It’s too soon to tell if the highly erratic and at times disastrous Iowa weather of the past six years is the result of greenhouse gas-fueled climate change, according to Iowa State University climate scientist Gene Takle.
Asserting that it takes about 40 years of data to establish a climate trend, Takle said during a telephone news conference Thursday that he believes the passage of time will prove that the floods of 2008, 2010 and 2011, the droughts of 2012 and 2013 and other aberrations such as last year’s and this year’s late springs have all been manifestations of climate change.
“I say that largely because climate models have predicted all this would happen,” said Takle, a lead author of the National Climate Assessment report, to be released Tuesday.
That report and the UN Intergovernmental Panel on Climate Change report, released March 31, both contend that climate change, including extreme weather and rising temperatures, will reduce crop yields, making it more difficult to feed the world’s growing population.
Takle said Iowa farmers so far have adapted well to wetter springs and more intense rainfall events.
“They have installed more drainage tile and adopted larger machinery to take full advantage of shrinking windows for planting and harvesting crops,” he said.
But climate change impacts will become increasingly negative as the century progresses, according to both Takle and another speaker at Thursday’s briefing, USDA scientist Lewis Ziska, a contributing author to both reports.
Over the past 20 years, Takle said climate data has been sending a consistent message — that human activity, the burning of fossil fuels, is responsible for the changes.
“We need to decrease the emission of heat-trapping gases,” he said.
Takle said corn yields, which had been climbing steadily for decades, actually have fallen well below the trend line during the past four years of unfavorable weather.
After establishing a record yield of 164.7 bushels per acre in 2009, national averages in the years since have been:
•152.8 in 2010
•147.2 in 2011
•123.4 in 2012
•158.8 last year.
Crop insurance payouts set records in 2011 and 2012, said another briefing speaker, fifth-generation Iowa farmer Matt Russell, who also serves as State Food Policy Project coordinator at Drake University in Des Moines.
“We’re getting the wrong weather at the wrong time,” he said, noting that last year’s growing season included the wettest May on record, one of the coldest Julys and one of the driest Augusts.
Russell said he saw a field that went unplanted because it was too wet in the spring across the road from a field that withered in the late-summer drought.
“It’s real, it’s happening. It’s already causing great harm to farmers, and it’s going to get worse,” Russell said.
Takle said Iowa is experiencing a 40-year trend in which rainfall is increasingly concentrated in the first half of the year.
That trend, which delays planting of corn and soybeans and increases soil erosion, “is likely to continue with wet regions getting wetter and more humid,” he said.
By midcentury, it is unlikely that adaptation will be sufficient to avoid negative effects, Takle said.
Ziska said many agricultural regions will experience declines in crop and livestock production from increased stress caused by weeds, diseases and insect pests that will flourish under altered climates.
Claire O’Connor, a lawyer and agricultural water policy analyst with the Natural Resources Defense Council, which sponsored Thursday’s briefing, said farmers can combat climate change by improving their soil’s resilience.
“Healthy soil can filter excess water and hold more water when it’s dry,” she said.
O’Connor advocated a policy change that would provide lower crop insurance premiums to farmers who adopt practices, such as the planting of cover crops, to improve their soil’s health and resiliency.
A draft of the National Climate Assessment report said the trend toward more dry days and higher temperatures will add stress to limited water resources and will negatively affect crop and animal production.
Hot nights also will increase, which can reduce grain yields and increase stress on livestock, reducing rates of meat, milk and egg production, according to the draft report.
Increasingly extreme precipitation will continue to erode soil and degrade water unless innovative conservation methods are implemented, the NCA draft report said.
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