Antarctica is the coldest and driest continent on Earth, with approximately 98% of its surface permanently covered by ice. Plant life is exceptionally sparse, restricted almost entirely to the less than 2% of ice-free land, mainly along coastal regions and the warmer Antarctic Peninsula. This extreme environment limits vegetation to specialized organisms that must endure low temperatures, high winds, and intense ultraviolet radiation. The flora here represents the physiological limits for terrestrial life.
The Two Flowering Plants of Antarctica
The most complex native plant life consists of two species of vascular, or flowering, plants: the Antarctic Hair Grass (Deschampsia antarctica) and the Antarctic Pearlwort (Colobanthus quitensis). Vascular plants possess specialized tissues for transporting water and nutrients, a structure rare in the Antarctic environment.
The Antarctic Hair Grass forms dense, small tufts of green blades, often creating extensive mats in sheltered, moist locations. The Antarctic Pearlwort, belonging to the carnation family, grows as small, compact, cushion-like clusters of bright green foliage. Both species are found almost exclusively in the maritime Antarctic, particularly on the milder western side of the Antarctic Peninsula.
These plants exhibit rapid growth during the brief austral summer months. Increased summer air temperatures have led to a noticeable expansion in the range and population density of both species. This warming trend allows them to colonize newly exposed ground and grow larger, with some Pearlwort cushions reaching up to 18 centimeters in diameter.
Widespread Non-Vascular Life: Mosses and Liverworts
Non-vascular organisms dominate the ice-free terrestrial landscape. This group, known as bryophytes, includes approximately 100 species of mosses and 25 to 30 species of liverworts recorded across the continent. Non-vascular life lacks the true roots, stems, and leaves found in flowering plants.
Mosses are successful and form extensive green, yellow, or reddish lawns, especially where meltwater provides moisture. They are structurally simple, absorbing water directly over their entire surface. In protected, high-moisture locations, slow accumulation over centuries results in deep, stratified masses known as moss banks.
Liverworts are generally smaller and less abundant than mosses, often growing prostrate or intermingled within moss carpets. Both mosses and liverworts function in the ecosystem by trapping fine soil particles and organic matter, contributing to limited soil structures. Their resilience allows them to survive far south of the flowering plants, reaching latitudes as far as 84° 30′ south.
Lichens, Fungi, and Snow Algae
Lichens are the most numerous and geographically widespread “plant-like” life forms, with over 400 species described in Antarctica. A lichen is a stable, symbiotic partnership between a fungus and a photosynthetic partner, typically an alga or cyanobacterium. The fungus provides structure and absorbs minerals, while the photobiont produces food through photosynthesis.
This arrangement allows lichens to colonize bare rock surfaces in the coldest, driest parts of the continent, including the Dry Valleys. They grow extremely slowly; some crustose lichens increase their diameter by only a fraction of a millimeter per year, meaning patches may be thousands of years old. Lichens are categorized by their growth form: crustose (crust-like), foliose (leaf-like lobes), and fruticose (shrubby) types.
Fungi also exist independently, often microscopic, and primarily act as decomposers of minimal organic material. Extreme cold limits decomposition, preserving organic materials for long periods. Snow algae, or cryoflora, are microscopic photosynthetic organisms that colonize the surface of snow and ice. These algae contain red or green pigments that cause “watermelon snow,” creating vibrant patches of color during the summer melt.
Strategies for Surviving Extreme Cold
Antarctic flora uses physiological and structural mechanisms to cope with polar stresses, including desiccation, low light, and freezing temperatures. One strategy is poikilohydry, the ability to tolerate the complete loss of free water and enter suspended animation. Mosses and lichens can dry out completely, then rapidly rehydrate and resume metabolic activity when meltwater becomes available.
Many species develop high concentrations of dark pigments, such as orange carotenoids and anthocyanins. These compounds serve a dual purpose: they protect photosynthetic machinery from intense ultraviolet light and increase the absorption of solar radiation. By darkening their surfaces, plants can raise their internal temperature several degrees above ambient air temperature, extending the period of photosynthesis.
Vascular plants and many bryophytes adopt a low-lying, cushion-like, or dwarf growth habit. This morphology keeps the plant close to the ground, where temperatures are warmer due to substrate heat absorption, and minimizes exposure to high winds. The hair grass and pearlwort are also freezing-tolerant, with the hair grass surviving internal ice formation down to an average of \(-22.8^\circ C\).