Claim: Climate Change Threatens Sharks

Guest essay by Eric Worrall

Sharks survived the dinosaur killer, the Cretaceous-Paleogene extinction event which wiped out 80% of Earth’s species, but apparently our gentle 0.1C / decade global warming is a grave threat to their continued survival.

How will sharks respond to climate change? It might depend on where they grew up

November 27, 2020 6.01am AEDT
Culum Brown Professor, Macquarie University
Connor Gervais Connor Gervais

They may have been around for hundreds of millions of years — long before trees — but today sharks and rays are are among the most threatened animals in the world, largely because of overfishing and habitat loss. 

Climate change adds another overarching stressor to the mix. So how will sharks cope as the ocean heats up?

An existential threat

In Australia, the grim reality of climate change is already upon us: we’re seeing intense marine heat waves and coral bleaching events, the disappearance of entire kelp forestsmangrove forest dieback and the continent-wide shifting of marine life

The southeast of Australia is a global change hotspot, with water temperatures rising at three to four times the global average. In addition to rising water temperatures, oceans are becoming more acidic and the amount of oxygen is declining. 

Any one of these factors is cause for concern, but all three may also be acting together.

One may argue sharks have been around for millions of years and survived multiple climate catastrophes, including several global mass extinctions events

To that, we say life in the anthropocene is characterised by changes in temperature and levels of carbon dioxide on a scale not seen for more than three million years.

Read more:

The study is available here.

I think most Australians if asked would suggest there are too many sharks.

I swim in Australia’s coastal waters a lot less than I used to, and never venture out too deep. The beloved politicians who run our country have cut back on shark culling near popular beaches, because you know, if you venture into their territory you should accept a little risk. Something to think about when our borders re-open, if you are thinking of visiting Australia for a New Year beach holiday.

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November 28, 2020 6:17 pm

Climate Change Threatens Sharks

That sounds like an argument for global warming.

Bryan A
Reply to  commieBob
November 28, 2020 10:28 pm

Along with a propensity for Fewer Sharknados
I guess SyFy channel will be affected by Climate Change

November 28, 2020 6:25 pm

Any reduction in the number of sharks comes as good news. Recently, Australian politicians have begun to cut back on shark netting and culling near popular beaches, in a futile attempt to mollify the Greens and possibly also to reduce rising Australian population numbers impinging on the Australian Budget.

John Anthony
Reply to  nicholas tesdorf
November 28, 2020 11:57 pm

Reducing population number’s ? Just appoint the premier of Victoria for four more years!

November 28, 2020 6:57 pm

Shark attacks are increasing because there are many more people now, and they go swimming in the oceans.

Plus, with warming seas, this prolific human shark-bait is now parboiled, making them much more tender and appetizing to the after-darks.

Someone more mathematically gifted than me will present the numbers that prove this correlation.

Sharks will die out from over-eating human meat. Meat is bad for you, as Greta told us.
I gave up eating human meat decades ago
– Hannibal Lecter.

Big Al
Reply to  Mr.
November 28, 2020 9:21 pm

Deep Statebook Zuckers wife sisters restaurant name?

HD Hoese
November 28, 2020 7:03 pm

I have been to the library at Macquarie University, Sydney, NSW where the first author claims to reside. Thought it was better than that, but that has been some years. Paper too expensive, but tables available. Last line of abstract “With climate change, intraspecific variation will manifest as populations move, demographics change or extirpations occur, starting with the most sensitive populations.” Also “However, under Adelaide temperatures, the MO2Rest of Jervis Bay sharks was greater than that of Adelaide sharks.” Might the nice people I met at Jervis Bay not take issue about “more sensitive” Adelaide sharks 1200 km away?

Table S1: Top GLMM/LMM model selections.
Statistical summaries for GLMM/LMMmodels…, and so on” I’ll leave the numbers to the stat guys, but didn’t look that bad, maybe made up anyway, would have to get the data from the authors.

Great whites are cold temperate sharks, suspect that it could be found in their library, overheating might cut down on the attacks. Anyway, Sydney had a great (among other) seafood market. Didn’t see any great whites.
Not about to go extinct, but maybe need to control killer whales better.

November 28, 2020 7:05 pm

When one variety of a species decreases, usually another, better adapted species increased to fill the other’s niche. Noticed the increase in lawyers?

Geoffrey Williams
November 28, 2020 7:10 pm

I emmigrated to Australia 40 years ago. I clearly remember for many years one never heard of a shark attack. These days they are a regular weekly if not daly occurrence. Culling large sharks seems to me to be a reasonable solution. Go ahead do it.

