Effects of Climate Change

Effects of Climate Change on the Environment

Imagine an entire biome packing up and moving north. As average global temperatures have risen by 0.85°C since 1880, ecosystems are being forced to shift toward the poles and higher altitudes.

The natural world faces severe biodiversity loss, with 20% of vulnerable regions at risk of catastrophic species decline. Polar and Tundra biomes face the highest extinction risk because they have a crucial negative feature: they have no further north to migrate to.

In our oceans, warmer sea surface temperatures cause coral bleaching. This occurs when stressed corals expel their symbiotic algae. On the Great Barrier Reef, a staggering 91% of the reef has shown signs of bleaching, leading to ecosystem collapse if the heat stress continues.

The Mechanisms and Impacts of Sea-Level Rise

If you heat a liquid, its molecules move faster and spread further apart. This simple physics principle, known as thermal expansion, accounts for about 50% of global sea-level rise.

The second major cause is the melting of continental land ice (such as the Greenland and Antarctic ice sheets), which adds new liquid volume to ocean basins. Crucially, melting sea ice does NOT significantly raise sea levels, as it already displaces its own weight in water. Sea levels are currently rising at a rate of 3.2 to 3.5 mm per year, submerging natural flood barriers like mangroves.

To calculate the rate of sea-level rise, use this formula:

$$\frac{\text{Total Rise (mm)}}{\text{Number of Years}} = \text{mm per year}$$

To protect communities, countries must use adaptation strategies (like building sea walls) and mitigation strategies (like reducing carbon emissions) to manage these impacts.

Effects on People: Social and Economic Impacts

Why does a fraction of a degree in global temperature matter to your health or your wallet? In AQA Geography, it is vital to distinguish between a social impact (affecting health and well-being) and an economic impact (affecting wealth and jobs).

Warmer, humid conditions are allowing disease vectors to spread to new areas. Malaria-carrying mosquitoes are now found at higher altitudes in Nepal and higher latitudes like Italy. Additionally, low-lying islands such as the Maldives and Tuvalu face becoming uninhabitable due to inundation. This forces people to migrate, creating climate refugees; in 2022 alone, 32.6 million people were displaced globally by disasters.

Economically, extreme weather causes massive financial damage, such as Hurricane Katrina costing approximately $125 billion. Governments must divert funds to flood defences; the Thames Barrier has been closed over 100 times since 1982 to prevent tidal surges. Tourism also suffers, with ski resorts in the Alps facing shorter seasons due to a lack of snow.

AQA examiners look for clear chains of logic when describing impacts on people. Example: Rising temperatures cause glaciers to melt $\rightarrow$ sea levels rise $\rightarrow$ coastal homes are flooded $\rightarrow$ people are forced to migrate (social impact).

Impacts on Food and Water Security

A single degree of warming can be the difference between a bumper harvest and widespread famine. Food security is severely threatened as yields of staple crops like wheat, maize, and rice decline in low-latitude regions.

Rising sea levels lead to salinisation, where saltwater contaminates aquifers and ruins soil. This directly threatens massive agricultural hubs like the Mekong Delta in Vietnam, risking the livelihoods of 40 million people. Furthermore, warmer climates accelerate the spread of pests, such as locust swarms that decimate crops in the Horn of Africa, worsening food insecurity.

In exams, you may need to calculate the percentage drop in a crop yield using a graph:

$$\frac{\text{New Yield} - \text{Original Yield}}{\text{Original Yield}} \times 100$$

To adapt, farmers are employing new strategies. These include planting drought-resistant seeds with deeper roots, or using "scuba rice" — a flood-tolerant variety that survives submergence for up to two weeks.