Lichens, the silent guardians of our ecosystem, are under threat from climate change and need to be saved, write BKP Sinha and Arvind Kumar Jha
Vibrant patches of colour adorning some tree trunks and rocks may draw your attention as you move in the forest. Although they appear as mere stains or growths; they are intricate organisms called lichens, a product of a mutualistic alliance between fungus and algae. Making it a unique creation of nature, the fungus absorbs water and nutrients from the air while an organic compound is generated by the photosynthetic partner. Thus while fungi build a house; its algal partner supplies food as the breadwinner. Similarly, if fungi did not provide a secure structure, the algae would die homeless in harsh places.
The absence of cuticles and roots and their direct reliance on the atmosphere for nutrients, however, makes lichens highly vulnerable to pollutants. Found in a variety of shapes and colours, ranging from delicate leafy structures to crusty patches, they thrive in diverse habitats, from rocky mountainsides to rain forests and deserts. They can grow on soil, humus, stones, rocks, bricks, plaster, leaves, tree trunks, decaying wood and even on glass. Overtly so simple and insignificant in the face of the dominant bias of human beings that often considers a forest just as an assemblage of trees and vegetation mix, lichens play an extremely vital role in ecosystems. Lichens are known to play a crucial role in soil formation, breaking down rocks through biogeochemical and biochemical weathering and creating nutrient-rich soil paving the way for other plants to grow. They produce unique compounds with potential medicinal properties, such as antibiotics and antifungals.
They are used in medicine, food, fodder, perfume, spices, and dyes. Researchers are exploring these compounds to develop new drugs and sustainable materials. By understanding the adaptations and biochemical properties of lichens, one can unlock new possibilities and contribute to a more sustainable future. Lichens can survive at extreme temperatures and altitudes in which no creatures can survive. One can see more lichen on the edge of the forest than deep in the forest. They will be lesser near the towns as the air quality deteriorates Many lichens are incredibly sensitive to air pollution, particularly due to sulphur dioxide and nitrogen oxides, as also to the level of heavy metal pollution. All lichens, however, are not equally sensitive to air pollutants. Different lichen species exhibit different sensitivity to specific air pollutants. Consequently, lichens are well-suited as biological indicators for monitoring environmental quality.
More than seventeen thousand species of lichens are reported to cover around seven per cent of the world’s surface. India, a land of diverse landscapes and climatic conditions, is home to rich biodiversity and harbours about 3,000 fascinating species of lichens. Some European countries like Germany, Italy, Portugal and Slovenia; considering lichen’s response to pollution; have positioned them as bio-monitors and bio-indicators and included them in their air-pollution-related policy documents. Much of India’s lichen diversity, however, remains relatively unexplored as regards their ecological significance and potential applications.Yet another crucial issue in the Indian context is the undervaluation of lichens in India.
When the diversion of forest land for rainforest purposes is proposed, the net present value (NPV) of the forest is calculated and the amount is recovered from the project proponents. Calculation of NPV does not consider the aspect of the immense value that lichens have from ecological as well as economic points of view. This is evident from the fact that the per hectare NPV of forests of Eco-class-I and Eco-class-II categories that have forests of types Tropical Wet-Evergreen/Semi-Evergreen/Moist-Deciduous/ Littoral and Swamp have been assigned the same value. It is essential that realistic values are assigned to the forests of different types and the monetised value of lichens and their services are duly incorporated therein.
Climate change has serious implications for the lichens. Higher temperatures can disrupt the delicate balance between the fungal and algal partners. Extreme heat can lead to desiccation and reduced growth rates. Altered rainfall patterns can affect the availability of water, which is crucial for lichen growth and reproduction. Further, climate change can exacerbate air pollution, harming lichens.
A rise in pollution load in the air breaks the lichen cell resulting in bleaching of the organism, and the same is followed by its demise. Again, acid rain, caused by releasing sulphur dioxide and nitrogen oxides, can damage lichen tissues. Climate change-induced alterations in habitats may result in the loss of suitable environments for their growth while fragmentation of habitats can critically limit dispersal and gene flow. The importance of exploring the roles of different organisms involved in the complex eco-processes in the context of global changes cannot be overestimated.
In this context, lichen is increasingly being recognised globally as a bio-indicator of ‘Global Change Drivers’ that are seen as interconnected stressors like climate change, pollution, land use change, and loss of biodiversity contributing to large-scale environmental impacts. The mapping of epiphytic lichen diversity to assess ecological changes has emerged as a popular bio-monitoring approach in Europe and a European standard has been adopted under the Committee European d Normalisation (CEN) framework. It aims to provide Standard Operating Procedures (SOP) to ensure reliability, consistency and objectivity while simultaneously improving data quality and comparability across space and time.
Needless to say, it is high time that India, possessing almost eighteen per cent of the world’s lichen species and being globally the third-highest air-polluted country only after Bangla Desh and Pakistan, prioritises her efforts in this direction. Detailed exploration and study of lichens can also yield many more useful species for an unexpectedly wide variety of ecological as well as human needs and pursuits including their widespread use as bio-prospecting agents.
An extremely valuable natural resource the lichens are, they are reportedly in a losing evolutionary race against climate change. A 2022 study reveals that it could need more than one million years to adjust to the ecological crisis created due to just one degree Celsius of warming.
With the unabated pace of global warming, lichens, considered one of the most unique and hardy species and a bio-monitoring tool, are facing the danger of getting obliterated from the face of our planet.
Well, the next time you encounter a tree or rock adorned with colourful lichens, take a moment to appreciate these remarkable organisms. Let us work towards their conservation as their beauty and ecological significance make them an integral part of our natural world.
(The writers are Former PCCFs of UP and Maharashtra; views are personal)