Clay Sanborn
Reply to  Geoffrey Williams
November 28, 2020 8:46 pm

“I clearly remember for many years one never heard of a shark attack. These days they are a regular weekly if not daily occurrence.” I hope you realize you just gave alarmists yet another reason (probably already used anyway) to claim proof of global warming. 🙂 Careful, these people are controlling nuts with way too much time on their hands.

Ian Coleman
November 28, 2020 7:15 pm

There seems to be a bit of ill-feeling towards sharks here. I don’t have a problem with them myself, although if I ever did I would just get a bigger boat.

Interested Observer
Reply to  Ian Coleman
November 29, 2020 7:10 am

Gotta blame it on Climate Change because, they can’t tell the truth. The biggest threat to sharks are the Chinese; they’ll eat anything and, with 1.5 billion mouths to feed, they’ll eat everything. Shark fin soup is disgusting but, it’s what kills a lot of sharks these days.

November 28, 2020 7:23 pm

The study is paywalled for me. But the Supplementary Materials make it look like the study was based on models. 6 pages.

Electronic Supplementary Materials
Population variation in the thermal response to climate change reveals differing sensitivity in a benthic shark

Top GLMM/LMM model selections. The top-ranked models are in bold and were determined via the lowest AICc score (Akaike’s information criterion corrected for small sample size). k is the number of model parameters, ΔAICc is the difference between the current model and the top-ranked model, wAICc is the model probability, and Rm is variance explained by the fixed effects (marginal variance).

November 28, 2020 7:26 pm

You actually missed the funnier part of the stupidity of that study … which is actually batsh$t crazy these tossers deny Evolution. The concern they have is “intraspecific variation will manifest” as defined by these over educated dropkicks from the university of autism.

So remember the basic law of Evolution that all species will evolve you must throw that out the window and replace it with the theory that there is an ideal optimum nature period apparent somewhere in the 1900’s. All nature must remain exactly as it was during this ideal period. You must deny Evolution and all variation is bad.

The study data simply says some shark species move more depending on water temperature. If the water temp changes then you will get a changed rate of intraspecific variation. That isn’t good or bad it’s just a fact and the study doesn’t even deal with other factors or how significant it might be. The effect could be very minor and of no interest at all.

The study itself isn’t the problem it is what crackpot Prof Culum Brown says that is the issue and example of another activist who can’t deal with the conflict between activism and science.

November 28, 2020 7:33 pm

My goldfish manage to survive in a bowl where the temperature changes by >10 degrees between summer and winter… but apparently 1 degree/decade will send sharks extinct. How desperate are the alarmists sounding?

November 28, 2020 7:41 pm

“oceans are becoming more acidic ”


As soon as you see a moronic anti-science statement like that…

.. you KNOW the rest is just AGW mantra BS !!

November 28, 2020 7:49 pm

Coral bleaching occurs during El Nino cycles because the sea level over the coral DROPS, exposing the coral to too much sunlight.

Mangrove die back in 2015 also due to LOW sea levels

“Diebacks in Mangrove Bay were coincident with periods of very low sea level, which were associated with increased soil salinization of 20–30% above pre-event levels”

Reply to  fred250
November 28, 2020 9:18 pm

“Mangrove die back” (Fred250) may also be caused by changes in coastal topography. Mangroves have a significant role stabilising coastlines, which is why it is an offence where I am to cut down mangroves. Sometimes the off-shore sand bars move faster than the mangroves can catch up with. Happened with one patch near the shoreline at QNI, and the (then) owners spent money clearing a flow path, so the company would not be accused of causing the problem by failing to manage sediment run-off or something.

November 28, 2020 7:50 pm

Sharks have lived through more climate changes than most species.

Joel O'Bryan
November 28, 2020 7:50 pm

Slapping a “climate change threatens the (studied species)” sticker on your latest study for a biologist or ecologist is just programmed behavior in the academic world where getting tneure means first getting grants. So these guys who study sharks and counting numbers are jumping onboard the climate gravy train to grant success, so they can do what they really want to do… count sharks and study their behaviors. The financial rewards (grant success) have been put in place to reward those who jump on the climate scam grant train, and punish those who refuse.

We see this programmed human behavior of course clearly in polar bears. The PB is the “poster child” for Arctic climate change and how Susan Crockford calls out certain researchers regularly for hyping and claiming impending PB demise even as their numbers steadily increase.

