Dead elephants and feral sea lions: how poisonous algal blooms harm the planet
Before the elephants collapsed, they walked in aimless circles. Some fell head first, dying where they stood moments earlier; their carcasses scattered near watering holes across the Okavango delta in Botswana.
The unexplained deaths in May 2020 alarmed conservationists. By July at least 350 elephants had died and nobody knew why.
'The animals all had their tusks, so poaching was unlikely. A lot of them had obviously died relatively suddenly: they had dropped on to their sternums, which was indicating a sudden loss of muscle function or neural capacity,' says Niall McCann, director of the conservation group National Park Rescue.
Nearly five years later, in November 2024, scientists finally published a paper indicating what they believe to be the reason behind the deaths: toxic water caused by an algal bloom.
READ MORE
A sudden shift between dry and wet conditions in 2019 and 2020 created perfect conditions for cyanobacteria that release toxins lethal to the elephants, although the researchers could not make definitive conclusions as samples were not taken quickly enough in 2020 due to the pandemic.
'Blooms' are a rapid increase in the amount of algae, often occurring in shallow, slow-moving warm water. They can transform a sea, lake or river into a mass of green, yellow, brown or even red, sometimes for several weeks. Not all blooms are harmful – many sustain important fisheries.
But sometimes algae forms such a thick layer that it blocks out sunlight in critical habitats; others can release harmful toxins. When the algae die, they rapidly deplete oxygen in water – often creating 'dead zones' where few fish can survive.
As the Earth warms, harmful algal blooms are on the rise – even creeping into polar waters. They are driven by a mixture of pollution from agriculture, runoff from human waste and, increasingly, global heating – sometimes with dramatic consequences for wildlife and humans. As they spread, they are changing the colour of the world's lakes, rivers and oceans.
[
UN Ocean Conference 3: will it lead to protecting the high seas from all extraction, forever?
Opens in new window
]
Nearly two-thirds of all lakes have changed colour in the past 40 years, a recent study shows. A third are blue – but as temperatures warm, they are likely to turn a murky green or brown, other research has found. The planet's oceans are turning green as they warm, a result of absorbing more than 90 per cent of excess heat from global warming.
At sea, the size and frequency of blooms in coastal areas has risen by 13.2 per cent and 59.2 per cent respectively in 2003-2020, a 2024 study revealed.
In freshwater systems blooms became 44 per cent more frequent globally in the 2010s, according to a 2022 global assessment of 248,000 lakes.
The rise was largely driven by places in Asia and Africa that remain reliant on agricultural fertiliser. While progress has been made in North America, Europe and Oceania to stabilise blooms, the climate crisis has driven their resurgence in some freshwater systems.
The fertilisers that people use to grow plants – including reactive nitrogen and phosphates – also supercharge algal growth. As they are washed off fields and pour into water bodies around the world, they significantly alter how ecosystems function.
'Humans are today loading more reactive nitrogen into the biosphere than the natural cycle [is],' said Johan Rockström, director of the Potsdam Institute for Climate Impact Research. He was co-author of a 2023 assessment that found that humanity had now gone far beyond the planet's natural limits for nitrogen and phosphorus.
[
Commitment to climate action hard to find in Government
Opens in new window
]
'We need to reduce the supply of reactive human nitrogen by over 75 per cent. It's a dramatic change and there's a lot of scientific debate about this,' he says.
'Most agricultural scientists say that it is not possible because we cannot feed humanity. We have a contradiction here: is our first objective to keep the planet's freshwater systems, coastal zones, ecosystems and climate stable – or is it to feed humanity?'
Others warn that it is not a simple choice between food and the environment. In northern Norway repeated algal blooms have wiped out millions of farmed salmon and cod in recent years. A single bloom killed more than seven million salmon in 2019. This year another has wiped out up to a million more fish.
As has just happened in South Australia, where it spanned 8,800 sq km, scores of fish and dead sea life wash up on beaches once a huge algal bloom spreads. Deepwater sharks, crabs, lobsters and prawns are among those found dead as a result of the toxic blanket created by Karenia mikimotoi algae, with the ocean 2.5 degrees hotter than usual for the season.
