong focus on mitigating climate change to below 2ºC, the lack of international action and the continued growth in greenhouse gas concentrations make it important to analyse the implications of higher-end scenarios (global average warming > 2°C with respect to pre-industrial level) for vulnerable areas. This will allow a better quantification of impacts and vulnerabilities associated with such climate changes, showing that adaptation is possible at an affordable cost (compared to risk) and will serve to inform policy and decision makers, contributing to raise awareness on the multiple dimensions of possible adaptation pathways. Coastal zones are amongst the most vulnerable regions of the world in the face of climatic change and variability (threatened by sea-level rise, run-off into coastal lowlands and coastal storms), as exemplified by the following points:
Coastal areas (below 100m) are the most densely populated on earth (e.g. Balk et al., 2009). Currently, more than 35% of the world’s GDP and 40% of population (e.g. Lichter et al., 2011 and own data) is located there. At the same time, combinations of specific economic, geographic and historical conditions attract people and drive coastward migration (Seto, 2011). This particularly applies to coastal urban areas, where expansion rates are statistically higher than in non-coastal ones (Seto, 2011). This phenomenon (affecting 22 out of 27 EU Members States with maritime boundaries) is expected to continue in the future, as a function of socio-economic development pathways.
Developing countries are particularly vulnerable to coastal impacts due to rapid urbanization, including growing mega cities in subsiding deltas. A recent World Bank (2010) study on the economics of adaptation identifies the coastal zone as the area with the largest adaptation costs for developing countries (about US$ 29 billion per year in 21st Century) and a high risk level (up to $35 trillion of assets in 2070) for major port cities (Nicholls et al, 2007).
Coastal systems are already amongst the most threatened ecosystems by human activities(Halpern et al., 2008), with climate compounding these problems. Environmental and climatic change will require many coastal interventions that, unless planned to “work with Nature”, will add further stress on these ecosystems, since their actual long term planning has been developed (in the best of cases) for climates significantly less extreme than high-end scenarios. Without conveniently planned adaptation this will make our coasts potentially unable to cope with the expected changes.
Coastal areas are among the most dynamic systems on the planet, in constant adjustment and providing a “natural” test case for analysing transient conditions. Their high vulnerability (e.g. Trenhaile, 2011) to long term variations of sea level, river flow and storm events makes them a good testing ground to assess dynamic interventions, impact, and risk under extreme conditions. Moreover some of them are already experiencing rising climatic (surrogate) drivers, for example subsiding deltaic units subject to high rates of relative sea level rise.
High end scenarios will not affect equally all world regions nor will the downscaling provide equally reliable results. For instance, the Mediterranean is a concentration basin with a deficit in the water budget, generating a net inflow through the Gibraltar Strait that makes it more sensitive to climatic variability (Martrat et al 2004). Projected increases in storminess in the North Sea may lead to troublesome combined scenarios of surges, waves and regional sea level rise (e.g. Katsman et al, 2011). For global warming above 2ºC by 2100 the global sea level rise could reach 1 m in the RCP8.5 scenario, with thermal expansion contributing up to 28cm (Yin, 2012), glaciers up to 21cm (Marzeion et al, 2012) and ice sheets up to 50 cm (Levermann et al, 2012). There are large uncertainties in process based model projections (e.g. with min of 3 cm and max of 66 cm contribution from Greenland) and semi-empirical projections are up to 1.6 m by 2100 (e.g. Jevrejeva et al, 2012). An upper limit for sea level rise by 2100 is 2 m (Pfeffer et al, 2008), which although highly unlikely cannot be excluded.
There is a perception that, if human societies cut emissions of greenhouse gases, global temperature increase would be stabilized and the most dangerous consequences of climate change could be avoided. However, even as temperatures stabilize, sea level would continue to rise for several centuries (Schaeffer et al., 2012). For all scenarios the rate of sea level rise would be positive for the coming centuries, requiring 200-400 years to drop to the 1.8 mm/yr 20th century average (Jevrejeva et al, 2012).This makes adaptation essential for coastal zones (i.e. there must be a commitment to adapt to sea-level rise).
The reality of a significant adaptation deficit around much of the world’s coasts means that climate change adaptation and economic development are intertwined issues implying large investments necessary to fully adapt to climate variability and hazards; these investments encompass technology, economy, education and social structure. The impacts and responses (particularly the policy and decision making) entail critical ethical questions associated with the displacement of people and their assets, the loss of entire island states, diminished ecosystem services, habitat and cultural (with numerous world-heritage sites on the coast) degradation or complete loss.
This need for adaptation requires developing strategies to deal with future scenarios; that information has economic value that should benefit all countries and social classes (e.g. regarding land planning or property values).
Despite these urgent challenges, the current knowledge on coastal impacts, vulnerabilities and feasible adaptation pathways is fragmented and partial. It is fragmented because coastal impacts have been assessed either at local scales using detailed hydro-morphodynamic models (Stralberg et al., 2011) or at regional and global scales using aggregated damage functions (Tol, 2007) or stylized models (Hinkel et al., 2011). The knowledge is partial because assessments have mainly focused on direct damages and have often disregarded the economy-wide impacts, in particular for high end climatic scenarios (large sea-level rise and possible changes in storms and hydrology). Also, past studies tend to assess impacts due to one climatic driver (coastal flooding due to sea level rise) whilst interactions with other climatic drivers may worsen extreme events (e.g. high river flows). Although global impact and adaptation models provide indications of who and what is at risk for different emissions and socio-economic pathways, they still require significant further development to determine optimum adaptation paths and optimisation of dual benefits from adaptation and mitigation (or to avoid adaptation and mitigation conflicts). Furthermore, except at the local scale, only a limited set of so-called “hard” adaptation measures, focusing on protection, have been considered versus the alternative of no defences (retreat). Trade-offs between mitigation and adaptation have only been addressed for hard options and at coarse (regional and global) scales (Tol, 2007; Hinkel et al., 2011). These analyses have seldom considered the direct/indirect economic impacts (e.g. Brower et al, 2008) or the effects on people redistribution (e.g. Husby et al, 2012) and macroeconomic evolutionary trends (Safarzynska et al 2013).
A number of recently funded European projects have dealt with the assessment of coastal impacts (e.g. CIRCE, ClimateCoast, IMPACT2C, MEDIATION, CLIMSAVE and BASE) but have not been able to address these limitations, because coastal impacts were considered in a partial manner, with limited scope for innovation or model development, including multi-scale investigations. A new dedicated and focused effort that takes into account the distinctiveness of coastal vulnerability and that explicitly includes adaptation is, thus, needed. RISES-AM- proposes such a novel approach