If you have been to Mount Nemo, or just about any park in Ontario, you have probably noticed that many of the trees and rocks are coated with a white, pale green, golden yellow or even rust red substance that looks a little like petrified moss and a little like some kind of terrestrial coral. But this substance is neither moss or coral.
It’s called lichen and, even though it looks like a single organism, it’s actually a composite organism—part fungus, part algae—that live together because they need each other to grow. The algae contain chlorophyll, which means that it can produce carbohydrates through the process of photosynthesis. The fungus, on the other hand, cannot produce its own carbohydrates, so it harvests it from the algae. In return, the fungus provides shelter for the algae.
The relationship that fungus and algae share as lichen is a symbiotic one but it isn’t the only relationship that these species are part of within the ecosystem around them. Lichens provide habitat for small insects, provide food for some animals, trap moisture and organic material to make barren surfaces more suitable for plants, bind sand and soil to prevent erosion and even break down rock surfaces to help form soil.
There are more than 20,000 species of lichen in the world and hundreds of them can be found here in Ontario. Not only are they beautiful and fascinating but, because different types of lichen prefer different growing conditions, they can tell us about a lot about our environment. Lichens do not possess roots, which means that they obtain most of their nutrients from the air. They also do not possess the layer, known as cuticles, that protects the shoots, stems, leaves and other parts of most plants, which means that they cannot filter pollutants from the air. As a result, lichens can be an accurate reflection of the quality of the air around them and a growing body of scientists and researchers are starting to use this in their studies.
Here in Canada, the Ecological Monitoring and Assessment Network (EMAN) uses a crowd-sourced monitoring program, NatureWatch, to collect data on everything from when the plants bloom to where milkweed is growing to what kinds of frogs are in a wetland to how many earth worms are under ground. Recently, NatureWatch has started looking at lichen.
In 2004, Earth Sciences Professor at Brock University, Dan McCarthy, used EMAN methods to look at the lichens on trees throughout Hamilton and found that there were “lichen deserts” throughout the city. In the industrial north end of the city, lichen was sparse. The closer you came to the escarpment, the more lichen there was. On the other hand, lichen was abundant in parts of the Dundas Valley. He then did a chemical analysis of the lichens from those industrial areas and found that they were filled with pollutants.
In 2011, McMaster University biologist and environmental activist, George Sorger, conducted similar research throughout Hamilton. He found that there was much less lichen in areas that had high levels of sulphur dioxide and nitrogen dioxide in the air, which is a known indicator of poor air quality. On the other hand, there was lots of lichen found in areas that had low levels of these pollutants.
It is more or less accepted in the scientific community that lichen can be used to monitor air quality but scientists in other parts of the world are starting to use lichen as an indicator of climate change — because it isn’t just air that lichen need to live. Like plants, lichen need water, but because lichen don’t have roots to obtain water from the soil, they absorb water from the atmosphere like a sponge. Also, unlike plants, they don’t have cuticle to seal that water in, so they lose water easily, which makes them vulnerable to hot or dry conditions. Even small changes in climate can impact lichen communities.
Sometimes, this impact looks like “range expansion” as lichen communities move in latitude, either north or south, or in elevation, either higher or lower, depending on their preference. Other times, this looks like lichen species that prefer certain climates appearing in areas where they have never been or disappearing from areas were they have always been.
For instance, some lichen species that prefer warm temperatures have recently been found in countries with cooler climates, such as Germany and the Netherlands. Research conducted in some southern parts of Alaska found that, as the climate changed, there was dramatic and rapid disappearance of lichen species that preferred a particular climate. Researchers were also able to pinpoint areas where they anticipate this disappearance to occur as a result of climate change.
Lichen has proven to be a promising indicator of climate change in these parts of the world—it might even be able to indicate climate changes before other plants, insects or animals—but there isn’t much research on using it here in Canada. Part of the reason for this is because we don’t have great records of what lichen species are present, where they can be found and which ones are sensitive to environmental change, so there isn’t much baseline data. Numerous government departments, including Conservation Halton, have been monitoring lichen communities for decades but there isn’t any standard monitoring protocol for lichens in Canada, which makes it difficult to use this data. The other reason is that the lichen monitoring that is conducted as part of EMAN has been more focused on air quality than climate change.
The use of lichens as an indicator of climate change is still a new concept but it’s one worth pursuing. This unassuming but impressive species has proven its ability to take the pulse of the natural world and, with a little planning, lichen could even help predict the future.
Last modified: July 3, 2018