University of Parma, Italy
Methane and CO2 have a different greenhouse effect. That of methane can be variable along with the age of the methane admitted to the atmosphere, but on average is 20 times higher than that of CO2. That of N2O is 10 times higher compared to that of methane. When we analyse the three gases simultaneously we have to homogenize the units, because the small amount can be absolutely relevant when normalized to the same greenhouse gas effect of CO2.
Dried wetlands should be rewetted, so we should find a way to keep the water in the wetland. There is a lot of spontaneous growth of vegetation in wetlands because sediments are incredible seed banks and we can be surprised to see the vegetation that can grow if the water quality is good enough. There are a lot of applied ecology papers describing the transplant techniques that are quite easy. I would focus on this group of plants that are submerged as the first category because the ecosystem services they provide in terms of greenhouse gas emissions are unique. A lot of plants disappeared because they suffered eutrophication.
Unfortunately, I am not an expert on this topic, but I see that the literature reports studies that have explored these issues. A few references are reported below.
Khudzari, J.M., Gariépy, Y., Kurian, J., Tartakovsky, B. and Raghavan, G.V., 2019. Effects of biochar anodes in rice plant microbial fuel cells on the production of bioelectricity, biomass, and methane. Biochemical Engineering Journal, 141, pp.190-199.
Zhang, K., Wu, X., Luo, H., Li, X., Chen, W., Chen, J., Mo, Y. and Wang, W., 2020. CH4 control and associated microbial process from constructed wetland (CW) by microbial fuel cells (MFC). Journal of Environmental Management, 260, p.110071.
Kumar, K., Manju, P. and Gajalakshmi, S., 2023. Harnessing plant microbial fuel cells for resource recovery and methane emission reduction in paddy cultivation. Energy Conversion and Management, 294, p.117545.
This is of course the main target, always. The reduction of nutrient excess from wetland watersheds is the most effective, relevant action to put in act to avoid environmental (water pollution, loss of biodiversity and functioning, loss of services, anoxia, GHG emission….) and economic issues (loss of expensive fertilizers from agroecosystems, cost avoided to restore ecosystems and to clean water…).
This is a nice question that probably has “plant-specific”, and “time-span dependent” multiple answers. Macrophytes can simultaneously favour methane oxidation in sediments and favour its release to the atmosphere, depending if they are submersed and oxygen is released from the roots or emergent. They can also be rapidly decomposed, enhancing the consumption of electron acceptors, or slowly decomposed, depending on their macromolecular composition, affecting methane fluxes. More studies are needed in this respect, taking into account not only the vegetative phase and the typologies of macrophytes, but also the fate of the produced organic matter. I would also always include both CO2 and CH4 in such evaluation, to calculate a net effect on the C budget.
I would say yes, but if this is the main target (and not for example biodiversity or other ecosystem services) more studies are required to set the best “active management practices” to maximize C sequestration and minimize C losses.
Yes, especially if they fix refractory C and grow under nutrient-limited conditions. Under these circumstances, the fixed C can be net buried within sediments.
By favouring floating plants, not anchored to sediments, promoting together with high air temperatures anoxia and large production (and emission) of methane.