🏗️ Habitat loss
Big idea: Habitat loss removes the space and resources species need to survive. When habitats shrink, biodiversity usually falls.
Habitat destruction is like bulldozing nature's homes.
- Cutting rainforests for cattle farms (Amazon loses about a football pitch per minute!)
- Draining wetlands for buildings and roads
- Clearing grassland for crops
How this affects food webs: Habitat loss is a direct human impact because it removes plants (producers). With fewer producers, less energy enters the food web, so fewer consumers can be supported and the food web becomes less stable.
Real example: Amazon deforestation: Large areas of the Amazon rainforest are cleared for cattle ranching. This removes habitat for species such as jaguars, birds, and insects, disrupts food webs, and reduces ecosystem resilience.
Habitat loss is a top driver of biodiversity decline — in exams, name it early and add a specific example, e.g. deforestation of the Amazon for cattle ranching removes habitat, reduces species richness, and lowers ecosystem resilience.
🧩 Fragmentation (not the same as destruction)
Habitat fragmentation The habitat still exists, but organisms are stuck in separate “islands”.
Simple picture: A road through a forest splits one population into two. Crossing becomes dangerous, so groups become isolated.
- Smaller populations → higher extinction risk
- Isolation → harder to find mates
- Inbreeding → lower genetic diversity
- Edge effects → edges are hotter/drier/windier and have more predators/invasive species
Real Example: Jaguars 🐆: Roads and farms have fragmented jaguar habitats in South America. Isolated groups can't meet to breed, causing inbreeding. Solution? Wildlife corridors — protected strips of land that reconnect fragments!
IB loves edge effects and wildlife corridors — know both the problem AND the solution!
Fragmentation reduces gene flow and increases edge effects.