Shark attacks are already much rarer than popular media makes them out to be. Soon, they may be even fewer and farther between.
A new study published in Nature Scientific Reports finds that climate change will destroy sharks’ ability to hunt. Rising CO2 levels and warmer oceans will require more energy for the sharks to get around and will also inhibit their ability to sniff out prey. This might be good news for surfers and seals, but it’s actually bad news for everyone else–potentially causing an unbalancing of the entire ocean food-chain, from top to bottom..
The true extent of the impact on sharks and the rest of the ocean ecosystem remains hard to predict, but the study out of the University of Adelaide in Australia used laboratory experiments to determine the direct effects of warmer water and ocean acidification on sharks.
“In warmer water, sharks are hungrier, but with increased CO2, they won’t be able to find their food,” lead author Ivan Nagelkerken told the University of Adelaide News.
Warmer waters initially lead to faster growth, but those same warm waters, stuffed with extra carbon dioxide, impair the sharks’ sense of smell. This is their primary means of finding food, something so well known we even have sayings about sharks being drawn to the smell of blood. At the same time, they need more energy to operate in warmer water (due to raised respiratory requirements), which makes efficient hunting all the more important.
Different species of sharks are affected to differing extents, but the results show that the news is bad all around. By the end of this century, a shark embryo is expected to take 40 days less than the 10 to 12 month average to fully develop. In the experiment, just-hatched sharks ”tripled their food consumption rates under elevated temperatures compared to the control treatments,” and took almost four times longer than usual to locate their prey. Worse, two out of nine sharks just gave up hunting at all, and didn’t even notice when prey was introduced.
Climate change won’t be uniform. Sharks might suffer from one or both of these problems. If they’re only facing warmer waters, they will need to kill more to stay alive, for instance. Or they may migrate into cooler, or more productive waters. However it works out, this pressure, combined with pressure from over fishing, will be a major stressor for sharks and the entire ocean.