Weather conditions, such as record flooding, extended periods without significant precipitation, warmer than average winter months and the possibility of drought loom for the growing season of 2012. What will the short- and long-term effects be on our horticultural practices?
“What we do know is that the climate has changed in the past, is changing today and will continue to change in the future,” says Ron Smith, North Dakota State University Extension Service horticulturist. “While the scientists argue why the climate is changing, gardeners and growers are being affected by the adverse impact of year-to-year variations in weather.”
The concentration of carbon dioxide (CO2) had increased by 1.5 parts per million (ppm) since the Mauna Loa Observatory started doing CO2 measurements in 1960.
While the models contain a great deal of uncertainty on future CO2 concentration amounts, conservative models say the rise will continue and may reach 700 ppm by 2100. The models also assume that humankind will be attempting to slow the rise of CO2 during that time.
“As this is taking place, the greenhouse gases, such as CO2 and water vapor, are absorbing Earth-emitted infrared radiation,” says Adnan Akyuz, North Dakota state climatologist and assistant professor of climatology in the NDSU Soil Science Department. “This causes the Earth’s temperatures to rise and is the main mechanism of the greenhouse gas effect. However, it is important to note that because of its connection with global warming, the general public has a negative perception about the greenhouse effect. However, without the greenhouse effect, the Earth’s average temperature would have been 0 F, or 59 degrees colder than its current temperature.”
Global temperature increases mean different things for various locations. With the trends not being the same everywhere, some will experience a higher than average increase in temperatures, while others will be less affected.
While some locations will enjoy the positive impact of climate change, others will have to worry about mitigating the adverse impacts. For example, increases in annual temperature in North Dakota allowed producers to utilize 12 longer growing seasons during the last century.
“We may have cooler than normal temperatures during the next couple of summers or a much higher average minimum temperature than previously experienced.” Smith says. “With our crops, we can mitigate some of the daytime increase with sprinkler irrigation, misters or shade cloth. However, due to the blocking of infrared radiation into the atmosphere at night, we have no effective way of lowering the night temperatures. These higher minimums will impact fruit maturation, which means crops, such as tomatoes and grapes, can be harvested earlier in the season. While good for annual crops, it may have an impact on meeting the total chilling requirements of some of the perennial fruit crops such as apples.”
There are some positives. Higher CO2 levels will allow stomatal pores on plants to close somewhat, which will increase water efficiency by cutting down on evapotranspiration. Because CO2 is a necessary component of photosynthesis, plants should grow better. CO2 “fertilization” is a somewhat common practice in greenhouses at higher elevations, such as the mountain regions of Colorado.
Warmer temperatures also may mean more disease and insect activity in horticultural crops. Up to a point, common maladies, such as powdery mildew, can be expected to show an increase. With milder winter temperatures, wood-boring and root-eating insect larvae that were somewhat kept in check with more severe weather, will now flourish and feast on crops.
“Adjustments in landscape management, pest control and the timing of planting and harvesting will have to be implemented during the next decade to maximize our horticultural objectives,” Smith says. “What was standard operating procedure in 1990 will not be the same in 2020 if we want to continue growing our favorite horticultural plantings successfully.”
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