Environmental Science
What this domain tests
Environmental Science tests ecosystems, biogeochemical cycles, pollution, biodiversity, climate change and the environmental effects of farming. Expect questions on carbon storage, greenhouse gases, pesticide pollution, soil and water conservation and sustainable practices.
Core rules and concepts
- An ecosystem has biotic components (producers, consumers, decomposers) and abiotic components (soil, water, air, light).
- Pollution may be point-source or non-point-source; agricultural runoff is usually non-point-source.
- Greenhouse gases include carbon dioxide, methane and nitrous oxide. Their global warming potential is expressed relative to carbon dioxide over a stated period.
- Soil organic carbon is a fraction of soil organic matter; organic matter is roughly organic carbon multiplied by 1.724.
- Biodiversity includes genetic, species and ecosystem diversity. Habitat loss is a major cause of biodiversity decline.
- Environmental impact assessment identifies likely effects before a project is approved.
Worked example
A hectare of soil has 0.5% organic carbon, a bulk density of 1.3 t/m³ and a depth of 0.15 m. Soil volume = 10,000 × 0.15 = 1,500 m³. Soil mass = 1,500 × 1.3 = 1,950 t. Carbon stock = 1,950 × 0.005 = 9.75 t carbon. The reasoning is to convert area and depth to volume, use bulk density for mass, then apply the percentage as a fraction.
Traps that cost marks
Do not report organic carbon as organic matter without conversion. Do not treat ppm and percentage as the same unit. Do not compare greenhouse gases without using the same global warming potential basis. Do not call agricultural runoff a point source. Do not ignore bulk density in carbon-stock calculations.