In March a teenager was attacked by a 'feral' sea lion off the coast of southern California, where there has been an increase in aggressive behaviour from the animals linked to a large algal bloom, which can poison and induce seizures in the mammals due to the domoic acid neurotoxin it produces.
While there are signs that the bloom is waning, it was the fourth consecutive year that California had experienced a significant outbreak.
However, not everything dies in a dead zone. Once the putrid expanse of algae has dispersed and those that can swim away have left, aquatic species better adapted to low levels of oxygen, or hypoxia, move in. This has led to a boom in jellyfish numbers in many parts of the world.
Denise Breitburg, of the Smithsonian Environmental Research Center, has studied Chesapeake Bay, the largest estuary in the US to experience algal blooms, for decades, says: 'The jellyfish we have here are way more tolerant of low oxygen in the water than species they would be competing with for food. They become more efficient predators and can utilise habitat that fin fish are excluded from.'
As the world heats, the disruptions that algal blooms cause to ecosystems will be hard to stop, experts warn. Prof Donald Boesch, who helped first identify the dead zone in the Gulf of Mexico, which last year reached 17,000 sq km, the 12th largest in 38 years of records, says the process will get worse if the world does not prevent rising temperatures.
'As the liquid heats up, its ability to dissolve gases is reduced, so it holds less oxygen. Warmer surface waters can increase the stratification of layers in the ocean. It means that the warmer waters at the surface are less dense than the bottom waters, so they don't get mixed up.
'It's going to get worse,' says Boesch.
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Irish Times
3 hours ago
- Irish Times
Restoring biodiversity on the Yangtze river: ‘You have to do some balancing and make some difficult choices'
Yang Jin was taking his daily walk along the Yangtze river, close to the Three Gorges Dam, when he spotted something worrying in the water. The 67 year-old pensioner has cultivated a hobby of photographing the Yangtze finless porpoise, an aquatic mammal endemic to the river which was on the verge of extinction a few years ago. A finless porpoise was thrashing about in distress on the water's surface and when Yang looked more closely, he saw that it was entangled in an abandoned fishing net. Although the porpoise lives in the water, it needs to surface for air and this one was in danger of drowning so Yang called the local fishing authorities. They halted all shipping in the area and sent a team via speedboat to cut through the net and rescue the porpoise. The animal had cut itself struggling to escape from the net but its rescuers decided it was not too serious so they released it into the river. READ MORE 'I was worried about its injury and whether it would get infected so I visited every day to photograph and monitor it,' Yang says. 'Fortunately, I captured the moment it leapt out of the water. Its tail showed scars when it emerged, and I found it was pregnant. Around late April to early May, it successfully gave birth to a calf.' The number of finless porpoises in the Yangtze river halved from 3,600 in the 1990s to 1,800 in 2006 and by 2012 there were 1,045 left. But the decline stopped around 2017 and in the five years after that, the population grew by 23 per cent. 'The main reason is the fishery ban,' says Wang Ding, a professor at the Institute of Hydrobiology in the Chinese Academy of Sciences and China's top representative in Unesco's Man and the Biosphere programme. China imposed a 10-year ban on commercial fishing in the Yangtze river, its seven main tributaries and two biggest lakes. Private, recreational fishing is allowed but anything on a bigger scale is punishable by law. 'That's the main measure we have been carrying out to protect the Yangtze river. Also to remove literally every chemical factory at least 1km away from the Yangtze river,' Wang says. 'If you are sitting right here on the bank, you have to go and of course, the government will pay you to move. The water quality has been improved quite a lot. Yang Jin, an amateur photographer of finless porpoises, on a bank of the Yangtze River 'The Yangtze finless porpoise sits right on the top of the food chain of the biodiversity . If he's doing well, it means the biodiversity of the Yangtze river is doing well. If the number is increasing, it means the situation of ecological conditions of the Yangtze river are improving.' Restoring the Yangtze river's biodiversity is made more challenging by the impact of the Three Gorges Dam, the world's biggest hydroelectric power station and one of the most controversial engineering projects ever undertaken. Built between 1994 and 2012, the dam is 2,335 metres long and 185 metres high, creating a reservoir that stretches for 600km. The dam's most important function was to control the flooding that caused huge damage and loss of life along the river, affecting cities like Wuhan and Nanjing, which were home to millions of people. It was also a major new source of cheap, sustainable energy and improved navigation on the river, especially for cargo ships. The Chinese Academy of Sciences warned in advance about the dam's likely impact on the environment and the plan met unusually strong resistance in the National People's Congress. China's generally compliant legislature approved the dam in 1992 with 1,767 votes in favour but 177 voted against it. There were 664 abstentions and 25 invalid ballots. The Three Gorges Dam and low water levels along the Yangtze river in Yichang, China. Photograph: Bloomberg More than 1.3 million people saw their homes disappear under water and were forced to relocate, often to less fertile places with inadequate compensation. Some 1,300 archaeological sites and ancient villages were submerged, including centuries-old temples. The dam destroyed forests, wetlands and habitats for endangered species, trapped industrial waste to create water pollution and triggered thousands of landslides along the river. One of the most seriously affected species was the Chinese sturgeon, a critically endangered species found only in the Yangtze river. 