Blue carbon benefits from global saltmarsh restoration

Abstract

Coastal saltmarshes are found globally, yet are 25%–50% reduced compared with their historical cover. Restoration is incentivised by the promise that marshes are efficient storers of ‘blue’ carbon, although the claim lacks substantiation across global contexts. We synthesised data from 431 studies to quantify the benefits of saltmarsh restoration to carbon accumulation and greenhouse gas uptake. The results showed global marshes store approximately 1.41–2.44 Pg carbon. Restored marshes had very low greenhouse gas (GHG) fluxes and rapid carbon accumulation, resulting in a mean net accumulation rate of 64.70 t CO2e ha−1 year−1. Using this estimate and potential restoration rates, we find saltmarsh regeneration could result in 12.93–207.03 Mt CO2e accumulation per year, offsetting the equivalent of up to 0.51% global energy‐related CO2 emissions—a substantial amount, considering marshes represent <1% of Earth's surface. Carbon accumulation rates and GHG fluxes varied contextually with temperature, rainfall and dominant vegetation, with the eastern coasts of the USA and Australia particular hotspots for carbon storage. While the study reveals paucity of data for some variables and continents, suggesting need for further research, the potential for saltmarsh restoration to offset carbon emissions is clear. The ability to facilitate natural carbon accumulation by saltmarshes now rests principally on the action of the management‐policy community and on financial opportunities for supporting restoration.

Mono-Specific Data Deficient Saltmarsh Species Has Climate Relevant Carbon Stocks From the East Coast of India

“…One of the reasons for these differences in sediment Corg stocks is the sediment core depth sampled. In this study we have used sediment core depth till 30 cm (thus including the long-term Corg stocks) and the other authors have used sediment Corg from the top 10 cm only, which is very dynamic and subjected to significant loss of OM and associated Corg due to tidal fluctuations and decompositions (Campbell et al, 2022b;Mason et al, 2023a;McMahon et al, 2023;Perera et al, 2022). Consequently, the other difference between mono-specific and adjacent/mixed with mangrove P. coarctata meadows may be the vegetation structure of P. coarctata, which is low when present with mangroves (due to shading, grazing or competition with other saltmarsh species) compared to monospecific meadows, where the plant canopy height can reach 60 cm in post-monsoon with dense shoots and roots (Mishra and Farooq, 2022a).…”

“…These ecosystem services include food and habitat provisioning for variety of fish and invertebrate species (Jinks et al, 2020;Whitfield, 2017), improved water quality and shoreline protection through sediment accretion and plays an important role in climate change mitigation through blue carbon sequestration (Campbell et Rendón et al, 2019). However, due to various human induced habitat disturbances related to marine food provisioning (such as aquaculture and grazing), coastal developmental activities (port development, mangrove plantation, tourism activities) and climate change (such as sea level rise and temperature change effects) impacts, these ecosystems are getting lost at alarming rates (0.28% yr -1 ) in the last decade (Campbell et al, 2022a), leading to loss of ecosystem services (such as blue carbon) and biodiversity assemblages (Campbell et al, 2022b;Mason et al, 2023a;Mishra and Farooq, 2022a;Perera et al, 2022). Despite saltmarsh ecosystems being ecologically important in climate change mitigation, there is a significant lack of studies on assessing their carbon storage potential in the Indian subcontinent (Bal and Banerjee, 2019;Mishra and Farooq, 2022a;Stankovic et al, 2023).…”

“…al., 2023;Mason et al, 2023b;Stankovic et al, 2023), but lack of regional scale information on saltmarsh carbon stocks data hinders their integration into intended nationally determined contributions (NDCs) under Paris Climate Agreement, 2015(Dencer- Brown et al, 2022). Further research gaps also include, few well -studied locations globally (e.g., Western Atlantic saltmarshes of the United States, North-western European saltmarshes), that are often contextualized as being comparable to other saltmarsh areas in the tropical settings.…”

Carbon Stock in Coastal Ecosystems of Tombolos of the White and Baltic Seas

“…Comparable to terrestrial forest types, these worldwide C burial rates are 53.0 Tg C•yr −1 for temperate forests, 78.5 Tg•C yr −1 for tropical forests, and 49.3 Tg C•yr −1 for boreal forests [2]. A recent review found that restored coastal marshes accumulate carbon at an average rate of 4.41 Mg C•ha −1 •yr −1 [6]. The amount of stored soil C per unit area in coastal ecosystems is greater than in terrestrial landscapes: for saltmarshes, global estimates vary from 1.8 to 6.2 Pg [3].…”

Latitudinal patterns and their climate drivers of the δ13C, δ15N, δ34S isotope signatures of Spartina alterniflora across plant life-death status: a global analysis

“…FIGURE 1Number of relevant studies included in this study (N=57) published per year. The figure style referenceMason et al, 2023. …”