Exacerbated Vulnerability in Coastal Ecosystems: The Impact of El Niño and Urban Development on Mangrove Dieback in the Bay of Panama

The El Niño phenomenon of 2015-2016 caused significant dieback of mangroves across the Pacific basin. Most noticeably, mangrove dieback from the arid regions in northwestern Australia has been reported, while a few reports have emerged from the eastern Pacific. This study reports on mangrove dieback associated with 2015-16 El Niño in the Bay of Panama in Central America, particularly highlighting how strong anthropogenic influences exacerbated mangrove tree mortality, increasing mangrove vulnerability to extreme climatic conditions and drought.

By mid-2016, the effects of the El Niño drought were evident, registering up to 70% mangrove dieback in mangroves near the city. This was not solely due to the drought conditions associated with El Niño, which typically extends the dry season four to five months rather than the usual 3 months. Instead, it appears that a combination of factors contributed to the observed high mangrove tree mortality, including aggressive urban development and land use changes, along with coastal erosion resulting from recurrent rainy years, increasing sedimentation that created new coastal areas. These new coastal areas resulted in the rapid colonization and structural overshoot of the Avicennia germinans (black mangrove) species, creating an “Ecological mirage.”

The El Niño drought of 2015-2016 intensified salinity-and-drought-mediated mangrove dieback in the Bay of Panama near the city due to freshwater shortages caused by reduced rainfall, declining water table levels, and increased evaporative demands from heightened temperatures. This study emphasizes how human-induced changes in the middle and upper watershed, mainly due to land use alterations, can lead to drought-related mortality during extreme years. This increases the vulnerability of mangrove ecosystems to climate change and extreme events. The research highlights the vital connection between land and coastal processes and underscores the necessity for integrated management of coastal ecosystems.