Lea's Bog Lichen: Rescued From Ash Trees

A Race Against a Beetle

Along wooded creek bottoms near Cincinnati, a conservation team spent recent weeks doing something that sounds almost like surgery for trees: carefully prying loose fist-sized chunks of bark colonized by one of North America's rarest lichens and moving them, by hand, onto healthier neighboring trees. The species at the center of the effort is Lea's Bog Lichen (Phaeophyscia leana), a pale, leafy lichen that grows almost exclusively on the bark of mature ash trees in bottomland forests of the eastern United States.

The rescue, reported by the Cincinnati Museum Center, was prompted by the emerald ash borer, an invasive beetle that has killed hundreds of millions of ash trees across North America since it was first detected in Michigan in 2002. As ash trees die, their bark sloughs off, and any lichen clinging to it disappears along with the tree. For a species that depends almost entirely on ash bark as habitat, that spells a compounding crisis on top of an already precarious existence.

Lea's Bog Lichen is classified as Endangered on the IUCN Red List, and its population size remains poorly documented — a data gap common among lichens, which rarely receive the survey attention given to birds or mammals despite their outsized ecological role. You can view the species' full profile, including its conservation status, on the Lea's Bog Lichen species page.

What the Transplant Actually Involved

According to the Cincinnati Museum Center's account, botanists and citizen-science volunteers identified ash trees in decline that still hosted colonies of the lichen, then extracted sections of bark bearing the organism and affixed them to trunks of surviving, disease-free trees nearby. The logic is straightforward but delicate: lichens grow slowly and cannot simply be replanted like a sapling. Success depends on matching light exposure, bark texture, and moisture conditions closely enough that the transplanted fragment can re-establish itself before it dries out or is dislodged.

This kind of active, hands-on intervention is unusual in lichen conservation, a field that has historically leaned on habitat protection rather than direct translocation. It reflects a growing recognition among botanists that some species are declining too fast, and too specifically tied to a vanishing host, for passive protection alone to work.

Why Ash Trees Matter So Much

Lea's Bog Lichen's fate is bound tightly to a single genus of tree, which makes it a useful case study in how narrow habitat specialization can turn one invasive insect into an existential threat for an entirely different, seemingly unrelated organism.

• Host specificity: The lichen grows almost exclusively on ash bark, offering it few alternative substrates when ash trees die en masse.
• Emerald ash borer spread: The beetle has devastated ash populations across dozens of U.S. states and parts of Canada since its introduction, with mortality rates approaching total loss in many untreated stands.
• Slow recolonization: Lichens grow at a fraction of the pace of vascular plants, meaning natural recovery after a host tree's death can take decades, if it happens at all.
• Limited range: The species is already known from a restricted set of bottomland forest sites in the eastern U.S., leaving little room for population loss before local extirpation becomes a real risk.

The Broader Lichen Conservation Picture

Lichens occupy a strange blind spot in conservation funding and public attention. They are neither fully plant nor fully fungus — technically a symbiotic partnership between a fungus and an alga or cyanobacterium — and they rarely inspire the same urgency as a tiger or a coral reef. Yet lichens perform essential ecological work: they stabilize soil, contribute to nutrient cycling, and serve as sensitive indicators of air quality, since many species cannot tolerate pollution.

The Endangered status assigned to Lea's Bog Lichen places it among a relatively small number of lichen species that have undergone formal IUCN Red List assessment at all. Most of the world's estimated 20,000-plus lichen species have never been evaluated, meaning population trends for the group as a whole are largely invisible in the same way this species' numbers remain unquantified. That data gap is part of why direct interventions like the Cincinnati transplant effort draw attention: they represent one of the few instances where a lichen's decline has been tracked closely enough to justify — and fund — physical rescue.

What Comes Next

The transplanted colonies will need monitoring over multiple growing seasons to determine whether they have successfully re-established on their new host trees. Lichen translocation is not a guaranteed fix — success rates vary depending on how well the microclimate of the donor and recipient trees align — but it buys time while longer-term ash tree recovery efforts, including breeding of borer-resistant ash varieties and biological control using parasitic wasps, continue elsewhere in the region.

For a species already living on the margins, the effort represents a rare second chance, and a signal that conservation attention is slowly expanding to include organisms most people will never notice growing on a tree trunk.

Frequently Asked Questions

What is Lea's Bog Lichen?

It is a rare lichen, scientifically named Phaeophyscia leana, that grows almost exclusively on the bark of ash trees in eastern U.S. bottomland forests and is classified as Endangered on the IUCN Red List.

Why is the emerald ash borer a threat to a lichen?

Because the lichen depends on living ash bark as its habitat, the beetle's destruction of ash trees removes the surface the lichen needs to survive, effectively causing habitat loss even though the beetle never touches the lichen directly.

How does a lichen transplant work?

Conservationists remove bark fragments colonized by the lichen from dying trees and attach them to healthy trees with similar light and moisture conditions, hoping the lichen re-establishes before the fragment dries out.

Is this kind of rescue common for lichens?

No — most lichen conservation focuses on protecting existing habitat rather than physically moving organisms, making this transplant effort an unusual and closely watched approach.