What the World’s Hottest Sea Can Teach Us About Coastal Cities in a Warming World

John A Burt
Professor of Biology and Co-Director of the Mubadala ACCESS Center
New York University Abu Dhabi
On summer fieldwork days in the Arabian Gulf, our research boat travels across water as warm as a bath. Instruments we lower over the side register temperatures of over 36 °C and salinities far higher than the open ocean. Behind us, a skyline of towers rises from reclaimed land. Ahead lies a narrow ribbon of mangroves, seagrass meadows, and coral reefs that support fisheries and protect our shorelines. It is a stark juxtaposition: some of the most extreme marine conditions on Earth, next to some of the fastest growing coastal cities on the planet.

For many coastlines, this is a glimpse of the future. In the Arabian Gulf, it is already the present. This shallow sea is heating rapidly, with today’s summer sea temperatures reaching what is expected for much of the tropics under end-of-century climate projections [1]. At the same time, we have transformed much of its shoreline with ports, industrial zones, artificial islands and waterfronts [2], all supported by dense desalination and wastewater networks [3,4]. After many years of conducting fieldwork here, one conclusion is unavoidable: under such extremes, the margin for error in how we build and manage coastal cities is shrinking [5].

The Gulf offers more than a regional case study. It is a living laboratory for how coastal cities will need to live with a hotter, more engineered sea.

The first lesson is that coastal growth must be planned within ecological limits. Urbanization in the Gulf has delivered housing, trade and recreation, but often at the expense of ecosystems that quietly underpinned those same benefits [2]. Dredging and land reclamation have degraded or fragmented coral reefs, mangroves, and seagrass beds that once buffered coasts, supported fisheries and trapped carbon. Where those natural defenses have been lost, communities have turned to costly built infrastructure to manage erosion and flooding.

A better approach begins with marine spatial planning that treats the Gulf as a connected system rather than a set of isolated shorelines. Critical ecosystems should be identified and ring-fenced as ‘no go’ areas for reclamation and heavy infrastructure [6]. Where new coastal development is unavoidable, nature-positive design can build ecological function into the hard edges of cities, using ecological engineering of seawalls and breakwaters and carefully placed artificial reefs to restore some of the complex habitat that has been lost [7]. Development visions that look to 2050 should align growth targets with explicit commitments to retain, and in some cases expand, key coastal ecosystems [8].

The second lesson is that water security cannot come at the expense of the sea it draws from. Desalination plants along the Arabian Gulf already produce vast quantities of freshwater every day, and regional plans suggest that capacity could double by mid-century [3]. Every facility takes in seawater and returns a concentrated brine, often slightly warmer and chemically altered. Individually, these discharges may be manageable; cumulatively, in a small, shallow basin that is already hot and salty, they raise legitimate concerns [9].

Wastewater tells a similar story. Coastal outfalls have allowed cities to grow without directly discharging untreated sewage into nearshore waters, yet treated effluents still carry substantial nutrient loads. In warm, stratified conditions like those common in the Gulf, these can fuel harmful algal blooms and low-oxygen events that stress marine life and interfere with fisheries [4]. The way forward is not to retreat from desalination or modern wastewater treatment, but to govern them as parts of a single coastal water system, with coordinated limits on cumulative brine and nutrient loads, greater efficiency and reuse, and rapid deployment of low-carbon, high-efficiency desalination powered by renewable energy [3,4].

The third lesson is that data and cooperation are as important as concrete and steel. Coastal currents, fish, and pollution do not recognize national borders, and neither do the benefits of healthy ecosystems. Over the past two decades, researchers and agencies around the region have begun to knit together data from long-term monitoring of ecosystems and water quality, and to couple those observations with oceanographic models. This shared evidence base has revealed how warming, desalination, wastewater, and coastal development interact at the scale of the whole basin [1,3,4].

Building on that progress, Gulf states now have an opportunity to create a regional coastal observing and data-sharing platform that tracks temperature, oxygen, salinity, nutrients and ecosystem responses in near-real time. It would allow environmental limits to be set on the basis of what ecosystems are actually experiencing, and to adjust them as conditions change.
When I look out from the deck of our research boat today, I do not see a simple story of decline, nor an easy story of resilience. I see an extreme sea that still supports diverse ecosystems, tightly linked to coastal cities whose growth depends on, and sometimes strains, that sea. What happens here in the coming decades will say a great deal about how other growing coastal regions will fare under climate change. If we can learn to plan growth within ecological boundaries, deliver water security without overwhelming the basin, and cooperate on the shared science needed to steer decisions, the world’s hottest sea can offer a blueprint for living with a warmer ocean.