Not every conversation with a climate denier has to lead to raised voices and hurt feelings. Here’s how to do it constructively. “Climate change has become one of the taboo topics — like sex, politics and religion — that doesn’t get talked about at the Thanksgiving table,” says Anthony Leiserowitz, director of the Yale Program…
Another case of mysterious naming is the Whitetip Reef shark (Triaenodon obesus). Not the English name, which is quite apt due to its white tips on dorsal and caudal fins and its exclusive habitat, but the Latin one is untrue: this slender shark is far from obese. On the contrary, as nocturnal hunter it can detect its prey by electroreception (using its ampullae of Lorenzini) and smell (with unique tubular nasal flaps) and follows it into their resting crevices (well adapted to this hunting practice due to its tough skin, sleek build, blunt snout and ridges to protect its eyes), and some sharks “actually squirm into a hole in one side of a coral head and exit through an opening on the other”.
The Whitetip Reef shark is gregarious (sometimes even hunts in groups) and can be seen resting in groups on the bottom or in caves during daytime. It doesn’t need to swim to breathe, unlike other requiem sharks. Not to be confused with the other Whitetip requiem shark (the Oceanic Whitetip), the smaller Whitetip Reef shark (up to 5.6 ft -1.7 m- long) isn’t dangerous to humans. Sadly, as opportunistic feeder it learnt to associate the sounds of boats and spearfishing with food – the curious shark can become bold and agitated and sometimes bites while trying to steal the fish.
Like all requiem sharks, the Whitetip Reef shark is ovoviviparous: every two years 2 to 3 living young are born at a length of 20 to 24 in -52 to 60 cm. There is a case of Parthenogenesis (asexually reproduction) in Whitetip reef sharks. They grow slowly, mature at about 3.4 feet -1.05 m- and live up to 25 years.
Whitetip Reef sharks live in coral reefs all around the world. They are homebodies and famous for their site fidelity. That means that dangers to their coral reef due to climate change, overheating and pollution have a deep impact on the shark population, too, in addition to commercial and recreational fisheries. They are considered as Near Threatened by the IUCN. Conservation measures like marine protected areas (MPA) seems to help, but only if they are completely no-entry. On the Great Barrier Reef, populations of Whitetip Reef sharks in fishing zones have been reduced by 80% relative to no-entry zones. However, populations in no-take zones, where boats are allowed but fishing prohibited, exhibit levels of depletion comparable to fishing zones, most likely due to poaching (IUU). Demographic models indicate that these depleted populations will continue to decline by 6.6–8.3% per year without additional conservation measures.
Many different shark species are used for fish-and-chips (under the name flake) in Australia: School sharks, several species of wobbegongs, and also the Gummy shark or Australian smooth hound (Mustelus antarcticus). It is named after its gummy-like, boneless fillets (don’t all sharks have no bones?) in English and its habitat off southern Australia (near Antarctica) in Latin.
Like all sharks of the family houndsharks, the Gummy shark has a smooth skin with tiny denticles and is viviparous. Every one of the one to 57 embryos (depending on the size of their mother) stays in their own separate compartment in one of the two uteri of their mother during the year long gestation. Born at a length of approximately 13 in -33 cm-, female mature at 5 years and reach a length of up to 73 in -185 cm-, males at 4 years with a maximal length of 58 in -148 cm. Gummy sharks live up to 16 years.
Living in two genetically distinct sub-populations, the Gummy shark is abundant in shallow waters off southern Australia. Nevertheless, regulations to manage fisheries like gillnets with a mesh-size around 6 in -16 cm- to protect smaller (juveniles) as well as larger (big female) sharks or a bag limit for recreational fishermen (see spotted wobby) and conservation measures like marine protected areas (MPAs) are in place to protect this shark species, too. It seems that climate change and subsequently warmer water “might trigger a change from the biennial reproductive cycle presently characteristic of Bass Strait to an annual cycle characteristic of the other regions (Walker 2007), which may increase pup production and hence productivity of the population and yield from the fishery.” This is no reason to give the all-clear, however.
Did you know that there are sharks in the Baltic sea? None of the species living solely in fresh water (like river sharks or Freshwater stingrays), and fortunately not the Bullshark, but emigrants from North sea or Atlantic. Many have probably been dragged along by saltwater floods due to storms, or wander temporarily into the afterwards more saline waters. But one species made itself at home and lives even in areas far away from saltwater passages. The small-spotted catshark (Scyliorhinus canicula) or lesser-spotted dogfish is the most common European shark species and lives in the Mediterranean, the north-east Atlantic and the North sea, for some time incl. Skagerrak and Kattegat. But now it is even native in the German Baltic sea (to be precise off Poel island), as shown in this report.
