Sharks are front of mind for many Sydneysiders and coastal New South Wales residents. In January, a teenager died amid a spate of attacks in and around Sydney. This month, a woman was bitten by a large great white while swimming close to shore and between the flags at Coogee Beach.
These incidents have made many swimmers and surfers fearful of returning to the ocean . Public figures have called for shark culls .
The NSW government has ruled out culling great whites, a protected species, but is considering a bull shark cull. This week, it announced $A34 million in new funding to expand its shark-spotting drone program , as part of a larger shark safety program. It will mean daily drone surveillance of around 70 beaches, including every Sydney beach and one for each coastal council.
While spotter drones are a genuine advance in shark detection, they're not foolproof. After flying spotter drones over Sydney beaches for a season, this article's lead author found shark detection didn't mean protection.
The more you look, the more you see
Before drones, authorities relied on infrequent spotter flights over popular beaches. As a result, few sharks were sighted.
Drones have made it much easier to watch the ocean from above for extended periods. As a result, spotting a shark is now more likely. But more sightings doesn't necessarily mean there are more sharks.
As authorities roll out their expanded drone program, we can expect to see a surge in shark sightings and more beaches closed as a precaution.
Detection doesn't mean protection
Researchers have used drone footage to map shark movements and assess the risk to help pilots decide when to evacuate beaches. This showed the risk was low. At three Queensland beaches, only 4% of sightings over four years were bull sharks and no white or tiger sharks were seen at all. Drones mostly spotted small whaler sharks.
To date, there's no published peer-reviewed research showing drone surveillance reduces shark bites. This isn't an oversight. Shark bites get a lot of media attention, which makes them seem common. In reality, they are extremely rare.
Millions of Australians swim in the ocean every year . Last year, there were 23 bites across all Australian waters.
Their rarity means no research could realistically gather enough data to prove drone spotting led to a fall in bites, given many other possible explanations and factors.
Drone spotting is not flawless. Even in good conditions, drone pilots only detect around 40% of sharks swimming under the surface in real time. The figure rises to about 50% after careful post-flight review.
Detection is even more challenging when water isn't clear. Murky water is common after periods of rain .
Drowning is a much bigger risk than sharks
Shark bites make headlines and capture public attention . This gives many of us a skewed view of what the real risks are of swimming in oceans and estuaries.
Deaths due to shark bites in Australia averaged about 3 per year over the last decade.
But in just the last year, 154 people drowned along the Australian coast. This included 30 deaths due to the single biggest beach hazard - offshore flowing rip currents .
In an average year, rip currents cause more deaths than bushfires, floods, cyclones and sharks combined . Each death causes significant trauma for loved ones and the community.
It's worth asking why a spate of shark bites led to major public investment while deaths from rip currents do not tend to attract the same spending.
If the goal of the NSW government was to save the most lives at the beach, it might have made sense to first tackle drownings due to rip currents. Local governments could be funded to extend and expand their beach lifeguard services.
Evaluation before expansion
Drones may well prove useful tools to boost beach safety. The scale and cost of the NSW drone spotting program makes it a world-first.
But it's an open question whether rapid expansion of drone spotting will boost the safety of beachgoers, given shark bites are the rarest hazard. The NSW government announced the investment without an evaluation of evidence for spotting program effectiveness.
It may not be possible to prove drones reduce bites, but we could still evaluate what they demonstrably do: shark detection and species identification, response times, and how often drones assist with other rescues.
We should expect the drone spotting program to lead to more frequent and more extended beach closures. That could have unintended consequences, such as a fall in beach visitors and a drop in revenue for coastal economies.
If closures get more frequent and become the new norm, people may seek out unpatrolled beaches with no flags, lifeguards or drones. That would be a dangerous outcome, as almost every coastal drowning occurs on unpatrolled beaches or outside lifeguard patrol hours and times.
Until we have evidence to say drone spotting will help, we should be honest about what this program will do.
Their clearest life-saving value may be elsewhere: in Queensland's trial , drones were also used to spot swimmers caught in rip currents and locate missing persons .
Spotting for sharks alone looks to be about reassurance - not true protection.
Samuel Cornell previously worked in a casual capacity as a drone pilot for the Australian UAV Service and received funding from Surf Life Saving Australia during his PhD via the Beach Safety Research Group.
Rob Brander receives research funding from Surf Life Saving Australia through philanthropic donations made to the UNSW Beach Safety Research Group.