'Chinese sturgeon used to go way up the river more than 1,000km from here to spawn. But because of this dam, the Chinese sturgeon can't go there, to their old spawning area,' Wang says. Prof Wang Ding, of the Chinese Academy of Sciences, is an expert on the Yangtze finless porpoise The Chinese sturgeon found a small spawning area downstream but their numbers have continued to decline, despite increasingly energetic efforts to save the species. At the Yangtze River Rare Fish Breeding Base, thousands of Chinese sturgeon swim in vast circular steel tanks as they wait to be released into the river. Last year, the breeding base released 200,000 into the Yangtze river and they are planning to increase the annual number to more than a million. Each fish is fitted with a tracking device and at least 70 per cent of those released make the journey downstream into the sea, where they typically spend more than 14 years before coming back to the river to breed for the first time. In the giant turbine room of the Three Gorges Dam power station, red lights mark the turbines that are currently in operation. In the control room, engineers monitor the inflow and outflow of water, the electricity generated and to which parts of central and eastern China it is distributed on the grid. 'If we want to generate more electricity, we must keep the water high. But if we want to control flooding, we must keep the level low. Now it is at a low level. It's not good for our electric power, but it's good for flood control,' says Yang Peng, deputy director of the operations department at the power station. 'We do our best to protect the fish. During the breeding time, we can control the water flow to meet the need of the fish so then fish can breed.' Chinese sturgeon and carp in cultivation tanks at the Yangtze River Rare Fish Breeding Base One problem created by the dam and its reservoir is the spread of algal blooms that form a green scum on the water surface, depleting oxygen in the water and harming aquatic life. The China Three Gorges Corporation, which runs the dam, has invested heavily in mitigation efforts in recent years, under instructions from Beijing, and the water quality is improving. 'We can't say the water quality in the Yangtze river is getting better because of the dam. The Three Gorges Dam creates some problems because it cut out the mainstream of the river. The water flow is getting slower and slower. So that provides a fundamental basis for this algal bloom and that's really bad,' Wang says. 'But the Three Gorges Corporation, they are investing quite a lot of money, required, of course, by central government who said you have to take care of this. So they set up wastewater processing stations in every single town along the river. And also some other big measures like not cutting trees, restoring the forest along the bank, and controlling pollution from farming and stuff like that. These are the reasons the water quality is becoming better. The corporation's actions reflect a remarkable shift in public attitudes and in government policy towards the environment in recent years. Years before he became the Communist Party's general secretary and China's president, Xi Jinping championed the closure of polluting factories as party secretary in Zhejiang province. China's president Xi Jinping championed the closure of polluting factories as Communist Party secretary in Zhejiang province. Photograph: Florence Lo-Pool/Getty Images 'Lucid waters and lush mountains are invaluable assets,' he wrote in 2005. 'Lucid waters and lush mountains can bring invaluable assets but invaluable assets cannot buy lucid waters and lush mountains.' Since becoming leader in 2012, Xi has embedded the requirement to balance environmental protection with economic development into national policy. This saw the establishment of five national parks in 2021, with plans to designate 49 by 2035 covering 10 per cent of China's land area. Among the leading candidates for such a designation is Shennongjia Forestry District, one of China's most biodiverse areas with dense primeval forests, alpine meadows and karst landscapes. The forest is also home to the golden snub-nosed monkey, one of China's most endangered primate species. 'When we first established this nature reserve, the population of golden snub-nosed monkeys was only a little over 500. Now, after more than 40 years of protection, there are more than 1,600,' says Yang Jingyuan, head of the reserve's scientific research institute, as he takes a peanut from his pocket and hands it to a monkey. 'We need to protect its living environment and provide a sufficiently large habitat with adequate food, water, and shelter, so that the golden monkey feels comfortable living here. In this case, its population will grow rapidly. Golden monkeys are very gentle. If you don't harm them, they will never actively harm you.' In the core area of the Shennongjia reserve, only those engaged in scientific monitoring can enter. A belt around that allows visitors under restricted conditions and an outer circle is developed with hotels, shops and other businesses. Golden snub-nosed monkeys in Shennongjia Forest, Hubei province 'Sometimes we have to balance all kinds of requirements. For example for the Three Gorges Dam, flood control is about life. It's very important because if the river bank is broken, it could cause many people to die. That's the first most important thing,' Wang says. 'Navigation is another big issue because the river section above the Three Gorges Dam was very narrow and the current was strong. So no big ship could go up all the way to Chongqing. Now it's much better and also, of course, we have clean energy. So you have to do some balancing and make some difficult choices, right?'