The up to 3 ft 3 in -1 m- long Small-spotted dogfish is used commercially, too: for its meat (its liver is poisonous), its sandpaper-skin, oil or fishmeal. Now and then catsharks (named after their catlike eyes: horizontally oval eyes with elongated pupils and a nictitating membrane) have been caught in the Baltic sea, too. Afterwards they would be discarded (with high chances of survival) or go, as mentioned here, to aquariums (in which small-spotted catsharks are easy to keep and therefore a common species). Sometimes you are able to even touch them there. Together with my family I visited such an aquarium in Denmark and curiously touched sharks, rays and starfish under water – until I learnt this summer in Scotland, that you shouldn’t do that since it may damage the protective layer of slime above the skin. Why didn’t the other aquarium operators know that?
Like all catsharks the small-spotted catshark lays eggs called mermaid’s purses with curly tendrils at each end to cling themselves to underwater structures. Inside the egg case one embryo (seldom two) develops during 5 to 11 month, which can be studied easily (as done in laboratories). After hatching, the 4 in – 10 cm – long pups have to fend for themselves. On them it was observed for the first time, that they anchor their prey on the dermal denticles on their tail and tear bits off – they are really flexible.
This egg cases as well as pups have now been found in the Baltic sea, too – proof that they are not only temporary visitors. It is assumed that the reason is the climate change. How do they cope with the small level of salinity?
Did you know that there are female bullhead sharks that deposit their eggs at the same place – like a communal nesting site? Up to 15 eggs of the Japanese bullhead shark (Heterodontus japonicus) can be found in the same patch. Each egg has to rotate out of the mothers cloaca during several hours, as with all bullheads. The reason is the auger shape of the egg case – even if the egg of the Japanese bullhead shark is a little less elaborate. The eggs take about a year to hatch, and the newborns are 7.1 in -18 cm- long.
The Japanese bullhead shark is up to 3.9 ft -1.2 m- long and lives in the northwestern Pacific Ocean off the coasts of Japan, Korea and China at depths of 20 to 121 ft -6 to 37 m- over rocky bottoms or kelp beds. Just like all bullhead sharks, it has a pig-like snout, a ridge above each eye and fin spines. It has a characteristic pattern of irregularly shaped, vertical brown bands and stripes.
The Japanese bullhead shark can often be found in aquariums in Japan. It is harmless to humans and can even easily be hand-caught by divers. Considered as Least concern by the IUCN, it vanished from the gulf of Bohai in China, assumedly due to climate change. But, given that there is one of the busiest seaways in the world, there could be other reasons as well.
Regarding those who point out that there where periods with much higher (not human-caused) carbon dioxide levels than today, implying it is only natural and no reason to change anything, I found this article that was originally published on The Conversation on October 13, 2015.
Yes, rising carbon dioxide levels happened in the past, but either so slow that nature could adapt, or as rapidly as now, but then coupled with a mass extinction event (Source). The sharks survived the last times (as below mentioned they wouldn’t now), and I think (and hope) mankind would survive, but: how would we live in the world we would find ourselves in after?
Bezüglich denen, die aufzeigen, dass es Perioden mit viel höheren (nicht vom Menschen verursachten) CO2-Pegeln als heute gab, damit unterstellend, dass es nur natürlich ist und es keinen Grund gibt irgendetwas zu ändern, habe ich diesen Artikel gefunden, der ursprünglich am 13. Oktober 2015 auf The Conversation veröffentlicht wurde.
Ja, in der Vergangenheit passierten steigende CO2-Pegel, aber entweder so langsam dass die Natur sich anpassen konnte, oder so schnell wie heute, aber dann mit einem Massenaussterben gekoppelt (Quelle). Die Haie überlebten es die letzten Male (wie unten erwähnt würden sie das jetzt nicht mehr), und ich denke (und hoffe) die Menschheit würde überleben, aber: wie würden wir leben in der Welt, in der wir uns danach befinden würden?
The oceans are changing too fast for marine life to keep up
Some of the ocean’s top predators, such as tuna and sharks, are likely to feel the effects of rising carbon dioxide levels more heavily compared other marine species.
That’s just one of the results of a study published today in Proceedings of the National Academy of Science.
Over the past five years we’ve seen a significant increase in research on ocean acidification and warming seas, and their effect on marine life. I and my colleague Sean Connell looked at these studies to see if we could find any overarching patterns.
We found that overall, unfortunately, the news is not good for marine life, and if we do nothing to halt climate change we could lose habitats such as coral reefs and see the weakening of food chains which support our fisheries.
Acidifying and warming oceans
Humans have been adding carbon dioxide to the atmosphere largely through burning fossil fuels. Under a worst-case scenario, without doing anything to stop increasing emissions, we’d expect concentrations of carbon dioxide to reach around 1,000 parts per million by the end of the century.
This increase in greenhouse gases is “acidifying” the oceans. It’s happening now. Carbon dioxide concentrations have reached around 400 parts per million, compared with around 270 parts per million before the industrial revolution.
This extra carbon dioxide, when it dissolves into the seas, is reducing the pH of the oceans – that is, making them more acidic.
