The definition and importance of biomes

Biomes are vast ecosystems that span across continents, each characterised by distinct climatic conditions, vegetation, and animal life. They play a crucial role in supporting biodiversity and maintaining ecological balance on a global scale. While most biomes are terrestrial, meaning they are found on land, some, such as coral reefs, are marine and exist in ocean environments.

Key features of biomes

• Large-scale ecosystems - Biomes cover extensive areas, often crossing multiple countries or regions.
• Unique environments - Each biome has specific conditions that shape the types of plants and animals that can thrive there.
• Biodiversity hubs - They support a wide range of species, contributing to global ecological diversity.
• Terrestrial and marine - Biomes include both land-based systems like forests and grasslands, and ocean-based systems like coral reefs.

The global distribution of major biomes

The distribution of biomes across the world is influenced by latitude, climate patterns, and geographical features. Their locations are often tied to specific latitudinal zones due to variations in temperature and precipitation caused by the Earth's position relative to the Sun.

Locations of major biomes

The climatic conditions of major biomes

Climate is a defining factor for each biome, determining the type of vegetation and animal life that can survive. Temperature, precipitation, and seasonal variations create unique environmental conditions in each biome.

Polar regions

• Antarctica (South) - Experiences long, harsh winters and brief, cool summers with constant snow and ice cover. Winter temperatures range from -61°C to -54°C, and half the year is spent in darkness. Circumpolar winds confine the cold within the continent.
• Arctic (North) - Similar long, cold winters and short summers with snow and ice, but warmer than Antarctica with winter temperatures between -44°C and -24°C. The sea remains around -1.5°C, and warm air from the south arrives via the Gulf Stream.

Marine and tropical biomes

• Coral reefs - Require consistently warm water with a mean temperature of 21°C, and clear, shallow depths (less than 28 metres) to allow sunlight for photosynthesis.
• Tropical rainforests - Hot and humid with no distinct seasons, monthly temperatures between 24°C and 28°C, and high annual rainfall exceeding 2100 mm, often with daily afternoon downpours.
• Tropical grasslands (savannah) - Feature a prolonged dry season and a short wet season, with 82% of rain falling in the wet months. Rainfall can drop to 7 mm in the dry season, with daily temperatures averaging 26°C.

Arid and temperate biomes

• Hot deserts - Extreme daytime heat up to 37°C, dropping to -9°C at night due to lack of cloud insulation. Annual rainfall is minimal, around 30 mm.
• Temperate grasslands - Hot summers above 36°C and freezing winters down to -39°C. Rainfall ranges from 220 mm to 720 mm annually, with 73% occurring in summer, aided by melting snow.
• Temperate forests - Four distinct seasons due to the Earth's tilt, with warm summers, mild winters, and rainfall between 850 mm and 1550 mm yearly, averaging a temperature of 11°C.

The flora and fauna adaptations in major biomes

Plants and animals in each biome have evolved specific adaptations to cope with the unique environmental challenges they face, such as extreme temperatures, water scarcity, or seasonal changes. These adaptations ensure their survival and reproduction in diverse conditions.

Adaptations in polar regions

Antarctica (South):

• Only 1% of land is ice-free, limiting flora to about 85 moss species and 360 lichen species on exposed rocks.
• Fauna includes penguin species like emperor and gentoo, fur and elephant seals, and whales such as killer and minke.
• Animals are supported by nutrient-rich seas with abundant phytoplankton.

Arctic (North):

• Hosts around 1650 plant species including mosses, grasses, and low shrubs up to 1.8 metres tall.
• No trees due to permafrost.
• Animals include polar bears, wolves, reindeer, walruses, and whales, with some migrating south in winter.

Adaptations in marine and tropical biomes

Coral reefs:

• Comprise coral polyps, animal relatives of jellyfish, forming calcium carbonate skeletons.
• Sea grasses like turtle grass provide shelter.
• Fauna includes parrot fish, starfish, eels, and dugongs, thriving in warm, shallow waters.

Tropical rainforests:

• Support over 13 million species with layered vegetation from tall emergents to shrub layers.
• Trees have buttress roots for stability, and lianas connect them.
• Animals like toucans, monkeys, and poison dart frogs use bright colours as predator warnings.

Tropical grasslands (savannah):

• Feature tall pampas grass over 2.8 metres and baobab trees with wide trunks (up to 9 metres diameter) for water storage and minimal leaves to reduce transpiration.
• Fauna includes 38 hoofed species like antelope, grazers like elephants, and predators like lions.

Adaptations in arid and temperate biomes

Hot deserts:

• Dominated by xerophytic plants like cacti with surface roots for water absorption.
• Animals such as camels store water in humps and have protective eyelashes against sand.
• Meerkats and sidewinder snakes adapt to dryness.

Temperate grasslands:

• Have tussock grasses up to 1.9 metres and shorter buffalo grasses at 45 cm, with few trees like willow in valleys.
• Fauna includes burrowing gophers, large herbivores like bison, and predators like coyotes and eagles.

Temperate forests:

• Feature deciduous trees like oak (up to 38 metres tall) shedding leaves in winter to conserve moisture, alongside ash and birch.
• Ground cover includes grass and bracken.
• Fauna like squirrels, deer, and hibernating black bears adapt to seasonal shifts.