Tag Archives: ecosystems

Climate change is choking the oxygen out of deep water, and it’s putting fish in a double bind

Being a fish was never easy, but a new paper reports that it’s been getting harder over the last 15 years or so. According to the findings, oxygen levels are dropping in the depths of the oceans, forcing fish to move ever closer to the surface.

Image via Pixabay.

New research from the University of California – Santa Barbara and the University of South Carolina is warning us that fish are slowly drowning. Changes in ecology, as well as the effects of climate change on seasonal patterns, water temperature, and its gradient over different depths, have been causing deeper layers of the ocean to lose their dissolved oxygen content. This, in turn, is forcing fish to either move closer to the surface, or asphyxiate.

It may seem like a trivial matter, but this shift is causing wide-scale changes in marine ecosystems and could have a very real impact on the health of the ocean as a whole. It also raises important questions for fishery management and conservation efforts, with the authors underscoring the importance of accounting for this shift with policy to avoid further damaging marine ecosystems.

Swimming out of breath

“This study finds that oxygen is declining at all the depths we surveyed: from 50 meters to 350 meters,” said lead author Erin Meyer-Gutbrod, assistant professor at the University of South Carolina, “and so fish seem to be moving up to shallower regions to get to an area where the oxygen is relatively higher.”

The findings are based on 15 years’ worth of recordings, surveys, and measurements. These included measurements of dissolved oxygen in samples of water taken at varying depths, of temperature, salinity, and surveys of the average depth at which certain fish species tend to congregate. A total of 60 different species of fish were encountered often enough during these 15 years to be statistically relevant and included in the study.

Data was collected on a yearly basis, every fall, from 1995 through to 2009. The team focused on three reef features between the Anacapa and Santa Cruz islands in Southern California. These were the Anacapa Passage area, with an average depth of 50m, a seamount known as the “Footprint”, at around 150m, and the “Piggy Bank”, with an average depth of around 300m. During the surveys, the team identified all fish species that came within two meters of the submarine or were visible and within two meters of the seafloor. They also estimated the length of each individual fish.

During this time, they saw depth changes in 23 species. Four of these shifted towards deeper waters, while the other 19 moved towards the surface in response to low oxygen conditions (as shown by analysis of water samples).

The team explains that surface waters tend to be better oxygenated (have higher levels of dissolved oxygen) due to surface motions such as waves continuously mixing gases into the top layer of bodies of water. Over time, as waters mix, this oxygen also finds its way lower along the column of water. However, the team explains that warming climates make for warmer surface waters, which increases the buoyancy of these layers compared to those deeper down, reducing their ability to mix. This process is known as ocean stratification.

In addition to this, warmer water has a lower ability to dissolve and hold oxygen compared to colder water, so there’s less of this gas being mixed into the ocean to begin with.

In the end, this means less oxygen makes it to the bottom layers of water. Although salinity and temperature gradients along the column of water also influence the extent of vertical mixing, the team reports that both remained relatively constant over the study period. In other words, the trend towards lower oxygen levels seen at the study site is primarily driven by climate-associated changes in surface water temperatures. That being said, the other factors can’t be discounted completely either.

“A third of [the 60 fish species’] distributions moved shallower over time,” Meyer-Gutbrod said. “I personally think that’s a remarkable result over such a short time period.”

The team acknowledges that their study only included a relatively small area, but it did include a wide range of depths, which was the ultimate objective of the research. This narrower area actually helps reduce confounding factors, they explain, since it allowed for most conditions (apart from depth) to be constant across all the survey areas.

“Other scientists have used lab experiments to show that fish don’t like low oxygen water,” Meyer-Gutbrod said, “but what nobody’s ever done is just return to the same location year after year to see if there’s actually a change in the distribution of fish stemming from a change in oxygen over time.”

In closing, the authors explain that this trend can have quite severe negative impacts on marine ecosystems, and indirectly, on all life on Earth. Fish are simply forced to move away from their optimal depths, which will eventually result in them being pushed out entirely out of several ecosystems. According to co-author Milton Love, a researcher at UC Santa Barbara’s Marine Science Institute, we could even see a point in which species are forced into depth ranges that they simply cannot survive in.

