Human impact on ecosystems
Biology · Key Stage 3 · The School
Several distinct kinds of impact
HABITAT DESTRUCTION clears land for farming or building. This removes the space a species needs to live. POLLUTION — chemicals, plastic, and extra nutrients from fertiliser — can harm living things even far from where it started. An INTRODUCED SPECIES arrives in a new area, by accident or on purpose. It can outcompete native species that never evolved a defence against it. OVEREXPLOITATION, such as overfishing, takes a resource faster than it can replace itself.
Effects ripple through a food web
Species in an ecosystem feed on each other, so they are linked. Removing or harming just one species can affect many others. None of those others were ever the actual target. Overfishing one predator lets its prey grow unchecked. That prey then eats too much of whatever IT feeds on. The disturbance spreads outward through the whole web, not just to the one species harmed at first.
Reducing human impact
PROTECTED AREAS ban or limit damaging activity by law. Fishing QUOTAS set a legal limit on how much of a species may be caught each season. CAPTIVE BREEDING raises endangered animals in controlled conditions, then releases them back into the wild. Each method targets one specific kind of harm. No single method fixes every problem at once.
Picture a coastal ecosystem. Sea otters eat sea urchins. Sea urchins eat kelp, a large seaweed that forms an underwater forest. Hunt the otters heavily, and urchins are no longer kept in check. Their numbers grow fast. More urchins eat far more kelp. The kelp forest can be destroyed. Many OTHER species lose their habitat, even though none of them were ever hunted directly. In real cases, protecting the otters by law let kelp forests recover as urchin numbers fell back. Protecting one species restored a whole ecosystem, not just that one species' own numbers.