Many ocean creatures, particularly those that build habitats such as corals and shellfish, make skeletons out of calcium carbonate, which they get from ions dissolved in sea water.
When carbon dioxide dissolves in seawater, it makes these calcium carbonate ions harder for marine life to collect and turn into skeletons. It’s like a person going on a diet without calcium.
At first this results in marine life producing brittle skeletons, but can ultimately lead to the skeletons dissolving.
A calcium-free diet
Many studies have looked at what will happen to these lifeforms that produce skeletons, but we wanted to look at how rising carbon dioxide would affect the ocean at a broader scale.
We analysed more than 600 experiments on ocean acidification and warming seas.
Overall it seems warming temperatures and acidifying oceans will have a negative effect on species and ecosystems. This means reduced growth, abundance, and diversity of marine species.
We also found these results were mostly consistent across latitudes – they weren’t just limited to tropical oceans.
It’s likely that acidification will interact with warming to have a worse effect. For instance, if you would see a 20% reduction in calcification rates because of rising temperatures, and a 25% reduction in calcification because of acidification, then the combined reduction might be 60%. We see these effects regularly in the studies we looked at.
Of course not every species will show the same response. We expect some species to be able to acclimate or adapt to changes, particularly over longer time periods perhaps like a couple of decades. For example, a recent study on a coral living in a tropical lagoon found it has some capacity to adapt. We found that more generalist species like microorganisms seem to be doing particularly well under climate change, and also some fish species at the bottom of the food chain may show increases in their populations.
Changing whole ecosystems
Most worrying are not only the changes to individual species but also whole ecosystems.
We found that reef habitats are vulnerable: coral reefs, but also temperate reefs built by molluscs such as oysters and mussels. A lot of shallow temperate waters used to have oysters reefs, but there are few natural reefs remaining.
There are also cold-water reefs formed by other species of coral, which grow slowly over thousands of years in the cooler temperatures. In our analysis we found that acidification could cause these habitats to show reduced growth. These habitats are often located in deep waters and are very sensitive to human impacts.
We also found that these changes affect whole ocean food webs.
We found that warmer temperatures mean more phytoplankton – the tiny plant-like lifeforms that form the basis of many ocean food chains. This means more food for grazing species that feed on phytoplankton.
Warmer temperatures also mean faster metabolisms, which require more food. However this didn’t translate into higher growth rates in grazing species. That’s fatal because the next level up in the food chain (the species that eat the grazing animals) would have less food, but still need more food because of faster metabolisms.
This effect is expected to become stronger as you go up the food chain, so predatory species like tuna, sharks, and groupers will be the species that would feel the strongest effects.
These species are also threatened by overfishing, which adds another level of stress. Overfishing alters important food web interactions (e.g. top-down control of prey species) and may also reduce the gene pool of potentially strong individuals or species that could form the next generation of more resilient animals. And this is on top of other threats such as pollution and eutrophication.
Therein lies an opportunity. We cannot change climate change (or ocean acidification) in the short term. But if we can mitigate the effects of overfishing and other human stressors we can potentially buy some time for various species to adapt to climate change.
Species can genetically adapt to changes over geological timescales of thousands of years – as we can see from modern species’ survival over many ups and downs in the climate. But the changes we have wrought on the oceans will take place over decades – not even one generation of a long-lived sea turtle or shark.
With such fast changes, many species in the ocean will likely be unable to adapt.
Read the original article.
Since I often stay helpless in the face of climate change denial (or rather human-caused global warming denial), I post some links I found to make sense of their arguments (including their motives and why discussing with facts doesn’t work):
Weil ich oft hilflos bin angesichts Klimawandel-Leugnung (oder eher Menschen-verursachte-Erderwärmungs-Leugnung), poste ich einige Links die Sinn in ihre Argumente bringen (inklusiver ihrer Motive und warum mit Fakten diskutieren nichts bringt):
“The researchers concluded that just a few more decades of “unabated” carbon emissions could result in more than three feet of sea-level rise from WAIS [West Antarctic Ice Sheet] by the end of this century. (The over-all rise would be much greater, as ice would also be lost from Greenland and from mountain glaciers.) Over the longer term, melt from Antarctica could raise sea levels by fifty feet.”
“Die Forscher schlussfolgerten, dass nur ein paar mehr Jahrzehnte von unverminderten Treibhausgas-Emissionen ausreichen könnten, um bis zum Ende des Jahrhunderts den Meeresspiegel wegen des WAIS [West Antarctic Ice Sheet=Eisdecke des westlichen Teils der Antarktis] um einen Meter steigen zu lassen (wegen Schmelzeis von Grönland und Gletschern würde der Gesamt-Anstieg viel höher sein). Auf lange Sicht könnte Schmeltzeis von der Antarktis den Meeresspiegel um 15 Meter ansteigen lassen.”
see also: New York Times