BROADCASTER ARCHIVES

Climate Change: What Experts Expect for the Upper Midwest
By Denise Thornton

This article was first printed in the July/Aug 2009 issue of the Organic Broadcaster, published by the Midwest Organic and Sustainable Education Service.

We’ve all read the headlines trumpeting the destructive potential of global warming, filled with phrases like melting ice caps, rising sea levels, and devastating tropical storms.  But what is this going to mean to those of us farming in the Midwest over the coming decades, and what can we do now to meet these challenges?

The Wisconsin Initiative on Climate Change Impacts (WICCI), completed a 9-part seminar series in June 2009 titled “Bracing for Impact.” The University of Wisconsin, the Wisconsin Department of Natural Resources and other state agencies and institutions have pooled resources to present cutting-edge climate predictions. Their goal:  to develop practical information that can guide all decision makers from government organizations to individuals. 

The WICCI study focuses on Wisconsin, and while Dr. Christopher Kucharik, Assistant Professor of Agronomy at UW-Madison, is not familiar with any similar state projects elsewhere in the Midwest, he notes that WICCI’s findings can be applied across state lines, particularly in Minnesota, Iowa, Michigan and parts of Illinois.

The Timeframe of Global Climate Change
WICCI researchers believe that climate change has already begun.  Dr. Michael Notaro, Associate Scientist in the Center for Climatic Research at the UW Gaylord Nelson Institute of Environmental Study, noted that the growing season is now two weeks longer than it was just 20 years ago.  Plant hardiness zones are marching northward.  “Between 1990 and 2006, zone 3 has gone from Wisconsin, and zone 5 has moved in,” he said.

Jack Williams of the Nelson Institute for Environmental Studies put the timeframe into perspective.  “You see curves of temperature rising over the century, and it seems pretty abstract, but it’s happening right here and right now.  We are in the beginning of a ramp up, and things will be happening faster and faster.  My three-year-old, Eliza, may see temperatures increase from 3.2 to 6.8 °F in her life time.  That is more than temperatures have changed in the past 22,000 years since the last glacier.”

Another perspective comes from Dr. Sara Hotchkiss, Assistant Professor of Botany at UW-Madison who studies pollen in sediment cores from lakes for a peek at the past thousand years.  She has compared sediments from the Medieval Warm Period (from 800 to 1200 A.D., when wine grapes were commonly grown in Britain) to the Little Ice Age (from 1400-1800, when all agriculture ceased in Iceland and Greenland).   The temperature change that caused this shift was less than 2° F.  “These were climate changes that were relatively mild compared to what we are looking at in the next 50 to 100 years,” Hotchkiss says.

Short-term Climate Change Expected in the Midwest
The phrase “global warming” is far too simplistic for what scientists are learning from climate modeling.  As temperature rises, the United States can expect to see the climate become wetter in the north and drier in the south, but where the dividing line between the two weather patterns will fall as it crosses the Midwest is not yet well understood.  Most of the Midwest may fall into the wetter category, but the changes in precipitation will not necessarily be more inches per year.  Instead, precipitation patterns are expected to shift.

Kucharik anticipates that spring, winter and fall will be wetter, and summer may be a time of increasing drought.  Rainfall events may decrease, especially in summer when rain will be delivered in heavy downpours followed by dry spells.  The type of flooding that occurred in south central Wisconsin in June 2008 could well become more common.  He added that increased heat can dry out the soil no matter how much rain we get.  In winter, some of the current snow season will be replaced by freezing rain. 

Some Good News
Extended growing season
An extended growing season has obvious advantages.  Kucharik says this would allow farmers to adapt to longer-season crops with higher yield potential.

Paradoxically, fewer days over 100 degrees
Even as average temperatures rise, the number of blistering hot days may decrease because of increased humidity. Eugene Tackle, Professor of Agricultural Meteorology at Iowa State University, says, “Summer temperatures are becoming more favorable for agriculture here in the Midwest.  Looking back 30 to 40 years, we often had summers with five to 10 days of temperatures above 100, but we hardly ever get those now.”  He speculates this is because of increased cloudiness and the fact that soils are generally wetter than they have been in the past.  “When soil is dry and sun shines on it, it heats up fast.  Wetter soils can lead to cooler daytime temperatures. The night time temperatures are also getting higher, that’s not necessarily good, but not as critical as day time temperatures.”