They also cite previous research showing that many fish species also cannot tolerate high water temperatures, and are migrating towards lower depths. In the end, these factors can leave many species in an impossible situation — where they cannot breathe if too low, and can’t bear the heat if too close to the surface.

In the end, even if we start working to redress climate change right now, meaningful progress will take quite a lot of time. Until then, policymakers need to recognize and react to the pressures faced by fish species and issue regulation that protects them as best as possible, or risk wide-ranging ecological collapse in the world’s oceans.

“If you throw your net in the water and you get a ton of fish — more than you’re used to getting — you may think, ‘Oh, it’s a good year for the fish. Maybe the population is recovering,'” Meyer-Gutbrod said. “But instead, it could be that all the fish are just squished into a tighter area. So you could have fishery regulations changing to increase fish allowances because of this increase in landings.”

The paper “Moving on up: Vertical distribution shifts in rocky reef fish species during climate‐driven decline in dissolved oxygen from 1995 to 2009” has been published in the journal Global Change Biology.

Shutting down for maintenance: Faroe Islands close to tourism, call volunteers help

The Faroe Islands, halfway between Norway and Island, will be closed to tourists and will only welcome volunteers in April 15-17, 2020, to help out on different maintenance projects.

Credit Wikipedia Commons

The territory, an archipelago controlled by Denmark but not a part of the European Union, has seen a record number of tourists in the last few years. While in 2013 68.000 people visited the islands, last year the number scaled to 110.000, double the population of the islands.

It is composed of 18 islands covering 1399 square km (545.3 sq miles), just 113 km (70 miles) long and 75 km (47 miles) wide. There are people living in 17 islands, leaving just one inhabited. There are a lot of smaller islets around the archipelago as well, making for a rugged, picturesque setting.

Visitors arrive from different corners of the world due to the islands’ rugged beauty, including a blue ocean, vertical sea cliffs, green mountains, and a picturesque valley. There are about 70.00 sheep and two million pairs of seabirds on the island, including the biggest colony of storm petrels in the world.

Such a tourism boom has caused fear among the local authorities, concerned over the effects it could cause on local ecosystems. But they came up with a solution, calling volunteers a few times per year to ask for help on different projects, from road maintenance to erecting signposts.

“For us, tourism is not all about numbers,” Guðrið Højgaard, Director at Visit Faroe Islands, told CNN recently. “We welcome visitors to the islands each year, but we also have a responsibility to our community and to our beautiful environment, and our aim is to preserve and protect the islands, ensuring sustainable and responsible growth.”

Getting ready for 2020

Back on April 26 and 27, the island decided to do a pilot of its volunteer initiative, preparing for the official start in 2020. While the hotels remained open and the flights operated normally, several tourisms attractions closed down. Thousands applied to volunteer but only 100 were accepted.

“Closed for maintenance, open for voluntarism,” read a notice on the Faroe Islands website back then, warning any potential visitors of the planned activities during the April weekend.

Volunteers arrived from Mexico, Israel, Australia, China, and the United States and were assigned in teams to different projects across the islands, each of a different level of difficulty. All involved handling equipment such as shovels, hammers, and screwdrivers.

A group went to the island of Mykines, usually visited by travelers due to the bird colonies. They built a new route as well as a bird-watching site. Another one went to Klakkur, one of the high mountains surrounding Klaksvík, the second largest town. They repaired the path, which was worn and muddy.

“It has been wonderful to see so many faces from around the world come together with local villagers and farmers with one united mission and a ‘roll-up-your-sleeves’ attitude,” says director Guðrið Hojgaard.

Not the first case

Fairly close to the archipelago, Iceland has been dealing with similar issues due to its growing popularity among tourists – with 2.2 million arriving there last year. That’s six times the population of the country, putting pressure on its infrastructure and ecosystems.

Iceland has taken efforts to limit the number of tourists and ensure the sustainability of its tourism industry. It’s not an easy thing to manage, and visitors are also asked to play a role in the process.

“As part of our welcome, we wanted to create a pledge which we’ll encourage all visitors to take, creating an army of people who know how to stay safe and also how to look after our delicate nature, said Icelandic Tourism Minister Þórdís Kolbrún R. Gylfadóttir.

