Abstract
BackgroundDetermining national carbon stocks is essential in the framework of ongoing climate change mitigation actions. Presently, assessment of carbon stocks in the context of greenhouse gas (GHG)-reporting on a nation-by-nation basis focuses on the terrestrial realm, i.e., carbon held in living plant biomass and soils, and on potential changes in these stocks in response to anthropogenic activities. However, while the ocean and underlying sediments store substantial quantities of carbon, this pool is presently not considered in the context of national inventories. The ongoing disturbances to both terrestrial and marine ecosystems as a consequence of food production, pollution, climate change and other factors, as well as alteration of linkages and C-exchange between continental and oceanic realms, highlight the need for a better understanding of the quantity and vulnerability of carbon stocks in both systems. We present a preliminary comparison of the stocks of organic carbon held in continental margin sediments within the Exclusive Economic Zone of maritime nations with those in their soils. Our study focuses on Namibia, where there is a wealth of marine sediment data, and draws comparisons with sediment data from two other countries with different characteristics, which are Pakistan and the United Kingdom.ResultsResults indicate that marine sediment carbon stocks in maritime nations can be similar in magnitude to those of soils. Therefore, if human activities in these areas are managed, carbon stocks in the oceanic realm—particularly over continental margins—could be considered as part of national GHG inventories.ConclusionsThis study shows that marine sediment organic carbon stocks can be equal in size or exceed terrestrial carbon stocks of maritime nations. This provides motivation both for improved assessment of sedimentary carbon inventories and for reevaluation of the way that carbon stocks are assessed and valued. The latter carries potential implications for the management of human activities on coastal environments and for their GHG inventories.
Highlights
Determining national carbon stocks is essential in the framework of ongoing climate change mitigation actions
We suggest that assessment of carbon stocks of continental margin sediments within the Exclusive Economic Zones (EEZ) of maritime nations may provide a useful framework for greenhouse gas emissions accounting, and for developing strategies for coastal carbon management as part of planning longterm responses to climate change
In locations characterized by little available data the mean value could be strongly biased or unrepresentative of EEZwide values
Summary
Determining national carbon stocks is essential in the framework of ongoing climate change mitigation actions. Assessment of carbon stocks in the context of greenhouse gas (GHG)-reporting on a nationby-nation basis focuses on the terrestrial realm, i.e., carbon held in living plant biomass and soils, and on potential changes in these stocks in response to anthropogenic activities. Reduced carbon fixed on land may be exported by fluvial and atmospheric processes to the aquatic realm, evolving as it moves through along a complex land–ocean continuum, with some fraction of this carbon contributing to the oceanic carbon reservoirs. This myriad of Avelar et al Carbon Balance Manage (2017) 12:10 processes is called carbon cycle (see Fig. 1). The carbon cycle operates on a broad range of spatial and temporal scales, and involves highly complex and dynamic interactions within as well as at the interfaces between atmospheric, terrestrial and aquatic spheres [17, 23]
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