by Alex McKenna
After the release of Jaws in 1975, people started thinking twice before getting in the water. Decades later, they still remember the stories, newspaper articles, and photographs of swimmers collapsed on the shore, covered in shark bites. But do they have reason to be concerned? Recent trends in climate change suggest that they actually do. Over the past 30 years, the frequency of unprovoked shark attacks has drastically increased, with the majority of bites being recorded in Florida, South Africa, Australia, and the Bahamas. While researchers argue that there are many reasons behind this influx, Dr. Blake Chapman, professor at Bond University in Australia, points to climate change as one of the principle explanations. He believes that rising temperatures, heavy rains, and anomalous weather patterns, all results of climate change, fundamentally alter marine ecosystems and are ultimately to blame for the recent spike in shark attacks.
The number of unprovoked attacks in the United States is rising by nearly 1.07 bites per year. While this may seem insignificant, it is actually quite an alarming statistic, especially considering that during the peak year of 2001, when 50 bites were recorded, all attacks occurred in the spring and summer months. This raises an important question. Do warmer temperatures correlate with shark attacks? Chapman argues that abnormally high sea surface temperatures can shrink the habitats of prey, forcing sharks to look closer to shore when feeding. If temperatures continue to rise, which is inevitable at this point, who knows how close they will get? Warmer waters are already drawing some species into shallower areas, and the predators will certainly follow, even if it means encountering a human.
Rising temperatures have also brought along heavy rains, especially in Volusia County, a shark attack “hotspot” in Florida that is highly susceptible to runoff. Nearly 75% of the bites between 1957 and 2008 occurred in turbid, muddy, or murky waters, a direct result of these heavy rains. In addition, runoff of pesticides and fertilizers can be lethal for fish, altering the trophic structure and forcing sharks to explore new habitats that may be occupied by humans.
An increase in anomalous and extreme weather patterns is also linked to the recent influx of bites. In South Africa, although the rate of unprovoked attacks has remained relatively stable at 4.4 per year, there were a record 16 in 1998. Unsurprisingly, this spike was attributed to an erratic climatic event that caused shifts in the current patterns, ultimately disrupting natural upwellings of nutrients. This altered biological productivity in the ecosystem, threatened prey availability, and forced sharks towards the shore, where there were more fish to feed on- and humans. Similar events have occurred in Australia, where in 2009 they experienced seven tropical cyclones and the highest annual bite record in history. Although this data was recorded nearly a decade ago, it can still be applied to attacks today. Climate change is producing stronger and more widespread storms, and because these storms naturally bring nutrients into shore, they draw in predators as well. Maybe in a few years they will be swimming by our feet.
So, what can we do to prevent future attacks? This question will become harder and harder to answer as the repercussions of climate change intensify. If temperatures continue to rise and storms persist, sharks will slowly begin inhabiting areas dangerously close to shore. Even worse, with diminishing habitats and toxic runoffs, these creatures must search for new prey, and at the moment, it may just as well be us.
Chapman, B., McPhee, D., 2016. Global shark attack hotspots: identifying underlying factors behind increased unprovoked shark bite incidence. Elsevier, 72-84. http://www.sciencedirect.com/science/article/pii/S0964569116302058