Irish Times
10-06-2025
- Irish Times
Dead elephants and feral sea lions: how poisonous algal blooms harm the planet
Before the elephants collapsed, they walked in aimless circles. Some fell head first, dying where they stood moments earlier; their carcasses scattered near watering holes across the Okavango delta in Botswana. The unexplained deaths in May 2020 alarmed conservationists. By July at least 350 elephants had died and nobody knew why. 'The animals all had their tusks, so poaching was unlikely. A lot of them had obviously died relatively suddenly: they had dropped on to their sternums, which was indicating a sudden loss of muscle function or neural capacity,' says Niall McCann, director of the conservation group National Park Rescue. Nearly five years later, in November 2024, scientists finally published a paper indicating what they believe to be the reason behind the deaths: toxic water caused by an algal bloom. READ MORE A sudden shift between dry and wet conditions in 2019 and 2020 created perfect conditions for cyanobacteria that release toxins lethal to the elephants, although the researchers could not make definitive conclusions as samples were not taken quickly enough in 2020 due to the pandemic. 'Blooms' are a rapid increase in the amount of algae, often occurring in shallow, slow-moving warm water. They can transform a sea, lake or river into a mass of green, yellow, brown or even red, sometimes for several weeks. Not all blooms are harmful – many sustain important fisheries. But sometimes algae forms such a thick layer that it blocks out sunlight in critical habitats; others can release harmful toxins. When the algae die, they rapidly deplete oxygen in water – often creating 'dead zones' where few fish can survive. As the Earth warms, harmful algal blooms are on the rise – even creeping into polar waters. They are driven by a mixture of pollution from agriculture, runoff from human waste and, increasingly, global heating – sometimes with dramatic consequences for wildlife and humans. As they spread, they are changing the colour of the world's lakes, rivers and oceans. [ UN Ocean Conference 3: will it lead to protecting the high seas from all extraction, forever? Opens in new window ] Nearly two-thirds of all lakes have changed colour in the past 40 years, a recent study shows. A third are blue – but as temperatures warm, they are likely to turn a murky green or brown, other research has found. The planet's oceans are turning green as they warm, a result of absorbing more than 90 per cent of excess heat from global warming. At sea, the size and frequency of blooms in coastal areas has risen by 13.2 per cent and 59.2 per cent respectively in 2003-2020, a 2024 study revealed. In freshwater systems blooms became 44 per cent more frequent globally in the 2010s, according to a 2022 global assessment of 248,000 lakes. The rise was largely driven by places in Asia and Africa that remain reliant on agricultural fertiliser. While progress has been made in North America, Europe and Oceania to stabilise blooms, the climate crisis has driven their resurgence in some freshwater systems. The fertilisers that people use to grow plants – including reactive nitrogen and phosphates – also supercharge algal growth. As they are washed off fields and pour into water bodies around the world, they significantly alter how ecosystems function. 'Humans are today loading more reactive nitrogen into the biosphere than the natural cycle [is],' said Johan Rockström, director of the Potsdam Institute for Climate Impact Research. He was co-author of a 2023 assessment that found that humanity had now gone far beyond the planet's natural limits for nitrogen and phosphorus. [ Commitment to climate action hard to find in Government Opens in new window ] 'We need to reduce the supply of reactive human nitrogen by over 75 per cent. It's a dramatic change and there's a lot of scientific debate about this,' he says. 