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The Persian Gulf is one of the warmest sea water bodies in the world and among those with the highest salinity. This means that many of its marine life already lives at, or close to, their natural limits. Yet the Gulf remains one of the least studied bodies of water in the world. As global warming threatens its ecosystem, other environmental stressors are leaving it that much more vulnerable to rising temperatures.

These stressors, all of them man-made, are localized along its coastline: desalination, pollution, overfishing, and poorly planned, excessive exploitation of the Gulf’s natural resources. If these stressors are not curtailed or made sustainable in the near future, the younger generation that lives around the Gulf will witness it lose much of the marine life to which they have been accustomed. And while the majority of the familiar sea life deteriorates, some organisms may well benefit from the new conditions. (In other parts of the world, jellyfish and mollusks have been especially able to adapt to new conditions considered hostile to other marine life.)

Iran, in particular, stands much to lose from a deterioration in regional marine ecology because it has more than 5 million people living in the coastal provinces, with around 3 million of them residing within 100 km of the shore. Iranian fishermen—both commercial and small operators—catch between 40 to 60 percent of the Gulf’s total annual catch, as explained by Abdulrahman Ben Hasan, a PhD candidate at the Institute for the Oceans and Fisheries at the University of British Columbia in Vancouver, Canada, during an online interview with Tehran Bureau. He and his team are studying the impact of environmental factors on the 500,000 pounds of fish caught annually in the Gulf, including Iran’s share, research that is “very challenging” because little data is available to understand the context of marine life there.

“In some circumstances, fisheries and environmental managers are flying blind because the few or [entire] lack of monitoring programs complicates the scientific guide for the policies,” he said, echoing other environmentalists who find it difficult to ascertain the best way to manage environmental stressors in the Gulf.

Many of these stressors are not unique to the Gulf. Increased levels of CO2—due to consumption of fossil fuels—is a global phenomenon. It gives rise to water acidification, which in turn translates into less oxygen available for marine life.

Rising temperature is also a global phenomenon, including in bodies of water. Marine life around the globe has been observed to migrate north in search of cooler waters. But shifting northward is a limited option for marine life in the Gulf because the body of water is fully enclosed in the north. In addition to direct impacts on marine organisms through shifts in distribution, rising temperatures will also have impacts on food chain dynamics and habitat dependencies.

“Actual species declines may be greater than those projected . . . on the basis of climate-driven changes in temperature and salinity alone. Indeed, other habitat characteristics related to coral reefs for instance will also be important to consider,” says Dr. Colette Wabnitz, a marine scientist at the University of British Columbia in Vancouver and the Stanford Center for Ocean Solutions at Stanford University in California. 

Making matters worse is the fact that many of the Gulf’s reefs have already disappeared as a result of increasing temperatures and other stressors, with declines in associated species richness. “While some work has indicated that corals are likely to persist, future reefs are likely to look very different to what they do today,” Dr. Wabnitz explained.

Overfishing in the Gulf is especially problematic, and some of the blame falls on Chinese fishing trawlers, which drag huge fishing nets through the water and sometimes scrape the seabed. This method is outlawed in some parts of the world because it entraps random marine life along with the targeted fish, leading to a poorly understood domino effect of marine life (over)exploitation. Chinese trawlers and other commercial fishing boats also use stun grenades as a fishing tool, which causes harm to everything in the vicinity of their explosions. Yet fishing boats use these methods with the full awareness of local authorities along the Gulf, which issue fishing licenses. Ben Hasan says that current licensing regulations do little to restrain overfishing.

“It is just a bureaucratic thing to get a license. Once you have your fishing license, you do whatever you want. It’s just to control who has access to the fishing. After that, it’s free for all,” he says. 

Managing overfishing in the Gulf is also tricky because many of the fishermen in Iran are small operators who rely entirely on their fishing nets for sustenance. “You can’t go to the fishermen in places where fishing is the only source of income and food and say: ‘Well, you can only catch this many fish.’ It’s their entire livelihood,” said Ben Hasan, adding that through his research he aims to find optimum management options. “In cases where countries are harvesting shared or transboundary fish stocks, as is the case between many of the Gulf countries, cooperation in harvesting these stocks does matter and might help in reducing overfishing, which in turn could translate into higher catches and profits compared with the status quo,” he said. 

He adds that Iranian fishing fleets have been observed moving further offshore, beyond their traditional waters, to catch fish in the international zone, which might indicate that overfishing along Iran’s coastline is already leading to a decline in fish populations. But as long as little research is available on the Gulf, this phenomenon presents yet another poorly understood variable contributing to the transformation of the Gulf’s marine life now and in the coming years.

Desalination plants, which take in sea water then remove salts and minerals to make fresh water before dumping a salty brine back into the sea, create yet another stressor in the Gulf. The Gulf is home to 50 percent of the world’s desalination capacity. At a daily capacity of 11 million cubic meters per day, according to Ben Hasan, these plants provide enough fresh water for local populations with a surplus to export. The Gulf’s large scale desalination plants—which not only make the water saltier but also warmer, with additional concerns regarding heavy metals and declines in oxygen—present a threat to existing species diversity and richness, creating a pressing need for research to better understand impacts at scale.

Adding to the problem is the fact that both Turkey and Iran are building a series of dams along rivers, including Turkey’s sections of the Tigris and Euphrates, that have long been integral to the health of the Gulf. These rivers would normally dump fresh water back into the Gulf, but the dams limit this discharge, which further increases the salinity of the Gulf’s water.

“I’m hoping that some species will be able to adapt, but many may not be able to,” says Dr. Wabnitz. “Many are likely to experience severe declines, with some going locally extinct.” Already there is one fish—hilsa shad, a fresh/saltwater fish found in northern Gulf waters that is popular with consumers—whose Gulf population is threatened, though this is mostly due to overfishing and poor management, with climate change being an additional threat. 

Large megafauna like sharks and stingrays, which are essential to maintaining a balanced ecosystem in the bodies of water they inhabit, are especially vulnerable to the environmental factors that are stressing the Gulf. A decline in their population has adverse and unpredictable ramifications for all the other species that have evolved alongside them.

“We need to worry about important human pressures such as overfishing and habitat degradation, and we need to worry about climate change and its impact,” Dr. Wabnitz said, adding that the time to act is now. “It’s already being felt in the region and will only be getting worse. Reducing other stressors and mitigating greenhouse gas emissions are both really important to the Gulf’s future.”

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