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Despite Wildfire, Australia's Carbon Sink Likely to Grow in the Future

Paper Reviewed
Kelley, D.I. and Harrison, S.P. 2014. Enhanced Australian carbon sink despite increased wildfire during the 21st century. Environmental Research Letters 9: 10.1088/1748-9326/9/10/104015.

In a study published in Environmental Research Letters, Kelley and Harrison (2014) write that "climate projections show Australia becoming significantly warmer during the 21st century, and precipitation decreasing over much of the continent," which changes, in their words, "are conventionally considered to increase wildfire risk," which is further presumed to reduce the continent's carbon sink. However, they show that although burnt area increases are projected for southern Australia, decreases are projected for its northern regions, such that "overall the projected increase in fire is small (0.72-1.31% of land area, depending on the climate scenario used)." In fact, they actually find that carbon storage increases by some 3.7-5.6 Pg C, depending on the climate scenario used.

Furthermore, using a process-based model of vegetation dynamics, the two researchers go on to demonstrate that (1) "increased fire promotes a shift to more fire-adapted trees in wooded areas and their encroachment into grasslands," which results in (2) "an overall increase in forested area of 3.9-11.9%," noting that (3) "both changes increase carbon uptake and storage." In addition, they state that (4) "the increase in woody vegetation increases the amount of coarse litter," which (5) "decays more slowly than fine litter," leading to (6) "a relative reduction in overall heterotrophic respiration," all of which phenomena play a role in (7) "further reducing carbon losses."

In light of these several intimately-related possibilities, Kelley and Harrison's ultimate take-home message is that, in the case of Australia, "direct CO2 effects increase woody cover, water-use efficiency and productivity, such that carbon storage is increased by 8.5-14.8 Pg C compared to simulations in which CO2 is held constant at modern values."

Posted 20 March 2015