Large-scale transgressive coastal dune behaviour in Europe during the Little Ice Age

The Little Ice Age is the most noted climatological event in recent history with dramatic consequences for a large part of the western European coastal landscape. A major morphological feature associated with this event is the presence of large-scale transgressive dune fields that actively advanced inland, encroaching, in some cases, human settlements and directly affecting coastal communities. Several hypotheses exist to explain the formation of such features, which purport increased storminess, sea-level changes, or human activities as the major drivers of the relatively well-documented enhanced aeolian activity during this event. However, these hypotheses do not explain entirely the whole process by which dunes are set into movement. Here, we show the temporal and spatial distribution of this event in terms of impact over the coast, focusing on the mobilization of coastal dunes and then elaborate a new conceptual model that explains the onset and evolution pathways of coastal dunes after the impact of the Little Ice Age. Our model proposes the combined effect of storms and other parameters to explain the initiation phases of the process, when sand becomes available and blown by the very strong winds associated with documented higher frequency and intensity of storms occurring during this period.Natural Environment Research Council NE/F019483/1 NERC Geophysical Equipment Facility 1082 "FCT Investigator" program IF/01047/2014info:eu-repo/semantics/publishedVersioninfo:eu-repo/semantics/publishedVersio

A global ‘greening’ of coastal dunes: An integrated consequence of climate change?

In the context of global climate change and sea-level rise, coastal dunes are often important elements in the coastal response to storm wave and storm surge impacts on coastal lowlands. Vegetation cover, in turn, has profound impacts on coastal dune morphology and storm-buffering function; it binds existing sediment, promotes fresh sediment accumulation and thereby increases dune volume and dune crest elevation where a sediment-plant interaction plays out with vegetation growth attempting to out-pace the vertical sediment accumulation. A global analysis shows that vegetation cover has increased substantially on multiple, geographically dispersed, coastal dune fields on all continents in the period 1984-2017. The observed 'greening' points to enhanced dune stability and storm buffering effects at a time when, paradoxically, coasts are being subjected to increased flood and erosion risk from rising sea levels and changing patterns of storminess. Causal attribution of biological trends to climate change is complicated, but we contend that the global scale 'greening' of coastal dunes is driven by a combination of changes to climate and atmospheric composition and reflects the cumulative effects of changes in temperature, precipitation, nutrient concentration and reduced windiness (global stilling). Global-scale increases in temperature, nutrients and precipitation (all of which are vegetation growth stimulants) and widespread reduction in windiness ("stilling") (which reduces sediment activity, promoting the spread of vegetation) coincide in time with the observed changes in vegetation cover. The observed changes in coastal dunefields enhance contemporary and near-future coastal resilience to climate change and may represent a previously unrecognised morphological feedback mediated by climate change.Agência financiadora NERC Natural Environment Research Council NE/F019483/1 NERC Geophysical Equipment Facility Grant 1082 "FCT Investigator" program IF/01047/2014 CIMA of the University of Algarve UID/MAR/00350/2013 Xunta de Galicia PlanI2C-ED481B 2018/021info:eu-repo/semantics/publishedVersio