At the end of the 20th century, the combination of climatic and anthropogenic events resulted in hyper salinity conditions in the coastal wetland Ciénaga Grande de Santa Marta (CGSM), Colombia. Although salinity concentrations are generally related to the type and quantity of water entering and exiting a wetland and to its internal hydrological dynamics, there have been no up to date hydrological studies on the CGSM. Here we show how a water budget can be used as a first-order of approximation to describe the CGSM's hydrology, despite data limitations. We collected hydroclimatic data to calculate and analyze the fluxes of water entering and exiting CGSM and their corresponding uncertainties. We find that the water budget is mostly affected by the precipitation regime, a result connected to studies of regional El Niño/La Niña effects. Scenario analyses show that contribution of freshwater from the streams coming down from the Sierra Nevada Mountain Range on the eastern side of CGSM is currently larger than that of the channels draining from Magdalena River to the west, in contrast to the general focus on the western side. However, Monte Carlo simulations suggest that the eastern freshwater inflow is insignificant in affecting the hydrological response of CGSM. These results outline the need to (1) increase understanding of the internal connectivity and circulation of CGSM and (2) further investigate the effect of agriculture on the eastern side of CGSM.

Mangrove forests are unique coastal ecosystems, formed through a complex network of terrestrial, estuarine, and marine processes that have provided a diverse assortment of societal benefits across time. Compounding anthropogenic pressures are driving critical mangrove degradation worldwide, threatening the wellbeing of coastal populations historically associated with these systems. The Ciénaga Grande de Santa Marta (CGSM) in northern Colombia is the largest coastal lagoon-delta in the Caribbean. It is inhabited by stilt-house communities who have developed an intricate livelihood and cultural relationship with the mangroves. The CGSM has experienced sustained social and ecological degradation over the last 6 decades, triggered by land-use change and disruption of hydrological connections. This study integrates Social-Ecological Memory and Palaeoecology to develop a historical contextualization of the biophysical and social dimensions of environmental change in CGSM. Integration of geochemical sediment analysis, C14 radiocarbon dating, and demographic inferences from archaeological evidence revealed three distinct periods over the last 5000 years. During this time sea level rise and hydroclimatic variability shaped the transition from freshwater to prevailing marine conditions, and modulated human occupation patterns in the area around 2000 years ago. In addition, participatory reconstructions with local communities offered nuanced descriptions about the spatial, temporal and contextual aspects of the degradation process, with profound social-ecological consequences. The interdisciplinary approach of this study indicates that CGSM is a highly dynamic social-ecological system that has been changing and reconfiguring across different time scales in response to both natural and human-induced processes, and contributes to the preservation of collective memory in this unique stilt-house community. Finally, it reveals the relative effects of biophysical and social drivers on driving social-ecological change under both millennial and decadal scales.