The Fate of Sharks
The apex predator Selachimorpha or as we call them sharks, have resided in the depths of the vast ocean on our planet for around 450 million years. Over that 450 million years, just like every living organism on our planet today, sharks have had to slowly evolve and adapt to Earth’s ever-changing climates. The question is, can sharks accomplish the same over the next 80 years? With Earth’s rapid climate change that is being caused by global warming, and with the “ocean ecosystems [that] are already being damaged by overfishing, pollution and noise” being caused by humans the odds are stacked against the sharks (Carrington). As climate change starts to add to the factors that continue to affect sharks in their habitats we need to look at why climate change might be the crucial factor that sharks may not be able to survive.
Being cold-blooded, mother sharks typically give birth to their young in the warmer coastal waters nearing the equator. One of the most common places for this to occur is off the coast of southern California. Sharks come here because it is what is referred to as a Goldilocks zone. A Goldilock zone is an area in the ocean where the water is “neither too hot nor too cold” (Copenhaver). Needless to say there are not a lot of areas around the world with these Goldilock zones for sharks to give birth in. Making matters worse, “water temperatures within their preferred thermal range are becoming harder to find”(Copenhaver). This leaves a scarce amount of places for mother sharks to give birth. After giving birth the mother sharks leave their adolescent offspring and continue with their lives. These young sharks then stay in these Goldilocks zones such as the one off the coast of southern California until they mature and “massive enough to keep warm even in cold water” (Copenhaver), but a “marine heatwave” that lasted between 2014 to 2016 hit the north Pacific bringing in more sharks (Carrington). Even after this marine heatwave ended in 2016 the temperatures in the water have not gone down, in fact it has been more common for there to be extreme temperature changes with the water. This zone is starting to be shifted northward at an alarming rate. As of now the “range shifted nearly 400 miles” already (Copenhaver).
Similar to the coast of southern California, The entire coast of New South Wales in Australia has one of these goldilocks zones. The sharks “tend to appear in coastal waters in late summer and fall”(Peterson). This occurs because this is when the water starts to warm to the specific temperature that the sharks are looking for. Typically they start to appear around and stay on “[the] coast of New South Wales during the January-February period but [are] predicted to occur from December to April by 2030”(Márquez). The sharks are predicted to be at the coast 3 months longer than before because the water will start to stay at that perfect temperature that is needed longer than before. A study done by researchers also provided that “[the] range could shift as much as 40 miles poleward per decade, pushing the sharks away from the warming oceans near the equator into different habitats”(Climate Central). Based on the fact that the migrations are happening on several different spots on the Earth, it helps to strengthen the claim that climate change is the reason for behavior. The average size of sharks in these areas may increase as well, because the sharks may have started to “have imprinted on this area”(Peterson). This happens because the sharks start to recognize that the places that they were before are no longer suitable for their young’s needs.
Another reason as to why the sharks are migrating is because they are listening to their instincts and following their food sources. The fish in the region also sense that the water temperatures are changing and the fish begin to “move poleward at a greater rate, causing the sharks to follow”(Climate Central). As the fish start to move up the coasts the sharks are bound to follow because they need to feed. Unlike humans like us sharks don’t have Ubereats or Grubhub so they must hunt for their food. These areas have “shrunk by about 5%”(Carrington). This is Seemingly insignificant because of just how huge the ocean is, but what it is actually doing is compressing the Sharks and their prey into a smaller area, which leaves the fish with less places to hide. It also means that “the appearance of new, more powerful predators (such as bull sharks) in these environments could lead to other species being forced to move into less protected areas that might also not have the same amount of prey options”(Chapman). With larger sharks such as bull sharks moving into new areas like this, it starts to affect the food chain in the ecosystem from the top to the bottom. The bottom of the food chain is being affected as well, “phytoplankton, the base of the marine food web, would decrease as the ocean warmed and create a chain effect up the ecosystem”(Climate Central). For other sharks in the area such as a reef shark, which is in the middle of the food chain, This means there will be less prey because of the bigger sharks eating the fish, and the fish below the reef shark on the food chain will also be losing their source of food the phytoplankton. Studies also show that because of the changing pH level of the ocean water that “fish were found to have lost the innate ability to fear predators. In fact, they were instead attracted to them”(Chapman). If the fish population is no longer in fear of the sharks, the sharks will soon start to be able to hunt the fish without fail, which will cause a lack of food overall because the population sizes of the fish will start to rapidly decrease.
