Coastal marshes are valuable ecosystems that provide important nutrients to coastal waters that help sustain local food webs. They are also increasingly recognized as valuable carbon sinks, sequestering significant quantities of carbon both above and below ground. In recent years, however, concerns have been expressed that these ecosystems are in danger of collapsing in response to rising sea levels that are projected to occur as a consequence of CO2-induced global warming. If such fears are correct, melting ice will increase the rate of sea level rise beyond which these ecosystems can keep up, essentially dooming them to a submerged death, which would have substantial repercussions on surrounding communities.
But how likely is it that this gloomy scenario will occur?
Investigating this very topic, the three-member research team of Ratliff et al. (2015) used a one-dimensional ecomorphodynamic model to “assess the direct impacts of elevated CO2 on marsh morphology, relating to ongoing and emerging environmental change.” According to the authors, previous works have revealed large increases in marsh plant biomass productivity in response to elevated concentrations of atmospheric CO2, yet “direct CO2 effects on vegetation and marsh accretion (as opposed to its indirect effects, e.g., via the increase in temperature) have not yet been incorporated into marsh models. As a result, they note the relative importance of CO2 effects on marsh dynamics “remains unknown” … until now, that is.