Coastal landforms and accumulation of mangrove peat increase carbon sequestration and storage

Significance Despite their small height and stunted appearance, mangroves along the desert coasts of Baja California have compensated for sea-level rise during the last two millennia by accreting on their own root remains. In doing so, they have accumulated very large amounts of carbon in their sediments (900–3,000 Mg C/ha), often higher than that accumulated under tall, lush, tropical mangrove forests. Mangroves represent the largest carbon sink per unit area in Mexico’s northern drylands. Our results highlight the global importance of mangrove conservation in this region. Given their relatively small area, mangroves and their organic sediments are of disproportionate importance to global carbon sequestration and carbon storage. Peat deposition and preservation allows some mangroves to accrete vertically and keep pace with sea-level rise by growing on their own root remains. In this study we show that mangroves in desert inlets in the coasts of the Baja California have been accumulating root peat for nearly 2,000 y and harbor a belowground carbon content of 900–34,00 Mg C/ha, with an average value of 1,130 (± 128) Mg C/ha, and a belowground carbon accumulation similar to that found under some of the tallest tropical mangroves in the Mexican Pacific coast. The depth–age curve for the mangrove sediments of Baja California indicates that sea level in the peninsula has been rising at a mean rate of 0.70 mm/y (± 0.07) during the last 17 centuries, a value similar to the rates of sea-level rise estimated for the Caribbean during a comparable period. By accreting on their own accumulated peat, these desert mangroves store large amounts of carbon in their sediments. We estimate that mangroves and halophyte scrubs in Mexico’s arid northwest, with less than 1% of the terrestrial area, store in their belowground sediments around 28% of the total belowground carbon pool of the whole region.

[1]  K. McKee,et al.  Biophysical controls on accretion and elevation change in Caribbean mangrove ecosystems , 2011 .

[2]  Carlos Troche Souza,et al.  Manglares de México : extensión, distribución y monitoreo , 2013 .

[3]  D. Cahoon,et al.  Caribbean mangroves adjust to rising sea level through biotic controls on change in soil elevation , 2007 .

[4]  M. Kanninen,et al.  Mangroves among the most carbon-rich forests in the tropics , 2011 .

[5]  I. Macintyre,et al.  Corrected western Atlantic sea-level curve for the last 11,000 years based on calibrated 14C dates from Acropora palmata framework and intertidal mangrove peat , 2003, Coral Reefs.

[6]  J. Bhattacharya,et al.  Wave‐influenced deltas: geomorphological implications for facies reconstruction , 2003 .

[7]  M. Wooller,et al.  A multiproxy peat record of Holocene mangrove palaeoecology from Twin Cays, Belize , 2007 .

[8]  J. Curray.  Origin of beach ridges: Comment on Tanner, W.F., 1995. Origin of beach ridges and swales. Mar. Geol., 129: 149–161 , 1996 .

[9]  Carlos M. Duarte,et al.  The fate of marine autotrophic production , 1996 .

[10]  K. McKee,et al.  Mangrove Peat Analysis and Reconstruction of Vegetation History at the Pelican Cays, Belize , 2000 .

[11]  G. Islebe,et al.  Mangrove history during middle- and late-Holocene in Pacific south-eastern Mexico , 2015 .

[12]  Ronald Amundson,et al.  The Carbon Budget in Soils , 2001 .

[13]  P. Tomlinson,et al.  Studies on the Growth of Red Mangrove (Rhizophora mangle L.) 3. Phenology of the Shoot , 1971 .

[14]  I. Macintyre,et al.  Blanchon P, Comment on Toscano MA and Macintyre IG (2003): Corrected western Atlantic sea-level curve for the last 11,000 years based on calibrated 14C dates from Acropora palmata framework and intertidal mangrove peat. Coral Reefs 22:257–270 , 2005, Coral Reefs.

[15]  J. López‐Portillo,et al.  The mangrove communities in the Arroyo Seco deltaic fan, Jalisco, Mexico, and their relation with the geomorphic and physical-geographic zonation. , 2007 .

[16]  James N Sanchirico,et al.  Global economic potential for reducing carbon dioxide emissions from mangrove loss , 2012, Proceedings of the National Academy of Sciences.

[17]  D. Murdiyarso,et al.  The potential of Indonesian mangrove forests for global climate change mitigation , 2015 .

[18]  Louis S. Santiago,et al.  Oceanographic anomalies and sea-level rise drive mangroves inland in the Pacific coast of Mexico , 2011 .

[19]  A. Búrquez,et al.  Aboveground biomass in three Sonoran Desert communities: variability within and among sites using replicated plot harvesting. , 2010 .

[20]  M. Guevara,et al.  Carbon stocks and soil sequestration rates of tropical riverine wetlands , 2015 .

[21]  John W. Day,et al.  Structure, litter fall, decomposition, and detritus dynamics of mangroves in a Mexican coastal lagoon with an ephemeral inlet , 1987 .

[22]  Donald R. Cahoon,et al.  Coastal Wetland Vulnerability to Relative Sea-Level Rise: Wetland Elevation Trends and Process Controls , 2006 .

[23]  E. Ezcurra,et al.  The productivity of mangroves in northwestern Mexico: a meta-analysis of current data , 2012, Journal of Coastal Conservation.

[24]  M. Stuiver,et al.  Discussion: Reporting of 14 C Data , 1977 .

[25]  P. Tomlinson,et al.  Studies on the Growth of Red Mangrove (Rhizophora mangle L.) 4. The Adult Root System , 1977 .

[26]  B. Murray.  Economics: Mangroves' hidden value , 2012 .

[27]  Ruben Abe Cisneros.  Provenance and origin of Holocene beach ridge and modern beach sands from the Costa de Nayarit, western Mexico , 2011 .

[28]  W. Oechel,et al.  Aircraft Regional-Scale Flux Measurements over Complex Landscapes of Mangroves, Desert, and Marine Ecosystems of Magdalena Bay, Mexico , 2013 .

[29]  Carlos M. Duarte,et al.  A blueprint for blue carbon: toward an improved understanding of the role of vegetated coastal habitats in sequestering CO2 , 2011 .