Some of Earth’s earliest forms of life on this planet date back 3.5 billion years! Life started about 3.5 billion years ago as algae and about 1.5 billion years ago, fungus began to take form. Over time, each life form evolved, diversified, and branched into new strains as the earth’s environments continued to develop and take shape.
Algae, Fungus, and Plants
For about one billion years, algae and fungus filled virtually every land mass that they could adapt to. 700 million years ago, land plants began to evolve and were slowly changing the landscape and ecosystem.
What was previously barren rock across the planet began to grow into the first forests! These forests were made up of giant horsetails, club mosses, and ferns that could grow up to 40 feet tall. These forested regions became damp and humus-rich environments. Because of that, algae and fungus could enjoy a new partner in the evolution and development of our planet’s growth.
Algae began to thrive in the damp environment among the basal shoots of early ferns, capturing what sunlight it could get through the forest floor for food. In the meantime, fungus found nourishment in the leaves and roots of the new plant varieties. It was only a matter of time before these two species would find themselves embraced in a relationship that would spawn the birth of a new branch within the fungal kingdom!
An Unplanned Union
It’s unclear who the culprit was but botanists suspect that sometime around 250 million years ago, a fungal spore from a ‘cup shaped’ fungus settled on an algae and took root. This root produced filaments that surrounded the cells of the algae and took hold with a hugging embrace. Sugars produced by the algae through photosynthesis gave nourishment to the developing fungus, which was then able to thrive and grow.
As the fungus continued to grow over the algae, it sheltered the algae from the weather, taking on a new form. The fungus also helped the algae absorb water by holding moisture in its encrusted fleshy folds. In return, the fungus continued to acquire nutrients from the algae. A new symbiotic relationship ensued and as evolution would have it, another fungal species was born!
The Greeks would call this plant “leikhēn” meaning ‘what eats around itself’.
The Arrival of Lichen
Small pieces of lichen would break off in easily the wind, allowing it to spread extremely quickly and efficiently. One fragment contained both partners of fungus and algae, so growth of a new lichen would begin immediately. Because of this, it didn’t take long for the lichen to find its niche in the world.
The ability to quickly absorb and retain water from many sources made it possible for lichens to live in the newly developing environments. The lichen was able to absorb moisture from dew or fog, even from the air itself if the humidity is very high and the temperature is low. And the lichen showed a remarkable resistance to drought. A dry lichen can quickly absorb from 3 to 35 times its weight in water!
This natural and unusual adaptability allowed the lichen to successfully colonize many different habitats.
Exposed faces of bare rock, solidified lava, tree surfaces, desert regions and even glacial fields were soon the home of lichen. It was this cooperation between algae and fungus that helped conquer the inhospitable territory that was previously the bare and lifeless surface of the continents.
The Diversity of Lichen
For the millions of years that followed, lichens pioneered the way into new territory, adapting with its environment by small evolutionary changes. The ability to travel by wind, water, spore reproduction and even animal encounters proved to be flourishing and soon every corner of the globe was touched by some variation of lichen.
Some would grow into crispy patches, leafy mats, or branching growths, on tree bark or wood. Others became powdery or crusty, and some resembled shrubs, beards, or cups. Lichens become most colorful in wet weather, often gray or green in color, but they would typically shrivel and fade during dry spells to protect their algae from drying out. When it rained again, the lichen expands and photosynthesis could resume.
Today, there are over 13,500 named lichen varieties in the world and they cover 6-8% of the lands earth surface.
Did you know that about 400 species of lichen can be found on Cape Cod?!
Lichens and Trees
Lichens are not harmful to trees and can actually be an indicator of good air quality. In fact, removing lichen from trees can damage the bark and create entry points for pests and disease. Lichen rarely develop on rapidly growing trees, probably because the bark is shed before the lichen has time to spread. There may be more lichen on a mature, declining, or less vigorous tree, due to a slower growth rate, but lichen themselves do not cause the trees to decline.
Lichen Can Only Grow in Clean Air Environments
Lichen are, and have always been, highly sensitive to changes in air pollution, especially nitrogen and sulfur containing pollutants. Some sensitive lichen species can develop structural changes in response to air pollution, such as reduced photosynthesis, bleaching, and discoloration. Pollution can also cause the death of the lichen algae, or kill the lichen completely.
