Climate change in Minnesota is already here

NERSTRAND – The tree canopy at Big Woods State Park was starting to thin.

It was 2018. Aerial photos of the park confirmed to the naturalists there that red oak, white oak, burr oak and basswood trees covering about 12% of the forested land in the park were dying.

“Two years later, there were 200 acres dead -- just like that,” said Molly Tranel Nelson, regional resource specialist with the Minnesota Department of Natural Resources.

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Naturalists looked at weather data and compared it to the time and rate of die-off. Increased rains and the flat terrain where the die-off was occurring made the soil too wet to support the trees -- many of which had been standing since the pre-settlement era.

“Sure enough, there was a pretty clear signal it was happening at the same time,” said Neil Slifka, regional nongame wildlife specialist with the Minnesota Department of Natural Resources.

Tanel Nelson pointed out the wide bases of the trees, indicating the trees had wide root bases, likely due to a high water table. The shift to a wetter climate made the terrain unlivable for them, she said.

“It really highlights how precarious some of these places on the landscape are as far as a changing climate,” Slifka said.

The forests at Big Woods stand out as an island of trees surrounded by farmland.

The forest land was divided into about 150 lots and sold for people to manage and use the lumber that grew there. Some trees date to the pre-settlement era. Much of the rest of the old forests across central Minnesota in that era were removed for lumber and cleared for farming, but Big Woods remained.

“Whether it was by intent or circumstances of the times, people would use it sustainably,” Slifka said.

“This was a good example of a big woods remnant,” Tranel Nelson said. “It was a very healthy and well-managed forest for many years.”

Little restoration was needed on the land when the state took over ownership to establish the park in 1945 after the U.S. Forest Service acquired title to much of the patchwork of plots.

Tranel Nelson checked on some of the trees planted in the test plots April 9. She wore a hard hat into the area for protection against falling branches. Most branches and many trees have already fallen.

"I hate coming out here on windy days," she said.

Those trees still standing had few branches covering the forest floor. The standing trunks are riddled with holes bored by woodpeckers.

Ed Quinn, DNR Natural Resource Program supervisor, says the target for most park management plans is to try to restore species and habitat to as close to pre-settlement conditions and varieties as possible. For decades, Big Woods was an example of success to that approach. Today, however, a new climate in Minnesota has changed the approach there and in other places.

“In some places, that can’t be the target anymore,” he said.

The management plan at Big Woods is now what Slifka calls “assisted migration.” DNR, the Parks Service and the University of Minnesota partnered in late 2019 to plant about 800 trees on 5 acres of test plots in the park. The species — silver maple, hackberry, swamp oak and a disease-resistant variety of elm — are native to Minnesota but weren’t originally found in the area of the park. They are species that generally grow better in wet conditions and could be key to restoring the forest.

“The goal right now is to see what works,” Slifka said.

Ash trees in the affected areas are doing well and helping provide enough shade canopy to keep invasive species such as reed canary grass from moving into the area. However, with emerald ash borer just a few miles from the park, naturalists say the situation requires some urgency.

Minnesota is getting warmer and wetter .

Heavy rainfalls are occurring more frequently and dropping more water on the state. According to the state climatologist office, Minnesota has experienced 11 “mega rainfall” events since 2000.

The DNR defines “mega rainfalls” as deluges of 6 inches of rain covering more than 1,000 square miles, with the core rain event topping 8 inches. The 30 years prior to 2000, six recorded “mega rainfalls” hit the state.

One of those was in 1978 when heavy rains led to major flooding in Southeast Minnesota including in Rochester . Five people died and the city suffered $60 million in damage. The Zumbro River at Rochester crested at an all-time record of 23.36 feet July 6, 1978.

Since then, three more similar heavy rain events have struck Rochester and Southeast Minnesota, including in 2010, when Rochester received a record 6.22 inches of rain over 48 hours, Sept. 22-23. However, each of those subsequent “mega rains” have hit after a $114 million flood control project was completed in 1995. That project was spearheaded by the U.S. Army Corps of Engineers and a reservoir project by the U.S. Department of Agriculture Natural Resources Conservation Service (NRCS) and funded with federal money and matching local funds through a local sales tax.

While the full effects of climate change in Minnesota have yet to be documented, more frequent, heavier rain and warmer temperatures are two clear trends.

“It’s easy to demonstrate we’ve had off-the-charts rainfall and off-the-charts warming,” said Ken Blumenfeld, DNR state climatologist and co-host of Minnesota climate podcast, “ Way Over Our Heads .”

