Global Changes Influencing Ecosystems (AQA A-Level Geography): Revision Notes

Global Changes Influencing Ecosystems

Climate change and ecosystem vulnerability

The natural environment forms the foundation for all human life and activities. Climate change is altering this environment in profound ways, and ecosystems worldwide are facing unprecedented challenges. Understanding these changes is crucial because we depend on the environment to help manage the impacts that a changing climate will bring.

Ecosystems are highly vulnerable to climate change. This vulnerability is particularly concerning because climate change can worsen existing pressures that ecosystems already face, such as:

• Pollution affecting air, water and soil quality
• Land conversion for agriculture, urban development and industry
• The spread of invasive non-native species

Impacts on UK ecosystems

Climate change affects UK ecosystems through two distinct pathways: direct environmental impacts and indirect impacts through human management responses.

Direct impacts of climate change

Direct impacts occur when changing climate conditions physically alter ecosystems and the species within them. These impacts include several interconnected processes:

Loss of physical space occurs along coastlines due to sea-level rise and coastal erosion. Low-lying habitats are particularly vulnerable, and areas at higher altitudes may also face pressure as temperatures increase, pushing temperature-sensitive species into ever-smaller zones.

Changes in climate space refer to shifts in the geographical areas suitable for particular species. As these parameters shift geographically, species distributions must shift accordingly, leading to changes in where species are found.

Seasonal timing shifts affect life cycle events such as flowering, breeding and migration. When these timing changes occur unevenly across species, it can create misalignment between species that depend on each other. For example, if insects emerge before the plants they pollinate have flowered, or if birds arrive after their food sources have peaked.

Arrival of non-native species becomes more likely as warming conditions allow species from warmer regions to establish populations in the UK. These new arrivals may thrive in the changed conditions.

Changes in community composition and inter-species competition result from the combined effects above. As some species decline, others expand, and new species arrive, the interactions between species change fundamentally. Competition for resources intensifies, and the ecological relationships that have evolved over millennia are disrupted.

Changes in ecosystem processes affect fundamental functions such as water quality, nutrient cycling and carbon storage. Extreme events like droughts, floods and storms become more frequent and severe, directly damaging ecosystems and altering how they function.

Indirect impacts through human responses

Indirect impacts occur when humans modify land management and policy in response to climate change. These management decisions affect ecosystems even when they are designed to address climate challenges:

Changes in land management include modifications to agricultural practices and forestry to achieve carbon sequestration (capturing and storing carbon dioxide from the atmosphere). Production of biomass crops for renewable energy also alters landscapes, potentially at the expense of natural habitats. The creation of ecological networks to help species move across landscapes represents another major change.

Catchment management involves managing entire river watersheds to address water resource availability, water quality issues, flood risk and erosion control. Hydropower development also falls under this category. These approaches can significantly alter aquatic and riparian ecosystems.

Management of the marine environment includes changes to fisheries policy aimed at sustainable harvesting and the development of renewable energy installations such as offshore wind farms. These alterations affect marine ecosystems directly.

International food trade effects influence domestic ecosystems because the UK's approach to importing and exporting food affects which crops are grown domestically and how much pressure is placed on agricultural land.

Planning and development of rural and urban areas determines how energy is used, where natural features are included in the landscape, and how biodiversity is incorporated into built environments. Development decisions affect the amount and quality of habitat available for wildlife.

Land used for leisure and recreation creates pressure on ecosystems through activities and infrastructure that support tourism and outdoor recreation.

UK-specific changes to wildlife and habitats

The UK faces particular challenges as its climate changes. Wildlife and plant species may need to adapt by shifting their ranges northwards to track suitable climate conditions. However, this movement brings its own problems, as species must compete with newly arrived non-native species that can thrive in the warmer conditions.

Global patterns of species extinction

On a global scale, atmospheric warming represents the greatest threat to biodiversity. The Intergovernmental Panel on Climate Change (IPCC), the international scientific body that assesses climate change, has concluded that rising temperatures, combined with habitat destruction and pollution, will place many species at risk of extinction in the coming decades.

Predictions about species extinction vary widely depending on the assumptions made in different studies. However, one conclusion consistently emerges from the research: extinction risks will increase as global temperatures rise. Some studies suggest that up to one in six species could face extinction as temperatures continue to climb.

The geographical patterns of extinction risk show clear disparities:

• Tropical and subtropical regions show the highest projected extinction rates, with some areas expected to lose between 195 and 521 vertebrate species. Plant extinctions in these regions could reach between 716 and 1,429 species
• Africa and Central America appear as particular hotspots for vertebrate extinctions, with large areas showing red (highest risk) on projected maps
• South and Southeast Asia face substantial plant extinction risks
• Polar and northern regions show lower absolute numbers of projected extinctions (fewer than 12-35 vertebrates in many areas), partly because these regions have fewer species to begin with

Climate-sensitive species at risk

Certain types of species are particularly vulnerable to climate change due to their specific ecological requirements. Two groups face especially severe threats:

Both examples illustrate a crucial principle: species with specialised habitat requirements and limited ability to disperse to new areas face the greatest extinction risk from climate change.

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