Our current best conceptual understanding of the stressor ‘litter’ is shown in Figure 1.
Figure 1. Potential causes of a change to litter and the condition responses observed as a result of this change.
The presence of litter in estuarine, coastal and marine systems detracts from the visual amenity of an area and can harm humans (e.g. broken glass, used needles) or animals (which eat, become entangled in, or are suffocated by, the litter). Toxic substances can leach out of litter effecting animals and plants. “One quite simple example of this is the toxic effect of cigarette butt litter. Toxic substances leach out of cigarette butts and can kill small animals. Animals also mistake butts for food. The toxic chemicals absorbed by cigarettes’ cellulose acetate filters and found in butts’ remnant tobacco, are quickly leached from the butts by water.” (Global litter information gateway ). Floating litter may aid in the movement (introduction) of marine animals and plants which may become pests.
Many species of endangered or threatened marine mammals, turtles and seabirds are particularly at risk from litter. According to figures provided in the ‘Global litter information gateway’ approximately 100,000 marine mammals and turtles, and 700,000 to 1 million seabirds are killed worldwide by litter every year.