The IPCC knows this. The CMIP folks know this. They need to make climate addicts out of as much of the academic research community as possible. Get them on that gravy train, because then they have loyal followers, like drug dealers have drug addicts. Grant money is the drug.
So the IPCC and the GCM CMIP community decided 20 years ago to put together unrealistic emissions-forcing scenarios, dishonestly call them business-as-usual (BAU), in order for non-climate researchers to grab that “worst case” scenario outputs and claim impending doom for whatever diverse area of study that alarmist warming touches.

Michael Jankowski
November 28, 2020 7:53 pm

The attacks in 1916 that inspired “Jaws” were viewed with skepticism. Many – including prominent scientists – believed sharks would not attack humans, let alone be capable of killing humans.

Greg Locock
November 28, 2020 7:53 pm

Sharks have been around a hundred million years. Will sharks survive climatic conditions last seen 3 million years ago? Both dates from the article. Um, they’ve survived them once, why not again?

Reply to  Greg Locock
November 28, 2020 8:24 pm

Except its currently cooler now than for most of the last 10,000 years.

Ocean heat content has only recovered slight from the LIA.

And none of that recovery has any human causation.

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sky king
November 28, 2020 8:18 pm

Yes, it’s not like sharks are mobile and could move to colder water south or north or something.

Al Miller
November 28, 2020 8:18 pm

Klimate change jumps the shark…again.

November 28, 2020 9:13 pm

Snorkeling on the Great Barrier Reef offshore Cairns in early 2005, I came face-to-face with a ~5 foot reef shark – it looked me right in the face from about 3 feet away, and concluded: Nah! Too old and too tough – not worth the trouble – and swam away. My only close encounter of that type.

The blue-bottle jellyfish were another story – got stung across my neck and foot, burns like fire but I got off easy. One of our team took a break, holding on the swim grate, and took out his mouthpiece. A blue-bottle wrapped around it and he put it back in his mouth! Poor guy had gigantic swollen Mick-Jagger-Lips for the rest of the week. Some people say uric acid helps to dull the pain – I say alcohol, lots of it, is better.

November 28, 2020 9:29 pm

… a really jaw-dropping piece of research.

Ed Zuiderwijk
November 28, 2020 11:55 pm

The great white has apparently disappeared from the waters near Cape Town. Because orcas have put them on the menu.

Patrick MJD
November 29, 2020 12:00 am

“The beloved politicians who run our country have cut back on shark culling near popular beaches,…”

More deaths from sark attacks.

“The beloved politicians who run our country have cut back on forest fuel load management,…”

More wild bush fires.

I see a trend here…

William Haas
November 29, 2020 12:35 am

More recently, about three million years ago it was considerably warmer than today with very similar levels of CO2 and sharks survived. More recent than that, the previous interglacial period, the Eemian, was warmer than this one with higher sea levels and more ice cap melting yet sharks survived. Concerning the survival of sharks, the climate change that we have been experiencing cannot possible be a concern.

Nick Graves
November 29, 2020 2:49 am

I’m sure sharks will survive the Cretinaceous period, too.

Bruce Cobb
Reply to  Nick Graves
November 29, 2020 8:06 am

Although, the Stupid might burn them.

Reply to  Nick Graves
November 29, 2020 7:21 pm

If a shark eats a warmist, does he get MSD (mad shark disease)?

Climate believer
November 29, 2020 2:57 am

I thought everything was threatened by “climate change™”.

According to University of Queensland and Griffith University researchers : “The key thing that our study shows is that large apex sharks on the Queensland coastline have been declining over the last 50 years,”’s-coastal-sharks

Looks like sharks have other problems more pressing than a timid water temperature change.

The research team said factors such as climate change, which is affecting shark populations, could not explain the scale of the decline.
“We can be fairly certain the cause of the decline is fisheries related. There’s not very many other things it can be,” Dr Roff said.

Alasdair Fairbairn
November 29, 2020 3:40 am

Oh dear! Just another boring grant induced paper by purported scientists infected by the CAGW virus. Best pat them on the head and say ‘There there- never mind’.

Tom Abbott
November 29, 2020 6:15 am

from the article: “So how will sharks cope as the ocean heats up?”

This is based on the assumption that the ocean will continue to heat up. Climate Alarmists are very prone to assuming too much, as is the case here.

It was a lot warmer in the ancient past than it is today, and that would include the oceans, and sharks were around at that time and are still around, so I would say a barely measureable increase in the ocean’s warmth today will have no effect on sharks.

This is just more wild speculation by Climate Alarmists, working on the unsubstantiated assumption that the Earth’s atmosphere and oceans will continue to get warmer as CO2 concentrations in the atmosphere increase.

