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.)