Climate change is affecting the Arctic ecosystem due to extreme weather events

Climate change is affecting ecosystems not only through warming but also by delivering more extreme weather events, according to a new study, which looked at the consequences of snow in the Arctic.

Image Credits: Wikipedia Commons

Back in 2018, snow was spread out in most of the Arctic and did not melt fully until late summer, if at all. Researchers looked at the consequences of this phenomenon by extensively monitoring all components of the local ecosystem for more than 20 years, comparting life last year with other more “normal” years.

The snow conditions of 2018 resulted in the most complete reproductive failure ever encountered and only a few plants and animals were able to reproduce due to abundant and late-melting snow. In order words, the extra snow completely destroyed the breeding season.

While poor reproduction had been observed in individual species before, such poor reproduction across all levels of the ecosystem had never been seen before, according to the research, published in PLOS Biology.

“One non-breeding year is hardly that bad for high-arctic species”, says Niels Martin Schmidt (Aarhus University, Denmark), lead author of the study. “The worrying perspective is that 2018 may offer a peep into the future, where increased climatic variability may push the arctic species to – and potentially beyond – their limits.”

For Schmidt, the study showed that climate change can be hard for ecosystems, highlighting the importance of long-term observations of the ecosystems and the effects of temperature increase.

Home to a diverse and specialized group of organisms, the Arctic and its ecosystems are used to living under severe climatic conditions. But, like the rest of the world, the Arctic is now changing, and the region is experiencing both long-term warming and retreating snow-cover.

The impacts of climate change are being observed earlier in the Arctic, and with more immediate and severe consequences, than in most of the rest of the world. The Arctic is warming at a rate almost twice the global average and reductions in Arctic sea-ice and permafrost and changes in weather are increasingly visible.

Climatic variability and the risk of extreme events is increasing in the Arctic, studies have shown. But, while the consequences of longer-term change are well-documented, almost nothing is known so far about the impacts of climatic variability and extreme events on the Arctic ecosystems.


Arctic ecosystems “highly responsive” to climate change — and very hard to fix once broken

Climate change is impacting the Arctic far quicker than we’ve assumed, an international team of researchers reports. Other research looking into how Arctic life fared after the meteorite impact that wiped out the dinosaurs gives us a glimpse into how ecosystems in the area might evolve under climate change.


Image credits Rolf Johansson.

Ecosystems in the Arctic undergo rapid, dramatic, and long-lasting changes in response to climate shifts — even those of average magnitude, according to a new study published in Environmental Research Letters. The study, conducted by an international research team led by members from the University of Maine, finds a “surprisingly tight coupling” between climate shifts and environmental responses in the Arctic. The paper thus overturns previous assumptions that environmental responses are delayed or dampened by internal ecosystem dynamics, allowing only significant climate shifts to have an effect on local ecosystems.

The heat is on

“Our analyses reveal rapid environmental responses to nonlinear climate shifts, underscoring the highly responsive nature of Arctic ecosystems to abrupt transitions,” the study’s abstract reads.

After 1994, mean air temperatures over West Greenland (as recorded in June) were 2.2°C higher than baseline, the team reports, and have increased by an additional 1.1°C since 2006. Mean winter precipitation also doubled in quantity (from 20mm to 40mm) over the area after 1994.

The findings come from over 40 years’ worth of weather data and paleoecological reconstructions. The team explains that these “abrupt climate shifts” were accompanied by “nearly synchronous” environmental responses in the area, including increased ice sheet discharge and dust, and advanced plant phenology (i.e. earlier onset of the life cycles of plants in the area). Lakes in the area experienced earlier ice-outs and greater diversity of algae.

In light of these findings, the team cautions that Arctic ecosystems are much more responsive to abrupt transitions — even moderate magnitude ones — than assumed. The strength of climate forcing (i.e. warming) in the area has also been underestimated, they add. Understanding how these ecosystems respond to abrupt climate change is key to predicting their evolution in the future and managing potentially damaging shifts says Jasmine Saros, the paper’s lead author.

“We present evidence that climate shifts of even moderate magnitude can rapidly force strong, pervasive environmental changes across a high-latitude system,” she says.