The problem with that assumption is CO2 concentrations have increased since the 1930’s, yet the temperatures declined for three decades after the 1930’s, while CO2 output was rapidly increasing, and then temperature climbed for decades but leveled off and rose no higher than it was in the 1930’s, and now temperatures are falling, down 0.3C since the highpoint of 2016.

All the while, CO2 has been increasing, yet the cyclical nature of the climate (it warms for a few decades and then cools for a few decades and then repeats) is still cycling like it did before the latest CO2 increase.

CO2 could not prevent the temperature decline from 1940 to 1980, and today CO2 has not been able to push temperatures higher than they were in the recent past, even though there is a lot more CO2 in the Earth’s atmosphere now than then.

CO2 is a minor player in the Earth’s climate. We should’t spend Trillions of dollars trying to fix something that doesn’t need fixing.

November 29, 2020 7:08 am

I thought it was the Asian demand for shark fin soup that was causing the shark decline. Doesn’t seem like 0.4 degrees warmer surface temp would do anything except maybe a little nicer weather to go shark fishing.

Don K
November 29, 2020 7:35 am

My impression is that sharks are actually in a bit of trouble. But the problem is a combination of slow breeding and intensive fishing practices like longlining, not climate change. I believe that lamnid sharks like the Great White — being somewhat warm blooded — can function well in cold waters, but are fine with warm water as well. There are a number of other sharks like the Tiger Shark that occasionally dine on humans and prefer warm water.

I doubt climate change has, or would have, much impact on shark attacks except to the extent that significantly warmer waters would probably lure more swimmers in areas like New England or California where even Summer water temps are on the bone chilling side.

Bruce Cobb
November 29, 2020 8:22 am

Life in the anthropocene is characterised by changes in IQ and levels of Stupid on a scale not seen since – ever.

November 29, 2020 1:01 pm

“anthropocene”. The use of that nomenclature told me all I need to know about this “study” without wasting my time reading further.

November 29, 2020 5:59 pm

I’ve researched Western Australia’s shark fatality increase over the decades since in 1981 I interviewed the country’s last whaleboat skipper who, after the commercial whaling industry closed in 1978, warned that when their numbers recovered the sharks would return.

All Australian whale populations have boomed since then, particularly the humpbacks with an approximate 12% per annum increase off the coast of Western Australia. The humpback population has increased from an estimated 640 surviving adults in West Australian waters in the 1970s to now being somewhere between 40,000 and 45,000.

“Sharks” aren’t a problem in Australia. “Great white sharks” are the killers because their dietary preference switches from fish to mammal meat post puberty (around 12 years old), and they now have about six to seven million tonnes of additional whale meat and blubber luring them toward the coast when humpbacks in particular make their Antarctic migration between roughly April and October.

Great whites eat whales and occasionally bite but rarely eat humans they encounter in their habitat. If great whites hunted humans, they’d die of starvation even if they gobbled up all of our bony little bodies.

There’s even evidence that the otherwise solitary great whites lose their aggression and mate while crowding around to fill their bellies with 40 tonnes of whale carcass. Survival of the great white species may depend on whales.

The whale populations have boomed, the great whites have been lured back and the incidental human fatalities began in the 1990s following a hiatus of many decades.

I don’t agree that great whites should be culled as there’s not that many of them despite protected species status since the late 1990s, and fatalities from great whites are minuscule compared to almost all other human activities – including car crashes when driving to and from the beach. The main reason Australians think shark fatalities are out of control is because when one happens, it’s lead TV news and dozens of front page headlines for the following week.

My point is that the climate furnace and boiling, acidic seas caused by CO2 since the 1970s don’t seem to have had much negative impact on either whale or shark survival.

Both species are going where the food is abundant and not where the water is a degree warmer or cooler.

It’s also worth noting that Southern Ocean temperatures where humpbacks feed in summer vary from -2C to 10C, while northern Australian waters where they birth vary from 25C to 30C. Great white fatalities happen off Esperance where ocean temperatures vary from 16C to 21C, and around Perth where they vary from 18C to 24C, and they enjoy swimming in the colder southern waters.

November 30, 2020 6:23 pm

Once the Global Warming disrupts the deep ocean thermal boundary, the Megalodons will escape in numbers too large for Jason Statham to hunt them all down. Then our beach going will truly be disrupted.

December 5, 2020 10:23 pm

Never read so much garbage for so called academics in my life. Ask any boat fisherman about the abundance of large sharks off the east coast … they’re at plague proportions. Not to mention the huge increase in attacks on humans.

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