By Alex Kirby
BBC News Online environment correspondent in Jeju, Korea
One of the biggest problems facing many small island states is a growing volume of rubbish, the United Nations says.
No tourist will want to return to an eyesore
The UN Environment Programme estimates the plastic wastes they have to tackle have risen fivefold since the 1990s.
It says the problem is now as serious as sea level rise, over-fishing, water shortages and inadequate sanitation; and may be putting off many tourists.
Unep is helping the island states to deal with their waste, but acknowledges much more should, and could, be done.
It cites the example of the Pacific island of Nauru, which now has a blue-green shoreline - not from the colour of the sea, but because of the mounds of discarded beer cans which disfigure its beaches.
Unep says the throw-away society threatens people's health, encouraging pests like rats which spread disease.
It also helps to undermine livelihoods, as tourists are less likely to return to a rubbish-strewn paradise.
Unep released several reports on the problems of small island developing states (which it calls Sids) during the annual meeting here of its governing council, which ends on 31 March.
A short walk along any coastline close to human habitation in the Pacific Islands will reveal many examples of inappropriate waste disposal
Dr Klaus Toepfer, Unep's executive director, said: "Small islands across the Caribbean, Indian Ocean and the Pacific are some of the most vulnerable nations on Earth.
"They are threatened by global warming in the guise of more extreme weather events and rising sea levels, and their water supplies are often restricted.
"Many are also found in remote locations and have limited natural resources, which in turn makes them economically vulnerable.
"Handling solid wastes from industry, households and tourism is emerging as another issue with which they need advice and help. Such wastes are not only unsightly and a threat to wildlife; they can also contaminate rivers and groundwater as they slowly degrade."
Unep and other UN agencies and waste experts have been helping the islanders to face the waste problem. But Dr Toepfer said: "We need to do much more right across the range of wastes if we are to ensure a clean, healthy and sustainable environment for the citizens of these states."
Unep's reports on the waste problem were compiled by its Global Programme of Action for the Protection of the Marine Environment from Land-based Activities and its Global International Waters Assessment.
They make clear that what happens to rubbish and litter is only part of a wider waste crisis: Caribbean islands discharge 90% of their wastewater untreated, and in parts of the north-east Pacific the level of untreated sewage is 98%.
And the reports say the provision of facilities for disposing of waste often leaves "social attitudes" unchanged.
One report says: "A short walk along any coastline close to human habitation in the Pacific Islands will reveal many examples of inappropriate waste disposal, even in areas where there is a municipal collection system such as the city of Suva, in Fiji."
Another says "the most critical issue" for island states in the Indian Ocean is disposing of solid wastes.