black tar lichen coating coastal rock like spilled oil
- Size
- Width: 5–30 cm
- Lifespan
- 20–100 years
- Diet
- Grows on rocks, stone walls, and occasionally bark in damp, shaded locations. Requires clean air, stable rock surfaces, and high humidity. Tolerates shade and moisture but cannot survive prolonged drought.
- Habitat
- Grows on rocks, stone walls, and occasionally on bark throughout New Zealand. A creature of the damp stone, the wet rock, the places where water trickles and the surface stays moist. Found from sea level to the alpine zone, particularly in shaded, humid locations where the rock is wet for long periods. The lichen of the dark stain, the one that blends into the wet rock like a shadow.
- Range
- Found throughout the North and South Islands on rocks, stone walls, and occasionally bark. Most common in damp, shaded locations near water. Also found in temperate regions worldwide. Grows on native and introduced rock types in natural and urban settings.
- Endemism
- Native
- Main Threats
- None significant. This species is common and widespread on rocks and stone walls. Localised threats include removal of stone walls, quarrying of rock outcrops, and air pollution. Classified as Not Threatened.
- Population
- Not Threatened. This is a common and widespread lichen in New Zealand, particularly in damp, shaded locations on rocks and stone walls. It grows on native and introduced rock types.
- Conservation Status
- Not Threatened
The one that looks like a splash of tar has a body that is a thin, crusty layer that grows on the surface of the rock, forming a dark black or dark brown patch. The colour is a deep, sooty black, sometimes with a hint of brown or green. It is the lichen of the dark stain, the one that blends into the wet rock like it has always been there, the one that looks like a shadow made solid.
What makes it special is the camouflage. The black tar lichen is one of the hardest lichens to see in New Zealand. Its dark colour blends perfectly with the wet, dark rock, especially in shaded, damp locations. You can walk right past it without noticing. It is the lichen of the hidden stain, the one that does not want to be seen, the one that hides in plain sight.
The black tar 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 a smooth or slightly cracked crust, often forming irregular patches that spread across the rock. The surface is often dotted with tiny, black bumps (perithecia) that are the spore-producing structures. Under a hand lens, the bumps are visible, tiny black dots on the black crust.
Biologically, the black tar lichen is a partnership, a fungus and an alga living together. The fungus provides structure and protection. The alga provides food through photosynthesis. The black tar lichen is adapted to damp, shaded locations where other lichens struggle. Its dark colour helps it absorb heat and moisture from the damp rock.
The black tar lichen grows slowly, a few millimetres per year, and a large patch may be decades old. It is often found on damp stone walls, on rocks in stream beds, and on shaded cliff faces.
To find black tar lichen is to find the dark stain on the wet rock. It is black, crusty, and hidden, a living shadow on the stone. You can run your finger over the surface and feel the smooth, crusty texture. It is the lichen of the dark stain, the one that blends into the wet rock like it has always been there, the one that proves that the most successful strategy is sometimes just to disappear.