Программа ООН по окружающей среде
27 Nov 2018 История Экосистемы и биоразнообразие

Managing wastewater to support coral reef health, resilience

Photo by Art Centre of Excellence for Coral Reef Studies/CRIB

Coral reefs provide food and livelihoods for hundreds of millions of people around the world, support more than a quarter of all marine life, and protect communities and coastlines from natural disasters—and if urgent action is not taken, we risk losing them forever. 

The spectacular marine diversity that corals offer has attracted snorkelers, divers and film-makers for decades, but these awe-inspiring ecosystems are now in serious trouble.

The alarming state of coral reefs around the world has been well-documented in the past few years. Climate change, ocean acidification and pollution are the main causes of coral bleaching, degradation and die-offs.

However, awareness and data on how wastewater pollution impacts coral reefs remain limited in most reef regions.

“For years, oceans have been used as dumping grounds for many types of waste, including sewage, industrial waste, chemicals and litter,” says head of UN Environment’s coral reef unit Jerker Tamelander. “More than 80 per cent of marine pollution originates from land, including wastewater, sediment and nutrients delivered via waterways.” 

A 2017 brief Wastewater Pollution on Coral Reefs compiled by UN Environment through the Global Coral Reef Partnership and the Global Wastewater Initiative and in collaboration with Coasts Climate Oceans, says coral exposed to excess nutrients, turbidity, sedimentation, pathogens or chemical pollutants is more susceptible to thermal stress and less able to survive a coral bleaching event.

Furthermore, chronic wastewater stress prevents reef communities from recovering after a bleaching event. The interaction of ocean acidification and localized, high-nutrient loading also accelerates coral reef loss.

Photo by Shaun Wolfe/CRIB

Minimizing land-based pollution reaching coral reefs is critical. The best way to do this is through policy decisions and management actions at the local and national level.

A new partnership, which includes UN Environment, the International Coral Reef Initiative, the World Wildlife Fund, The Nature Conservancy, Wildlife Conservation Society, Vulcan Inc., The Ocean Agency, and the Convention on Biological Diversity Secretariat, was unveiled at the November 2018 Convention on Biological Diversity Conference of Parties meeting in Egypt. It aims to raise awareness about the coral reef crisis and urge governments to take greater action. 

A lethal concoction

Wastewater contains a range of pollutants that harm coral reefs, including sediment, nutrients, pesticides, trace metals, hydrocarbons, organochlorines and various emerging pollutants, such as pharmaceuticals and microplastics. Even sunscreen might be damaging coral reefs.

“A root cause of wastewater pollution is the limited understanding of its environmental significance, among both the general public and decision-makers,” says Jon Brodie, a senior scientist at Coasts Climate Oceans.

Sources of wastewater pollution on coral reefs include urban areas and other coastal development, e.g. tourism and industry, as well as animal husbandry, agriculture and logging.

Lang Tengah Island, Malaysia. Photo by Yen-Yi Lee/CRIB

Nutrients and sediment can have very significant and widespread negative impacts on coral reefs; other pollutants may be significant locally. Furthermore, wastewater pollution reduces the climate change resilience of coral reefs and makes them more sensitive to ocean warming and acidification.

In general, point-source sewage and industrial discharges are easier to manage than indirect and diffuse wastewater streams, as there are technologies that can be applied at the source, such as sewage treatment and on-site treatment technologies. Indirect and diffuse wastewater pollution requires broader, often cross-sectoral policy and management responses, spanning catchment as well as reef.

Major obstacles to managing wastewater discharges into coral reef environments include: poor enforcement of existing legislation and, in some instances, a lack of appropriate legislation or water quality standards; limited funding for installing or upgrading wastewater treatment systems; some remaining technological barriers, e.g. in relation to low-cost, small-footprint treatment systems; and poor monitoring of the effectiveness of treatment and other wastewater reduction measures, including their suitability from a marine-ecological perspective.

For further information please contact Jerker Tamelander