Adventures in Lichenology

By: Julia McHugh

Rikke Reese Næsborg, Ph.D., has scaled a coast redwood (Sequoia sempervirens) in Big Basin Redwoods State Park and is now secured by ropes in the crown of the swaying, nearly 300-foottall (91-meters-tall) tree. After peering through a magnifying hand lens to examine tiny, complex organisms encrusting the tree’s bark, she makes a few notes before securing a small sample and carefully repelling back to the forest floor.

Rikke is Santa Barbara Botanic Garden’s lichenologist, one of only two paid, full-time lichenologists in California. She travels throughout California to perform inventories, collect specimens, and conduct studies of this unique, often misunderstood life form.

Happily foraging for lichen diversity 200 feet (60 meters) above the ground, Rikke Reese Næsborg, Ph.D., collects data in a coast redwood (Sequoia sempervirens).

Photo: Wendy Baxter

Many people think lichens are a type of moss, but they are not. They are neither plants nor animals, and not even a single organism. Lichens are unique organisms in which algae (or cyanobacteria) live among fungi in a mutually beneficial, or symbiotic, relationship. The fungi provide a structure and protection from the environment for the algae, while the algae use photosynthesis to produce food for themselves and the fungi. Lichens take no nutrients from the growing surface itself — instead they receive moisture and other nutrients from air. They can grow on nearly any undisturbed surface: bark, wood, rock, soil, glass, metal, plastic, and even cloth.

Macrolichens, more specifically gray lace lichen (Ramalina menziesii) and orange golden-eye lichen (Teloschistes chrysothalmus) are growing on an oak branch near Grass Mountain, Santa Barbara County.

Photo: Rikke Reese Næsborg, Ph.D.

That means lichens can grow almost anywhere on Earth — and they do. Incredibly diverse, there are more than 5,300 species of lichens in North America alone, and new species are discovered regularly. Rikke has described six new species, which involves giving them scientific names, and she has one more to describe.

Lichens can range in color from bright yellow, red, and orange to green, black, brown, silver, and gray, and they may change color when wet. Colors are usually a result of the lichen chemistry which may contain pigments. The chemical compounds have different functions such as protecting the lichen against excess sunlight or preventing herbivory (discouraging animals from feeding on them). Side products of these pigments are the vibrant colors. “Lichens are very complex little ecosystems in themselves,” says Rikke. “They even have been taken into space and

A tiny sliver of really hard rock on an otherwise highly erosive island offers a stable surface for lichens. Here, Tucker Lichenologist Rikke Reese Næsborg, Ph.D., hopes to discover species that are new additions to the San Nicolas Island’s biodiversity checklist. (Photo: Cameron Williams)

exposed to ultraviolet radiation and were still able to reproduce and photosynthesize when they returned to Earth.”

Recently, Rikke spent several days on San Nicolas Island, 61 miles (98 kilometers) off the California coastline. Managed by the U.S. Navy, it is usually off-limits to civilians, but she’s there to conduct a lichen inventory, which is expected to be completed by June 2023.

Four to five different species of microlichens are growing on a rock near Grass Mountain in Santa Barbara County. Notice the rusty-green moss to the left for scale.

Photo: Rikke Reese Næsborg, Ph.D.

Even more travel is required for another of her projects: a guidebook to macrolichens in California.

The “macro” in macrolichen not only refers to size but also to the growth form. These lichens appear bushlike or leafy, and their physical features are visible to the naked eye. All other lichens are called microlichens which look two-dimensional and often require a microscope for identification (See: A Magnified Look at Microlichens). “The research for the guide is taking place at the speed of lichenology, which means very, very slowly,” says Rikke. “The previous guide only included 300 of California’s lichen species, but there are 600 to 700 species of macrolichens in the state.”

Rikke also helps evaluate the extinction risk of California lichens for the International Union for Conservation of Nature’s Red List and works with the California Lichen Society and California Native Plant Society to evaluate possible endangered lichen species.

She earned her bachelor’s and master’s degrees at University of Southern Denmark and earned a doctorate in systematic botany from Uppsala University in Sweden. A California resident since 2011, she joined the Garden staff in February 2019 as the Tucker lichenologist and curator of the Garden’s Lichenarium.

The Lichenarium currently holds around 35,500 lichen specimens, but that’s about to change. The Garden is absorbing the entire lichen collection of more than 16,000 specimens from the Herbarium of the University of California, Riverside (UCR). The Garden also is the official repository for specimens from the Channel Islands National Park, which is one reason why the UCR Herbarium collection came here.

With the help of Lichenarium Technician Danielle Ward, Rikke is integrating the two collections, which will take at least a year. It means they handle every single specimen to add bar codes, update genus and species names, and confirm that specimen information is correct in the online database managed by the Consortium of North American Lichen Herbaria (LichenPortal.org).

Back in the redwoods, Rikke is involved in two studies. The first, in the southernmost part of the redwood range, explores environmental drivers behind the organization of lichen communities on the trees. We are finding that the redwoods are hosts to many more lichens than previously thought. These trees are incredibly species rich. We found over 100 species in one tree alone, and a lot of diversity even in new species. The second study, in northern California, examines the lichens that grow on other plants that also grow on the coast redwoods. That’s three layers — for example, a lichen on a huckleberry shrub (Vaccinium ovatum) on a redwood tree. “Epiphytes are plants that grow on other plants — ‘epi’ means ‘on top of’ and ‘phyte’ is ‘plant,’” says Rikke. “Lichens are also epiphytes, and this study focuses on the lichens growing on other epiphytes, namely huckleberry (Vaccinium ovatum and V. parvifolium) and western hemlock (Tsuga heterophylla), growing on redwoods.”

The goal of the second study is to identify any differences in the lichen communities on branches of redwood versus branches of epiphytic shrubs and trees. “We expect not just a difference but that the epiphytic shrubs and trees will host a more diverse lichen community, which amplifies the biodiversity contained within old-growth redwood forests,"

Rikke notes. Lichens face pressure from smog and other forms of air pollution, and their habitats are threatened by real estate development and fire. Rare or endangered lichens could be completely wiped out by fires in regions where they grow. Since it can take more than 50 years for a lichen population to recover, Rikke’s work is critical given the reality of a warming planet.

“Lichens are a big part of the planet’s ecosystem,” says Rikke. “They are the first to arrive after a glacier melts and contribute to soil-making by slowly breaking down rocks. Up to 50% of nitrogen and many other nutrients in a forest come from lichens. Reindeer depend on them for up to 90% of their winter diet, and they provide food and shelter for other animals. Not to mention, I’ve always enjoyed seeing when hummingbirds use lichens to decorate their nests.”

This hummingbird nest is decorated with pieces of ruffle lichen (Parmotrema sp.) and common greenshield lichen (Flavoparmelia caperata). Two hatchlings are cozying up in the nest.

Photo: Rikke Reese Næsborg, Ph.D.

It’s been 17 years since Rikke climbed her first tree, a giant sequoia (Sequoiadendron giganteum) in the Sierra Nevada. She recalls being terrified as she peered both above and below on her accent. However, she pushed on, all the way to the top. “In many ways, science in general and my research in particular is like my initial climb,” she says. “It can be challenging and a bit overwhelming, but it has the potential to lead to a greater understanding of our environment and it will hopefully increase protection of the natural world.”

A tiny sliver of really hard rock on an otherwise highly erosive island offers a stable surface for lichens. Here, Tucker Lichenologist Rikke Reese Næsborg, Ph.D., hopes to discover species that are new additions to the San Nicolas Island’s biodiversity checklist.

Photo: Cameron Williams