That doesn’t mean climate change is a cause of severe weather. Other weather events don’t show any significant trend changes.

“We’ve always had hail storms,” Blumenfeld said. “But there’s no evidence they’re getting more frequent or worse.”

More frequent and heavier rain means more stress on waste water infrastructure. As heavy rains occur more frequently, water treatment plants get inundated and face a no-win decision: allow the system to go above capacity and risk backing wastewater into people's homes, or open the system and discharge partially treated or untreated sewage into the watershed and nearby bodies of water.

There were about 200 such releases throughout Minnesota in 2020, said Katrina Kessler, MPCA assistant commissioner for Water Policy and Agriculture. Much of the stress comes from the outdated size of treatment systems and old pipes and systems that allow stormwater into them.

“These systems are under stress and need investment,” Kessler said.

The Minnesota Pollution Control Agency has identified more than 980 water treatment infrastructure projects that need to be upgraded, for an estimated $4 billion in costs, Kessler said.

Whether funding for such projects gets funding this legislative session has yet to be determined. The MPCA is also asking for $2.9 million in state money for grants to cities and counties to study their stormwater infrastructure upgrade needs.

That request is just to study the needs and get an approximate cost for those upgrades, Kessler said.

“I wouldn’t be surprised if it was on par (with the wastewater costs),” she said.

The Minnesota Department of Transportation is also looking down the road at costs associated with climate change.

More severe and more frequent flooding means higher chances of washed-out bridges, roads and culverts. While the department leaders say they don’t have exact costs that can be tied to climate change, they are working on ways to identify the more vulnerable transportation infrastructure.

In June 2018, the Minnesota Highway 23 bridge over the south fork of the Nemadji River was washed away by flash flooding following heavy rains. Heavy rains had hit the area in 2012 and the state transportation officials had documented the bridge’s vulnerability to such flash flooding.

Replacing the bridge as it was built was too much of a cost risk, considering the area’s increased vulnerability to flooding. Instead, MnDOT made the case for more federal funding to improve the bridge. With documentation including weather data and the recent flooding, MnDOT was able to file a “betterment justification” for more federal money to improve the bridge and build it higher above the waterway.

“That’s the kind of case study we want to normalize,” said Jeffrey Meek, MnDOT sustainability coordinator.

MnDOT plans to have a list of the top 10% of transportation structures most vulnerable to climate change. With nearly 90,000 structures, MnDOT is looking for some computer help to see which ones are most vulnerable. Staff are working to overlay climate data with data on transportation structures, elevation and other factors to see which ones are most vulnerable. Once that information is compiled, MnDOT will pair it with qualitative data -- experience and knowledge of local MnDOT staff.

“They already know what keeps them awake at night if there’s a major rain event,” Meek said.

The goal is to use the data and input from staff to help MnDOT file “betterment justifications” to apply for extra state or federal aid when flooding and major rain events damage infrastructure in the future.

How much state aid is ultimately provided for various climate-related projects depends on the fate of about 70 bills that address climate at the state Legislature at the beginning of this session. Topics range from funding solar panels on school buildings to establishing an environmental justice board.

However, environmental advocates say that not enough is on the docket to address climate change.

One key criticism of Gov. Tim Walz’s proposed budget is that it doesn’t offer additional funding for transit.

According to the Minnesota Department of Transportation’s Pathways to Decarbonizing Report in 2019 , transportation has overtaken agriculture and electricity generation as the biggest contributor of carbon emissions in the state. Carbon emissions are linked to the warming of the climate and are the biggest driver of human-driven climate change.

Mary Blitzer, engagement manager with the Sierra Club North Star Chapter, said that expanding transit services and access to transit would give more people the option not to drive and cut back on the state’s top greenhouse gas contributor.

“Walz has called climate change an ‘existential threat,’” Blitzer said in an interview at the start of the legislative session in January. “His budget doesn’t reflect that.”

Blitzer also noted Walz and the MPCA have not taken steps to halt a planned pipeline, known as Enbridge Line 3, that would move oil from Canadian tar sands across Minnesota. The line would cross 200 bodies of water, including lakes, wetlands and rivers, and Native American tribal land where wild rice is grown, Blitzer said.

The MPCA approved a permit for the project in November last year, prompting most of the members of the Environmental Justice Advisory Group to the MPCA to resign.

“So far, Walz has been big on talk and short on action when it comes to addressing causes of climate change,” Blitzer said.