In the past month, the eyes of the world have been on the geopolitical drama being played out in the Strait of Hormuz. Yet recent research suggests that the greatest threat to life in and around the Arabian Gulf is to be found not on the surface of waters churned by warships, but in the depths below. And the news is very serious indeed. A new study by New York University Abu Dhabi concludes that rapid warming of the Arabian Gulf is accelerating the transformation of Arabian Sea into a dead zone that can no longer support fish and plant life.
Thanks to human activity, including coastal development and increasing output of greenhouse gases, ever larger areas of the world’s oceans are becoming oxygen-deprived marine wastelands. Over the last 50 years, the total size of these so-called “oxygen-minimum zones” has quadrupled and now occupies an area of ocean as large as the European Union.
The ramifications are potentially catastrophic. In the words of one paper published last year, if dead zones continue to expand, the world faces “major changes in … biodiversity [and] ecosystem collapses which ultimately will cause societal and economic harm.”
Scientists have known for years that one of the largest dead zones in the world is in the Arabian Sea, but limited research has masked the full extent of the problem. Now, following two major studies, the mask has been torn away, exposing a previously unrecognized consequence of runaway coastal development in the Arabian Gulf. The full extent of the Arabian Sea dead zone is now known to be the largest in the world, thanks to an innovative and exhaustive underwater survey carried out in 2015-2016 by a team of British oceanographers working with Sultan Qaboos University College of Agricultural and Marine Sciences in Oman, who published their findings in a paper last year.
Other than two periods of sampling in the 1960s and 1990s, “piracy and geopolitical tensions” have recently made the region a no-go area for such research. Their solution was to deploy a pair of underwater drones equipped with measuring devices. For eight months, the machines trawled back and forth beneath the waves in the Gulf of Oman, sampling oxygen levels at different depths and times of the year. What they found was alarming.
Computer modeling had predicted that oxygen levels in the Arabian Sea would continue to drop. But when the researchers compared the results of their survey with historical data, they found the situation was far worse than the predictions. The dead zone had grown and its core had changed from being “hypoxic” (with low levels of oxygen) to “suboxic,” a condition in which levels are so low that not only does the ocean struggle to support life, but its entire ecological system is disrupted.
When deprived of oxygen, phytoplankton – the microscopic organisms that usually perform an invaluable role in keeping carbon dioxide out of the atmosphere – go rogue and begin producing large volumes of nitrous oxide, an extremely potent greenhouse gas. The survey findings have been compounded by the study released only last week by NYU Abu Dhabi’s Center for Prototype Climate Modelling, which concludes that the rapid warming of the Arabian Gulf is contributing to the intensification and expansion of the Arabian Sea dead zone.
It is already clear that coastal development in the economically thriving GCC countries is having a dramatic ecological impact. A year ago, researchers at the University of British Columbia predicted that “multiple human stressors” would render extinct one-third of all marine species in the Gulf by 2090. They blamed the “synergistic effects” of climate change (in which water temperatures rise and oxygen levels fall), the destruction of marine habitats, overfishing and desalination, which produces vast amounts of carbon dioxide and pumps highly concentrated salt water back into the sea. These fears appeared to be confirmed in January when Abu Dhabi’s environment agency revealed that more than 85 percent of the three most commonly eaten species of fish in the Gulf had already been wiped out by overfishing.
The research done at NYU Abu Dhabi has now revealed a terrible example of mutually destructive symbiosis: the rapidly heating waters of the Gulf are contributing toward the size and intensity of the Arabian Sea dead zone. And the Gulf’s problems are only going to get worse as the dead zone edges ever closer to the Strait of Hormuz.
One of the main sources of oxygen for the Arabian Sea is the flow of water from the Gulf. Historically, as it pours through the strait it has sunk to a depth of between 200 and 300 meters, replenishing oxygen levels and reducing the intensity of the dead zone. But, with an average depth of only 35 meters, the Arabian Gulf is, as the NYU researchers note, “particularly vulnerable to amplified warming under climate change” and, since 1985, the water temperature has been increasing at a rate of 0.6 degrees Celsius each decade. These warmer waters, less buoyant and carrying less oxygen, are unable to replenish the oxygen in the dead zone.
A paper published in the journal Geophysical Research points out that humans could help reduce deoxygenation and halt the expansion of the dead zone by reducing carbon dioxide emissions. But in a region driven by the need for constant economic expansion and with an ever-increasing demand for energy and fresh water, that is wishful thinking.
The reality is that the human inhabitants, animals and plant life of the Gulf, each dependent for survival upon the other and the environment they share, are locked into the very definition of a vicious cycle. As such, the drama unfolding beneath the waves in the seas beyond the Strait of Hormuz is a microcosm of the seemingly unsolvable conundrum facing the entire planet. It also serves as a sobering object lesson in the unforeseen cause-and-effect complexities of global warming, and a reminder that human activity at every level is affecting the environment in ways that most of us can’t even begin to comprehend.
Jonathan Gornall is a British journalist, formerly with The Times, who has lived and worked in the Middle East and is now based in the UK.