Coastal Restoration Trust of New Zealand

Coastal Dune Ecosystem Reference Database

Subtidal benthic marine litter at Kawau Island, north-eastern New Zealand Journal Paper

Backhurst, M.; Cole, R.
Journal / Source
Journal of Environmental Management
boating, environmental impact, litter, subtidal
It is widely perceived that litter diminishes appreciation of environmental quality, and therefore may require management. Litter in coastal-marine environments has not been studied intensively, although these are likely to be encountered by humans. In order to assess the severity of litter impacts, we studied the existing litter fauna of shallow embayments in north-eastern New Zealand, in an area where boating is intense. We sought an understanding of existing patterns of litter distribution, how long litter items might take to break down or disperse, and considered possible management options. The distribution, abundance, and persistence of subtidal benthic litter were studied at Kawau Island, north-eastern New Zealand, where high densities of pleasure craft concentrated in sheltered bays during summer. A survey of the benthic subtidal environment at 37 sites found numerous litter items. Glass beer bottles dominated sites with histories of high boating usage, but litter was sparse elsewhere. Litter items placed at a popular anchorage were displaced and rapidly lost, whereas at an infrequently visited site nearby their abundances declined more slowly. Tin cans and to a lesser extent aluminium cans showed signs of physical decay over a 10-month experimental deployment, while glass and plastic did not. Although litter is locally very abundant, it does not currently affect most users, and attempts to remove it would be a more intense disturbance than any existing impact. We suggest that the appropriate management approach is to reduce the amount of litter that arrives in the shallow coastal area, by providing rubbish collection facilities over the period of intensive usage in summer.