
By Jen Sawada
Sharks have been around for 400 million years, before the time of the dinosaurs, but there's much more to them than big teeth and summer blockbusters. Consider these facts, which will change what you think about sharks.
No Need to Fear the World’s Biggest Shark
Andre Seale
Whale sharks are gentle giants of the ocean, often growing as long as 40 feet. They swim with their mouths open to filter-feed on small fish, invertebrates and plankton. While whale sharks aren't seen on Shark Week as often as jagged-toothed great whites are, they do attract large audiences of divers—contributing about $47.5 million worldwide each year.
Some Sharks Can Walk
There's a shark species found off the coast of Indonesia that doesn't just swim around. It gets from place to place by walking on the ocean floor.
Rays Are Flat Sharks
Christian Grondin
Though they look different, rays are closely related to sharks—so closely, in fact, that they're often referred to as flat sharks. These species have cartilage skeletons and float through the water thanks to their oil-rich liver—not the swim bladder on which other fish rely. Mobula rays, pictured above and manta rays have received protections through the Convention on International Trade in Endangered Species of Wild Fauna and Flora.
This Shark Has Many Names—Just Don’t Call Him ‘Jaws’
iStock
You've heard of a great white shark, but what about a white or blue pointer? Turns out, they're all the same species! In Australia, the world's most famous shark is called a white pointer, while in South Africa, it's a blue pointer.
Greenland Sharks Are the World’s Longest-Living Vertebrate
NOAA Okeanos Explorer Program
Last year, scientists discovered a Greenland shark estimated to be 400 years old. That makes this species the oldest known living vertebrate. These slow-growing sharks don't reach reproductive age until around 150, so it's fortunate that they have a long life span to make up for lost time.
Many Sharks Give Birth Like Mammals
Have you ever seen a shark give birth? This may come as a surprise, but many shark species give birth to live young instead of laying eggs. That makes them more like mammals than other fish. Researchers released a video in 2015 of what they think is the first thresher shark birth caught on camera.
Blue Sharks Top the Fin Trade
iStock
These sleek indigo sharks are found in nearly all the world's oceans—and are also the most caught. About 20 million blue sharks are killed every year, most of them for their fins. This heavy fishing has caused their numbers to drop sharply. Fortunately, Samoa and Sri Lanka have proposed giving blue sharks protections through the Convention on Migratory Species (CMS). Other shark species that could receive protections through CMS this year are whale sharks, dusky sharks, wedgefish, guitarfish and angel sharks.
Sharks Prove You Can Go Home Again
Shutterstock
There's no place like home. There's no place like home. Sharks don't have ruby slippers to help them get home, but some species have an amazing innate ability called philopatry, the tendency to return to where they started their lives. Female lemon sharks, for example, swim all the way back to where they were born in The Bahamas to give birth to their young. The island chain is one of 15 shark sanctuaries worldwide, where sharks are safe from commercial fishing.
There Are Some Very Surprising Sharks in the Sea
It's a coral! It's a carpet! It's a … shark? The tasseled wobbegong is one of the more unusual sharks in the ocean, but this bottom-dweller isn't the only unexpected species swimming around reefs. There are more than 500 species of sharks in the world's oceans—and there may be many more that scientists still have not identified.
Jen Sawada is an officer for Pew's global shark conservation campaign, managing efforts to encourage countries in the Pacific and Caribbean to adopt domestic measures to protect sharks, including creating shark sanctuaries.
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By Peter Giger
The speed and scale of the response to COVID-19 by governments, businesses and individuals seems to provide hope that we can react to the climate change crisis in a similarly decisive manner - but history tells us that humans do not react to slow-moving and distant threats.
