Dynamics of American mangroves at austral and boreal limits on secular and decadal scales

Abstract

Studies based on sedimentary features, pollen content, isotopic and radiocarbon dates have allowed to evaluate the influence of allogeneic mechanisms (sea level fluctuations, climate changes, tectonism,) and autogenic mechanisms (e.g. abandonment and reactivation of channels) on the dynamics of wetlands in the interior of the Amazon and mangroves along the Brazilian coast. Such interdisciplinary studies have evidenced the migration of mangroves on the continental shelf according to sea level rise since the Last Glacial Maximum, approximatelly 18000 years ago. At the same time, these forests expanded to northern and southern coasts as the temperature has risen (e.g. Cohen et al., 2014b, 2014c, 2015, 2016). Regarding the last century and decades, such process may be occurring due to emissions of greenhouse gases to atmosphere since the Industrial Revolution, triggering the migration of the isotherms toward the poles. This warming has caused an increase in the global sea level rise in recent decades (3.5 mm/year), with moderate estimates of 65 cm up to the end this century. Following this warming trend and sea level rise, mangroves should be migrating to temperate zones and to topographically higher sectors. In order to test the hypothesis of the mangrove expansion to more temperate latitudes due to recent global warming, this project intends to obtain pollen data, isotopic (13C and 15N) and elemental (C / N) characteristics as well as radiocarbon dates and sedimentation rates based on Pb-210 of sediment cores sampled from the southern and northern limits of the American mangroves (Santa Catarina-Brazil, Florida and Louisiana-US). Satellite/drone images and Lidar data will be used to trace the presence of mangroves in these new temperate climate boundaries on a century and decadal scale. These results will be compared with the equatorial mangrove dynamics (Marapanim- Pará). (AU)