Heat, carbon dioxide and air pollution are already having significant effects on trees, plants and crops, and for most plant scientists, the debate over climate change ended long before the arrival of extreme weather like Hurricane Sandy. Now, some of those scientists have moved beyond political questions to explore how rising levels of heat and emissions might provide at least some benefits for the planet.
“There is a lot of emphasis on the mitigation of global warming, and we need that,” said Lewis H. Ziska, a plant physiologist for the Department of Agriculture, US, who is one of a growing number of scientists studying how plants react to elevated levels of greenhouse gases and other pollutants. At the same time, he added, “we need to think about the tools we have at hand, and how we can use them to make climate change work for us.”
Among the tools are cities, which have conditions that can mimic what life may be like in the temperate zone of a heated planet. “The city is our baseline for what might happen in future decades, and with all the negative effects global warming may have, there may be a bit of a silver lining,” said Stephanie Searle, a plant physiologist who led a Columbia University research project on tree growth, and now works as a biofuels researcher at the nonprofit International Council on Clean Transportation. “Higher nighttime temperatures, at least, may boost plant growth.”
Robust growth takes more carbon dioxide out of the atmosphere. Still, some emissions are not helpful to plants. There are also plenty of modern pollutants, like ozone and heavy metals, which are toxic to plants, to humans or to both. And so far, the long-term effects on plant life on a heated planet are unclear.
The effects of higher, mostly urban emissions are what prompted Ziska to reappraise global warming as a potential benefit to humanity. In an essay last summer in the journal Proceedings of the Royal Society B, Ziska and a group of colleagues from across the world argued that an expected increase in world population to 9 billion people from 7 billion by 2050 necessitated a “green revolution” to enhance yields of basic grains. Carbon dioxide, the group suggested, could be the answer.
Since 1960, world atmospheric carbon dioxide concentrations have risen by 24 per cent to 392 parts per million and could reach 1,000 parts per million by the