Increased organic matter in soil
As the climate gets warmer it may be easier to build up organic material in the soil.  According to Fred Magdoff and Harold van Es, authors of Building Soil for Better Crops, as the climate gets warmer, more vegetation is produced and the rate of decomposition also increases because soil organisms work more efficiently in warm weather and for longer periods of the year.  Soil with better moisture-holding capacity can better withstand the destructive action of flash flooding.

The Bad News
More days above 95 degrees
Extreme heat is hard for plants to deal with.  An increase in days above 95º F will cause plants to shut down during the growing season.

More flooding
With rain concentrated in spring and fall, and increasing heavy rain events, erosion is going to be a more common problem. Also, more precipitation in the spring can make it harder to get into the fields.

More livestock mortality
The U.S. Climate Change Science Program Report on the Effects of Climate Change on Agriculture warns that higher temperatures can hit livestock hard.  The benefits of warmer overnight lows in winter may be offset by greater mortality during hotter summers.  Hot summers also reduce productivity of livestock and dairy animals.

Weeds increase in growth and variety
Weeds grow more rapidly under elevated atmospheric CO2, and the Climate Change Report predicts that warm-climate weeds will migrate northward.

New insect and disease pests
Insects and disease pests are also moving northward. There are many invasive plant species and insects that have previously not been an issue in the Midwest because they could not overwinter here.  “A lot of the warming we have been seeing is not evenly spread across all seasons,” says Williams.  “Winter overnight low temperatures have been increasing faster than summer temperatures.  That has big implications on the limits that winter sets on pest species.”

Increase in humidity stress
Takle has observed an increase in humidity in both summer and winter.  “Higher humidity can bring fungus, molds and pathogens, for example, apple scab, which is related to the number of accumulated hours that dew is on leaves and fruit.”

More deer damage
Deer damage may increase.  Herds may grow in size due to more deer being born and less starvation during warmer winters.

Dramatic change in forest type
Forestry will be changing along with the climate.  Rapid climate change hits slow-growing trees hard, says David Mladenoff of the UW-Madison’s Department of Forest and Wildlife Ecology.  Tree species that are projected to decline in the Midwest include Red Pine, Jack Pine, White Spruce, Balsam Fir and Paper Birch.  Southern oaks and hickory will migrate into the region.  Sugar Maple and hickory are expected to do relatively well here as the climate changes. 

Guidelines for Survival
Takle advises, “Start thinking about making your own measurements and observations. In many cases, this information does not yet exist.  Our goal as climate scientists is to report what we are observing and get into a dialog with farmers.” 

Some of the growing season conditions worth keeping records on would include:

1. air temperature (and frequency of extreme heat, > 86° F, or extremely cool conditions, < 50°F), 
2. precipitation / total rainfall each week,
3. soil moisture conditions,
4. existence of any extended periods of dry weather - although those could be derived from rainfall and soil moisture,
5. cloudy vs. sunny days.

Organic farmers may be in a strong position to contend with climate change.  Takle noted, “Organic and natural systems have a way of working with the situation, and locally-adapted strains of particular crops might have more local adaptability.”

On the other hand, James Nienhuis, Professor of Horticulture at UW-Madison, advises farmers to identify cultivars that are better adapted to the new environment.  “Farmers will have to be aware that the traditional cultivars they have grown are adapted to an environment that existed 20 years ago,” he says.  “They may have to shift to varieties that flower or mature at a different time or that germinate and grow under different conditions.”

Mladenoff, suggests getting seeds from southern, rather than northern suppliers.  “Even southern strains of the same species may be better conditioned to our changing climate,” he says.  Takle adds that we may need to look for southern strains that have more resistance to newly-arrived warm-weather pests.

The U.S. Climate Change Report recommends, “a continuation of the trend toward increased water use efficiency” to mitigate the impacts of climate change on water resources.

Kucharik says, “The best way is for farmers to keep track of how their particular plants have been responding through time, and what aspects are correlated with better or worse yields in relation to growing season conditions.  In essence, farmers have the largest natural field experiment taking place each year; they have to hedge their bets and hope that the strains they plant mesh well with the season’s growing conditions.  There is a lot to be gained if they know what seems to be working and what doesn’t over the long term.

Recordings of the WICCI Seminar Series presentations have been posted on the UW Biotech Auditorium website. http://www.biotech.wisc.edu/webcams/ and are currently being broadcast on Wisconsin Public Television.

Denise Thornton recently completed her MA in Journalism from UW-Madison and posts regularly on what she is doing and learning on her own 44 acres at http://digginginthedriftless.wordpress.com.