No abstract

See Letter to the Editor on this article by Adam et al., 26, 3756–3758. See also Response to the Letter by Bradstock et al., 26, e8–e9.

[1] Sulfate in acid rain is known to suppress methane (CH 4 ) emissions from natural freshwater wetlands. Here we examine the possibility that CH 4 emissions from rice agriculture may be similarly affected by acid rain, a major and increasing pollution problem in Asia. Our findings suggest that acid rain rates of SO 4 2À deposition may help to reduce CH 4 emissions from rice agriculture. Emissions from rice plants treated with simulated acid rain at levels of SO 4 2À consistent with the range of deposition in Asia were reduced by 24% during the grain filling and ripening stage of the rice season which accounts for 50% of the overall CH 4 that is normally emitted in a rice season. A single application of SO 4 2À at a comparable level reduced CH 4 emission by 43%. We hypothesize that the reduction in CH 4 emission may be due to a combination of effects. The first mechanism is that the low rates of SO 4 2À may be sufficient to boost yields of rice and, in so doing, may cause a reduction in root exudates to the rhizosphere, a key substrate source for methanogenesis. Decreasing a major substrate source for methanogens is also likely to intensify competition with sulfate-reducing microorganisms for whom prior SO 4 2À limitation had been lifted by the simulated acid rain S deposition.

The 2019–20 Australian fire season was heralded as emblematic of the catastrophic harm wrought by climate change. Similarly extreme wildfire seasons have occurred across the globe in recent years. Here, we apply a pyrogeographic lens to the recent Australian fires to examine the range of causes, impacts and responses. We find that the extensive area burnt was due to extreme climatic circumstances. However, antecedent hazard reduction burns (prescribed burns with the aim of reducing fuel loads) were effective in reducing fire severity and house loss, but their effectiveness declined under extreme weather conditions. Impacts were disproportionately borne by socially disadvantaged regional communities. Urban populations were also impacted through prolonged smoke exposure. The fires produced large carbon emissions, burnt fire-sensitive ecosystems and exposed large areas to the risk of biodiversity decline by being too frequently burnt in the future. We argue that the rate of change in fire risk delivered by climate change is outstripping the capacity of our ecological and social systems to adapt. A multi-lateral approach is required to mitigate future fire risk, with an emphasis on reducing the vulnerability of people through a reinvigoration of community-level capacity for targeted actions to complement mainstream fire management capacity.