Forgive me but I just had to use this title before the end of the month!
I call your attention to several new studies on the responses of coastal wetlands to increases in both atmospheric carbon dioxide and sea level. “Marsh madness” doesn’t relate specifically to college basketball but, as shown by the following, there are as many uncertainties re the final outcome of the coastal science as about the outcomes of the NCAA men’s and women’s basketball conferences.
Unfortunately, the scientific uncertainties won’t be resolved in early April!
First, a new study on coastal marshes and carbon dioxide by Smithsonian scientists was summarized on March 26 in Science Daily: excess atmospheric CO2 makes some wetlands grow faster.
“Our findings show that elevated CO2 stimulates plant productivity, particularly below ground, thereby boosting marsh surface elevation,” said Adam Langley, the paper’s lead author. Patrick Megonigal, the paper’s corresponding author, added “We found that by stimulating root growth, thus raising a marsh’s soil elevation, elevated CO2 may also increase the capacity for coastal wetlands to tolerate relative rises in sea level.” Both scientists are ecologists at the Smithsonian Environmental Research Center in Edgewater, Md.
This sounds like good news but read this disclaimer:
Though marshes appear to benefit from CO2 in the short-term, the scientists stress that increasing CO2 levels will continue to warm the Earth, melt glaciers and expand ocean water, thus accelerating sea-level rise. Ultimately, rapidly rising seas could outstrip the positive effects of CO2 on the marshes that they have observed.
Now I call your attention to a recent paper by Sherwood B. Idso and Keith E. Idso on tidal marshes sequestering CO2 that was summarized in CO2 Science. This time there is no disclaimer.
Tidal marshes typically exhibit high rates of productivity. In the southern coastal region of North America, for example, the net primary production of these ecosystems averages approximately 8000 g m-2 yr-1 (Mitsch and Gosselink, 1993). Tidal marshes also exhibit low rates of organic matter decomposition, because the anaerobic decomposers of these oxygen-depleted environments operate at slower rates than do their aerobic counterparts of terrestrial environments (Humphrey and Pluth, 1996; Amador and Jones, 1997). Thus, it can readily be appreciated that as seas rise and encroach upon the land, rates of carbon sequestration in coastal marsh soils rise right along with them.
Next I call your attention to a USGS study summarized in the Weekly Carboholic on California salt marshes sequestering CO2. Note that while salt marshes provide a net benefit re CO2, freshwater marshes emit more methane as CO2 levels increase.
Salt water marsh restoration may efficiently sequester carbon
Deforestation. Biodiversity. Clean water. Carbon sequestration. Wetlands protection. Shoreline restoration. Most major environmental problems facing the world are connected in some way to other. For that reason, most of the connected environmental problems must be solved more or less simultaneously. Take clean water, shoreline restoration, wetlands protection, and climate change – wetlands are known to efficiently clean both freshwater and salt water, they help restore the shoreline and protect it from storm damage, and, if the preliminary results from a recent U.S. Geological Survey (USGS) hold, they grow fast enough to sequester significant amounts of carbon too.
Two months after starting a wetlands restoration research project in California’s Sacramento?San Joaquin River delta, the USGS researchers reported that their project was capturing 30 times the amount of carbon per square meter than Kyoto Protocol-compliant reforested agricultural land. This is because wetlands grow so fast and convert that growth into low-oxygen, slowly decomposing peat bogs and, ultimately, into new land over hundreds or thousands of years. However, freshwater wetlands have enough oxygen in the water to produce large amounts of methane. And since the USGS study hasn’t yet measured the amount of released methane, the total carbon sequestered may in fact be largely or even entirely negated by methane releases.
According to the ACS article, though, salt water marshes don’t suffer from the same problem, or at least not to the same degree. Because the salt water marshes grow as fast as their freshwater counterparts, they sequester as much carbon. But because there’s a lot more sulfate in salt water, bacteria don’t produce methane in significant amounts, and so methane emissions are unlikely to offset the CO2absorption in the marsh. And as the marshes pull CO2 out of the air, they’ll also clean the water, reduce shoreline erosion, slowly build new land, and provide food and shelter for wildlife.
Finally, I call your attention to a study in Physorg.com showing that tropical wetlands sequester much more carbon per acre than temperate marshes. This study, by Ohio State University scientists including Bill Mitsch*, compared wetlands in Costa Rica and Ohio. It would make sense that the subtropical wetlands in coastal Louisiana would be closer to the Costa Rican wetlands than those in Ohio.
*Dr. Mitsch has worked for years with Louisiana scientists on coastal wetlands. For example, he is cited in the above Idso and Idso reference.