Declining crop yields limit the potential of bioenergy
Global-warming projections that rely on bioenergy strategies to offset carbon dioxide emissions could be unduly optimistic, according to a study that accounts for how climate change affects crop yields.
Climate change is beset with unpleasant surprises. Yields of maize (corn), wheat, rice and soya beans all fall precipitously when temperatures exceed certain thresholds — for example, 29 °C for maize. These four staple crops together account for 75% of the calories consumed by humans, so the non-linear temperature dependence of their yields calls for rapid action to avoid the tipping points, either by limiting the carbon dioxide emissions that are warming the planet or by relocating crop fields on a vast scale — probably both. But efforts to curb global warming rely increasingly on the use of plant biomass to reduce emissions, and introduce a feedback loop that endangers attempts to meet essential climate goals, as Xu et al. report in a paper in Nature.
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Much like the prospect of distant technological salvation from climate change, the expected future effectiveness of BECCS must not detract from the need to cut emissions now. Xu et al. have offered further evidence that relying on technological breakthroughs down the line is a fraught endeavour. As their analysis demonstrates convincingly, waiting for salvation could well hasten our demise, because delays might restrict the technologies available to us now.
Although US President-elect Donald Trump and his fellow Republicans give climate advocates plenty to worry about, all hope is not lost. Clean-energy technologies still have decisive physical advantages over the alternatives, and economic common sense will eventually win out.
