Tag Archives: freshwater

World

World’s biggest freshwater fish, a 660-pound stingray, caught in Cambodia

Leave a comment

Named Boramy — meaning “full moon” in the Khmer language — because of her bulbous shape, the four-meter (13-foot) female was released back into the river after being electronically tagged to allow scientists to monitor her movement and behavior.

“This is very exciting news because it was the world’s largest (freshwater) fish,” said biologist Zeb Hogan, ex-host of the “Monster Fish” show on the National Geographic Channel and now part of Wonders of the Mekong, a conservation project on the river.

“It is also exciting news because it means that this stretch of the Mekong is still healthy…. It is a sign of hope that these huge fish still live (here).”

Boramy was netted last week off Koh Preah, an island along the northern Cambodian stretch of the river. She took the record from a 645-pound (293-kilogram) giant catfish that was caught upstream in northern Thailand in 2005.

After a fisherman hooked the stingray — an endangered species — he contacted Wonders of the Mekong, which helped tag the ray and release it back into the river.

The Mekong has the third-most diverse fish population in the world, according to its River Commission — though overfishing, pollution, saltwater intrusion and sediment depletion have caused stocks to plummet.

Stingrays in particular have been vulnerable to these changes, with mass death events, despite conservation measures in place including fishing restrictions and river guards, according to Wonders of the Mekong.

Read original article here

World

Cambodian catches world’s largest recorded freshwater fish

Leave a comment

The world’s largest recorded freshwater fish, a giant stingray, has been caught in the Mekong River in Cambodia, according to scientists from the Southeast Asian nation and the United States.

The stingray, captured on June 13, measured almost four meters (13 feet) from snout to tail and weighed slightly under 300 kilograms (660 pounds), according to a statement Monday by Wonders of the Mekong, a joint Cambodian-U.S. research project.

The previous record for a freshwater fish was a 293-kilogram (646-pound) Mekong giant catfish, discovered in Thailand in 2005, the group said.

The stingray was snagged by a local fisherman south of Stung Treng in northeastern Cambodia. The fisherman alerted a nearby team of scientists from the Wonders of the Mekong project, which has publicized its conservation work in communities along the river.

The scientists arrived within hours of getting a post-midnight call with the news, and were amazed at what they saw.

“Yeah, when you see a fish this size, especially in freshwater, it is hard to comprehend, so I think all of our team was stunned,” Wonders of the Mekong leader Zeb Hogan said in an online interview from the University of Nevada in Reno. The university is partnering with the Cambodian Fisheries Administration and USAID, the U.S. government’s international development agency.

Freshwater fish are defined as those that spend their entire lives in freshwater, as opposed to giant marine species such as bluefin tuna and marlin, or fish that migrate between fresh and saltwater like the huge beluga sturgeon.

The stingray’s catch was not just about setting a new record, he said.

“The fact that the fish can still get this big is a hopeful sign for the Mekong River, ” Hogan said, noting that the waterway faces many environmental challenges.

The Mekong River runs through China, Myanmar, Laos, Thailand, Cambodia and Vietnam. It is home to several species of giant freshwater fish but environmental pressures are rising. In particular, scientists fear a major program of dam building in recent years may be seriously disrupting spawning grounds.

“Big fish globally are endangered. They’re high-value species. They take a long time to mature. So if they’re fished before they mature, they don’t have a chance to reproduce,” Hogan said. “A lot of these big fish are migratory, so they need large areas to survive. They’re impacted by things like habitat fragmentation from dams, obviously impacted by overfishing. So about 70% of giant freshwater fish globally are threatened with extinction, and all of the Mekong species.”

The team that rushed to the site inserted a tagging device near the tail of the mighty fish that will send tracking information for the next year, providing unprecedented data on giant stingray behavior in Cambodia.

“The giant stingray is a very poorly understood fish. Its name, even its scientific name, has changed several times in the last 20 years,” Hogan said. “It’s found throughout Southeast Asia, but we have almost no information about it. We don’t know about its life history. We don’t know about its ecology, about its migration patters.”

Researchers say it’s the fourth giant stingray reported in the same area in the past two months, all of them females. They think this may be a spawning hotspot for the species.

