Vegas-Vilarrúbia, T., and V. Rull (2016), Undervalued Impacts of Sea-Level Rise: Vanishing Deltas, Frontiers in Ecology and Evolution, 4, doi: 10.3389/fevo.2016.00077.
Located in the transition between the continent and ocean, most deltas are strongholds of biodiversity. They encompass marshes, islands, tidal channels and lakes, as well as mosaics of forests, grasslands and dunes in the wetland area, thus providing a large variety of habitats, ecosystem goods and services. Most deltas have experienced intense transformations with significant loss of biodiversity due to direct human activities (Syvitski et al., 2009). Many major deltas harbour a fast growing population (Suppl. Fig. 1) and are important economic hubs with intense urbanisation, industrialisation and agriculture. In recent decades, deltas have been threatened by sea-level rise (SLR), which, in combination with subsidence and/or extreme meteorological events (cyclones, storm surges), places the ecosystems and human populations at risk (IPCC, 2007). In the 20th Century, the global mean sea level increased by 0.19 m, and the forecasts for the 21th Century foresee an increase of 0.26 m - 0.98 m, provided that no changes in ocean mass or volume occur and no regional factors such as ocean circulation or sediment transport arise. Many deltaic or delta-dependent habitats are expected to profoundly change or disappear from now until 2100, and human and deltaic ecosystems will become progressively more exposed to SLR because of the landward transgression of seawater (IPCC, 2013; 2014). There are initiatives to protect or save deltas from drowning, but the involved actions (e.g., rebuilding, restoring, channelization) are expensive and only offer generic solutions because of crucial knowledge gaps (Giosan et al., 2014). In this paper, we warn against the possibility that many deltas will disappear as a result of the near-future SLR and emphasize that, even without knowing when, where and how this will occur, we can take conceptually simple steps to decrease the impacts on deltaic diversity and human beings by applying common sense and extending the time horizon of our predictions.