Nairobi — Raw sewage is posing an increasing threat to the coastal waters of many developing nations, according to the UN Environment Programme (UNEP).

In a report released last week (4 October), the agency said that as much as 80-90 per cent of sewage entering the sea from such countries is raw and untreated. It warns that this is threatening marine life and livelihoods linked to fisheries and tourism.

The report says that governments need to invest an extra US$56 billion each year to address the problem. But this should pay off in economic, social and environmental benefits, estimated to be worth US$3-34 per US$1 invested.

The findings will be presented to representatives of more than 100 governments meeting in Beijing, China, on 16-20 October.

UNEP says that while oil and chemical pollution are declining, other forms of nutrient-rich pollution -- such as agricultural waste -- are 'fertilising' the sea. This can trigger toxic algal blooms and a rising number of oxygen deficient 'dead zones'.

The report blames rising coastal populations and a lack of adequate infrastructure and waste handling facilities for the increase in pollution.

"An estimated 80 per cent of marine pollution originates from the land and this could rise significantly by 2050 if, as expected, coastal populations double in just over 40 years time and action to combat pollution is not accelerated," said Achim Steiner, UNEP's executive director.

"Old problems persist and new ones like nutrient-rich 'dead zones' and the impacts of climate change are emerging," said Steiner. "We have a long way to go politically, technically and financially if we are to hand over healthy and productive seas and oceans to the next generation."

The report says improved monitoring and data collection are needed in Africa and other regions where information on marine pollution is lacking.

It also highlighted concerns over the destruction of economically important coastal ecosystems such as mangrove forests, coral reefs and sea-grass beds.