Climate factors determine which plants can colonise a wasteland. Buildings and debris create subtle variations in microclimates that encourage different types of colonisation.
Concrete surfaces provide a stable environment for initial colonisation, while topography influences drainage and accumulation of debris.
Absent or thin soil is typical; pioneer species such as mosses and lichens thrive in these conditions. Debris accumulates on horizontal surfaces and slopes, helping to develop soil over time.
Porosity: The more porous the surface, the easier it is to colonise. Cracks and hollows provide depth for deeper-rooted plants and trees. Impermeable surfaces make root penetration difficult.
Pollution levels: Previous land use determines whether chemicals may be toxic to colonisation. Compacted subsoil has low oxygen, low porosity, and difficult root penetration. Soil pH determines nutrient solubility and availability to plants.
Wastelands have low soil levels, resulting in poor moisture retention. When potential evaporation exceeds precipitation, a negative soil water budget results.
Plants adapt through shallow root systems, allowing quick absorption of any precipitation. In areas where precipitation exceeds runoff, water-loving plants such as ferns, ragwort, and brambles thrive.
Key principle: Slower drainage areas allow for greater diversity of flora and fauna by creating varied moisture niches.
Different urban wasteland types produce varied fauna and flora. Adaptation in urban wastelands is faster because new mutations are needed to survive in extreme environments.
Urban crows place walnuts under car tyres to crack them; this habit has spread. Urban animals are opportunistic with a keen sense for food, shelter, and nesting. City blackbirds have shorter beaks, breed earlier (urban heat island effect), and sing at different pitches than rural counterparts.
Reproductive isolation: The London Underground mosquito is a distinct subspecies found only in underground railways, achieving barriers to reproduction with other species.
Key principle: One adaptation does not cover all conditions; cities and their wastelands vary, so flora and fauna must adapt quickly to dynamic environments.
| Factor | Favours colonisation | Hinders colonisation |
|---|---|---|
| Shade | Shade-tolerant species only | Limited diversity |
| Sun traps | Buddleia, butterflies | — |
| Moisture | Damp: mosses, ferns | Dry: spiders only |
| Soil | Porous, cracked surfaces | Impermeable, compacted |
| pH | Species-specific | Toxic if polluted |
Pioneer vs climax species: Pioneers (mosses, lichens) tolerate bare, infertile surfaces; later stages require developed soil and outcompete pioneers through shading.
Wind dispersal vs bird dispersal: Exposed areas receive wind-blown seeds; sheltered areas rely on birds. The larger the area, the greater the seed input and species diversity.
Always link factors to species: When asked about colonisation, connect climate (shade, moisture) and soil (porosity, pH, pollution) to which plants can establish.
Succession stages: Know the five stages in order. Examiners expect recognition that different substrata in the same area can support different successions (e.g. alkaline vs acidic surfaces).
Soil water budget: Negative budget (evaporation > precipitation) is typical in wastelands; plants adapt with shallow roots. Slower drainage increases diversity.
Use located examples: Canvey Wick, Essex (93 hectares, first brownfield SSSI, landfill/oil refinery closed 1980s) demonstrates high biodiversity and conservation value.
