We’re committed to protecting the world’s coral reefs, which are home to 25% of the world’s marine species and support the livelihoods of millions across the globe. Our work is no easy task. Reefs face a multitude of threats, from overfishing to coral bleaching caused by climate change. But you might be surprised to learn that one of the most serious threats to these delicate ecosystems is untreated wastewater—an often-overlooked global problem increasingly jeopardizing the health of our oceans.
CORAL is a proud member of the Ocean Sewage Alliance (OSA), a coalition of organizations shedding light on and addressing this issue. This month, OSA helped support the release of “The scourge of untreated wastewater: The economic, environmental and human costs of inaction.”
This groundbreaking report estimates economic losses suffered from domestic wastewater pollution in five countries: Brazil, India, Kenya, the Philippines, and the UK. As a part of the Economist’s Back to Blue Initiative, the report’s findings reveal how poor sewage treatment is depleting fishery and agricultural food sources, burdening health systems, and costing the global economy billions, with consequences for coral reefs and many other ocean ecosystems.
Wastewater Effects on Marine Ecosystems
Untreated wastewater disrupts the delicate balance of coral reefs and the marine life that depends on them.
When wastewater enters the ocean, it carries excess nutrients, harmful chemicals, and bacteria that can damage marine ecosystems, including coral reefs. Nutrient pollution, for instance, can cause explosive growth in algae, resulting in harmful algal blooms that can encompass hundreds of square miles. When these algae eventually die, they are consumed by bacteria that deplete oxygen levels in the water, creating “dead zones” where marine life—including coral reefs—cannot survive.
Fisheries and Agriculture at Risk
The innovative study found that countries with high levels of untreated wastewater, such as India and Kenya, experience significant disruptions to their fisheries, which rely on healthy ecosystems for sustainability. Coral reefs, as sensitive habitats, are also vulnerable to these pollutants.
Fisheries, which provide a major source of income for coastal communities, are suffering. The report suggests annual losses in the billions for some countries, as is the case in India, which is estimated to lose $2.2 billion annually due to loss in fish populations. These losses may be similar in other coastal nations with poor wastewater treatment infrastructure and not only harm marine life but also threaten the livelihoods of millions of people who rely on the ocean for food and income.
The consequences of wastewater pollution extend beyond the ocean. In developing countries, a significant amount of agricultural land is irrigated with raw or partially treated wastewater, exposing crops to heavy metals that are toxic to humans and degrade soil quality. These practices, in turn, lead to lower agricultural yields and a decrease in food security. The costs can be staggeringly high. In Brazil, for instance, the report estimates total economic loss to the agriculture sector from not treating wastewater may be up to $15.7 billion dollars annually.
Even Higher Costs of Inaction
The true cost of inaction on wastewater treatment is almost certainly higher than what is described in the report. For instance, to model the cost of untreated wastewater for fisheries, the authors only looked at reductions in fish populations specifically. Left out of these estimates are ecosystem impacts (like the ones caused by harmful algal blooms) or reductions in tourism. Similarly, in their models assessing harm to agriculture, the authors only look at each country’s most highly produced and water-intensive crops. As a result, the true cost of untreated wastewater to fisheries, agriculture, and human health, is likely far worse than what is described, particularly when considering the long-term effects of untreated wastewater on human health, biodiversity, and the global economy.
For coral reefs, this issue is not just a local problem—it is a global crisis. Protecting coral reefs requires action on multiple fronts, including improving wastewater treatment systems, reducing pollution, and supporting sustainable fishing practices.
What Can Be Done?
As the Back to Blue Initiative emphasizes, we must take urgent steps to address wastewater pollution. These include investing in wastewater infrastructure, promoting sustainable agricultural practices, and strengthening regulations on industrial discharges. Coral reef conservation efforts must go hand in hand with addressing pollution at its source.
For the sake of our oceans, coral reefs, and the communities that depend on them, we cannot afford to ignore the hidden costs of wastewater any longer. It is time to act—before it’s too late.
The implications of this report highlight the importance of CORAL’s work on wastewater and the necessity of working with the Ocean Sewage Alliance and others to scale this work up further.
Helen Fox, Conservation Science Director of CORAL
Back to Blue and the Ocean Sewage Alliance are calling on governments, the private sector, and policymakers to invest now in their sewage infrastructure for a healthier and more vibrant future for citizens and economies. When we address wastewater issues, we lean into a sorely underutilized solution. This strengthens ocean resilience by preventing the loss of biodiversity and protecting the well-being of communities around the world.
Download the full report here >