Local residents nicknamed the stingray “Boramy,” or “full moon,” because of its round shape and because the moon was on the horizon when it was freed on June 14. In addition to the honor of having caught the record-breaker, the lucky fisherman was compensated at market rate, meaning he received a payment of around $600.

Read original article here

Science

Antarctic ‘Megaberg’ Released 152 Billion Tons of Freshwater Just Before Melting

Leave a comment

Scientists have been keeping a close eye on the ‘megaberg’ designated as A68a since it split off from Antarctica back in July 2017 – and new research highlights just how much freshwater it’s released into the ocean during its late melting process.

 

Satellite monitoring systems indicate that for three months at the end of its lifetime, up to March 2021, the iceberg released an astonishing 152 billion tons of freshwater around the remote island of South Georgia – that’s the equivalent of 61 million Olympic-sized swimming pools.

There are worries about how this sudden injection of freshwater and the nutrients flowing off the iceberg could affect marine habitats around the island in terms of both ocean circulation and the biological food chain.

“This is a huge amount of meltwater, and the next thing we want to learn is whether it had a positive or negative impact on the ecosystem around South Georgia,” says Anne Braakmann-Folgmann, a glaciologist from the University of Leeds in the UK and the study’s lead author.

A total of five satellites were employed to keep tabs on the position, area, thickness, and volume change of A68a. At its peak, the iceberg was melting at a rate of 7 meters or 23 feet per month.

Drifting icebergs can affect the patterns of the ocean, block routes used by wildlife, and leave damaging plow marks on the seafloor. It looks as though A68a broke up early enough to avoid scraping the seafloor, though the sheer amount of freshwater released could still be a problem.

A more direct hit on South Georgia – home to millions of penguins, seals, and other marine animals – was narrowly avoided. However, researchers are still keen to investigate the ongoing impacts of A68a now that it has finally disappeared.

 

“Because A68A took a common route across the Drake Passage, we hope to learn more about icebergs taking a similar trajectory and how they influence the polar oceans,” says Braakmann-Folgmann.

A68a eventually traveled for three-and-a-half years and covered a distance of 4,000 kilometers (2,485 miles) before melting away into nothing by April last year. Some smaller, ‘child’ icebergs broke off over time, designated as A68b, A68c, and so on.

At the beginning of its trip, A68a was the sixth-largest iceberg ever recorded on satellite, with a surface area of 5,719 square kilometers (2,208 square miles). When it carved away into the sea, it reduced the size of the Larsen C ice shelf by nearly 12 percent.

As time has gone on, we’ve seen the iceberg battered by winds and waves, and by charting its slow disintegration so closely, scientists now have a better idea of how other icebergs might behave in the open ocean in the future.

“A68a was an absolutely fascinating iceberg to track all the way from its creation to its end,” says Laura Gerrish, a specialist in mapping and geographic information systems from the British Antarctic Survey (BAS).

“Frequent measurements allowed us to follow every move and break-up of the berg as it moved slowly northwards through iceberg alley and into the Scotia Sea where it then gained speed and approached the island of South Georgia very closely.”

The research has been published in Remote Sensing of Environment.

 

Read original article here

Science

Iceberg Spilled 168 Billion Tons of Freshwater Near Wildlife-Rich Island

Leave a comment

A satellite view of iceberg A-68A as it approached South Georgia island in late 2020.
Image: MODIS from NASA Worldview Snapshots

Iceberg A-68a—the sixth largest in recorded history—released a hideous amount of freshwater near an ecologically sensitive island, according to new research chronicling the berg’s life.

Iceberg A-68a disintegrated in early 2021, but not before captivating the world with its eventful three-and-a-half year life. In a new paper published in Remote Sensing of Environment, researchers with the British Antarctic Survey and the Centre for Polar Observation and Modelling chronicle the ‘berg’s life using satellites.

The long journey taken by iceberg A-68A.
Illustration: Copernicus Sentinel/ESA/Antarctic Iceberg Tracking Database

Among the key findings was the rate at which the iceberg melted over time, the intense amount of freshwater spilled near the sub-Antarctic island of South Georgia, and how, thankfully, the iceberg failed to damage the seafloor along the island’s sensitive coast.

