Lichens are fascinating composite organisms that form through a symbiotic relationship between fungi and algae. Although they may resemble plants, they are not true plants. Instead, lichens derive their nutrients through photosynthesis, with the algae component producing food while the fungi provide structure and protection.
Because of their adaptability, lichens are found in nearly every environment on Earth, from arid deserts to lush forests and even the frozen tundra. They are capable of growing on an astonishing variety of surfaces, including rocks, tree bark, soil, and even man-made structures. In North America alone, scientists have identified approximately 3,600 different species of lichens, with new discoveries still being made each year.
Lichens take on a variety of physical forms, each uniquely suited to their specific habitat. Some species grow in a branched, shrub-like structure, while others resemble delicate leaves, a thin crust, or even a fine powder. Their diversity in shape and color makes them a striking feature in many landscapes. Despite their fragile appearance, lichens are remarkably resilient. Many species are incredibly long-lived, with some believed to be among the oldest living organisms on the planet. Because they are able to colonize barren surfaces, lichens are often the first life forms to establish themselves on freshly exposed rock. Over time, their slow but persistent growth plays a crucial role in breaking down rock into soil, paving the way for more complex plant life to take root.
Lichens cover approximately 7% of Earth’s surface, making them an important contributor to many ecosystems. They are particularly vital in the Arctic tundra, where harsh conditions limit plant growth. In these extreme environments, lichens grow alongside mosses and liverworts, forming a dense ground cover that helps insulate the soil and regulate temperature. This ground cover also serves as a primary food source for grazing animals such as caribou. The caribou, known as reindeer when domesticated, rely on lichens for sustenance, particularly in the winter months when other vegetation is scarce.
Reindeer herding has long been an important part of Indigenous Arctic cultures, particularly among the Sámi people of Scandinavia and the Inuvialuit of Canada. In March 1898, a significant reindeer herd was transported from Norway to North America in an ambitious effort to introduce domesticated reindeer to Alaska. The journey was an arduous one. A herd of 539 reindeer was first shipped across the Atlantic to New York. From there, the animals were transported by rail across the United States to Seattle, where they were loaded onto boats bound for Alaska. However, the expedition faced unexpected challenges—one of the most critical being a shortage of lichen to feed the animals. Without their primary food source, only 134 of the original 539 reindeer survived the journey.
Despite this initial setback, the reindeer population in North America eventually flourished. Today, the Canadian Arctic is home to a managed, free-ranging herd of roughly 6,000 animals, overseen by the Inuvialuit. These reindeer continue to play a crucial role in the region, both ecologically and economically.
Beyond their importance as a food source for Arctic wildlife, lichens also play a significant role in shaping the natural landscape. When they grow on rock surfaces, they gradually break down the minerals through chemical and physical weathering. Over time, this process contributes to soil formation, making it possible for other plant life to grow. While this slow degradation is beneficial in nature, it can become a problem when lichens grow on human-made stone structures.
One of the most well-known examples of this issue is Mount Rushmore in South Dakota. The granite faces of the monument are continually affected by lichen growth, which can weaken the stone over time. Because of this, maintenance crews must regularly remove lichens to preserve the integrity of the monument. Interestingly, rock climbers are sometimes hired for this task, scaling the enormous carvings to carefully clean the surfaces without causing additional damage.
Lichens are a remarkable example of nature’s resilience and adaptability. Their ability to thrive in some of the most extreme conditions on Earth makes them an essential part of many ecosystems. Whether providing food for Arctic wildlife, contributing to soil formation, or even posing challenges for historic monuments, lichens continue to leave their mark on the world in ways both subtle and profound.
