A RECENT STUDY found that while large, continuous natural areas are best, small patches in fragmented landscapes are important as well. (Michal Jarmoluk/Pixabay)

LANSING — Biologists have long debated whether it’s better to protect many small and isolated natural areas or focus on large, continuous areas to maximize the number of plant and animal species that can survive over the long term.

Now a study has the answer: Large, continuous natural areas protect more plants and animals than many small patches.

Thiago Goncalves-Souza, the lead author and a research scientist at the University of Michigan, and colleagues spent three years poring through more than a hundred studies from all over the world on the effects of disconnected and isolated natural areas on biodiversity.

Scientists from Michigan State University and research institutions in Montana, Germany, Brazil, the U.K., Australia, Argentina, Switzerland and Mexico collaborated on the project.

The study appeared in the journal Nature.

PATRICK DORAN IS the Midwest division director of strategy, measures and science with the Nature Conservancy. (Courtesy photo)

It was a large undertaking. Some of the studies had published their information online, but others did not, so Goncalves-Souza contacted them to secure the data.

Another challenge was the difficulty of accounting for methodological differences in so many studies, so the authors ran several statistical models to make sure their results were solid.

“We demonstrated that after accounting for a bunch of stuff, continuous patches hold more biodiversity,” he said.

However, that doesn’t mean that fragmented landscapes aren’t important.

“Forty-eight percent of the species live in the fragments,” he said. That means that almost half of the species would not be protected in large patches.

The researchers’ definition of a continuous patch was about 2,500 acres, or about three times the area of Central Park in New York City.

“We’re saying that yes, continuous patches hold more biodiversity,” Goncalves-Souza said, “but if you want to keep protecting biodiversity, we need to think about the fragmented landscapes.”

In many areas in the world, few continuous natural areas are left, he said.

The Upper Peninsula of Michigan still has large chunks of forest, Goncalves-Souza said. But the Lower Peninsula has more isolated and smaller patches.

“We need to think about ways to connect those fragments,” he said.

Connectivity of natural areas is important in Michigan, said Gary Roloff, a professor of fisheries and wildlife at Michigan State University. He wasn’t part of the project team.

Roloff has been working with the Department of Natural Resources and timber companies to study how deer affect regeneration of northern hardwoods in northern Michigan.

“When I look at a map of that (tree) cover type in Michigan, it’s kind of naturally fragmented,” he said. “It’s mixed in with conifers and cedar swamps and emergent marshes and all that stuff that we find in Michigan.”

Many wildlife species in the state need large, continuous patches of forest, he said. “Things like pine martens, black bears, depend on forests.”

But different vegetation types respond differently to fragmentation, he said.

For example, jack pine forests are accustomed to frequent fires and other natural events and need frequent disturbances to regenerate and thrive.

But, he says, the type of fragmentation matters.

The effects of timber management are often temporary, he said.

But natural habitats are also fragmented through urbanization and agriculture, and those effects are usually permanent.

Ensuring connectivity between forest patches is important, Roloff said.

“Maybe it draws attention to different landowners working together to ensure some of that connectivity,” he said. “That’s something that rarely happens, right?”

In 2022, the Nature Conservancy, a nonprofit conservation organization, protected about 30,000 acres in the Keweenaw Peninsula.

Patrick Doran, the conservancy’s Midwest division director of strategy, measures and science, said the area is a major bird migratory pathway.

“Many, many migratory birds, from hawks to eagles to owls to all the amazing songbirds that make their home in this part of the world, use the Keweenaw Peninsula as a migratory corridor and a launching point to fly across Lake Superior,” he said.

Doran said the organization doesn’t intend to keep long-term ownership, but plans to eventually transfer the parcels to state or township ownership and management.

The organization had many discussions with local residents about what they needed.

“The community really wants recreational lands that are connected for people,” he said. “They want to be able to use them for ATV recreational use and snowmobile use.”

Intact natural areas offer human benefits too, Doran said.

“We designed the management in a way that will maintain that connectivity,” he said. “They want to retain access to these lands for recreation, for hunting, for foraging, for wildlife watching, for hiking and trail running.”

Doran said many Midwest farms have small forest patches that can be valuable for wildlife.

“Farmers maintain a forest patch for some wood, where they go in for cherry trees, for building or firewood,” he said. “So you have a lot of these small patches.”

Small habitat patches can be vital for migrating species that need to fuel up on some food and rest, he said, comparing such small wooded lots to shopping at a Kwik-E-Mart.

It “might not be the most healthy food,” he said. “But you’re going to get what you need.”

Maintaining these natural areas is important for many species, Doran said.

“That might include working with agricultural producers to have cover crops in the wintertime that have multiple benefits” for birds and insects, he said.

“Even the smallest of fragments might provide a small benefit in time for that particular species as they’re moving along,” Doran said.