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Photos: Gregory Han

I came across Nature all Around Us: A Guide to Urban Ecology the other day, remembering briefly flipping through its pages as a student. I decided to read it during my commute last week, remembering how the book’s subtitle first caught my eye. “A Guide to Urban Ecology”– the book’s subtitle made me ponder the meaning of the word ‘ecology’, formulating a picture in my mind about what systems come into play out in nature versus urban ecology.

Nature all Around Us sheds some light on the subject, utilizing explanations spanning across micro to macro scales of basic ecological concepts and processes.  Of the numerous takeaways and inspirations discovered within the pages of this book, I’m motivated to focus on a single topic of interest: lichens.

Ecology is first and foremost a science, an interdisciplinary field related to the landscape, and in turn indirectly to our profession. With this foundation recognized, the authors go into detail to define landscape ecology as, “A branch of ecology that emphasizes the relation between patterns, processes, and scales, focusing on broad-scale ecological and environmental issues.  Studies often consider large spatial scales and examine the relation between human or natural development and ecological processes.”

Simply put, urban ecology is the science of those processes and relationships between living organisms (plants, animals, insects, us, etc.) occurring within the urban environment that we commonly live and interact with.  And one of the many, many things these ever-changing relationships impact is the appearance of lichens, a symbiosis of algae and fungi, and also are an important bioindicator of a healthy urban environment.

Before reading Nature all Around Us, I mistakenly believed lichen a parasite. Nor did I know about the distinct difference between lichen and moss. When I researched more about lichens found growing on rocks and the trunks of older trees (which remain unharmed by the lichen), I discovered a stunning variety of forms, textures, and colors, including a spectacular seafoam blue-green.

Photo: Gregory Han

Lichen discovered along the Morro Bay coast growing on cypress trees. Photo: Gregory Han

Tree lichen are uncommon in Southern California. Why don’t we see more of them growing on our trees?  In short: air quality. Pollutants in our air are absorbed by lichens, a slow grower to begin with; lichen lack a filtering mechanism for these chemicals, thus rendering them unable to survive around our urban environments. Additionally, populations of older trees with lichen growth have been cut down in favor of urban sprawl.

Lichen go above and beyond mere bioindicators. They are capable of filtering light radiation, inhibit algae growth, provide protection from herbivores, and protect both parties in their mutualistic relationship (lichen and trees) with antibiotic properties.

Furthermore, lichen are beneficial to humans too. Lichens can be used to produce antibiotics for medicine,  and ingredients for cosmetics, perfumes, and paints! As is often the case, I’m amazed how nature is able to accomplish so much with so little – small organisms operating silently behind the scenes, easily unnoticed, yet too important to our ecosystems at large. The unique beauty of tree lichen, the benefits they offer, and their integral relationship to our environment is all the more reason to work toward improving air quality.  Next time I gaze up at our trees to observe a perched bird, springtime blooms, or the falling leaves in autumn, I now know to keep an eye out for another of nature’s beauties.

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