Predators help protect carbon stocks in blue carbon ecosystems

NATURE CLIMATE CHANGE | VOL 5 | DECEMBER 2015 | www.nature.com/natureclimatechange Climate change is an urgent societal issue that can be addressed by a combination of reduced emissions and climate mitigation strategies, including those based on natural carbon (C) stores (that is, biosequestration). The need to reduce atmospheric CO2 concentrations combined with global interest in C trading and pricing has intensified research on the C storage capacity of natural ecosystems. To date, most C conservation programs have focused on managing and/or restoring terrestrial ecosystems, such as tropical forests, to maintain/boost their role in climate change mitigation. Recent studies1–3 suggest, however, that despite their small global extent, vegetated coastal habitats (seagrass meadows, mangroves and salt marshes) play a disproportionately large role in the global capture and storage of C. Biosequestration in vegetated coastal habitats, a process that takes up atmospheric CO2 and stores it for millennia in plant biomass and sediments (that is, blue C), is emerging as one of the most effective methods for long-term C storage4,5. Vegetated coastal habitats bury C 40 times faster than tropical forests and contribute 50% of the total C buried in ocean sediments6. The quantity of C (up to 25 billion tonnes) estimated to be stored in vegetated coastal habitats makes them the most C-rich ecosystems in the world (Table 1)2,4. Because of the remarkable capacity of vegetated coastal habitats to sequester and store C for millennia, they should be prominent in our strategies to combat climate change7. Yet our ability to conserve these natural C sinks is hampered by our limited understanding of the mechanisms that are conducive to high C accumulation and preservation rates. There is growing evidence that trophic downgrading, the disproportionate loss of species high in the food chain, can have far-reaching effects on ecosystem function8,9. This research has revealed that predators play important and potentially irreplaceable Predators help protect carbon stocks in blue carbon ecosystems