Kiera Jefferson
Lichens are highly sensitive to air pollution and can act as an early warning system for chemically sensitive vascular plants. They absorb nutrients and water from the air through rain and dust, and pollutants can accumulate in them, becoming toxic quickly. Sulphur and nitrogen dioxide are two major air pollutants that affect lichen growth. Sulphur dioxide pollution from coal burning and industry has killed many lichens, while nitrogen oxides from car engines and farm emissions can harm human health. Lichens are bioindicators of air quality, and their presence or absence indicates the level of pollution. They are also used to monitor the quality of their environment and the potential health risks associated with it.
| Characteristics | Values |
|---|---|
| Use as pollution indicators | Lichens are sensitive to air pollution and can indicate the quality of the air in their environment. |
| Sensitivity to nitrogen | Nitrogen deposition can harm and kill lichens. Nitrogen dioxide is a powerful pollutant that can be harmful to human health. |
| Sensitivity to sulphur | Sulphur dioxide is a pollutant that has killed many lichens. |
| Impact on growth | Air pollutants can reduce the growth of lichens and cause discolouration. |
| Impact on reproduction | Air pollutants can affect the reproductive potential of lichens. |
| Impact on morphology | Air pollutants can cause structural changes in lichens, including reduced photosynthesis and bleaching. |
| Impact on physiology | Air pollutants can affect a wide variety of physiological processes in lichens. |
| Impact on ultrastructure | Air pollutants can cause ultrastructural changes in lichens. |
| Tolerance | Some lichen species are more tolerant of pollution than others. Crustose lichens are the most tolerant, while shrubby and leafy lichens are the most sensitive. |
| Distribution | Pollution-tolerant lichen species are more commonly found in areas with poor air quality. |
| Species loss | Industrialisation and pollution have led to the decline and extinction of many lichen species. |
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What You'll Learn
- Lichens are sensitive to nitrogen, sulphur, acidity, halogens, heavy metals and ozone
- Lichens absorb pollutants from the air, through rain and dust
- Lichens can indicate air quality—the more polluted the air, the less variety and the smaller the lichens
- Lichens have been used as indicators of air quality for over a century
- Lichens can develop structural changes in response to air pollution, including reduced photosynthesis and bleaching
Lichens are sensitive to nitrogen, sulphur, acidity, halogens, heavy metals and ozone
Lichens are highly sensitive to nitrogen, sulphur, acidity, halogens, heavy metals, and ozone. Due to their unique composition, they are highly susceptible to changes in atmospheric chemistry and deposition, making them excellent bioindicators of ecological health.
Nitrogen
Lichens are very sensitive to nitrogen availability in their environment. Nitrogen is a macronutrient and plays a crucial role in the growth of lichens and their host plants. Some lichens can fix nitrogen from the atmosphere with the help of cyanobacteria, allowing them to survive in nutrient-poor environments. However, an increase in nitrogen availability can negatively affect lichens, especially when it comes from nitrogen-based agricultural fertilizers and atmospheric pollution. Nitrogen oxides, formed when nitrogen is heated and combined with oxygen, are powerful pollutants that can harm human health and impact lichen growth.
Sulphur
Sulphur dioxide (SO2) pollution, resulting from coal burning and industrial activities, has been detrimental to lichens in the past. High concentrations of sulphur dioxide can irritate the mucus lining of the eyes, nose, throat, and lungs, causing coughing and respiratory issues. Lichens like Usnea, commonly known as old man's beard, are absent in areas with sulphur dioxide pollution. With the reduction in coal burning, sulphur dioxide levels have decreased, allowing some lichens to return.
Acidity
Lichens also exhibit varying sensitivities to acidity (pH). Some lichens prefer acidic environments, while others are sensitive to acid deposition. Changes in acidity levels can shift the composition of lichen species, favoring those that are more tolerant of acidity. High levels of ammonia, for example, have led to the disappearance of acid-loving lichen species in certain regions.
Heavy Metals
Lichens are valuable bioindicators of heavy metal pollution in ecosystems. They can accumulate fine particles containing heavy metals, such as arsenic, in their surface and intercellular spaces, retaining them for prolonged periods. By studying the physiological responses of lichens, scientists can assess the presence and impact of heavy metals on the ecosystem.
Ozone
Ozone, particularly when reacting with nitrogen compounds, can contribute to the formation of nitrogen oxides, which are harmful pollutants. While the direct impact of ozone on lichens requires further investigation, the presence of nitrogen oxides in the atmosphere can influence lichen growth and distribution.
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Lichens absorb pollutants from the air, through rain and dust
Lichens are composite organisms made of fungus and algae or cyanobacteria. They are sensitive to air pollution and can act as indicators of air quality. They absorb water, minerals, and pollutants from the air, through rain and dust. This is because they have no roots or protective surface to filter what they absorb, so anything in the air is taken straight inside.
Lichens are exposed to their environment, and rainwater and air directly enter the organism. Dust is trapped between mycelium filaments, and lichenic acids fix pollutants. This makes them true "sponges" that recover compounds present in the atmosphere throughout the year and throughout their life cycle. Lichens can absorb more sulphur dioxide (SO2) for a given concentration than typical vascular plants. Sulphur dioxide is a pollutant produced by burning coal and through industrial processes. In the past, it has killed many lichens in the UK, but now that coal burning has reduced, lichen populations are recovering.
Lichens are also sensitive to nitrogen (N) in the air. Nitrogen oxides are created when nitrogen is heated and combined with oxygen, as in a car engine. Nitrogen dioxide is a powerful pollutant and is harmful to human health in high concentrations. Lichens can absorb nitrogen through both nitrate (NO3-) and ammonium (NH4+) forms. Nitrogen deposition can increase the load of nutrients, harming or killing the algae's chlorophyll, which feeds the lichen.
