Species in Restored Forests and Wetlands Are Vanishing

Tiny Species Vanish From Restored Forests and Wetlands

A forest can look healthy again after being regrown. Wetlands can once again fill with insects, birds and lush vegetation. But scientists are discovering that some of the smallest species in restored forests and wetlands may still be missing.

These overlooked inhabitants include mosses, lichens, algae and fungi. Even decades after a habitat has been restored, some species in restored forests and wetlands can remain rare or absent.

Restoring forests and wetlands can help declining plants and animals recover and rebuild their populations. But recent research suggests that different species return at very different speeds. For some of the smallest organisms, recovery can take decades, raising concerns about biodiversity and the long-term health of restored ecosystems.

The slow return of species in restored forests and wetlands shows that simply bringing back trees, plants and visible wildlife may not be enough to fully restore an ecosystem.

Ellen Macdonald, a botanist at the University of Alberta, has spent her career studying forests, but her focus is not primarily on trees. She studies the tiny flowers, mosses, liverworts and lichens that grow in the shade, around tree roots and across the rough surfaces of bark.

“There’s way, way, way, way, way more species there than there is a tree species,” Macdonald said.

To most people, Macdonald said, a forest that has regrown for several decades after logging can look much like an untouched forest. Tall trees may be everywhere, along with birds and insects.

But Macdonald remembers walking through regrown coniferous boreal forests and feeling that something was missing, even though she could not immediately say what it was.

“To really notice what was maybe missing, you’d have to be collecting data,” she said.

Chiloscyphus pallescens, a liverwort frequently found on rotting logs. (Michael Lüth)

Macdonald eventually did exactly that. She combined her own research with data from around the world to investigate how long plants and animals take to return as boreal forests grow back after clearcutting.

The study, recently published in the journal Nature Sustainability, found that birch and aspen forests and their inhabitants appeared to recover within 25 years. Conifer forests, however, took much longer.

In those forests, understory plants, particularly lichens, mosses and liverworts, needed 85 years or more to return. In some cases, they had not recovered even during the century covered by the available data.

The findings suggest that species in restored forests and wetlands may follow very different recovery timelines depending on the type of habitat and the conditions they need to survive.

Linnea borealis (twin flower) and other understory plants in a boreal forest. (E. Macdonald)

‘They may not come back easily’

The problem is not limited to boreal forests. Research on wetlands and other restored habitats has found a similar pattern. A landscape can appear healthy while some of its less noticeable species are still missing.

The same pattern has been found among species in restored forests and wetlands, showing that a landscape can look healthy while important but less visible organisms are still absent.

Years ago, CBC News spoke with German botanist Michael Melkonian about research into how plants evolved to live on land. He described wetlands near his home in the village of Jexmühle in southern Germany that were once filled with carnivorous plants, sphagnum mosses, frogs and dragonflies.

The bogs “superficially looked very nice,” Melkonian said in a more recent interview.

They had been restored and replanted decades after being drained for industrial activities such as logging. The restored wetlands provided habitat for wildlife and helped store carbon, an important tool in fighting climate change.

But Melkonian expected to find hundreds of species of the unusual desmid algae he studies beneath the water. Instead, he found only a handful.

“The diversity of algae was not there,” he said.

Sphaceleria, top, Stylonema, bottom left, and Stephanosphaera, bottom right. Some of the diverse algae in different habitats that Michael Melkonian and his colleagues are trying to preserve. (Gerd A. Guenther/Central Collection of Algal Cultures)

Viktoria Wagner, an associate professor in the Department of Biological Sciences at the University of Alberta, calls this kind of decline “a silent form of loss.”

Species do not necessarily become completely extinct, she explained. Instead, they can disappear from many of the places where they once lived, reducing the number of species found at individual sites.

Wagner refers to this as “dark diversity” and has found evidence of it among plants in habitats around the world. Algae are not technically plants, although they are related.

Once species disappear from a particular location, Melkonian said, “they may not come back easily.” Some could already be locally extinct.

This means species in restored forests and wetlands can remain missing even when the surrounding landscape appears to have recovered.

Wagner said restoring landscapes is possible, but “it’s not easy, it’s not always guaranteed that it works.”

Micrasterias rotata, another kind of freshwater desmid algae. (Gerd A. Guenther/Central Collection of Algal Cultures)

Missing Species May Slow Recovery

The loss of species in restored forests and wetlands can create effects that are difficult to see at first, particularly when small organisms play important roles in the ecosystem.

Despite their tiny size, Melkonian said algae have a huge influence on the planet’s supply of oxygen and food.

“It’s thought that algae in general are responsible for half of global photosynthesis,” he said.

Wagner said many species play important roles within ecosystems. When biodiversity declines, she said, the effects can “trickle down” and negatively affect other species.

In boreal forests, Macdonald said it is not surprising that mosses, lichens and other understory plants can take decades to return after a clearcut. Many depend on shade and old-growth trees for their habitat.

“That’s all the stuff that’s missing in a forest after harvesting and the things that take a really long time to recover,” she said. “You know, you can’t just get old big trees, except by waiting for trees to grow older.”

Lichen on a branch of an old spruce tree in a boreal forest. (E. Macdonald)

Understanding these recovery patterns could help people managing forests and other landscapes find better ways to protect biodiversity. It could also help explain why some species in restored forests and wetlands remain absent long after a habitat appears to have recovered.

For species in restored forests and wetlands, the availability of shade, old trees, water conditions and other specific habitat features can determine whether they are able to return.

Macdonald said the research suggests conifer forests could be harvested more selectively or partially instead of being completely clearcut.

An Algal ‘Zoo’

Melkonian said habitats supporting algae are also under threat around the world, along with the species that depend on them.

Many algae look like little more than a patch of colour on snow or a spot of slime on a rock or in water. They may not even look like living organisms to most people.

Melkonian carefully collects these tiny samples from different habitats, using spoons and pipettes to place them into vials.

Michael Melkonian at the Central Collection of Algal Cultures in Essen, Germany, in 2025. (Submitted by Michael Melkonian)

The work is part of an effort to preserve these species. Melkonian and his colleagues have collected and grown more than 5,000 strains.

“An algal zoo, if you wish … that’s a way maybe to ensure that we have a repository of these species as living organisms,” he said.

For Wagner, the widespread “silent loss” of species shows that protecting biodiversity requires more than preserving isolated pockets of habitat.

It also means maintaining and restoring enough habitat across the landscape so species in restored forests and wetlands can continue to survive.

Protecting these habitats may give species in restored forests and wetlands a better chance of returning and surviving over the long term.

“Loss happens all the time and it’s a continuous process and it needs active interventions.”

This is part of a series of articles highlighting the work of scientists looking at disappearing groups of species you may not have thought much about. It’s a chance to get to know them and how they impact our lives, and find out what can be done to keep them around.