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 GervaisThey 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 forests, mangrove 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: https://theconversation.com/how-will-sharks-respond-to-climate-change-it-might-depend-on-where-they-grew-up-150460
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.
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
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’.
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.
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.
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.
Life in the anthropocene is characterised by changes in IQ and levels of Stupid on a scale not seen since – ever.
“anthropocene”. The use of that nomenclature told me all I need to know about this “study” without wasting my time reading further.
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.
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.
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.