Lichens have been used as bioindicators of air quality in Europe for more than a century. Scientists study the types of lichens present and the size of the lichens. Large individual lichens generally mean better air quality. Shrubby and leaflike lichens can only survive in clean air, and lichens are relatively rare in large cities.
If you see lichen where you are, take a long and deep inhale! This more than likely means that you’re in a place with clean air. We’re lucky to have a large presence of lichen among us here in Cape Cod.
Nature’s Role
Some say that everything in nature has a purpose and that everything together makes the whole. Our forests, rivers, oceans and soils provide us with the food we eat, the air we breathe, the water we irrigate our crops with. Insects help sustain the ecosystems by pollinating and aerating soil. Animals keep nature running smoothly and maintain harmony and balance. All organisms have a purpose because they are about something for something and lichens are a prime example!
Lichen and Our Environment
Mother Nature is constantly innovating, experimenting, adapting and evolving. Nature produces new mutations all the time, yet many of them fail. But sometimes a new variation finds its ecological niche and thrives!
This success doesn’t come from any kind of plan, but rather from nature throwing around new ideas and seeing which ones succeed or fail. 250 million years ago, when a fungus spore met with an algae, nature had no idea what would happen (or maybe she did!). The chance coupling of algae and fungus would create a new organism changed the landscape of the earth forever in a hugely positive way.
Facts About Lichen
- Lichen that grow on rocks use pressure and chemical action to wedge apart pieces of rock. Their acidic secondary products help dissolve the rock’s surface, releasing mineral grains. Over centuries, this process can weather nutrients from barren rock and form thin soils that other plants can colonize.
- Lichen enables algae to live all over the world in many different climates. The photosynthetic ability of the algae converts carbon dioxide into oxygen, which we all need to survive.
- Lichen contributes nutrients to the soil through weathering minerals from rocks and incorporating them into their bodies. When lichen decomposes, these nutrients become available to other plants.
- Lichen also captures and slowly releases nutrients from rain, dew, fog, air-borne particles, and gases.
- Cyanobacteria lichen converts atmospheric nitrogen into forms that can be used by other plants and animals.
- Lichen protects trees and rocks from extreme elements like rain, wind, and snow. They also hold moisture when growing on trees, which moderates the humidity and temperature within the canopy.
- Lichen can help detect air pollution.
- Lichen are a food source for many animals, including deer, birds, and rodents. They also provide nesting materials for birds.
- Some insects living among the lichen have adapted their appearance, blending in with the habitat.
- Lichens can add color and beauty to natural areas. For example, the long drapes of bearded lichen (old mans beard) can grow to be five feet long hanging off the branches in humid mountainous regions of the North Pacific and Northeast. The reds, yellows, and greens of crust lichens decorate the Rocky Mountains.
Lichen’s Impact on The Human Race
Man has discovered and utilized many uses of lichen over the years. Their sensitivity to air pollution has been used to map different concentrations of pollutants. Some lichen compounds are used as anti-viral and anti-bacterial medications. Dyes and perfumes are made using secondary compounds found in lichen. Lichen dye is also used to make litmus paper, to test the acidity of liquids. The litmus dye turns blue in “basic” (low-acid) solutions like ammonia, and red in acid solutions like vinegar.
Lichens can also be an important food source in extreme environments.
The Lapp people, who live above the Arctic Circle in Scandinavia and Russia, harvest lichens as winter food for their reindeer. Sheep in the deserts of Libya survive, in part, by eating crustose lichen that grows on rocks. Some lichen species are edible by humans and have been used as food in many cultures throughout history.
It’s easy to accuse lichen as being damaging when we see dying trees and shrubs that are encrusted with it. Much like believing that all bugs are bad because a few are known to eat your plants or all ants are problems because a few invaded your house. Wrong assumptions can be made based upon first impressions. By taking the time to step back and educate ourselves to natures wonders, we begin to realize that everything created truly does serves a purpose.
Good or bad, nature finds a way to balance things out, and for this symbiotic story…..lichen or not, they are here to stay!
–Agway’s David Christopher