7.3.5—Ecosystem waste absorption

An ecosystem can transform or store some waste, but pollution occurs when harmful inputs arrive faster than they can be transformed into harmless substances.

Biodegradable materials can be broken down biologically, but the rate depends on conditions such as oxygen, temperature and decomposer activity. Persistent pollutants may remain for long periods.

Half-life is the time required for half of a substance to decay or transform. Repeated inputs can still accumulate when each new input arrives before earlier material has sufficiently declined.

Compare input rate with transformation and removal rate, then consider toxicity, persistence and receiving-system capacity.

Biodegradable does not mean harmless at any quantity or in every environment.