The iceberg split off from the Larsen C ice shelf in July 2017. At more tha 2,000 square miles (5,180 square kilometers), the chunk of ice encompassed an area 1.6 times the size of Rhode Island. The ‘berg lost a chunk of itself almost immediately, resulting in its renaming to A68a and the naming of its offspring to A68b.

G/O Media may get a commission

57% off

iMazing iOS Backup Software

Take control of your iOS backups
This software allows you to choose your backup location, export, save, and print iMessages, individual third party app data, and restore your iPhone with ease.

Iceberg A68a managed to rack up some serious mileage as it drifted some 2,485 miles (4,000 kilometers) northwards, and ominously, toward South Georgia island. Scientists feared that the iceberg—resembling a pointing finger—might damage the seafloor along the island’s coast, causing harm to the island’s abundant, but sensitive, wildlife.

Five different satellite missions were used to track A68a over time: Copernicus Sentinel-1, Copernicus Sentinel-3, Terra with its MODIS instrument, CryoSat, and ICESat-2. With these satellites, the team measured the thickness and area of the iceberg over the course of A68a’s entire life cycle. This took some extra work, however, as the gigantic ‘berg “had significant undulations in topography across its surface,” according to the paper.

Video showing the chronology of A-68A’s life. Credit: CPOM/GEBCO Compilation Group/WOA/Antarctic Tracking Database

As the scientists point out, A68a didn’t stray too far from its birthplace, and it didn’t melt very much, during the first two years of its life. The situation changed, however, as it moved northwards through the warmer waters of the Drake Passage.

“Frequent measurements allowed us to follow every move and break-up of the berg as it moved slowly northwards through an area called ‘iceberg alley,’ a route in the ocean which icebergs often follow, and into the Scotia Sea where it then gained speed and approached the island of South Georgia very closely,” Laura Gerrish, a mapping specialist at BAS and a co-author of the study, said in a press release.

The iceberg’s position on December 17, 2020.
Image: British Antarctic Survey/ESA

From the time of its birth through to early 2021, A68a thinned from 770 feet (235 meters) thick to 550 feet (168 meters), representing 32% of its total loss. The researchers confirmed in the study that the “distinct environmental conditions in the Weddell and Scotia Sea lead to rapidly increasing rates of melting and fragmentation once icebergs travel north of the Antarctic Peninsula.”

The iceberg had sufficiently melted such that, by the time it arrived at South Georgia, it was no longer deep enough to inflict extensive damage by scraping the seafloor. Ecologists were concerned at the time that if the ran aground near the island, it would prevent penguins from accessing their breeding grounds, block foraging marine animals, and disrupt ocean currents. Mercifully, A68a scraped the seafloor only very briefly; the bottom, or keel, of the iceberg reached 460 feet (141 meters) beneath the surface, whereas the main seabed is 490 feet (150 meters) below the surface. What’s more, the iceberg broke up shortly after arriving at South Georgia, greatly reducing any blocking effects.

Visualization showing the amount of freshwater released by the iceberg.
Image: CPOM/ESA/Google basemap

That said, iceberg A68a released 168 billion tons of freshwater filled with nutrients in the immediate vicinity of South Georgia. That’s akin to 61 million Olympic-sized swimming pools. Simply put that’s… a lot of water. This is certain to have an effect on the local ecology, as a statement from ESA points out:

When icebergs detach from ice shelves, they drift with the ocean currents and wind, releasing cold fresh meltwater and nutrients as they melt. This process influences the local ocean circulation and fosters biological production around the iceberg.

As to the potential positive and negative effects of this process, the researchers can only guess, writing that “[m]ore research should be conducted to study the impact of this alteration on the marine life around South Georgia.”

The new paper will likely be helpful to scientists who study the movements of icebergs in this area. “As this is a common iceberg trajectory, our results could also help to predict the disintegration of other large … icebergs and to include their impact in ocean models,” the scientists wrote.

