Annie Grey explores the economic and ecological consequences of a continued decline of the shark population.

Photo by Greg Jeanneau
The number of oceanic sharks and rays worldwide has fallen by 71% since 1970, according to the latest research from Nature. The study finds that more than three-quarters of these oceanic species are now threatened with extinction.
Of the 31 oceanic species of sharks and rays, 24 are currently vulnerable to extinction, and numbers of three shark species (the oceanic whitetip shark, the scalloped and the great hammerhead sharks) have declined so sharply that they are now classified as critically endangered by the International Union for Conservation of Nature (IUCN).
The risk to marine species is primarily caused by overfishing, with a threefold increase in global fishing rates of sharks recorded since 1970. Sharks are targeted by both small and large fishing operations for meat and other products, including shark fins. Across the ocean, an estimated 75 million sharks are brutally killed each year for use of their fins in traditional soup dishes found in Chinese cuisine.
Global action is needed immediately to stop shark populations collapsing, which would result in countless negative consequences for associated economic and ecological systems.
Ecological Disaster
As well as sharp falls in the numbers of oceanic sharks, previous research has recorded a universal loss of sharks on tropical reefs, upsetting the ecological balance of these delicate coral-dominated ecosystems.
Many types of shark are important to Australia’s coastal ecosystems, including great whites and the critically endangered scalloped hammerhead which, like other sharks, are still legally fished in Australia. Sharks alter the food webs they are a part of, often keeping prey numbers balanced through the alteration of diversity, behaviours, diets and even the shapes of their prey (e.g., coral reef fishes).
When sharks feed on the dominant prey in an area, they promote biodiversity among those species they eat. Remains are also left for other animals to scavenge on, creating another food source for the community. For these reasons, the food web dynamics can change as the predator population declines. Remarkably, some sharks are even having a positive impact on climate change mitigation. Research has shown that the presence of Tiger Sharks in Western Australian waters has caused dugongs and sea turtles to limit how much seagrass they eat. By preventing overgrazing, these carbon absorbing habitats can continue to take in CO2 and alleviate climate change. The overfishing of large sharks, the primary green turtle predators, could facilitate turtle populations growing beyond historical sizes and trigger detrimental ecosystem impacts, mirroring those on land when top predators were wiped out.
Shark Ecotourism
In addition to their ecological role, sharks also act as an important economic value for many local economies. Ecotourism is one of the fastest growing sectors in the tourism industry, thus encouraging locals to utilise natural resources in a sustainable manner and can promote conservation.
Currently, shark ecotourism generates $314 million (approx. £225.47m) annually worldwide, which encompasses all forms of shark-watching activities. Surges in shark tourism are particularly evident in the Caribbean and Australia.
However, shark ecotourism is both popular and controversial – there has been debate based on the risks to human safety, such as associating food with humans, and perceptions of behavioural shifts. Public awareness of sharks increases with documented shark bite incidents, rather than issues addressing conservation, which further exacerbates the perceived human risk.
Annual figures for 2020 showed that 10 shark-bite deaths occurred globally, of which six were in Australian waters. The fatalities, while tragic, were likely down to chance, as the number of shark encounters was only slightly above average, as reported by the ISAF.
Shark diving has local economic benefits and encourages conservation by creating public awareness, but it is argued that ecotourism also has the potential to affect species by altering their natural behaviours. It is important to assess the impact shark ecotourism has on their natural behaviours to determine whether it is detrimental to their health.
With the oceans holding around 96.5% of all Earth’s water, sharks play an important role in its ecosystems. As threats from climate change begin to build, it’s even more vital to protect shark populations, rather than fearing them.
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