Agriculture and Ecosystems

Agricultural impacts

Agricultural production represents a significant portion of regional land use and is responsible for a major portion of the Great Lakes’ economy. Crops in the region vary from corn, soybeans, and wheat in the southern and western portions of the region to fruit orchards and vineyards in the northern and eastern portions. Tree fruits such as apples, cherries, and peaches have been a specialty of the Great Lakes region for more than 150 years. Annually, over $1 billion in fruit and nut crops are produced in the eight U.S. states bordering the Great Lakes.

The productivity of traditional field crops in the Great Lakes is constrained by the length of growing season and the timing and amount of precipitation during that time. In contrast, the primary weather-related constraint for tree fruit crops is the frequency and severity of frosts and freezes during the spring.

Observed changes in the length of the frost-free season by region. Click the image for more information.

The Great Lakes growing season has lengthened by one to two weeks across the region, primarily due to earlier occurrence of the last spring frost in recent decades. Paradoxically, the frequency of spring freeze events occurring after the initial stages of plant development has increased at the same time, which has resulted in an increased risk of production losses. Future crop yields will likely be affected more by anomalous weather events rather than changes in annual precipitation and annual average temperature alone. Springtime cold air outbreaks are projected to continue to occur throughout this century.

Impacts attributable to a warming climate will not be restricted to fruit and specialty crops. For corn, small long-term average temperature increases will shorten the duration of reproductive development, leading to yield declines—even when offset by increases of carbon dioxide (CO₂) stimulation that will likely occur in a warmer climate. For soybeans, yields have a two-in-three chance of increasing early in the near future due to increased CO₂ stimulation, but yields will likely decline toward the end of the century due to increased heat stress from an increased number of days with temperatures above 95°F and 100°F.

Soybean field, Superior Township, Michigan.

Changing precipitation patterns could also significantly impact agriculture in the Great Lakes region. In the future, the average number of days without precipitation is predicted to increase, which could lead to more frequent occurrences of agricultural drought and suppressed crop yields.

The preceding text is excerpted and abridged from the Synthesis of the Third National Climate Assessment for the Great Lakes Region.

Forests and land cover

The Great Lakes region encompasses a variety of land cover types and ecosystems. Natural ecosystems—including prairies, forests, streams, beaches, dunes, and wetlands that are often rich with varied species of wildlife—are often fragmented by urban and agricultural areas. The combined effects of climate change, land use change, and increasing numbers of invasive species are the primary threats to natural ecosystems in the Great Lakes region.

North Bar Lake Overlook Trail, Lake Michigan.

The habitat ranges of iconic tree species such as paper birch, quaking aspen, balsam fir, and black spruce are projected to shift northward as the climate warms. In the northern stretches of the region, species such as white/red/jack pine and spruce are predicted to exit the region entirely. Note, however, that there is considerable variability in the likelihood of a species’ habitat changing and the adaptability of the species with regard to climate change.

When drought is present, a condition which may increase as precipitation patterns change, environmental damage increases. Examples include loss of wetlands, ecological habitat destruction, and reduced water quality. Additionally, the direct effects of increased heat stress and drought may be magnified by changes in other areas such as disease and pest prevalence and increased competition from non-native or opportunistic native species.

Average amount of carbon stored in all terrestrial ecosystems in the conterminous United States in 2005 as estimated by a national assessment of carbon stocks and sequestration capacity performed by the U.S. Geological Survey.

Currently, global forests capture and store more carbon than they emit. With climate change, the ability of forests to act as large, global carbon absorbers (or “carbon sinks”) may be reduced by increases in tree mortality and carbon emission, forest fires, and drought. Some regions may shift from being a carbon sink to a carbon source, although large uncertainties exist. Forests in the Great Lakes region are more resilient to forest carbon losses than most western forests because of relatively high moisture availability, greater nitrogen deposition, and lower wildfire risk.

The preceding text is excerpted and abridged from the report Synthesis of the Third National Climate Assessment for the Great Lakes Region and the report State of Climate Change Science in the Great Lakes Basin.

To learn more about climate-related impacts on ecosystems and agriculture, visit Topics. The following topics may be particularly helpful:

• Food
• Ecosystems