Scientists monitor the health of lichens and pair this data with atmospheric deposition data to determine the sources and levels of pollution causing detrimental effects. Lichens can indicate the presence of pollutants and the effects of air pollution on ecosystems. They can also be used to study the historical presence of pollutants, as seen with the rise in atmospheric lead deposition in the early 20th century.
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Lichens can indicate air quality—the more polluted the air, the less variety and the smaller the lichens
Lichens are sensitive to air pollution and can act as bioindicators of air quality. They are like sponges, absorbing water, minerals, and pollutants from the air through rain and dust. Due to their unique biology, they are especially sensitive to sulphur dioxide and nitrogen. Sulphur dioxide is produced by coal burning and industry, and nitrogen is produced by car engines and farm emissions. When exposed to these pollutants, lichens can exhibit structural changes such as reduced photosynthesis and bleaching, and can even die.
Lichens have been used as bioindicators of air quality for over a century in Europe. Their presence or absence in an environment can indicate the level of air pollution. For example, if there are no lichens present, the air quality is very poor. Only crusty lichens like Lecanora conizaeoides or Lepraria incana can tolerate high levels of sulphur dioxide. In moderate to good air quality, leafy lichens such as Parmelia caperata or Evernia prunastri can survive. In areas with very clean air, rare species like Usnea articulata or Teloschistes flavicans may grow.
The variety and size of lichens in an area can also indicate the level of air pollution. Generally, the less variety and the smaller the lichens, the more polluted the air is. Lichens with higher sensitivity to pollutants include shrubby and leafy species, while crustose lichens are more tolerant. Scientists monitor the health of lichens and pair this data with atmospheric deposition data to determine the sources and levels of pollution.
In the United States, lichens from Plummers Island, Maryland, showed a dramatic rise in atmospheric lead deposition before the 1980s, coinciding with the construction of a bridge and the use of leaded gasoline. As a result of industrialisation, many lichen species have become extinct or seen their ranges contract in large areas of lowland Britain. However, with the decrease in coal burning and the implementation of policies to reduce nitrogen deposition, some lichen species are beginning to return and recolonise these areas.
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Lichens have been used as indicators of air quality for over a century
Lichens have no physical means of defence against their environment, so they behave like sponges, absorbing water, minerals, and pollutants from the air. This makes them very sensitive to changes in air quality, and they can quickly become toxic if exposed to high levels of pollution. Their sensitivity means they can act as an early warning system for chemically sensitive vascular plants, indicating potential ecosystem decline due to pollution. Scientists monitor the health of lichens and pair this data with atmospheric deposition data to determine the sources and levels of pollution.
The presence of certain lichen species in an area can indicate the typical levels of sulphur dioxide and nitrogen oxides. For example, the oakmoss lichen is sensitive to nitrogen in the air and can be found in clean environments. In contrast, pollution-tolerant species like Flavoparmelia caperata can be found in areas with poor air quality. The variety and size of lichens in an area can also indicate pollution levels, with fewer and smaller lichens generally indicating more pollution.
Lichens have been used to monitor air quality in Europe for over a century. For example, in the 19th century, lichenologist Wilhelm Nylander observed the total disappearance of lichens in the Jardin du Luxembourg in Paris due to sulphur dioxide pollution from coal heating and industrial changes. Similarly, lichens from Plummers Island, Maryland, showed a dramatic rise in atmospheric lead deposition in the 20th century, coinciding with the construction of a bridge and the use of leaded gasoline.
Overall, lichens are valuable bioindicators of air quality due to their sensitivity to pollutants, their ability to absorb and accumulate pollutants, and their long-term presence in ecosystems.
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Lichens can develop structural changes in response to air pollution, including reduced photosynthesis and bleaching
Lichens are sensitive to air pollution due to their unique biology. They absorb nutrients and water from their surroundings, including pollutants in the air, rainwater, and dust. This makes them excellent bioindicators of air quality.
Lichens do not have any physical means of defence against their environment, so they absorb pollutants directly. This can lead to structural changes in lichens, including reduced photosynthesis and bleaching.
The algae in lichens photosynthesize, creating food from sunlight energy. When exposed to pollution, the algae's chlorophyll, which is used to produce sugars, can be harmed or killed. This reduces the lichen's ability to photosynthesize, leading to slower growth and even death.
Additionally, pollution can cause discoloration in lichens. The fungi in lichens can also be affected by pollution, leading to reduced growth or the complete death of the lichen. Over time, sensitive lichen species may be replaced by pollution-tolerant species. For example, Flavoparmelia caperata is a pollution-tolerant lichen species that has been found in areas with poor air quality.
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Frequently asked questions
Lichens absorb pollutants from the air, through rain and dust. They can become toxic and die due to pollution. They are very sensitive to air pollution and make good air quality indicators.
Nitrogen and sulphur dioxide are two major air pollutants that affect lichens. Other examples include nitrogen oxides, lead, and heavy metals.
Lichens are sensitive to atmospheric pollution and can absorb pollutants from their surroundings. By studying the health of lichens and pairing this data with atmospheric deposition data, scientists can determine the sources and levels of pollution.
Pollution-sensitive lichen species may be replaced by pollution-tolerant species over time. As a result, certain lichen species have become extinct or confined to areas with cleaner air due to industrialization and pollution.
Exposure to pollutants can lead to reduced photosynthesis, bleaching, discoloration, and reduced growth of lichens. It can also cause the death of the lichen algae and even kill the lichen completely.
