Sobering: The (real) odds of shark attack!

If you live on the Byron stretch, think… ten percent. Oowee!

First, the numbers. On the seventy-click stretch of coast between Byron Bay and Evans Head, there have been 13 shark attacks since September 2014: an average rate of one shark attack every nine weeks.

Eight of those attacks occurred within 12 kilometres of Ballina, four of ’em happened within one kilometre of the rivermouth.

Despite the high concentration of shark attacks, some people insist that the risk is still extremely low. You might hear, for example, that many more people die on the roads. But, it is not appropriate to compare the rate of shark attacks with the national road toll because practically everyone is at risk of being in a car accident while very few people are exposed to the risk of shark attack.

Unfortunately, we don’t have reliable figures of how many people surf in Australia. But, if we say that one percent of the population surfs, then two shark attack deaths per year is equivalent to 200 road deaths. While this compares favourably with the road toll, which was almost 1,300 last year, the risk of shark attack is not evenly distributed throughout the surfing population. It varies depending on which stretch of coastline is surfed and how long each surfer spends in the water.

As for time spent in the water, this obviously varies a lot from surfer to surfer, but if we apply the 80/20 rule to, say, two percent of Ballina’s total population of 40,000 (800 surfers), approx. 160 surfers (20%) would account for eighty percent of the total time spent surfing.

Since there have been four attacks in two years, the risk would be about 1:20,000 for every hour spent in the water (200 x 200 / 2). The longer you spend in the water, the greater the risk; so if you spend an average of one hour in the water each day, the risk of being attacked in the course of a year would be about 1% or 10% in ten years.

On the basis of exposure, we can then match this subset of 160 surfers with 0.8 x 4 attacks per year, which elevates the risk of shark attack for these surfers to 3.2/160, or 2%. Since 3 of the area’s 14 shark attacks since 2008 were fatal, the risk of being killed by a shark would be almost 0.5%. There would still be variation within this group, so the risk to some could easily be double the average, approaching 1% for death and 3% for injury.

Another way to calculate the risk of shark attack is to consider the total number of hours spent in the water. I would estimate that over the past two years, about 200 days of the year produced surfable conditions at Ballina’s Lighthouse Beach and Shelly Beach, with a total average of about 200 hours spent in the water each day of surf.

Since there have been four attacks in two years, the risk would be about 1:20,000 for every hour spent in the water (200 x 200 / 2). The longer you spend in the water, the greater the risk; so if you spend an average of one hour in the water each day, the risk of being attacked in the course of a year would be about 1% or 10% in ten years.

Of course, the problem with numbers is that they tend to escape people who, deep down, don’t really care about other people’s lives. But, if you take the time to look at the statistics, you really can’t conclude that driving to Lighthouse Beach is more dangerous than surfing there. Sure, more people die on the nation’s roads. But, there are so many cars on the road, all day and every day, that the risk of dying in a car accident is a tiny fraction of the risk of shark attack in Ballina.

Imagine if tens of thousands of people died on the roads each year. Ponder that for a moment and you will get a sense of how it feels to surf around Ballina. The same applies to all the other mortality rates that people insist are worse than shark attacks. The inaccurate use of statistics only shows how little they care about the people affected by shark attacks.

(Note: this story first appeared on the Facebook page Ballina Happens.)