Kew Lichens

Royal Botanic Gardens, Kew | UNESCO World Heritage Site

Revealing the Hidden Beauty of Lichens through Awareness, Research, and Conservation

Edited by: Sohrabi, M. (2026)

KEWLICH Project?

KEWLICH is a collaborative, volunteer-driven project; explores the rich and often overlooked world of lichens at the Royal Botanic Gardens, Kew. Bringing together research, historical records, and field observations, the project documents lichen diversity across trees, rocks, soils, and historic structures.

Through accessible guides, species profiles, and visual storytelling, KEWLICH connects science with public engagement—highlighting why lichens matter for biodiversity, air quality, and conservation at Kew and beyond.

Lichens at Kew: Diversity, Resilience, and Conservation Value

The Royal Botanic Gardens, Kew—designated as a UNESCO World Heritage Site—hosts one of the richest lichen floras in the London area, with around 200 species, approximately 10% of all British lichens, recorded. This remarkable diversity reflects a major resurgence after decades of pollution. As London’s air improved from the 1980s onward, lichens returned to trees, rocks, and historic buildings. Their recovery underscores nature’s resilience and the significance of Kew’s conservation strategy, which prioritises long-term ecosystem health and environmental monitoring. From intricate crusts to delicate fruticose forms, lichens reveal hidden beauty while supporting research in biodiversity, conservation, and air-quality science.

In the heart of Kew stands an old and distinguished tree, a specimen that has witnessed well over a century of seasonal change. From the base of its trunk to the very tips of its uppermost branches, its bark is richly colonised by lichens—a continuous living layer that marks the tree as part of a healthy and enduring landscape.

These lichens are more than colourful surface growths. They represent complex symbiotic systems, in which fungi, algae, cyanobacteria, bacteria and yeasts coexist to form a single, dynamic organism. This partnership embodies a quiet philosophical message: that diversity, cooperation and mutual tolerance can create stability and resilience.

The vitality of these lichen communities also serves as an indicator of clean air and low environmental stress, reflecting conditions where such delicate organisms can thrive. In this sense, the tree and its lichens together offer a subtle reminder that harmony—both ecological and social—emerges not from uniformity, but from the respectful integration of many different forms of life.

What Are Lichens?

Lichens are remarkable partnerships between a fungus and an alga or cyanobacterium — two very different organisms living together as one. This unique relationship allows them to survive in some of the harshest environments on Earth, from bare rock to tree bark and even historic buildings. At Kew, lichens reveal the hidden beauty of resilience and balance in nature. They play vital roles in producing oxygen, forming soil, and monitoring air quality, making them essential indicators of a healthy environment. Exploring lichens at Kew offers a glimpse into the delicate yet powerful connections that sustain life in every corner of our world.

Usnea hirta

Usnea hirta is a fruticose, beard-like lichen with pale green branches, thriving in clean air, sensitive to pollution, and ecologically valuable.

Hypogymnia physodes

Hypogymnia physodes at Kew Gardens showcases lichen resilience, air-quality sensitivity, ecological value, and the beauty of symbiosis thriving on the bark of trees.

Parmelia sulcata

Parmelia sulcata forms silvery, cracked thalli on tree bark at Kew Gardens, serving as a sensitive indicator of air quality and a key contributor to epiphytic diversity

Growth Forms

Foliose

Lichens with a leaf-like, flattened body (thallus) that is loosely attached to the surface at several points. They have distinct upper and lower surfaces and often form broad lobes (e.g., Parmelia, Hypogymnia).

Fruticose

Lichens with a three-dimensional, branched or hair-like form, often resembling tiny shrubs or coral. They’re usually attached at a single point and stand upright or hang down from their substrate (e.g., Usnea, Ramalina).

Crustose

Lichens that form a thin, crust-like layer tightly attached to their substrate (rock, bark, or soil). They lack a lower surface and cannot be removed without damaging the surface beneath (e.g., Lecanora, Buellia).

Substrate

Trees & Wood

Lichens on trees and wood in Kew form diverse communities, from foliose greens to crustose patches, each responding to bark chemistry, moisture, light, and the garden’s varied microhabitats.

Rocks & Bricks

Lichens on rocks and bricks in Kew create vivid crusts and mosaics, thriving on mineral-rich surfaces where sunlight, moisture, and time shape remarkably resilient communities.

Soil

Between cracks in the bricks and in scattered spots across Kew Gardens, several resilient lichen species appear, quietly colonizing surfaces and highlighting intricate ecological interactions.

Lichen Diversity & Conservation

Lichens are key indicators of biodiversity and ecosystem health. At Kew Gardens, lichenologists study and identify species growing on trees, rocks, and soil, revealing the hidden diversity of this UNESCO World Heritage Site. Understanding where and how lichens grow helps scientists track environmental changes, conserve rare or sensitive species, and maintain ecological balance. Tree bark hosts leafy and shrubby forms, rocks harbour crusty species, and soils support tiny pioneering lichens — each contributing to habitat complexity. Accurate identification and monitoring are essential for protecting these remarkable organisms and the environments they enrich.

Lichen Biodeterioration

At Kew Gardens, a UNESCO World Heritage Site, lichens quietly colonise stone walls, monuments, and glasshouse structures. Their subtle growth adds beauty and colour, yet over time, they can slowly weather delicate surfaces. Kew’s lichenologists study these organisms to understand how they interact with historic materials — how fungal filaments penetrate stone, how pigments change surface chemistry, and how moisture cycles influence decay. This research helps balance heritage conservation with natural ecology, revealing lichens not as simple destroyers, but as storytellers of time, air, and place.

Lichen Biomonitoring

Lichens are living indicators of air quality. At Kew Gardens, lichenologists use detailed species checklists and long-term monitoring to study how nitrogen and pollution affect lichen diversity and health. Sensitive lichens disappear as nitrogen levels rise, while tolerant species expand — offering a natural record of changing air conditions. By analysing species distribution, growth forms, and chemistry, researchers at Kew track urban air trends, link lichen vitality to ecosystem resilience, and support conservation of clean-air habitats within this UNESCO World Heritage landscape.

Lichen Outreach and Education

Lichens may seem small, but they reveal Kew Gardens’ hidden beauty and ecological richness. Educational programs introduce visitors to their fascinating forms, colours, and growth on trees, rocks, and soil. Learning to identify lichens helps people appreciate their role in clean air, biodiversity, and ecosystem health. Kew’s lichen education highlights how these subtle organisms connect nature, history, and science, inspiring curiosity and conservation awareness among all ages.

Lichen Biotechnology

In Kew’s laboratories, lichenologists explore the hidden potential of lichens for science and industry. These symbiotic organisms produce unique compounds with antibacterial, antifungal, and antioxidant properties. Researchers study their chemistry for applications in medicine, natural dyes, cosmetics, and ecological restoration. By combining traditional identification with advanced biotechnology, Kew unlocks the biochemical treasures of lichens, demonstrating how these ancient organisms can inspire innovation while conserving biodiversity.