Climate and Natural Vegetation
Map Your Gaps
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Equatorial climate
Hot and wet all year round, found within about 5° of the equator.
The Amazon Basin, Congo Basin and Indonesia have equatorial climates.
Equatorial climate — Key Knowledge
- Temperature high all year — around 26–28°C; very small annual range, typically 1–2°C
- Rainfall high all year — over 2,000 mm; no real dry season
- Convectional rainfall intense solar heating causes air to rise, cool and condense — afternoon thunderstorms
- Humidity constantly high
Hot desert climate
Very hot days and cold nights, with extremely low rainfall.
The Sahara, Arabian and Kalahari deserts have hot desert climates.
Hot desert climate — Key Knowledge
- Temperature very hot during the day — can exceed 40°C; cold at night — can drop below 10°C
- Large diurnal temperature range clear skies and dry air mean heat escapes rapidly at night
- Rainfall very low — under 250 mm per year; unreliable and irregular
- Located around the tropics of Cancer and Capricorn — roughly 15–30° north and south
Factors affecting climate
Several factors explain why different places have different climates.
Climate is always explained by a combination of these factors — not just one.
Factors affecting climate — Key Knowledge
- Latitude nearer the equator = more direct sunlight = hotter
- Altitude higher up = cooler — temperature drops about 1°C per 150 m
- Distance from the sea coastal areas have smaller temperature ranges — sea heats and cools slowly
- Ocean currents warm currents raise coastal temperatures; cold currents lower them
- Prevailing winds winds from the sea bring moisture; winds from land are drier
- Pressure systems low pressure = rising air = rain; high pressure = sinking air = dry
Types of rainfall
Rainfall forms when moist air rises, cools and condenses.
The exam may ask you to draw and label a diagram of either type — know the sequence.
Types of rainfall — Key Knowledge
- Convectional rainfall sun heats the ground, air rises, cools and condenses — common in tropics and on hot summer days
- Relief/orographic rainfall moist air forced to rise over high ground, cools and condenses on the windward side; rain shadow on the leeward side
Tropical rainforest ecosystem
A dense, layered forest found in equatorial regions with high biodiversity.
Rainforests contain more than half of the world's plant and animal species.
Tropical rainforest ecosystem — Key Knowledge
- Emergent layer tallest trees — up to 50 m, above the canopy
- Canopy continuous layer of treetops at 30–40 m — most life and photosynthesis here
- Under-canopy smaller trees and saplings — less light
- Shrub layer low-growing plants adapted to shade
- Forest floor dark, hot, humid — rapid decomposition of leaf litter
Rainforest nutrient cycle
Nutrients cycle rapidly between the soil, biomass and litter in a rainforest.
This is why cleared rainforest land becomes infertile after just a few years of farming.
Rainforest nutrient cycle — Key Knowledge
- Most nutrients stored in the biomass living trees and plants — not in the soil
- Rapid decomposition hot, humid conditions break down dead material quickly
- Nutrients recycled fast taken up by tree roots almost immediately
- Soil is nutrient-poor thin, infertile layer — if trees are removed, nutrients are quickly washed away by rain
Hot desert ecosystem
A harsh environment with low biodiversity, adapted to extreme heat and drought.
Despite appearances, deserts are not lifeless — organisms have evolved remarkable adaptations.
Hot desert ecosystem — Key Knowledge
- Sparse vegetation plants widely spaced to reduce competition for water
- Sandy or rocky surfaces little soil development
- Low biodiversity few species, but those present are highly adapted
- Food chains are short limited energy available from producers
Desert plant adaptations
Plants have evolved features to survive extreme heat and drought.
Every adaptation is a solution to the same problem — how to find, store or conserve water.
Desert plant adaptations — Key Knowledge
- Long tap roots reach deep underground water
- Shallow, spreading roots capture surface moisture from rare rainfall
- Small, waxy or no leaves reduce water loss through transpiration
- Water storage succulent stems — e.g. cacti store water in thick stems
- Short life cycle ephemeral plants germinate, flower and seed rapidly after rain
Desert animal adaptations
Animals have evolved behaviours and features to survive heat and drought.
Behavioural adaptations (when and where to be active) are just as important as physical ones.
Desert animal adaptations — Key Knowledge
- Nocturnal behaviour active at night when it's cooler
- Burrowing underground is cooler during the day
- Large ears increase surface area for heat loss — e.g. fennec fox
- Concentrated urine conserves water
- Light-coloured skin or fur reflects heat
- Ability to survive without drinking get moisture from food — e.g. kangaroo rat
Causes of deforestation
Tropical rainforests are being cleared at a rapid rate for several reasons.
Deforestation is driven by economic demand — often from developed countries consuming the products.
Causes of deforestation — Key Knowledge
- Logging hardwood timber for furniture and construction
- Agriculture cattle ranching, soya, palm oil plantations
- Mining minerals and metals beneath the forest
- Road building opens up previously inaccessible areas to further development
- Population pressure growing populations need more land for farming and settlement
Effects of deforestation
Deforestation has both local and global consequences.
Deforestation is both a cause and consequence of development — balancing economic needs with environmental protection is the key challenge.
Effects of deforestation — Key Knowledge
- Local effects soil erosion — no tree roots to hold soil; flooding — less interception, faster surface runoff; loss of biodiversity — habitats destroyed; indigenous communities displaced
- Global effects increased atmospheric CO₂ — trees no longer absorb carbon, and burning releases stored carbon; contribution to climate change; disruption of the water cycle — less transpiration, less rainfall
Case studies required
The spec requires named examples for both climates and ecosystems.
Case studies should include specific named locations with detail on climate, vegetation and human impacts.
Case studies required — Key Knowledge
- An area of tropical rainforest ecosystem, biodiversity, threats
- An area of hot desert ecosystem, adaptations, opportunities and challenges
Map your gaps
Climate and Natural Vegetation
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