Warming brings home the value of a meal

The 2012 Plant Hardiness Zone Map unveiled by the US Department of Agriculture this year shows average annual extreme minimum temperatures based on data from 1976-2005. In this version 2012 is modified to use the same colour code as 1990. Much of the US was one 5°F (2.8°C) half-zone colder in the 1990 Plant Hardiness Zone Map compared to the latest version. Credit: US Department of Agriculture/Friend of the Earth

Part one of two

Over the past few days I’ve been lucky enough to enjoy the kind of celebrations that would have been called feasting in the past. They’ve brought home how important food is as basic fuel, a source of pleasure and a reason for friends and family to get together. This year, that importance has drawn me increasingly to research into what climate change means for our food supply. What I’ve covered only begins to scrape the surface of the effects we can expect. However, these studies highlight how life could become yet harder for farmers, and what that could cost us all.

The warming world has already noticeably changed plant growing conditions, for example shifting the regions they are suited to grow in the US. In January, the US Department of Agriculture (USDA) redrew its map of planting zones to reflect warming seen since the 1990 version. Partly due to climate change, and partly due to new technology and better weather data, many places are now one 5°F (2.8°C) half-zone warmer. At around the same time, Chinese researchers found that the phases in the seasonal cycle of crop growth in their country had shifted between 1960 and 2008. Springtime events are now 6-15 days earlier and Autumn events 5-6 days later, they found.

21^st century outlook

Largely because we rely so much on burning fossil fuels, producing the greenhouse gas CO2 as we do so, we can expect further climate changes. When these changes affect farming, large and rapidly growing countries like China and India will have much to lose. So India will be concerned by projections that monsoon rains will dry as the world warms into the 22nd century. In November Jacob Schewe from the Potsdam Institute for Climate Impact Research agreed with other projections that the monsoon is expected to get wetter in the near term. But then an unstable balance between dry and wet monsoon years could become more important during the 21st century, and drive a sharp decrease in rainfall. “If you’re trying to gauge the implications of climate change for monsoon rainfall and agriculture, you might have to take into account if this finding is robust, and you have to plan your adaptation measures accordingly,” he told me.

In the US Midwest region, a drought from 2000-2004 was the worst the region has seen in 800 years according to Christopher Schwalm, from Northern Arizona University in Flagstaff. But his team’s model projections say such “megadroughts” will become normal by the end of the century. Consequently, rather than the region absorbing CO2 overall thanks to plant growth, the region will become a net CO2 emitter, worsening climate change. “What we now call a drought event will become an abnormally wet episode by the end of the 21st Century,” Christopher told Simple Climate.

Economic truth

The US is still suffering from widespread exceptional drought, as it has through much of 2012. Credit: US Drought Monitor

Such droughts would clearly impact farming in the future. So you’d expect the US government to include them in the first estimates of the money value of benefits from CO2 cuts some of its top departments made in 2010. These benefits, which come from avoiding losses through damage caused by climate change, are important because they affects rules on CO2 emissions, such as those from cars and power stations. But their assumptions for farming surprised Laurie Johnson of the Natural Resources Defense Council in Washington, DC, in the face of another drought in the US this year, and the threat of more to come. “The models also estimate net gains from agriculture from now up to 2300 globally,” she said. “By contrast the insurance industries appear to be estimating $25 billion dollars for crop losses in the US this year. That’s just one year for one country, and their calculation is for more than two hundred years, all countries.” Thanks to this and other problems, the government underestimated benefits from CO2 cuts by at least 2.6 times, she said in September.

Another economic impact of climate on farming could be big swings in US corn prices, found economist Tom Hertel from Purdue University in West Lafayette, Indiana and his colleagues. They found that climate measurements were strongly linked to the amount of corn produced, and could accurately explain past price volatility. When they used temperatures and other conditions from climate projections though to 2040, that volatility doubled. That wouldn’t affect food prices for the US public too much, Tom noted, as most corn is fed to livestock. However it would impact those livestock farmers, as well as ethanol producers. Yet he remained optimistic that problems could be minimised by farmers altering their approach. “These are really big effects, assuming that nothing else changed, but that’s not the way the world works,” Tom said. “Farmers adapt, they may change the crops they’re producing, the whole corn belt might move northward. Breeders are even now, as we speak, working on heat stress tolerant corn, which may moderate these effects.” But breeding better crops is a big challenge, as I’ll explain next week.

Journal references:
Qian, C., Yan, Z., & Fu, C. (2011). Climatic changes in the Twenty-four Solar Terms during 1960–2008 Chinese Science Bulletin, 57 (2-3), 276-286 DOI: 10.1007/s11434-011-4724-4
Schewe, J., & Levermann, A. (2012). A statistically predictive model for future monsoon failure in India Environmental Research Letters, 7 (4) DOI: 10.1088/1748-9326/7/4/044023
Schwalm, C., Williams, C., Schaefer, K., Baldocchi, D., Black, T., Goldstein, A., Law, B., Oechel, W., Paw U, K., & Scott, R. (2012). Reduction in carbon uptake during turn of the century drought in western North America Nature Geoscience, 5 (8), 551-556 DOI: 10.1038/ngeo1529
Laurie T. Johnson and Chris Hope (2012). The social cost of carbon in U.S. regulatory impact analyses: an introduction and critique Journal of Environmental Studies and Sciences DOI: 10.1007/s13412-012-0087-7
Diffenbaugh, N., Hertel, T., Scherer, M., & Verma, M. (2012). Response of corn markets to climate volatility under alternative energy futures Nature Climate Change DOI: 10.1038/nclimate1491