More: Boaty McBoatface Prepares to Dive Under Antarctica’s Doomsday Glacier

Read original article here

Science

Mass Extinction Events Can Turn Freshwater Into Toxic Soup, And It’s Already Happening

Leave a comment

Apart from the global catastrophe that killed off most of the dinosaurs, some experts think almost all the mass extinctions in Earth’s history were followed by a proliferation of microbes in rivers and lakes.

 

After the Permian extinction event 252 million years ago – the largest mass extinction event in Earth’s history – there appears to have been a burst in bacterial and algal blooms, lasting for hundreds of thousands of years.

According to the geologic record in Australia, the damaging impacts of climate change and climate-driven deforestation during the Permian extinction event most likely caused a toxic soup to sprout in the Sydney Basin, one of the oldest known freshwater ecosystems in the world.

That’s disconcerting, the authors say, as human activity is leading to a similar mass extinction event today.

“We’re seeing more and more toxic algae blooms in lakes and in shallow marine environments that’s related to increases in temperature and changes in plant communities which are leading to increases in nutrient contributions to freshwater environments,” says geologist Tracy Frank from the University of Connecticut

“So, a lot of parallels to today. The volcanism was a source of CO2 in the past, but we know that the rate of CO2 input that was seen back then was similar to the rate of CO2 increases we’re seeing today because of anthropogenic effects.”

 

Algae and bacteria are normal parts of a healthy freshwater environment, but sometimes they can grow out of control and deplete the water of oxygen, creating ‘dead zones’. 

This tends to happen with global warming, deforestation, and the rush of soil nutrients into waterways, which can feed microbes. All three of these factors are in play today, which is why we are probably seeing increases in toxic blooms already.

Considering what’s happened in the past, that’s a disturbing sign.

According to soil, fossil, and geochemical data from the Sydney Basin, researchers think the spread of microbes in the wake of the Permian extinction “was both a symptom of continental ecosystem collapse, and a cause of its delayed recovery.”

Volcanic eruptions in the Permian first triggered an accelerated and sustained rise in greenhouse gas emissions. This caused higher global temperatures and sudden deforestation due to wildfires or drought.

Once the trees were gone, it wasn’t long before the structure of the soil began to erode, and its nutrients slipped into freshwater ecosystems.

For more than three million years, Earth’s forests struggled to recover. The Sydney Basin was instead littered with lowland ecosystems that “were regularly inundated by stagnant, fresh/brackish waterbodies hosting thriving algal and bacterial populations”, the authors write.

 

In turn, these persistent dead zones prevented the reestablishment of important carbon sinks, like peatlands, and slowed down climate and ecosystem recovery.

Other deep-time records around the world have also found microbial blooms are common after warming-driven extinction events. The exception seems to be the very large asteroid event that caused the mass extinction of dinosaurs 66 million years ago.

This major episode caused vast amounts of dust and sulfate aerosols to rise into the atmosphere, but compared to volcanic activity, the meteorite only caused a modest increase in atmospheric carbon dioxide and temperature, not a sustained one. As such, freshwater microbes only seemed to undergo a short-lived burst after the extinction event.

Unfortunately, that’s very different from what occurred during the Permian extinction and what is happening today.

For instance, the researchers note that the “optimal temperature growth range” of these harmful algae in freshwater environments is 20-32 °C (68-89.6 °F). That range matches the estimated continental summer surface air temperatures for the region during the early Triassic. That range is what’s projected for mid-latitude continental summer surface air temperatures in 2100.

Scientists are noticing other similarities, including an increase in forest fires and the subsequent destabilization of soils.

“The other big parallel is that the increase in temperature at the end of the Permian coincided with massive increases in forest fires,” says geologist Chris Fielding, also from the University of Connecticut.

“One of the things that destroyed whole ecosystems was fire, and we’re seeing that right now in places like California. One wonders what the longer-term consequences of events like that as they are becoming more and more widespread.”

The good news is that this time many of the changes are in our control. The bad news is that whatever happens next is our own fault.

“The end-Permian mass extinction event took four million years to recover from,” Fielding says. “That’s sobering.”

The study was published in Nature Communications. 