“Prior research on ecological response to abrupt climate change suggested delayed or dampened ecosystem responses. In the Arctic, however, we found that nonlinear environmental responses occurred with or shortly after documented climate shifts in 1994 and 2006.”

How does this pan out?


Penguins don’t live in the Arctic but they’re cute, so here’s a picture of some.
Image credits Siggy Nowak.

Another unrelated study published in the journal Palaeontology looked at how life on the other end of the planet — Antarctica — recovered after the impact of Chicxulub, the dinosaur-killing meteorite. This impact triggered a massive, planet-wide extinction event known as the Cretaceous-Paleogene (K-Pg) mass extinction some 66 million years ago.

Although the effects of this impact (e.g. transient cooling, global darkness, and expansion of anoxic waters) were “probably short-lived, […] biogeochemical cycling and ecosystem function remained disturbed for an extended period”. It took local marine ecosystems roughly one million years to return to pre-extinction levels, they explain.

The K-Pg event was caused by the impact of a 10 km asteroid on the Yucatán Peninsula, Mexico, and took place while our planet was already in the throes of environmental instability caused by a major volcanic episode. In the end, Chicxulub’s visit would wipe out around 60% of the marine species around Antarctica, and 75% of species around the world. This turned out to be quite a fortunate development for us humans, as the impact fundamentally changed the evolutionary history of life on Earth. Most of the animal groups you know today, including us mammals, were only able to rise as a direct consequence of this impact.

“This study gives us further evidence of how rapid environmental change can affect the evolution of life,” says Dr. Rowan Whittle, a palaeontologist at British Antarctic Survey and the study’s lead author.

“Our results show a clear link in the timing of animal recovery and the recovery of Earth systems.”

For over 320,000 years after the extinction, the team reports, the Antarctic sea floor was dominated by burrowing clams and snails. It took roughly one million years for the number of species to recover to pre-extinction levels.

“Our discovery shows the effects of the K-Pg extinction were truly global, and that even Antarctic ecosystems, where animals were adapted to environmental changes at high latitudes like seasonal changes in light and food supply, were affected for hundreds of thousands of years after the extinction event.”

Now, needless to say, the K-Pg extinction event was way more abrupt and dramatic than the shifts we’re causing in the Earth’s climate today. And this study focuses on its effects in Antarctica, not the Arctic. However, it does serve as an adequate case-study to see how long such ecosystems need to recover from major environmental shocks.

And climate change (plus human activity) is a major environmental shock. It’s much slower than an asteroid impact, sure, but it’s still happening unbelievably fast from a geological and evolutionary point of view. The first study we’ve discussed here shows that Arctic ecosystems do feel the heat, and feel it fast. Life here is very specialized to thrive in its frigid niche and if we let these ecosystems collapse, the same ancient dynamics that Whittle’s team found in the Antarctic will likely apply — our Arctic will only recover as the Earth’s systems recover.

The paper “Arctic climate shifts drive rapid ecosystem responses across the West Greenland landscape” has been published in the journal Environmental Research Letters.

The paper “Nature and timing of biotic recovery in Antarctic benthic marine ecosystems following the Cretaceous–Palaeogene mass extinction” has been published in the journal Palaeontology.

Grand study finds that diversity of life on Earth dropped below “safe” limits

In the most comprehensive study of its kind, scientists have merged big data with our knowledge of ecosystems to reach a troubling conclusion — the abundance of the overall number of animal and plant species across the majority of Earth’s land surface has fallen bellow what biologists consider the “safe” limit.

Image credits geograph.org.uk

The cause at least is clear: from grasslands to tropical forests, humans are taking over ever more land to use in agriculture, for roads, infrastructure, and housing. This requires clearing the land so we can use it — an act which doesn’t cause ecological collapse in itself, but it does reduce the abundance of species that make up an intact ecosystem. If biodiversity falls too low, ecosystems lose their resilience to external factors (such as shifting climate) or, in extreme scenarios, cease to function altogether.

“Exploitation of terrestrial systems has been vital for human development throughout history, but the cost to biosphere integrity has been high,” notes the study led by Tim Newbold of the United Nations Environment Programme and University College London with colleagues representing several British, Australian, Danish and Swiss universities and institutions.

