http://chge.med.harvard.edu/sites/default/files/resources/agricultureclimate.pdf
We highlight the following conclusions regarding the current state of the U.S. agricultural sector:
Since the 1970s, U.S. agriculture has achieved enhanced productivity, but has also experienced
greater variability in crop yields, prices, and farm income. The changes in variability
are, in part, climate-related, either directly (through extreme weather events) or
indirectly (due to agricultural pests and diseases).
Extreme weather events have caused severe crop damage and have exacted a significant
economic toll for U.S. farmers over the last 20 years. Total estimated damages, of which
agricultural losses are a part, from the 1988 summer drought were on the order of $56 billion
(normalized to 1998 dollars using an inflation wealth index), while those from the
1993 Mississippi River Valley floods exceeded $23 billion.
Both pest damage and pesticide use have increased since 1970. Nationally, in the 1990s,
pests were estimated to have destroyed about one third of our crops, in spite of advances
in pest control technology over the last half century.
The ranges of several important crop pests in the U.S., including the soybean cyst nematode
[the most destructive soybean pest in the U.S.] and corn gray leaf blight [the major
disease causing corn yield losses] have expanded since the early 1970s, possibly in
response, in part, to climate trends.
Pest and disease occurrences often coincide with extreme weather events and with
anomalous weather conditions, such as early or late rains, and decreased or increased
humidity, which by themselves can alter agricultural output. Recent climate trends, such
as increased nighttime and winter temperatures, may be contributing to the greater prevalence
of crop pests.