 

Read original article here

Science

First images of freshwater plumes at sea

Leave a comment

Eric Attias and team deploy CSEM system offshore Hawai’i island. Credit: University of Hawai’i

The first imaging of substantial freshwater plumes west of Hawai’i Island may help water planners to optimize sustainable yields and aquifer storage calculations. University of Hawai’i at Mānoa researchers demonstrated a new method to detect freshwater plumes between the seafloor and ocean surface in a study recently published in Geophysical Research Letters.

The research, supported by the Hawai’i EPSCoR ‘Ike Wai project, is the first to demonstrate that surface-towed marine controlled-source electromagnetic (CSEM) imaging can be used to map oceanic freshwater plumes in high-resolution. It is an extension of the groundbreaking discovery of freshwater beneath the seafloor in 2020. Both are important findings in a world facing climate change, where freshwater is vital for preserving public health, agricultural yields, economic strategies, and ecosystem functions.

Profound implications

While the CSEM method has been used to detect the presence of resistive targets such as oil, gas and freshwater beneath the seafloor, this study is the first time CSEM was applied to image freshwater in the ocean water column, according to ‘Ike Wai research affiliate faculty Eric Attias, who led the study.

“This study has profound implications for oceanography, hydrogeology and ocean processes that affect biogeochemical cycles in coastal waters worldwide,” said Attias. “Using CSEM, we now can estimate the volumes of freshwater emanating to the water column. This is indicative of the renewability of Hawai’i’s submarine freshwater system.”

Conceptual illustration showing freshwater plumes at sea. Credit: Eric Attias

Submarine groundwater discharge (SGD), the leaking of groundwater from a coastal aquifer into the ocean, is a key process, providing a water source for people, and supporting sea life such as fish and algae. According to UH Mānoa Department of Earth Sciences Associate Professor and study co-author Henrietta Dulai, the location of offshore springs is extremely hard to predict because of the unknown underlying geology and groundwater conduits.

“The flux of such high volumes of nutrient-rich, low salinity groundwater to the ocean has great significance for chemical budgets and providing nutrients for offshore food webs,” said Dulai. “It is great to have a method that can pinpoint discharge locations and plumes as it opens up new opportunities to sample and identify the age of the water, its origin, chemical composition, and its significance for marine ecosystems in this otherwise oligotrophic (relatively low in plant nutrients and containing abundant oxygen in the deeper parts) ocean.”

Four Olympic swimming pools

This study included electromagnetic data driven 2D CSEM inversion, resistivity-to-salinity calculation, and freshwater plume volumetric estimation. Through the use of CSEM, the research team was able to image surface freshwater bodies and multiple large-scale freshwater plumes that contained up to 87% freshwater offshore Hawai’i Island. The results imply that at the study site substantial volumes of freshwater are present in the area between the seafloor and the ocean’s surface. A conservative estimate for one of the plumes suggests 10,720 cubic meters or approximately the volume of four Olympic-sized swimming pools.

Eric Attias, University of Hawai’i affiliate researcher. Credit: University of Hawai’i

The methodology used in this study can be applied to coastal areas worldwide, thus improving future hydrogeological models by incorporating offshore SGD and optimizing sustainable yields and storage calculations. Attias plans to extend the novel use of CSEM to further prove its application in imaging freshwater at other volcanic islands around the globe.

Attias will present his work at the International Tropical Island Water Conference taking place April 12-15, 2021. Hosted by the UH Water Resources Research Center and Hawai’i EPSCoR, this conference brings together water scientists, water managers and community members from around the world to share cutting-edge research and learn from each other’s experiences managing and understanding water resources across a broad range of tropical island settings.

Offshore submarine freshwater discovery raises hopes for islands worldwide

More information:
Eric Attias et al. Marine Electromagnetic Imaging and Volumetric Estimation of Freshwater Plumes Offshore Hawai’i, Geophysical Research Letters (2021). DOI: 10.1029/2020GL091249
Provided by
University of Hawaii at Manoa

Citation:
First images of freshwater plumes at sea (2021, March 31)
retrieved 31 March 2021
from https://phys.org/news/2021-03-images-freshwater-plumes-sea.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.