'Most agricultural scientists say that it is not possible because we cannot feed humanity. We have a contradiction here: is our first objective to keep the planet's freshwater systems, coastal zones, ecosystems and climate stable – or is it to feed humanity?' Others warn that it is not a simple choice between food and the environment. In northern Norway repeated algal blooms have wiped out millions of farmed salmon and cod in recent years. A single bloom killed more than seven million salmon in 2019. This year another has wiped out up to a million more fish. As has just happened in South Australia, where it spanned 8,800 sq km, scores of fish and dead sea life wash up on beaches once a huge algal bloom spreads. Deepwater sharks, crabs, lobsters and prawns are among those found dead as a result of the toxic blanket created by Karenia mikimotoi algae, with the ocean 2.5 degrees hotter than usual for the season. In March a teenager was attacked by a 'feral' sea lion off the coast of southern California, where there has been an increase in aggressive behaviour from the animals linked to a large algal bloom, which can poison and induce seizures in the mammals due to the domoic acid neurotoxin it produces. While there are signs that the bloom is waning, it was the fourth consecutive year that California had experienced a significant outbreak. However, not everything dies in a dead zone. Once the putrid expanse of algae has dispersed and those that can swim away have left, aquatic species better adapted to low levels of oxygen, or hypoxia, move in. This has led to a boom in jellyfish numbers in many parts of the world. Denise Breitburg, of the Smithsonian Environmental Research Center, has studied Chesapeake Bay, the largest estuary in the US to experience algal blooms, for decades, says: 'The jellyfish we have here are way more tolerant of low oxygen in the water than species they would be competing with for food. They become more efficient predators and can utilise habitat that fin fish are excluded from.' As the world heats, the disruptions that algal blooms cause to ecosystems will be hard to stop, experts warn. Prof Donald Boesch, who helped first identify the dead zone in the Gulf of Mexico, which last year reached 17,000 sq km, the 12th largest in 38 years of records, says the process will get worse if the world does not prevent rising temperatures. 'As the liquid heats up, its ability to dissolve gases is reduced, so it holds less oxygen. Warmer surface waters can increase the stratification of layers in the ocean. It means that the warmer waters at the surface are less dense than the bottom waters, so they don't get mixed up. 'It's going to get worse,' says Boesch.
Irish Examiner
10-06-2025
- Irish Examiner
Dead elephants and feral sea lions: how poisonous algal blooms harm the planet
Before the elephants collapsed, they walked in aimless circles. Some fell head first, dying where they stood moments earlier; their carcasses scattered near watering holes across the Okavango delta. The unexplained deaths in May 2020 alarmed conservationists. By July, at least 350 elephants had died and nobody knew why. 'The animals all had their tusks, so poaching was unlikely. A lot of them had obviously died relatively suddenly: they had dropped on to their sternums, which was indicating a sudden loss of muscle function or neural capacity,' says Niall McCann, director of the conservation group National Park Rescue. Nearly five years later, in November 2024, scientists finally published a paper indicating what they believe to be the reason behind the deaths: toxic water caused by an algal bloom. A sudden shift between dry and wet conditions in 2019 and 2020 created perfect conditions for cyanobacteria that release toxins lethal to the elephants, although the researchers could not make definitive conclusions as samples were not taken quickly enough in 2020 due to the pandemic. Foul-smelling algae along the St Lucie River in Stuart, Florida, in 2016. The algae spoiled coastal waterways and closed beaches. Photo: Joe Raedle/Getty 'Blooms' are a rapid increase in the amount of algae, often occurring in shallow, slow-moving warm water. They can transform a sea, lake or river into a mass of green, yellow, brown or even red, sometimes for several weeks. Not all blooms are harmful – many sustain important fisheries. But sometimes algae forms such a thick layer that it blocks out sunlight in critical habitats; others can release harmful toxins. When the algae die, they rapidly deplete oxygen in water – often creating 'dead zones' where few fish can survive. As the Earth warms, harmful algal blooms are on the rise – even creeping into polar waters. They are driven by a mixture of pollution from agriculture, run-off from human waste and, increasingly, global heating – sometimes with dramatic consequences for wildlife and humans. As they spread, they are changing the colour of the world's lakes, rivers and oceans. Nearly two-thirds