A Deep Dive Into How Global Warming Affects Sharks

Climate change has posed significant threats to the planet, from rising sea levels to poor air quality and extreme weather events. However, something else is happening underwater where there are few witnesses. Although many believe marine apex predators are resilient against environmental pressures, global warming affects sharks in unimaginable ways.  

Shark Populations on a Sharp Decline

According to a widely cited 2021 study, 71% of global shark and ray populations have declined since 1970. Although much of the species depletion is due to overfishing, other factors — including global warming — also contribute to an increased risk of endangerment. In fact, three-quarters of these species are threatened with extinction.

Contributing author Dr. Andrea Marshall says these large oceanic creatures often suffer from human threats because their pelagic habitat is overlooked. Fishing is underregulated in many places where strict, enforceable rules are direly needed. To conserve shark populations, the world must also address coastal development, habitat destruction, various economic factors, and climate change implications. 

How Global Warming Affects Sharks

Global warming is not just a buzzword. It is a scientifically backed phenomenon that has created a critical situation for biodiversity, including sharks. Here is how global warming affects sharks and their ability to survive. 

Physiological Impacts

Warming ocean temperatures negatively impact sharks’ physiological and metabolic functions, such as reproduction, growth and digestion. Sharks expend more energy to live and swim as their metabolic rates increase, meaning they intake fewer nutrients with less efficient digestion.

Sharks already have slow reproduction rates and may also reproduce less often with warming temperatures, while some are born smaller than average. For instance, one study found that epaulet sharks born at 31 degrees Celsius weighed much less than those born at 27 C. 

Habitat Degradation

Blue carbon ecosystems (BCEs), such as mangroves, salt marshes, sea kelp forests, and seagrass beds, are vital habitats for sharks. Scalloped hammerhead sharks, especially, rely on these coastal areas to give birth, while juveniles thrive in inshore nurseries where they remain protected from deepwater threats.

A 35-year study has shown that mangrove distribution has declined by 21.6% from 1985 to 2020. Scientists have observed a similar effect in coral reefs — another common nursery for juvenile sharks. In fact, sharks have gone nearly extinct in 20% of global coral reefs.

Behavioral Changes

Deoxygenation in ocean water has impacted migratory sharks’ ability to breathe. Sharks continuously swim to ensure their gills receive oxygen for their muscles and organs. Unfortunately, oxygen loses solubility in warm water.

Blue sharks, in particular, conserve energy by staying at deeper depths. However, as bacteria consume oxygen at these levels and create “dead zones,” the sharks are forced to venture near the surface, becoming targets for fishing vessels.

Prey Availability

Warming ocean temperatures disrupt the food web, making sharks’ prey unavailable. Many fish alter their migration patterns or endure population declines, while acidification harms shellfish, which are crucial for their diets. Many sharks must change their hunting and migration routes as they struggle to find enough food for healthy development.

For example, oceanic whitetip sharks primarily prey on large fish and squid, which change course to follow nutrient cycles. The oceanic whitetip sharks must move with their prey to continue feeding. 

The Importance of Marine Apex Predators

Sharks are apex predators critical to maintaining the delicate balance within marine ecosystems. Among their many functions are the following:

• They feed on sick, weak or dead wildlife, helping prevent disease spread and promoting healthier fish populations. 
• They protect seagrass beds by preventing species such as turtles from overgrazing or damaging them.
• They help regulate mid-level predators that deplete vital fish stocks.
• They enable fish to remove harmful parasites by allowing them to rub against their rough scales.

Robust shark populations further promote ecotourism by attracting divers and snorkelers, boosting tourism economies from recreation to hospitality. These apex predators also play an essential role in maintaining fisheries, benefiting the seafood industry.

How to Help Save the Sharks

Many people find the thought of combating global warming daunting. As such, they might wonder how they could make a difference for sharks’ survival alone. However, there are several “green” habits you can adopt to help save these important creatures:

• Reduce your carbon footprint by consuming less energy, driving less often or using public transportation, and eating less meat.
• Support sustainable seafood by selecting fish and shellfish sourced ethically. 
• Avoid shark products, including shark fin soup.
• Create awareness about the importance of sharks and their conservation.

Participating in citizen science projects is also an excellent way to get directly involved in conservation initiatives and research. For instance, the Cooperative Shark Tagging Program encourages recreational anglers to partner with the National Oceanic and Atmospheric Administration and commercial fisheries in voluntarily tagging shark bycatch and releasing them.

Other citizen science opportunities include shark identification, data collection and analysis, reported sightings and habitat monitoring. You can submit your findings to databases, which experts may use in scientific research.

Frequently Asked Questions

What else should you know about global warming’s effects on sharks, and how can you get involved in their protection?

Can sharks survive the increasing impacts of global warming?

Scientific evidence suggests a grim future for shark populations as global warming threatens survival. However, they have endured previous warming events, giving hope that they will be resilient once again amid rising ocean temperatures.

According to one study, a volcanic eruption 93 million years ago increased carbon dioxide levels and caused the ocean to reach its hottest point. After viewing 500 living and fossilized shark species, researchers discovered their pectoral fin shape evolved as they ventured into the open seas. The longer fins made it easier for sharks to move, reducing the amount of energy they needed and allowing them to swim faster. 

Where can you find citizen science projects related to shark conservation?

Are you interested in participating in citizen science projects to save sharks from warming temperatures? Here are a few good places to start your search:

• Online citizen science networks like SciStarter and Zooniverse
• Various conservation organizations, such as Shark Trust, eShark, World Wildlife Fund and Sharkbook
• Local aquariums, marine research institutions, and universities
• Social media platforms and online forums

Turning the Tide for Shark Survival

Global warming will continue threatening shark survival without swift interventions to curb rising temperatures. As scientific studies suggest, their decline could have cascading effects on the marine ecosystem, biodiversity, and the economy. Fortunately, no individual effort to limit global warming and conserve sharks is too small.