Amid a deeply cold winter that often socked much of North America on the chin, to the point of widespread propane shortages, many quipped, “So much for global warming” – both humorously and seriously.
But climate isn’t just about temperatures, and this isn’t the only continent. Jerry Hatfield, director of the National Laboratory for Agriculture and the Environment under the USDA’s Agricultural Research Service as well as chief of the USDA’s Midwest Climate Hub, reminds farmers to recall this winter “on a global basis.” One notable example was the shortage of snow for the Winter Olympics in Sochi – perhaps the most obvious problem among many plaguing the Russian city during the Games.
“I think people need to realize it’s about climate change; climate variability,” said Hatfield.
He and Iowa State University Climate Science Program Director Gene Takle were the two convening lead authors of the “Agriculture” section in the National Climate Assessment released last week, updated from 2009. Hatfield said they and contributing authors spent about three years compiling data for their topic – which is still just one of several sections the federal report covers, with the help of more than 300 experts.
The 800-plus-page report is a daunting read. Agriculture alone covers many pages with several points, a big one being “climate is not just about crops,” according to Hatfield. The Ag section also addresses observed and probable effects on livestock and, for the first time in detail, soil health – particularly erosion.
“We’re seeing decreasing amounts of soil carbon (organics that nourish plants) and increasing amounts of soil erosion,” he explained.
Changes in rainfall patterns are an easily observed cause of erosion. When even rich soil’s ability to filter the water hitting it is overcome by the volume and severity of rain and flooding, there’s runoff. And in Iowa alone, the authors say while annual precipitation has not increased, there has been “a large increase in the number of days with heavy rainfall.”
In fact, to combat spring flooding and erosion, they reported some farmers have lately been spending upwards of $500 per acre to install tiling.
As with precipitation, Hatfield said climate change doesn’t mean each year will necessarily be warmer than the last – global warming isn’t that linear. It warms during a number of decades, but the immediate effects each season will vary and weather is likely to be more extreme. “It’s going to bounce all over the place,” he said of temperatures.
He said farmers can already see variances. Cherry growers in Michigan lost a crop to a mild winter, early budding and a killing freeze in the spring of 2012. In the Dakotas, some farmers are making money from corn and soybeans who couldn’t have cultivated them as easily 15 years ago. Southern Corn Belt growers are having to find ways to cope with corn and soybeans not getting as much moisture in recent years.
Saying global temperatures will be higher and that temperate growing zones will shift by a matter of counties or states, not just fields, half a century from now may be too “out there” as a concern for someone whose work depends on what the next season is like, Hatfield said. One aim of this report, he explained, is to try to convey the “right here, right now” effects of climate change so farmers – and everyone else – can think of smaller changes now to adapt better later.
“I try to ground people by getting them to think about what’s happened the past few years in their growing seasons,” he explained. “I keep telling them, ‘Here’s the thing you have to consider’” with respect to economics and conservation.
AG FINDINGS
While the report goes into much more detail on its agricultural findings (as well as for the sectors of water, energy, transportation, forests, ecosystems, health, land use, rural living and others), what follows are some general points Hatfield and Takle cover.
By the mid-21st century, global temperatures are projected to be between 1.8-5.4 degrees higher than now. But, temperature change is not the only influence on crop viability and yield; precipitation and soil water play into it, and they’re affected by climate change. The report estimates climate shifts will affect the quantity of food produced and as such, impact the amount available for import/export – and, of course, pricing.
Also, the authors note: “Crop production projections often fail to consider the indirect impacts from weeds, insects and diseases that accompany changes in both average trends and extreme events, which can increase losses significantly.”
For example, European corn borer is just one pest that benefits from milder winters. For now, the bug only produces one generation a year in the Northern Corn Belt and 1-2 generations in the Southern Corn Belt where winters are warmer. But as warmer temperate zones move northward – as changes in the USDA Plant Hardiness Zones map indicate happened more rapidly between 1990 and 2012 than from 1960 to 1990 – the borer may begin reproducing more frequently.
These same climate alterations are likely to mean a shift of disease vectors that impact plants and livestock. Pathogens previously unfamiliar to a county or state will present problems for those farmers.
One mixed play of factors involves increased carbon dioxide emissions, or CO2, in the air. Elementary science teaches that plants breathe CO2 and expel oxygen, so one might think increased CO2 is only good for crops. “Though changes in temperature, CO2 concentrations and solar radiation may benefit plant growth rates,” the authors wrote, “this does not equate to increased production.”
Indeed, though a corn plant may mature more quickly this way, the soil may not be able to keep up with its rapid need for nutrients – and sufficient water may be lacking as well, in warmer temperatures. Added to this is the fact weeds flourish even better on extra CO2 than do crops, and don’t need as many nutrients to do so.
“Plants love CO2,” Hatfield said. “In fact, the scary part is that weeds respond really well to CO2.”
With higher temperatures during pollination, especially at night, corn faces another risk. He explained the plant during this phase is so sensitive to temperature that to expose it to heat higher than 90 degrees for too long at this time could lead to sterility.
In soy and alfalfa, high CO2 levels have been associated with reduced nitrogen and protein content, which means less nutrition for feeding livestock. In addition, animals respond directly to more heat and humidity – a fluctuation of 4-5 degrees in a body’s core temperature can reduce productivity or milk output and a change of 9-12.6 degrees “often results in death.”
Again, the authors note it’s not the gradual decades-long change in climate temperature that will do this – it’s the extreme weather events, such as a prolonged shorter period of high heat. “Within physiological limits, animals can adapt to and cope with gradual thermal changes,” they wrote.
“The accelerated pace of climate change and the intensity of projected climate change represent new and unprecedented challenges to the sustainability of U.S. agriculture,” the report notes, adding while farmers can adapt, any economic hardship is likely to hit smaller-scale producers harder because they have less capital and credit access than larger operations.
On a larger scale, “The globalized food system can buffer the local impacts of weather events on food security, but it can also increase the global vulnerability of food security by transmitting price shocks globally.”
-Originally published in Farm World, May 2014