For months last year, Florida’s beachgoers were plagued by rotting tangles of decaying seaweed that had washed ashore. Known technically as sargassum, the thick clumps were part of a record-setting 8,000-kilometre-long seaweed belt in the Atlantic Ocean.
Sargassum blooms cause a range of environmental problems, including coastal “dead zones” bereft of aquatic life. Past sargassum outbreaks have been linked to the excessive release of phosphorus and other chemical substances known as nutrients.
Phosphorus and another nutrient, nitrogen, are key ingredients in synthetic fertilizers. They have become increasingly popular in recent decades but can have devastating effects when they enter lakes, rivers and the ocean.
At the upcoming sixth session of the United Nations Environment Assembly (UNEA-6), the world’s top decision-making body on the environment, delegates from UN Member States are expected to discuss how to advance global cooperation around nutrients. In particular, they are slated to explore ways to rein in excess phosphorus in the environment without compromising efforts to end hunger. This builds on work already done by Member States through past UNEA resolutions to decrease nitrogen pollution.
“Reducing nutrient pollution and recovering nutrients, such as phosphorus, for reuse is a win-win both for the environment and human health,” says Leticia Carvalho, head of the Marine and Freshwater Branch at the UN Environment Programme (UNEP). “But to succeed, we need governments, scientists, the private sector and civil society to come together."
Ahead of UNEA-6 discussions, here are some facts about phosphorus use and how the mineral can be better managed.
What is phosphorus and what are its main uses today?
Discovered more than 350 years ago, phosphorus is an indispensable nutrient that helps plants to grow. Its primary use is in manufacturing synthetic fertilizer to increase crop yields, making it crucial to food security. Phosphorus is a key ingredient in animal feed and is also used to produce steel, food additives, electric car batteries, certain pesticides and household cleaning products.
Where does phosphorus come from?
Phosphate rock is the main source of easily accessible phosphorus for manufacturing synthetic fertilizer and has been produced in large quantities since World War II.
So, phosphorus reserves are limited?
Yes. The amount of phosphorus in the world is finite and there is a need to reduce how much of the mineral we are extracting. This can be done by making phosphorus mining and processing more efficient. Also important: optimizing how phosphorus is used in agriculture and recovering phosphorus from waste.
Where does phosphorus pollution come from?
Agriculture is a major source of phosphorus pollution, both from the production of crops and raising of livestock. Phosphorus is also lost through sewage, food that is thrown away and other waste streams.
Why is too much phosphorus a bad thing?
Excess phosphorus, like the other key nutrient, nitrogen, depletes soils of their richness. It also pollutes lakes, rivers and the ocean in a process known as eutrophication. This leads to algal blooms which contaminate supplies of drinking water and create oxygen-starved dead zones, which can kill fish and other aquatic species. Phosphorus pollution is a prime driver of biodiversity loss and contributes to the degradation of ecosystems on which humanity depends. Eutrophication is estimated to cost the US economy alone US$2.2 billion annually.
Is the rate of phosphorus pollution increasing?
Yes. Globally, phosphorus losses from land to fresh waters have doubled in the last century and continue to increase. Despite large-scale efforts to reduce nutrient pollution, Carvalho said the release of phosphorus is already overwhelming the planet’s ability to cope. As much as 80 per cent of the mineral is lost or wasted during use. Along with the environmental fallout, that costs farmers, factory owners and others about US$265 billion a year.
“We’ve long since crossed the red line on phosphorus pollution and the effects on the Earth have been devastating,” says Carvalho. “If humanity continues down this path, we risk compromising countless ecosystems around the world."
Does that mean humanity should just stop using phosphorus?
No. The key is for phosphorus to be used more sustainably and to prevent excessive amounts of it from seeping into the environment. There is a common misconception that the more phosphorus-based fertilizer used, the more crop yields will rise. This is not necessarily true. The key is to use the right amount, so that crops will still thrive and the environment will not suffer unduly.
How can humanity more sustainably use phosphorus?
Changes in agricultural practices can help reduce phosphorus pollution. The use of manure, for example, can lessen the need for phosphorus-based fertilizers. Farmers can also plant cover crops and avoid tilling the soil, which will improve soil health and reduce the need for fertilizer. These practices should be part of a larger shift towards regenerative agriculture, a more planet-friendly approach to farming that improves soil health and maintains biodiversity.
As well, synthetic fertilizers should only be used at the stage when crops need phosphorus the most. The livestock sector must also explore ways of recovering phosphorus from manure.
Finally, wastewater discharges some 3 millions tonnes of phosphorus into the environment every year globally. Proper treatment could reduce the concentration of phosphorus and nitrogen in wastewater by at least 80 per cent.
The solutions will require innovation—not just in technology but also in ways of working. It will require cooperation within and across sectors that may not have traditionally worked together.
How much do we need to reduce phosphorus pollution by?
A lot. The Our Phosphorus Future report calls for a 50 per cent reduction in global phosphorus pollution, coupled with a 50 per cent increase in the recycling of phosphorus lost in residues and wastewater by 2050. The report said that would bolster food security and improve water quality, among a host of other benefits.
What is UNEP doing to tackle phosphorus pollution?
UNEP hosts the Global Partnership on Nutrient Management, launched in 2009. It promotes effective nutrient management, particularly of nitrogen and phosphorus, to both achieve food security and protect the environment.
UNEP’s efforts to control the environmental fallout of phosphorus come amid a wider global effort to rein in pollution, which received a boost last year with the landmark Global Framework on Chemicals. Based around 28 targets, the framework sets out a roadmap for protecting people and the planet from harmful chemicals and waste. UNEP will manage a trust fund that will help implement the agreement.
As the leading global authority on the environment, UNEP is also helping countries implement the Kunming-Montreal Global Biodiversity Framework, including Target 7, which addresses phosphorus. The framework calls for a 50 per cent reduction in excess nutrients lost to the environment by 2030 and for the risk from pesticides to be reduced by at least half.
The sixth session of the United Nations Environment Assembly (UNEA-6) will be held from 26 February to 1 March 2024 at the UNEP headquarters in Nairobi, Kenya, under the theme: Effective, inclusive and sustainable multilateral actions to tackle climate change, biodiversity loss and pollution. Through its resolutions and calls to action, the Assembly provides leadership and catalyzes intergovernmental action on the environment.
