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The World's Longest Ecosystem CO2 Enrichment Study

Paper Reviewed
Drake, B.G. 2014. Rising sea level, temperature, and precipitation impact plant and ecosystem responses to elevated CO2 on a Chesapeake Bay wetland: review of a 28-year study. Global Change Biology 20: 3329-3343.

Back in 1985, a Chesapeake Bay (USA) wetland - sustaining both pure and mixed stands of the C4 grass Spartina patens and the C3 sedge Scirpus olneyi - was selected for an open-top chamber study of the effects of full-day (24-hour) atmospheric CO2 enrichment to 340 ppm above the then-ambient concentration of the same value. And now, in a paper published 28 years later in Global Change Biology, the director of the project summarizes some of the important findings of this unique and unparalleled undertaking. So what has been learned from this longest of all such studies?

Advising us that "the question of whether rising atmospheric CO2 will cause the land sink for anthropogenic carbon to expand or contract has been the basis for most ecosystem studies to date," Drake writes that we now have, from the Chesapeake Bay study, "strong evidence that shoot and root biomass and net ecosystem production increased significantly" under real-world conditions of growing fossil fuel usage. And he thus infers - from the fact that (1) methane emission (Dacey et al., 1994) and (2) nitrogen fixation were also stimulated by elevated CO2 (Dakora and Drake, 2000), and that (3) inputs of soil carbon also increased - that "ecosystems will accumulate additional carbon as atmospheric CO2 continues to rise, as suggested by Luo et al. (2006)."

In a closely related matter, Drake also writes that the long duration of the Chesapeake Bay wetland study allows for a test of "the idea that some process, such as progressive nitrogen limitation, may constrain ecosystem responses to elevated CO2 in native ecosystems." But his and his associates' findings, as well as those of Norby et al. (2005) and Norby and Zak (2011), imply, as he notes, that quite to the contrary, Earth's ecosystems will continue to accumulate carbon as the air's CO2 content continues its upward trajectory.

Thus we find clear evidence from data obtained in the real world of important benefits conferred by rising atmospheric CO2 upon nature, evidence that many unfortunately continue to deny.

References
Dacey, J.W.H., Drake, B.G. and Klug, M.J. 1994. Simulation of methane emission by carbon dioxide enrichment of marsh vegetation. Nature 370: 47-49.

Dakora, F. and Drake, B.G. 2000. Elevated CO2 stimulates associative N2 fixation in a C3 plant of the Chesapeake Bay wetland. Plant, Cell and Environment 23: 943-953.

Luo, Y., Hui, D. and Zhang, D. 2006. Elevated CO2 stimulates net accumulations of carbon and nitrogen in land ecosystems: a meta-analysis. Ecology 87: 53-63.

Norby, R.J. and Zak, D.R. 2011. Ecological lessons from free-air CO2 enrichment (FACE) experiments. Annual Review of Ecology, Evolution, and Systematics 42: 181-203.

Norby, R.J., DeLucia, E.H., Gielen, B., Calfapietra, C., Giardina, C.P., King, S.J., Ledford, J., McCarthy, H.R., Moore, D.J.P., Ceulemans, R., De Angelis, P., Finzi, A.C., Karnosky, D.F., Kubiske, M.E., Lukac, M., Pregitzer, K.S., Scarasci-Mugnozza, G.E., Schlesinger, W.H. and Oren, R. 2005. Forest response to elevated CO2 is conserved across a broad range of productivity. Proceedings of the National Academy of Sciences 102: 18,052-18,056.

Posted 27 January 2015