map lichen charting bare rock in yellow and grey continents
- Size
- Width: 2–15 cm
- Lifespan
- 20–100 years
- Diet
- Grows on rocks and boulders in exposed, sunny locations. Requires clean air, stable rock surfaces, and good light. Tolerates sun, wind, drought, and extreme temperatures. Forms cracked, map-like crusts on rock surfaces that look like an ancient chart that nobody can read.
- Habitat
- Grows on rocks and boulders throughout New Zealand, particularly in exposed, sunny locations. A creature of the stone, the boulder field, the cliff face. Found from sea level to the alpine zone, on native and introduced rock types. The lichen of the cracked map, the one that looks like an ancient chart that nobody can read.
- Range
- Found throughout the North and South Islands on rocks and boulders in exposed, sunny locations. Most common in the South Island's high country and the North Island's volcanic plateau. Also found in temperate and cold regions worldwide.
- Endemism
- Native
- Main Threats
- None significant. This species is common and widespread on rocks in exposed, sunny locations. Localised threats include quarrying of rock outcrops, air pollution, and climate change affecting rock surface conditions.
- Population
- Not Threatened. This is a common and widespread lichen in New Zealand, particularly in the South Island's high country and the North Island's volcanic plateau. It grows on rocks and boulders in exposed, sunny locations.
- Conservation Status
- Not Threatened
The one that looks like a puzzle has a body that is a thin, crusty layer that grows on the surface of the rock, forming a cracked, irregular pattern. The colour is pale grey to yellowish-green, with dark black lines separating the patches. The patches look like countries on a map, the black lines like borders or rivers. It is the lichen of the ancient map, the one that looks like a chart that nobody can read, the one that makes the rock look like a world waiting to be explored.
What makes it special is the pattern. The map lichen is a crustose lichen, meaning it grows flat on the rock, like a crust of paint, rather than upright or leafy. Its body is divided into small, irregular patches called areoles. The areoles are separated by dark black lines called cracks. The pattern looks exactly like a map, a patchwork of countries, islands, and continents. It is the lichen of the geography lesson, the one that turns the rock into a world, the one that invites you to trace the borders with your finger.
The map lichen grows very slowly, a few millimetres per year. A large patch may be centuries old. Scientists use map lichen to date rocks, a technique called lichenometry. The size of the lichen patch tells them how long the rock has been exposed. It is the lichen of the timekeeper, the one that records the age of the mountain, the one that has been watching the landscape change for hundreds of years.
Biologically, the map lichen is a partnership, a fungus and an alga living together. The fungus provides structure and protection. The alga provides food through photosynthesis. The map lichen is a pioneer species, one of the first to colonise bare rock. It can survive extreme conditions, heat, cold, drought, and intense sunlight.
To find map lichen is to find the cracked pattern on the rock. It is pale, crusty, and mapped, a living chart on the stone. You can run your finger over the surface and feel the cracks, the borders, the texture of the map. It is the lichen of the ancient map, the one that looks like a chart that nobody can read, the one that proves that the mountains have their own language.