Agriculture Reference
In-Depth Information
Implications for Row-Crop Production
Changes in climate greatly impact row-crop agriculture: temperature, precipita-
tion amount and distribution pattern, cloud cover, and carbon dioxide (CO
2
) levels
affect plant growth, field practices, pests, and plant diseases, sometimes in con-
flicting ways (Tubiello et al. 2007, Hatfield et al. 2011, Hatfield et al. 2014, NRC
2010c). Over the last forty years, agricultural production in the United States has
been affected by more climate disruptions, a trend that is expected to continue
(Hatfield et al. 2014). The magnitude of the impacts on crop yields depends on
location, the agricultural system, and the degree of warming (NRC 2010b) as well
as the availability of water to the crop. We have used the CSI as a metric to assess
the effects of changes in temperature and precipitation on corn and soybean yields
in the NCR. While other factors will also affect crop yield, including rising atmo-
spheric CO
2
levels, weed pressure, herbicide efficacy, and the spread of pests and
diseases (Tubiello et al. 2007, Hatfield et al. 2011), there are too few data to develop
an index that incorporates these effects.
A recent global analysis showed that from 1980 to 2008, corn and wheat yields
were suppressed 3.8% and 5.5%, respectively, in many important agricultural coun-
tries because of increasing temperatures (Lobell et al. 2011). The United States was
a notable exception, showing no detectable yield loss due to climate change. In
fact, for the years 1982-2002, increased corn and soybean yields in the central and
eastern United States were attributed to favorable climate conditions: a combina-
tion of more precipitation, longer growing seasons, and decreased summer average
temperatures (Twine and Kucharik 2009). These favorable climate trends may have
contributed 20-25% to the observed U.S. yield increases over this period. Kucharik
and Serbin (2008) examined the variability of past temperature and precipitation
county-level trends and their effect on crop yields in Wisconsin during 1976-2006.
Yield trends were suppressed 5-10% in counties that had warmer summer tempera-
tures. This negative impact was, however, counterbalanced by increases in precipi-
tation that favored crop yields.
Our work shows that, in the 30-year period we analyzed, most periods of crop
stress in the NCR have been short-term events in May through July (Fig. 4.9) that
were characterized by high temperatures and below-average precipitation. For every
unit increase in the CSI, yields decreased 0.14 Mg ha
−1
for corn and 0.04 Mg ha
−1
for soybean (Fig. 4.10). During this period, there were few years with back-to-back
severe crop stress events (Fig. 4.4). Further back in the region's recorded climate
history, however, severe continuous crop stress events helped create the 1930's Dust
Bowl and depressed yields to near zero for several years in succession, illustrating
the vulnerability of agricultural systems to prolonged and repeated climatic stress.
To date, U.S. agriculture has been effective at adapting to climate change
(Hatfield et al. 2014), and under local temperature increases of up to 2°C adap-
tation has the potential to offset projected crop yield declines in North America
(IPCC 2014a). At temperature increases of 4°C or more, however, the effectiveness
of adaptation will be reduced and large risks to food security at global and regional
scales are likely (IPCC 2014a,b). Climate disruptions are anticipated to have an
increasingly negative impact on most U.S. crops by mid-century (Hatfield et al.