Looking further into the growing acidity of the water, the sharks will soon also be affected by this change caused by the climate. In a study that was run by “the National Oceanic and Atmospheric Administration (NOAA), nine of the 10 years with the warmest ocean temperatures have occurred since 2000. And 93 percent of warming from greenhouse gas emissions is absorbed by the oceans”(Climate Central). The absorption of the gasses into the ocean doesn’t only affect the temperature of the ocean, it also is changing the pH level of the water in the Earth’s oceans. The gas that gets absorbed the most by the ocean is carbon dioxide. Knowing this, researchers set up an experiment where they put a shark in a tank with the same concentration of carbon dioxide that they predict the ocean will be at by the year 2100. The researchers then added a squid to the tank to see how the shark would react. As a result, it was found by the researchers that the shark was “not attracted to the smell of squid at carbon dioxide levels” that would occur in 2100 (Climate Central). This possibly could be what is the last straw for the sharks. If the ecosystems of the ocean continue to fall apart and food becomes harder to find as well, without a sense of smell sharks will start dying in masses because they are unable to obtain food.
To exacerbate the problem, studies have also shown that the rising temperature and pH at the same time also negatively impacts the health of adolescent sharks. In a study, “researchers placed the shark embryos in water that matched the projected scenarios of warming and acidification, a pH 0.5 lower and about 7°F higher than today’s levels and allowed them to incubate and hatch normally. Thirty days after hatching, survival of the sharks rapidly declined, resulting in more than half of the sharks dying”(Climate Central). This is frightening because if half of the sharks die every time they are born, the population will start to rapidly decrease. There is also no saying that at a higher pH and temperature than those that it wouldn’t affect the health of fully developed sharks as well.
With climate change being a factor that is affecting the survival of sharks so drastically, the ocean’s entire ecosystem will potentially be changed forever. This is the initial warning, “These sharks — by venturing into territory where they have not historically been found — are telling us how the ocean is being affected by climate change”(Oceanographic). Now the next part is up to you, will you do something to help with this increasingly dire situation or will you just watch as the sharks begin to slowly disappear?
WORKS CITED
Carrington, Damian. “Climate Crisis Pushing Great White Sharks into New Waters.” The Guardian, Guardian News and Media, 9 Feb. 2021, 5:00, www.theguardian.com/environment/2021/feb/09/climate-crisis-pushing-great-white-sharks-into-new-waters.
Chapman, Blake. “Climate Change Is Predicted to Have a Huge Impact on Our Sharks.” Australian Geographic, 9 Oct. 2019, www.australiangeographic.com.au/blogs/shark-blog/2019/10/climate-change-is-predicted-to-have-a-huge-impact-on-our-sharks/.
Copenhaver, Athena. “Young White Sharks Tell the Story of a Changing Monterey Bay.” Montereybayaquarium.org, Monterey Bay Aquarium, 9 Feb. 2021, www.montereybayaquarium.org/stories/white-sharks-tell-story-changing-monterey-bay.
Márquez, Melissa Cristina. “Climate Change Is Already Impacting Sharks.” Forbes, Forbes Magazine, 3 June 2020, www.forbes.com/sites/melissacristinamarquez/2020/06/01/climate-change-is-already-impacting-sharks/?sh=1545ef2b3e00.
Oceanographic. “Climate Change Forcing White Sharks to Hunt for New, Cool Waters.” Oceanographic, Oceanographic, 16 Feb. 2021, www.oceanographicmagazine.com/news/white-sharks-climate-change/.
Peterson, Ken. “New Kids on the Block: Young White Sharks in Monterey Bay.” Montereybayaquarium.org, Monterey Bay Aquarium, 28 July 2018, www.montereybayaquarium.org/stories/new-kids-on-the-block-young-white-sharks-in-monterey-bay.
“Sharks Face a Growing Threat in Warming and Acidic Seas.” Climate Central, 10 July 2015, www.climatecentral.org/news/climate-change-sharks-19221.