A Game of Jenga
<p>Think of it as a game of Jenga and the planet's climate system as the tower. For generations, we have been slowly removing blocks. But at some point, we will remove a pivotal block, such as the collapse of one of the major global ocean circulation systems, for example the Atlantic Meridional Overturning Circulation (AMOC), that will cause all or part of the global climate system to fall into a planetary emergency.</p><p>But worse still, it could cause runaway damage: Where the tipping points form a domino-like cascade, where breaching one triggers breaches of others, creating an unstoppable shift to a radically and swiftly changing climate.</p><p>One of the most concerning tipping points is mass methane release. Methane can be found in deep freeze storage within permafrost and at the bottom of the deepest oceans in the form of methane hydrates. But rising sea and air temperatures are beginning to thaw these stores of methane.</p><p>This would release a powerful greenhouse gas into the atmosphere, 30-times more potent than carbon dioxide as a global warming agent. This would drastically increase temperatures and rush us towards the breach of other tipping points.</p><p>This could include the acceleration of ice thaw on all three of the globe's large, land-based ice sheets – Greenland, West Antarctica and the Wilkes Basin in East Antarctica. The potential collapse of the West Antarctic ice sheet is seen as a key tipping point, as its loss could eventually <a href="https://science.sciencemag.org/content/324/5929/901" target="_blank">raise global sea levels by 3.3 meters</a> with important regional variations.</p><p>More than that, we would be on the irreversible path to full land-ice melt, causing sea levels to rise by up to 30 meters, roughly at the rate of two meters per century, or maybe faster. Just look at the raised beaches around the world, at the last high stand of global sea level, at the end of the Pleistocene period around 120,0000 years ago, to see the evidence of such a warm world, which was just 2°C warmer than the present day.</p>Cutting Off Circulation
<p>As well as devastating low-lying and coastal areas around the world, melting polar ice could set off another tipping point: a disablement to the AMOC.</p><p>This circulation system drives a northward flow of warm, salty water on the upper layers of the ocean from the tropics to the northeast Atlantic region, and a southward flow of cold water deep in the ocean.</p><p>The ocean conveyor belt has a major effect on the climate, seasonal cycles and temperature in western and northern Europe. It means the region is warmer than other areas of similar latitude.</p><p>But melting ice from the Greenland ice sheet could threaten the AMOC system. It would dilute the salty sea water in the north Atlantic, making the water lighter and less able or unable to sink. This would slow the engine that drives this ocean circulation.</p><p><a href="https://www.carbonbrief.org/atlantic-conveyor-belt-has-slowed-15-per-cent-since-mid-twentieth-century" target="_blank">Recent research</a> suggests the AMOC has already weakened by around 15% since the middle of the 20th century. If this continues, it could have a major impact on the climate of the northern hemisphere, but particularly Europe. It may even lead to the <a href="https://ore.exeter.ac.uk/repository/handle/10871/39731?show=full" target="_blank" rel="noopener noreferrer">cessation of arable farming</a> in the UK, for instance.</p><p>It may also reduce rainfall over the Amazon basin, impact the monsoon systems in Asia and, by bringing warm waters into the Southern Ocean, further destabilize ice in Antarctica and accelerate global sea level rise.</p>The Atlantic Meridional Overturning Circulation has a major effect on the climate. Praetorius (2018)
Is it Time to Declare a Climate Emergency?
<p>At what stage, and at what rise in global temperatures, will these tipping points be reached? No one is entirely sure. It may take centuries, millennia or it could be imminent.</p><p>But as COVID-19 taught us, we need to prepare for the expected. We were aware of the risk of a pandemic. We also knew that we were not sufficiently prepared. But we didn't act in a meaningful manner. Thankfully, we have been able to fast-track the production of vaccines to combat COVID-19. But there is no vaccine for climate change once we have passed these tipping points.</p><p><a href="https://www.weforum.org/reports/the-global-risks-report-2021" target="_blank">We need to act now on our climate</a>. Act like these tipping points are imminent. And stop thinking of climate change as a slow-moving, long-term threat that enables us to kick the problem down the road and let future generations deal with it. We must take immediate action to reduce global warming and fulfill our commitments to the <a href="https://www.ipcc.ch/sr15/" target="_blank" rel="noopener noreferrer">Paris Agreement</a>, and build resilience with these tipping points in mind.</p><p>We need to plan now to mitigate greenhouse gas emissions, but we also need to plan for the impacts, such as the ability to feed everyone on the planet, develop plans to manage flood risk, as well as manage the social and geopolitical impacts of human migrations that will be a consequence of fight or flight decisions.</p><p>Breaching these tipping points would be cataclysmic and potentially far more devastating than COVID-19. Some may not enjoy hearing these messages, or consider them to be in the realm of science fiction. But if it injects a sense of urgency to make us respond to climate change like we have done to the pandemic, then we must talk more about what has happened before and will happen again.</p><p>Otherwise we will continue playing Jenga with our planet. And ultimately, there will only be one loser – us.</p>By John R. Platt
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