CCEA A-level Geography · A2 1 Option B · Tropical Ecosystems: Nature and Sustainability
Mini-Lesson
A2 Option: Tropical Ecosystems
This mini-lesson covers A2 1 Option B - Tropical Ecosystems: Nature and Sustainability: the location and climate of tropical biomes, the role of the Hadley cell and ITCZ, management and sustainability in arid and semi-arid environments (irrigation), and sustainability in the tropical forest.
This is one of four A2 1 options; you study two. Answer each question to unlock the next screen. Press Start.
Tropical biomes
Locations, climates and biomass
Three tropical ecosystems: tropical forest, tropical grassland (savanna) and desert. You must know their distribution and biomass (flora and fauna) characteristics.
Tropical forest - equatorial; hot and wet all year; very high biomass and biodiversity.
Tropical grassland - marked wet and dry seasons; grasses with scattered drought-tolerant trees.
Desert - hot and arid; sparse xerophytic vegetation; very low biomass.
Quick check
Reading the ITCZ
?The seasonal migration of the Inter-Tropical Convergence Zone (ITCZ) best explains the climate of which ecosystem?
Hadley cell and ITCZ
Circulation and climate
The Hadley cell controls tropical climates. Intense heating at the Equator drives rising air and the low-pressure ITCZ, giving heavy convectional rain over the rainforest. Air descends around 20-30 degrees, creating high pressure and the great hot deserts. Between them, the seasonal shift of the ITCZ produces the savanna wet/dry rhythm.
Calculate
Calculate — water balance deficit
1At a semi-arid station, annual precipitation is 200 mm and potential evapotranspiration is 260 mm. Calculate the annual water deficit.
2An irrigation scheme supplies 10 000 m³ of water, of which 6 000 m³ reaches the crop root zone. Calculate the irrigation efficiency as a percentage.
%
Hint: (6 000 ÷ 10 000) × 100.
Arid/semi-arid management
Irrigation and its problems
In arid and semi-arid tropical environments, irrigation makes farming possible but brings problems:
Benefits - higher, more reliable yields; new land brought into production; economic development.
Problems - salinisation and waterlogging, falling water tables, silting of channels, and disputes over water.
Solutions - efficient drip irrigation, drainage, lining channels, and careful water management.
CCEA uses a regional case study (for example a region in Pakistan or Sudan), treated qualitatively.
Sort it
Sort the tropical biome
Tap a feature, then tap the ecosystem.
🌴 Tropical forest
🦁 Tropical grassland
🏜️ Desert
Quick check
Salinisation
?Why does poorly managed irrigation in a hot, arid area often lead to salinisation?
Tropical forest sustainability
Nutrients, threats and solutions
The tropical forest has a distinctive trophic structure, rapid nutrient cycle and a leached, zonal latosol soil. Most nutrients are stored in the biomass, so clearance quickly degrades the system.
You must evaluate the threat of large-scale development (logging, ranching, mining) and attempts at sustainable development - for example agroforestry (such as at Tome-Acu), selective logging and community forestry. CCEA uses a regional case study such as the Amazon Basin, kept qualitative.
Match it
Match the sustainability term
Tap an item on the left, then its matching partner on the right.
Term
Meaning
Quick check
Rainforest soils
?Why are cleared tropical rainforest soils often infertile within a few years?
Quick check
Sustainable option
?Which is the most sustainable way to use tropical forest land?