Read original article here

Science

Humans Now Control The Majority of All Surface Freshwater Fluctuations on Earth

Leave a comment

A regime change of almost unimaginable scale has taken place in the natural world, reflecting humanity’s vast and growing dominance over one of our planet’s most vital resources: freshwater.

 

In what researchers say is the first global survey of human impacts on the water cycle, scientists have used NASA satellite measurements to remotely quantify changes in the level of water held in a stunning number of water bodies: 227,386 of the world’s ponds, lakes, and reservoirs, whether small or large.

While human-managed reservoirs such as artificial dams comprise only 3.9 percent of this giant planetary-scale system of surface-level water storage, that tiny fraction masks a mind-boggling truth about how much control humanity really exerts over freshwater fluctuations.

When the amount of overall change in water levels across both natural and human-managed systems is calculated, it turns out the human-controlled reservoirs represent 57 percent of all surface water variability – more than half of all the ebb and flow in freshwater systems.

“We tend to think of the water cycle as a purely natural system: Rain and snowmelt run into rivers, which run to the ocean where evaporation starts the whole cycle again,” explains geophysicist Sarah Cooley from Stanford University.

“But humans are actually intervening substantially in that cycle. Our work demonstrates that humans are responsible for a majority of the seasonal surface water storage variability on Earth.”

 

The results, gleaned from 22 months of data collected by NASA’s Ice, Cloud and land Elevation Satellite 2 (ICESat-2), provide a first-of-their-kind snapshot of water storage around the globe, capturing and measuring water bodies as small as a football field within the survey.

“Previous satellites have not been able to come anywhere close to that,” Cooley says, but while the scientific achievements are admirable, the takeaways are not.

“There are a lot of ways in which this is bad for the environment.”

Risks range from negative effects on natural ecosystems due to water shortages, to the spectre of greenhouse gas emissions emanating from artificial reservoirs.

Of course, there are other positives of human-run reservoirs too: beyond simply controlling water supply, they enable things like hydropower systems, while dams can also offer protection against flooding.

Still, the realisation that we’ve assumed majority control over something as natural as the ebb and flow of freshwater is a disquieting discovery.

Another stark reminder of just how much effect our species has on the environment around us – with consequences so impossibly big, we can only hope to see them from space.

 

“Of all the volume changes in freshwater bodies around the planet – all the floods, droughts and snowmelt that push lake levels up and down – humans have commandeered almost 60 percent of that variability,” says environmental scientist Laurence Smith from Brown University.

“That’s a tremendous influence on the water cycle. In terms of human impact on the planet, this is right up there with impacts on land cover and atmospheric chemistry.”

The findings are reported in Nature.

 

Read original article here

Science

A Major Ocean Current Could Be on The Verge of a Devastating ‘Tipping Point’

Leave a comment

The Atlantic Meridional Overturning Circulation (AMOC) sea currents are vital in transporting heat from the tropics to the Northern Hemisphere, but new research suggests climate change might knock the AMOC out of action much sooner than we anticipated.

 

That could have profound, large-scale impacts on the planet in terms of weather patterns, upending agricultural practices, biodiversity, and economic stability across the vast areas of the world that the AMOC influences.

The problem is the rate at which Earth is warming up and melting the ice in the Arctic: according to the researchers’ new models, this speed of temperature increase means the risk of hitting the tipping point for the AMOC going dormant is now an urgent concern.

(University of Copenhagen)

“It is worrying news,” says physicist Johannes Lohmann, from the University of Copenhagen in Denmark. “Because if this is true, it reduces our safe operating space.”

Lohmann and his colleague Peter Ditlevsen adapted an existing ocean climate change model to study the consequences of an increased rate of freshwater input into the North Atlantic Ocean, driven by the rapid melting of the Greenland ice sheets.

The model showed that a faster rate of freshwater change could cancel out the AMOC much sooner. In a rate-induced tipping scenario like this, it’s the rate at which change is occurring, rather than a specific threshold, that’s most important – and once the tipping point is reached, there’s no going back.

 

In other words, the speed at which we’re pushing out greenhouse gases and melting ice in Greenland is leaving us with very little room to manoeuvre when it comes to protecting the climate systems that keep global weather patterns in check. The same problem could threaten other climate sub-systems across the world too, the researchers say.

