DUNE EVOLUTION AND LOCAL CLIMATE CHANGE IN ISLA SALAMANCA NATIONAL PARK, COLOMBIA

Isla Salamanca National Park (ISNP), a biosphere reserve and Ramsar Site located on the Colombian Caribbean coast, is a valuable wetland ecosystem associated with the Magdalena River, the most important river of Colombia. At least since the early 1950s, ISNP has been affected by the combined effect of reduced sediment supply and presumably a relative sea-level rise, resulting in eroding trends along the park's shoreline. Particularly, most of today's parabolic dunes are located close to the coastline, forming scarped dunes regularly affected by storm wave-action. In that sense, this project's aims to analyze the causes producing dune stabilization and erosion in ISNP, placing emphasis on the interplay between weather variables and vegetation cover.

To assess rainfall tendencies for the series available, namely Santa Marta and Barranquilla weather stations, the data were fit to a linear regression model, resulting in a statistically significant increasing rainfall trend since the early 1950s. Conversely, wind velocities taken hourly at the Santa Marta airport since 1981 indicate a statistically significant decreasing trend for the number of wind episodes with velocities above 6 m/s. In terms of coastal changes, erosion increases from east to west, locally reaching average erosion rates up to 15 m/year in front of the lagoon known as Cuatro Bocas. However, close to the Magdalena river mouth, at the westernmost extreme of area, accretion processes are dominant, giving place to embryo dunes with isolated patches of Sesuvium portulacastrum. When comparing dune vegetation on erosive and accretive sectors, the former have not just more diverse and mature species, but they are also more populated. Common species found on erosive dunes are Calatropis procera, Stenocereus griceous and Cnidoscolus urens.

Overall, high erosion rates added to increasing rainfall and decreasing windiness over time, contribute to explaining why most of the dunes in Isla Salamanca are not mobile, but instead are impeded dunes fixed in position by vegetation. Nonetheless, it is considered that given the high erosion rates existing in ISNP, vegetation on erosive dunes contribute to hindering erosive processes. Hence, installing dune fences and planting native pioneer species may temporarily mitigate erosive processes affecting the dunes.