Geography - biosphere, ecological processes and land cover change

Ecosystems

Biosphere

The zone of Earth where life exists, including parts of the atmosphere, hydrosphere and geosphere that support living organisms.

Ecosystem

A system of interactions between living organisms and their non-living physical environment.

Ecology

The study of how organisms interact with each other and with their non-living environment.

Terrestrial ecosystem

An ecosystem primarily based on land, such as a forest, grassland or desert.

Aquatic ecosystem

An ecosystem centred around water, such as an ocean, river, lake or wetland.

Factors affecting ecosystems

Climatic factors

Climate-related factors such as precipitation, temperature, light and wind that influence ecosystem functioning.

Precipitation

A major factor determining ecosystem type because water availability influences vegetation growth and productivity.

Temperature

A climatic factor affecting biological processes such as photosynthesis, growth and reproduction.

Light

The amount of solar energy available to plants for photosynthesis.

Wind

Can increase evaporation and water loss, affect plant growth and transport seeds and pollen.

Topographic factors

Physical characteristics of the landscape, including altitude, gradient and aspect, that influence ecosystem conditions.

Edaphic factors

Factors relating to soil, including soil moisture, nutrients, texture, pH and oxygen availability.

Biotic factors

Factors resulting from interactions between living organisms, such as competition, predation, herbivory and disease.

Altitude and ecosystems

Increasing altitude generally results in lower temperatures, lower atmospheric pressure and increased exposure to wind.

Aspect and ecosystems

The direction a slope faces affects its exposure to solar radiation, influencing temperature and moisture conditions.

Gradient and ecosystems

Steeper slopes are generally more vulnerable to erosion and mass movement.

Energy and nutrients

Energy flow

The movement of energy through an ecosystem, beginning primarily with solar energy captured by producers and moving through trophic levels.

Biomass

The total mass of living biological material within a particular area or ecosystem.

Food chain

A sequence showing how energy and nutrients are transferred as organisms consume other organisms.

Food web

A network of interconnected food chains showing the complex feeding relationships within an ecosystem.

Trophic level

The position an organism occupies in a food chain or food web based on how it obtains energy.

Nutrient cycle

The continuous movement and recycling of nutrients such as carbon, nitrogen and water between organisms and the physical environment.

Land cover change

Land cover

The physical material covering Earth’s surface, such as forests, grasslands, water, cropland, snow and artificial surfaces.

Land use

The way humans use and manage land, such as for agriculture, housing, industry, forestry or recreation.

Land cover change

The alteration of Earth’s physical surface over time due to natural processes and human activities.

Natural climate change

Long-term changes in Earth’s climate caused by natural processes and cycles.

Glacial period

A period when large areas of Earth’s surface are covered by expanded ice sheets and glaciers.

Interglacial period

A warmer period between glacial periods when ice sheets and glaciers are reduced.

Glacial-interglacial cycle

The repeated pattern of cooling and warming that causes Earth to move between glacial and interglacial conditions.

Surtsey Island

A volcanic island formed by an underwater eruption off Iceland in 1963. Its isolation and protection allowed scientists to observe natural ecological succession as plants and animals colonised the previously barren island.

Human causes of land cover change

Population growth

Increasing population creates greater demand for land for housing, infrastructure, agriculture and resources.

Technology

Advances in machinery and technology allow humans to modify land more rapidly and extensively through activities such as deforestation, mining and dam construction.

Anthropogenic climate change

Human-caused changes to Earth’s climate, primarily resulting from increased greenhouse gas emissions, which can alter vegetation, glaciers, coastlines and ecosystems.

Impacts of land cover change

Albedo

The proportion of incoming solar radiation reflected by a surface. Clearing vegetation can increase surface albedo.

Soil water-holding capacity

The ability of soil to retain water. Vegetation removal can reduce this capacity and increase the risk of drought and runoff.

Land cover change and precipitation

Removing vegetation can reduce evapotranspiration and atmospheric moisture, potentially reducing cloud formation and precipitation.

Land cover change and biodiversity

Habitat destruction and fragmentation can reduce biodiversity and cause species populations to decline or disappear.

Land cover change and pollution

Increased erosion can transport sediments and nutrients such as phosphorus and nitrogen into waterways, potentially causing algal blooms and ecosystem damage.

Urban heat island effect

The tendency for urban areas to be warmer than surrounding rural areas because vegetation is replaced by heat-absorbing buildings and surfaces and there is less evaporative cooling.

Earth system interactions

Biosphere–atmosphere interaction

Plants remove carbon dioxide from the atmosphere through photosynthesis and release water vapour through transpiration.

Biosphere–hydrosphere interaction

Organisms depend on water for survival, while vegetation influences water movement through transpiration, infiltration and runoff.

Biosphere–geosphere interaction

Organisms contribute to soil formation and nutrient cycling, while soils provide plants with water, nutrients and physical support.

Four Earth systems

The atmosphere, hydrosphere, geosphere and biosphere are interconnected systems that constantly exchange matter and energy.