“These tipping points have been shown previously in climate models, where meltwater is very slowly introduced into the ocean,” Lohmann told Molly Taft at Gizmodo. “In reality, increases in meltwater from Greenland are accelerating and cannot be considered slow.”

The AMOC operates a bit like a giant, looped conveyor belt of seawater, redistributing water and heat around the Northern Hemisphere as the water’s temperature, saltiness, and relative weight fluctuates. It’s part of the reason that European winters are relatively mild even at higher latitudes.

While it’s not clear exactly where the tipping point of the AMOC is, it has been slowing down in recent years, and this new study suggests that the more rapid climate change becomes, the more at risk these currents are. An influx of cold freshwater from Greenland is likely to stop warm water from spreading north, scientists think.

Climate change modelling is incredibly complicated, with so many factors to take into account, and Lohmann and Ditlevsen themselves admit that there’s more work to do to figure out the exact details of this rate-induced tipping scenario.

 

However, they hope it acts as a reminder of just how urgent action on the climate crisis now is: our targets to reduce greenhouse gas emissions need to be as ambitious as possible, whatever the scenario that eventually ends up unfolding in the North Atlantic. We’ve quite probably got no margin for error left.

“Due to the chaotic dynamics of complex systems there is no well-defined critical rate of parameter change, which severely limits the predictability of the qualitative long-term behaviour,” write the researchers in their paper.

“The results show that the safe operating space of elements of the Earth system with respect to future emissions might be smaller than previously thought.”

The research has been published in PNAS.

 

Read original article here

World

Extinction threatens third of freshwater fish species, report finds

Leave a comment

LONDON — Nearly a third of all freshwater fish species are threatened by extinction, according to a new report released by 16 conservation groups on Tuesday.

“The World’s Forgotten Fishes” says that 80 freshwater species — which make up more than half of all the world’s species — have already been declared extinct, with 16 disappearing in 2020 alone.

Migratory populations have declined by more than three-quarters since the 1970s, while populations of larger species, weighing more than 60 pounds, have fallen by an even more “catastrophic” 94 percent, it said.

Female sturgeons at Walter Gruell’s fish farm in Groedig village near Salzburg, Austria, in December.Joe Klamar / AFP via Getty Images file

While freshwater fish are important for the healthy functioning of the world’s rivers, lakes and wetlands, millions of people around the world also depend on them for food security and their livelihoods, including in vulnerable and indigenous communities. Their rapid decline could therefore put societies and economies across the globe in peril, the report said.

Conservation groups behind the report, including World Wide Fund for Nature (WWF) and Global Wildlife Conservation, point to a combination of pressures on global freshwater fish populations, including habitat degradation, damming and draining of rivers and wetlands, pollution, introduction of invasive species, wildlife crime and the ever-increasing threat of climate change.

Of more than 10,000 species whose conservation status has been assessed by the International Union for Conservation of Nature, 30 percent are considered at risk of extinction, the report said.

Download the NBC News app for breaking news and politics

The study calls freshwater fish “undervalued,” with the WWF’s Stuart Orr saying freshwater fish are often forgotten in global debates about climate, biodiversity and global development.

“I think this report is 16 organizations coming together to highlight on the one hand the incredible diversity of freshwater fish species, but on the other hand remind people that these species are in decline and linked to a lot of food security, jobs and cultural services,” Orr told NBC News on the phone from Gland, Switzerland.

“As we look to adapt to climate change and we start to think about all the discussions that governments are going to have on biodiversity, it’s really a time for us to shine a light back on freshwater,” he added.

The report calls for an emergency recovery plan to reverse decades of decline by protecting and restoring natural river flows, water quality and critical habitats while undoing the harm caused by overfishing.

Orr said a United Nations biodiversity conference taking place in China later this year will be a chance for governments to talk about the crisis and, for the first time, pay just as much attention to protecting and restoring freshwater life support systems as the world’s forests and oceans.

Yuliya Talmazan

Yuliya Talmazan is a London-based journalist.



Read original article here