Vulnerability assessment of mangroves to climate change and sea-level rise impacts

Abstract

Climate change, particularly its associated sea level rise, is major threat to mangrove coastal areas, and it is essential to develop ways to reduce vulnerability through strategic management planning. Vulnerability has three dimensions of exposure to stresses, associated sensitivity, and related adaptive capacity, and ways to measure components of each were trialled at sites in Africa and the South Pacific to develop an analysis procedure based on ranking. The approaches of the ranking system for vulnerability assessment of mangrove systems integrate biotic and abiotic factors along with human management components, using validated methods previously developed for other research questions. These include determining mangrove forest health, adjacent ecosystem resilience, the extent and effects of human impacts, and the environmental conditions of different mangrove settings. Results of the vulnerability assessment ranking using up to 20 measurements found all sites to have some components of vulnerability. Douala Estuary, Cameroon showed the highest vulnerability, owing to low tidal range, impacts from nonclimate stressors, and evidence of moderate seaward edge retreat. Tikina Wai, Fiji showed inherent vulnerability owing to location on a subsiding coastline with a low tidal range, but this was offset by strong local community management capacity. Rufiji Delta, Tanzania showed inherent resilience owing to location on an uplifting coastline with a macrotidal range, but showed vulnerability from human impacts and lower local community management capacity. The most critical components to the vulnerability assessment were found to be exposure components of relative sea level trends and sediment supply, and sensitivity components of forest health, recent spatial changes and net accretion rates. The results provide a baseline against which to establish long-term ongoing monitoring, allowing continued assessment of the complex dynamics of climate change impacts, and providing an information base for strategic management decisions.

Assessing climate change associated sea‐level rise impacts on sea turtle nesting beaches using drones, photogrammetry and a novel GPS system

“…This workflow can be used for other sea turtle species and populationsas we demonstrate in Patrício, Varela, Barbosa, Broderick, Airaud, et al (2018) and , but can also be broadly applied to any vulnerable species or coastal habitats, e.g. mangroves (Ellison, 2015;Spencer et al, 2016;Woodroffe, 2018), and shorebirds (Galbraith et al, 2002;Kane, Fletcher, Frazer, & Barbee, 2015;Thorne et al, 2018) or forecasting likely extent of oil spill contamination (Lauritsen et al, 2017), which require a realistic model for SLR projections. Finally, our surveying solution can also be deployed by researchers in other disciplines where SfM is routinely used for topographic characterization as it reduces costs while increasing portability when replacing the dGPS with an alternative RTK solution.…”

Climate changes in mangrove forests and salt marshes

“…The present scenarios suggest that the increase in air and water surface temperatures may alter the distribution and composition of species, increase or decrease productivity (depending on intensity), increase respiration rates and modify the reproductive phenology of mangrove forests and salt marsh species (FIELD, 1995;CHEESEMAN et al, 1997;SOARES et al, 2012). Increased rates of rainfall may raise silt deposition rates, plant productivity and diversity and alter species distribution (ELLISON, 2000(ELLISON, , 2015KRAUSS et al, 2003;WHELAN et al, 2005).…”

“…For example, at the delta of the Ganges River a difference in relative sea level of 10-15 mm/yr, is small compared to the amplitude of the macrotidal regime allowing adaptations in mangrove coverage to occur (WOODROFFE, 1990). However, in a microtidal regime such as that in Bermuda (Caribbean Sea), an increase of only 2.8 mm/yr promoted a reduction in sediment deposition rates below the level required for mangrove persistence, resulting in the loss of this ecosystem (ELLISON, 1993(ELLISON, , 2015. In contrast, salt marsh ecosystems present high tolerance to flooding, surviving under more than a meter of permanent flooding, as observed in the Conceição Lagoon (Santa Catarina State, Brazil) (SORIANO-SIERRA, 1989).…”

Neotropical mangroves: Conservation and sustainable use in a scenario of global climate change

“…Additionally, increasing temperature may allow mangrove expansion poleward, as suggested by some observations (Jennerjahn et al, ; Saintilan et al, ). However, indirect impacts related to global sea‐level rise—such as increasing frequency of extreme climatic events, strengthening of oceanic forcing upon continental shelves, and, consequently, upon estuaries (Ellison, ; Lacerda et al, ), as well as anomalies of rainfall regimes—seem more significant as sources of environmental pressures on mangroves (Lovelock et al, ). All these stressors interact among themselves and with other anthropogenic drivers, in particular damming and pollutant emissions.…”