It's a critical moment for a species on the brink of collapse. The monarch butterfly population in eastern North America dropped by half from last year, and the fragile insects are now winging north from Mexico toward Minnesota.

Crews with the Monarch Joint Venture, a national conservation organization based in St. Paul, are eager to head south to research the migration to determine what conservation work can keep the beloved orange butterfly from disappearing.

They will have to wait. The nonprofit has delayed its field work as the nation fights to outwit the novel coronavirus. The monarch research is one of a host of environmental projects across the state delayed, suspended or thrown into uncertainty by the pandemic.

The Department of Natural Resources (DNR) canceled the first meeting of its wolf advisory committee, which is working to update the state's wolf management plan as the animal loses federal protection under the Endangered Species Act. It's not clear when it will reconvene.

The Minnesota Pollution Control Agency (MPCA) has stopped its monitoring network for nitrate, sediment and other pollutants in 200 rivers and streams across the state.

Volunteer work on the Redheaded Woodpecker Research and Recovery Project, part of the Audubon Chapter of Minneapolis, has been canceled, as have a number of long-term soil health, prairie restoration and climate change studies. Meanwhile, the DNR has stopped collecting springtime measurements that show how the makeups of dozens of lakes are changing due to warmer temperatures.

How much research is lost depends on how long the shutdown continues, administrators say. It may also depend on how nimble and creative groups become in the new world of Zoom meetings.

Even seemingly solitary field work can be risky, they say. Researchers are out and about, fueling up cars, using restrooms, eating and finding lodging.

"We're already on plan B for our field season and have mapped out what plans C and D might look like," said Monarch Joint Venture director Wendy Caldwell.

Plan B means crews will miss the crucial first weeks of the migration — the butterflies are in Texas right now. Researchers who were supposed to head out shortly will now head south in May to scour roadsides, pastures, rights of way, protected grasslands and urban areas, where they will measure milkweed density with a square made of PVC pipe and count eggs, larvae and butterflies. The research helps inform government agencies such as the U.S. Fish and Wildlife Service, local nature centers and universities.

"There's so little of that data" already, said Caldwell.

Lee Ganske, who supervises the MPCA's Watershed Pollutant Load Monitoring Network, said the measurements don't determine the suitability of water for drinking. But they helps determine whether a river is unfit for swimming or supporting fish and other aquatic life.

"The longer the work is suspended, the more the year 2020 will just sort of be a hole in the data, and it will just make it more difficult for us in retrospect to say something about what the water quality was," Ganske said. "If we're suspended for a couple of months or longer, then it will just be a bigger hole."

Gene Merriam, a former DNR commissioner who volunteers with the redheaded woodpecker project, said he doesn't know when the group can get back to work. They typically work at the U's Cedar Creek Ecosystem Science Reserve in Anoka County, and it has suspended volunteer work there for the 2020 field season.

Volunteers, who have helped band birds and outfit them with transmitters, are trying to figure out why the bird's numbers have plummeted.

Often confused with other woodpeckers, the redheaded woodpecker doesn't frequent backyard bird feeders and depends on nesting in the cavities of dead and dying trees. Oak savannas with a low understory seem to be an ideal environment for them, Merriam said. He said he suspects a lower understory doesn't hide predators as well, and helps the woodpeckers catch the flying insects they eat during nesting period.

Merriam said he doesn't know what impact the delay in field work will have.

Meanwhile, the DNR's Wolf Plan Advisory Committee is on pause. Agency spokeswoman Kim Pleticha said "they are planning on full steam ahead" with the committee.

But it's not clear what that will look like.

"We're looking at ways that we can still engage the group but we haven't fully developed that yet," said Dan Stark, the DNR's large carnivore specialist.

Committee member Collette Adkins, carnivore conservation director at the Center for Biological Diversity, said she's disappointed. There's urgency, she said, because the U.S. Fish and Wildlife Service is expected to remove the gray wolf from protection under the Endangered Species Act any day now.

That hands management of the state's 2,700 gray wolves — the largest population in the Lower 48 states — back to the state. The state's wolf management plan is badly outdated, she said.

A key point is that the state allows farmers and others to kill wolves themselves to protect livestock or pets. In Zone A in northeast Minnesota the wolf must be an "immediate threat" to livestock or pets, but in the rest of the state the wolf doesn't have to be an immediate threat.

"We've learned so much about wolf biology and management in the last two decades," Adkins said. "That knowledge needs to be incorporated into the state's wolf plan."

The DNR's lake work has also been delayed. By now the agency would normally have started taking extensive measurements on more than 20 "sentinel" lakes around the state. For years, the DNR has been tracking just about every change that can be measured in fresh water, from acidity and chemicals within the lake to temperatures, ice coverage and populations of fish and other life.

While any data gaps, even yearlong ones, in long-term studies are unfortunate, they do happen, said Pat Rivers, DNR deputy director of fish and wildlife.

"Our data sets have gaps from government shutdowns and things like that," Rivers said. "Our research will be able to work through any new ones. The important thing is we keep our employees safe."

jennifer.bjorhus@startribune.com 612-673-4683

greg.stanley@startribune.com 612-673-4882