The Biosphere as a Life Support System

The biosphere is the thin layer of the Earth where life exists — stretching from the deepest ocean trenches to the highest mountaintops. It includes all living organisms and the environments they inhabit. For the Edexcel B specification, you need to understand that the biosphere provides essential goods (tangible resources we can harvest) and services (processes that support life on Earth). Without the biosphere, human civilisation simply could not exist.

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What Is the Biosphere?

The biosphere is the zone of life on Earth. It extends from approximately 11 km below sea level (the Mariana Trench) to around 9 km above sea level (the summit of Everest), although most life is concentrated in a much narrower band — from the ocean surface to a few hundred metres above and below.

The biosphere interacts with three other Earth systems:

System	Description	Interaction with Biosphere
Atmosphere	The layer of gases surrounding the Earth	Plants absorb CO₂ and release O₂ through photosynthesis
Hydrosphere	All water on Earth (oceans, rivers, ice, groundwater)	Water sustains all life; the water cycle distributes freshwater
Lithosphere	The rocky outer layer of the Earth (crust and upper mantle)	Weathering of rocks releases minerals; soil supports plant growth

graph TD
    B["BIOSPHERE<br/>All living organisms"] --> A["ATMOSPHERE<br/>Gases — O₂, CO₂, N₂"]
    B --> H["HYDROSPHERE<br/>Water — oceans, rivers, ice"]
    B --> L["LITHOSPHERE<br/>Rock and soil"]
    A -->|"CO₂ for photosynthesis<br/>O₂ for respiration"| B
    H -->|"Water for life<br/>Nutrient transport"| B
    L -->|"Minerals and nutrients<br/>Soil for roots"| B

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Goods from the Biosphere

Goods are tangible, physical resources that humans obtain directly from the biosphere. They are sometimes called provisioning services.

Food

The biosphere provides all of our food, whether from farming, fishing, hunting or gathering. Globally, agriculture uses approximately 38% of the world's land surface. Different biomes support different types of food production:

• Tropical grasslands: Cattle ranching, cereal crops (maize, sorghum, millet)
• Temperate deciduous regions: Wheat, barley, potatoes, dairy farming
• Oceans: Fish and shellfish — the global fishing industry landed approximately 80 million tonnes of wild-caught fish in 2022
• Tropical rainforests: Indigenous communities harvest fruits, nuts, bushmeat, and fish from rivers

Exam Tip: When discussing food from the biosphere, give specific examples tied to specific biomes. Saying "the Amazon provides indigenous communities with fish, fruits such as açaí berries, and Brazil nuts" is far more effective than simply saying "rainforests provide food."

Timber and Building Materials

Forests cover approximately 31% of the world's land area (around 4.06 billion hectares) and provide:

• Hardwoods from tropical rainforests (mahogany, teak, ebony) — used for furniture, flooring and construction
• Softwoods from the taiga (spruce, pine, fir) — used for paper, cardboard, packaging and construction timber
• Bamboo from tropical and subtropical regions — one of the fastest-growing building materials, increasingly used as a sustainable alternative

The global timber industry is worth over $600 billion per year and employs tens of millions of people, particularly in countries like Canada, Russia, Brazil, Indonesia and Sweden.

Medicines

An estimated 25% of all modern medicines are derived from plants, and many more are based on compounds first discovered in natural ecosystems:

Medicine	Source	Biome
Aspirin	Willow bark (Salix species)	Temperate deciduous forest
Quinine	Cinchona tree bark	Tropical rainforest
Morphine	Opium poppy (Papaver somniferum)	Temperate grassland/farmland
Taxol	Pacific yew tree (Taxus brevifolia)	Temperate coniferous forest
Curare	Various tropical vines	Tropical rainforest
Vincristine	Rosy periwinkle (Catharanthus roseus)	Tropical forest (Madagascar)

The rosy periwinkle from Madagascar provides vincristine, used to treat childhood leukaemia, increasing survival rates from 20% to over 80%. This single example illustrates why biodiversity loss in tropical rainforests could mean the loss of undiscovered medicines.

Fuel

• Fuelwood: Approximately 2.4 billion people worldwide depend on wood as their primary fuel for cooking and heating, particularly in Sub-Saharan Africa and South Asia.
• Fossil fuels: Coal, oil and natural gas are derived from ancient biosphere organisms — coal from ancient forests, oil and gas from marine plankton. While technically part of the lithosphere, they originated from the biosphere.
• Biofuels: Crops like sugar cane, corn (maize) and oil palm are grown to produce ethanol and biodiesel.

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Services from the Biosphere

Services are the processes that the biosphere carries out which benefit humans indirectly. These are sometimes called ecosystem services and they are arguably even more valuable than goods because they are difficult or impossible to replace with technology.

Climate Regulation

The biosphere plays a critical role in regulating the Earth's climate:

• Carbon sequestration: Forests absorb CO₂ from the atmosphere through photosynthesis and store it as carbon in wood, leaves and soil. The world's forests store an estimated 861 gigatonnes of carbon — more than is currently in the entire atmosphere.
• The Amazon rainforest alone absorbs approximately 2 billion tonnes of CO₂ per year, acting as a massive carbon sink.
• Oceans: Marine phytoplankton produce approximately 50% of the world's oxygen through photosynthesis and absorb vast amounts of CO₂.
• Albedo regulation: Forests are darker than bare ground or ice, so they absorb more solar radiation. Deforestation can change the albedo (reflectivity) of a surface, altering local and regional climates.