The team analyzed over 1.8 million measurements of the abundance of species (39,123 different species to be exact) from almost 19 thousand locations across the world. Because of the sheer quantity of data used, an accompanying essay in the journal Science by University or Reading Tom Oliver calls it the “most comprehensive quantification of global biodiversity change to date.”

From the results in these points, the researchers extrapolated for the whole area of the planet, then compared the figures to a “Biodiversity Intactness Index” to find out where species decline could have destabilizing effects on ecosystems. This approach is based on a “planetary boundaries” concept, which according to lead author Newbold:

“.. attempts to set some sort of safe limit to the amount of biodiversity we can lose, while biodiversity still supports important ecosystem functions.”

It’s important to note that “safe” here means the ecosystem can still support the processes humans require for a normal continuation of our lives — not that the ecosystem is unaffected. The concern is that as these systems lose their biodiversity, the processes that allowed them to supply stored carbon, clean water, fertile soil, and every other bio-related resource will falter — this is bad news for both humans and the animals that rely on these ecosystem “services.”

“Biodiversity supports a number of functions within ecosystems, things like pollination, nutrient cycling, soil erosion control, maintenance of water quality,” Newbold said. “And there’s evidence that if you lose biodiversity, that these functions don’t happen as well as they would have done in the past.”

The researchers assumed that a decline of more than 10% in the abundance of species — after human interference — in a given area corresponds to a dangerous drop in biodiversity. The study worryingly found that on average, global decline is already inching close to 15 percent, meaning original species are roughly 85 percent as abundant (85.6 percent to be exact) as they were before we started changing the land. Overall, 58 percent of the Earth’s surface has fallen below 90% intact biodiversity, and into the danger zone.

Places with little human habitation naturally fare better than the rest — the team found that northern tundra and boreal forest ecosystems are relatively intact, as was much of the Amazon rain forest. On the other end of the spectrum, large swaths of central North America show areas with less than 60% of their original biodiversity, stretching all the way from Canada to Texas. The correlation is staggering — that 58 percent I mentioned in the previous paragraph houses 71 percent of the human population, the team reports.

Total abundance of species occurring in primary vegetation (areas above safe limit in blue)
Image credits Newbold et al/Science

Critics point out that there are some major uncertainties and matters left open to interpretation in the study. For example, is the 10 percent biodiversity loss threshold that the researchers picked accurate? Does it vary from case to case? And moreover, humans don’t only remove species from ecosystems — they also introduce non-original or “invasive” species — is this a benefit or a further strain on these systems?

The authors openly admit these criticisms and have actually considered some of the points being raised. They found that if new species are considered to benefit ecosystems, or if they set the danger threshold lower, so ecosystems can ‘safely” reach 80 or 70 percent of their original species abundance, then considerably less of the world is in trouble. But as a personal note, everything is over the bar if you set the bar low enough. In the end, it all comes down to how much of a risk we want to take with mother nature’s resilience.

So in the end, we won’t start seeing ecologic collapse all around us as ecosystems reach exactly 90 percent intact biodiversity. But it does mean that they are considerably weakened, and less likely to successfully withstand future hurdles like global warming, according to Newbold.

“We’re entering a space where things become more uncertain, and we expect that things will be less resilient in the face of other changes,” he said.

Mark Urban, who directs the newly founded Institute of Biological Risk at the University of Connecticut which focuses on biodiversity losses, believes that the study will set a stepping stone in our fight to preserve the environment around us and ourselves along with it, but has some criticisms of his own to add:

“Newbold and colleagues find sobering evidence that we have already crossed that line in terrestrial ecosystems,” said  “Human land use has reduced local populations to 85 percent of original abundances on average. What this means is we have not only crossed a planetary boundary, but have kept going. At least now we’re looking back.”

However, he also noted that “this result ignores the accelerating threat from a warming climate,’ focusing on land use. “Climate change is about to make things more complicated as we try to pull back from the edge of the Earth’s resilience.”

In the end, even if the details are not yet clear the general picture is what matters — and this one paints a warning, at least in my eyes.

The full study titled “Has land use pushed terrestrial biodiversity beyond the planetary boundary? A global assessment” has been published online in the journal  .