Reasons why lichens do not like to grow in cities:
There are several factors that contribute to the reluctance of lichens to grow in cities. These include:
1. SO₂ pollution: Lichens are highly sensitive to air pollution, particularly sulfur dioxide (SO₂) emissions. Cities tend to have high levels of air pollution due to industrial activities, vehicle emissions, and other human activities. The presence of SO₂ in the air can be toxic to lichens and inhibit their growth.
2. Missing natural habitat: Lichens typically thrive in natural environments such as forests, grasslands, and wetlands. Cities, on the other hand, are characterized by concrete structures, asphalt roads, and limited green spaces. This lack of natural habitat and suitable substrate for lichen growth makes cities unfavorable for their establishment and development.
3. Absence of right type of algae and fungi: Lichens are symbiotic organisms composed of a fungus and an alga or cyanobacterium. The availability of the right combination of algae or fungi is crucial for lichen growth. Urban environments often lack the specific species of algae and fungi that are compatible with each other to form lichens.
4. Lack of moisture: Lichens require a certain level of moisture to survive and grow. In cities, the presence of impervious surfaces like concrete and asphalt limits the absorption of water into the ground, resulting in reduced moisture availability for lichens. Additionally, urban heat island effects can lead to increased evaporation, further exacerbating the lack of moisture.
In conclusion, lichens do not like to grow in cities primarily due to SO₂ pollution, the absence of natural habitat, the lack of the right type of algae and fungi, and the limited availability of moisture. These factors make urban environments inhospitable for lichens, which prefer more pristine and natural habitats.