of all lakes have changed colour in the past 40 years, according to a recent study. A third are blue – but as temperatures warm, they are likely to turn a murky green or brown, other research has found. The planet's oceans are turning green as they warm, a result of absorbing more than 90% of excess heat from global warming. A satellite image of algal blooms in Lake Saint Clair on the US-Canadian border in 2015, showing the run-off from farms compared with the clear Detroit shoreline to the west. Photo: Nasa At sea, the size and frequency of blooms in coastal areas has risen by 13.2% and 59.2% respectively between 2003 and 2020, according to a 2024 study. In freshwater systems, blooms became 44% more frequent globally in the 2010s, according to a 2022 global assessment of 248,000 lakes. The rise was largely driven by places in Asia and Africa that remain reliant on agricultural fertiliser. While progress has been made in North America, Europe and Oceania to stabilise blooms, the climate crisis has driven their resurgence in some freshwater systems. The fertilisers that people use to grow plants – including reactive nitrogen and phosphates – also supercharge algal growth. As they are washed off fields and pour into water bodies around the world, they significantly alter how ecosystems function. 'Humans are today loading more reactive nitrogen into the biosphere than the natural cycle [is],' said Johan Rockström, director of the Potsdam Institute for Climate Impact Research. He was co-author of a 2023 assessment that found that humanity had now gone far beyond the planet's natural limits for nitrogen and phosphorus. 'We need to reduce the supply of reactive human nitrogen by over 75%. It's a dramatic change and there's a lot of scientific debate about this,' he says. 'Most agricultural scientists say that it is not possible because we cannot feed humanity. We have a contradiction here: is our first objective to keep the planet's freshwater systems, coastal zones, ecosystems and climate stable – or is it to feed humanity? Others warn that it is not a simple choice between food and the environment. In northern Norway, repeated algal blooms have wiped out millions of farmed salmon and cod in recent years. A single bloom killed more than seven million salmon in 2019. This year, another has wiped out up to a million more fish. In March, a teenager was attacked by a 'feral' sea lion off the coast of southern California, where there has been an increase in aggressive behaviour from the animals linked to a large algal bloom, which can poison and induce seizures in the mammals due to the domoic acid neurotoxin it produces. A dead fish is floating in the foul-smelling algae in Florida's St Lucie River in July 2016. Low levels of oxygen, or hypoxia, suffocate fish. Photo:While there are signs that the bloom is waning, it was the fourth consecutive year that California had experienced a significant outbreak. However, not everything dies in a dead zone. Once the putrid expanse of algae has dispersed and those that can swim away have left, aquatic species better adapted to low levels of oxygen, or hypoxia, move in. This has led to a boom in jellyfish numbers in many parts of the world. Denise Breitburg, of the Smithsonian Environmental Research Center, has studied Chesapeake Bay, the largest estuary in the US to experience algal blooms, for decades, says: 'The jellyfish we have here are way more tolerant of low oxygen in the water than species they would be competing with for food. They become more efficient predators and can utilise habitat that fin fish are excluded from.' PORT MAYACA, FL - JULY 13: A sign warns of Blue-Green algae in the water near the Port Mayaca Lock and Dam on Florida's Lake Okeechobee in July 2018. Photo:As the world heats, the disruptions that algal blooms cause to ecosystems will be hard to stop, experts warn. Prof. Donald Boesch, who helped first identify the dead zone in the Gulf of Mexico, which last year reached 17,000 sq km, the 12th largest in 38 years of records, says the process will get worse if the world does not prevent rising temperatures. 'As the liquid heats up, its ability to dissolve gases is reduced, so it holds less oxygen. Warmer surface waters can increase the stratification of layers in the ocean. It means that the warmer waters at the surface are less dense than the bottom waters, so they don't get mixed up. 'It's going to get worse,' says Boesch. The Guardian
