GC009-0006
Carbon losses following a climate-induced mangrove mortality in Brazil

Monday, 7 December 2020
Poster
Luiz Eduardo Gomes1, Christian J Sanders2, Gabriel Nuto Nobrega3, Lucas Carneiro Vescovi4, Hermano Melo Queiroz5, J Boone Kauffman6, Tiago Ferreira5 and Angelo Fraga Bernardino7, (1)UFES Federal University of Espírito Santo, Vitoria, Brazil, (2)National Marine Science Centre, School of Environment, Science and Engineering, Southern Cross University, Coffs Harbour, NSW, 2450, Australia, Coffs Harbour, Australia, (3)Universidade Federal Fluminense, Departamento de Geoquímica, Niteroi, Brazil, (4)Universidade Federal do Espirito Santo, Department of Oceanography, Vitória, Brazil, (5)USP University of Sao Paulo, Soil Science, São Paulo, Brazil, (6)Oregon State University, Corvallis, OR, United States, (7)Universidade Federal do Espírito Santo, Department of Oceanography, Vitória, Brazil
Abstract:
Drought events may induce mangrove mortality and dieback events worldwide and may potentially impact nearly 50% of the world’s mangroves as a result of climate extremes. As mangroves sequester large quantities of carbon (Blue Carbon), quantifying the losses of these stocks following disturbances may guide wetland governance strategies globally. We determined the total ecosystems carbon stock (TECS) of dead mangroves (n=2) and undisturbed forests (n=4) in the Piraquê Açú-Mirim estuary (PAM estuary, SE Brazil, 19°57′S, 40°10′W) 15-months after the onset of forest mortality. In a 100-m transect with 6 plots, we quantified aboveground stocks composed of forest biomass (live and dead trees) and dead wood; within their belowground and soil stocks in each replicated plot up maximum depth of 3m. Mangroves in SE Brazil sequester up to 1,851 megagrams of carbon per hectare (Mg C ha-1), suggesting that Brazil’s mangroves total ecosystem carbon stocks (TECS) are close to 0.5 Pg of C. The mangrove mortality following an intense drought event resulted in a 14% decrease in TECS (271 Mg C ha-1) and loss of 20% of mangrove soil carbon within less than 2-years. Furthermore, most of the carbon loss occurs in the topsoil (0-30 cm). Carbon dioxide equivalent emissions from this impact were 992.8 Mg CO2e ha-1. Most of the carbon losses likely occur through sloughing and transport of the unconsolidated soil, as well as, decomposition of the stocks formerly stored in their suboxic/anoxic soils, resulting in CO2 and CH4 emissions. As a result, impacts on forest cover may cause peat collapse through the loss of sediment and associated organic carbon decomposition; which could amount over 177-fold (32,955 Gg CO2e) the emissions from mangrove deforestation in Brazil. Currently there is limited recognition of the potential vulnerability of mangrove carbon stocks to climate change and needed discussions as to if these impacts are “natural” or if they should be classified within the Land Use/Land Cover Change (LULCC); but these processes may intensify during drought periods as noted through global warming scenarios, indicating that climate effects on mangroves need to be monitored globally.
<< Previous Abstract | Next Abstract >>