Abstract:
Intertidal mangrove ecosystems are sensitive to climate change impacts,
particularly to associated relative sea level rise. Human stressors and low tidal range add to
vulnerability, both characteristics of the Doula Estuary, Cameroon. To investigate
vulnerability, spatial techniques were combined with ground surveys to map distributions
of mangrove zones, and compare with historical spatial records to quantify change over the
last few decades. Low technology techniques were used to establish the tidal range and
relative elevation of the mapped mangrove area. Stratigraphic coring and palaeobiological
reconstruction were used to show the longer term biological history of mangroves and net
sedimentation rate, and oral history surveys of local communities were used to provide
evidence of recent change and identify possible causes. Results showed that the seaward
edge of mangroves had over two thirds of the shoreline experienced dieback at up to 3 m
per year over the last three decades, and an offshore mangrove island had suffered 89%
loss. Results also showed low net sedimentation rates under seaward edge mangroves, and
restricted intertidal elevation habitats of all mangroves, and Avicennia and Laguncularia in
particular. To reduce vulnerability, adaptation planning can be improved by reducing the
non-climate stressors on the mangrove area, particularly those resulting from human
impacts. Other priorities for adaptation planning in mangrove areas that are located in such
low tidal range regions are to plan inland migration areas and strategic protected areas for
mangroves, and to undertake management activities that enhance accretion within
the mangroves.
