Mega cities in the desert. A smart long term idea?

The growth of desert mega cities over the last 20+ years has been nothing short of explosive. Unlike traditional cities that grew organically around resources like water or trade routes, modern desert mega cities are often artificial constructs, built on the back of desalination technology, air conditioning, and massive government investment.

Here is a breakdown of how these cities (primarily in the Middle East and the Southwestern United States) have grown recently, the trends driving them, and the challenges they face.

The Pace: Explosive vs. Regulated Growth

The growth patterns differ depending on the region:

• The Gulf States (e.g., Dubai, Riyadh, Doha): These cities have experienced hyper-growth.

  • Dubai's population: In 2000, it was under 1 million. By 2024, estimates put it around 3.8 million. This growth is almost entirely driven by expatriate labour and economic diversification (tourism, finance, real estate).

  • Riyadh's population: It has jumped from roughly 3.8 million in 2000 to over 7.5 million today. Saudi Arabia's "Vision 2030" plan is actively trying to move the population away from oil and toward urban centres, aiming for Riyadh to reach 15–20 million by 2030.

• The American Southwest (e.g. Phoenix, Las Vegas): These cities have seen steady, sprawling growth.

  • Phoenix, Arizona: The fastest-growing city in the US for much of the last decade. The metro area population recently surpassed 5 million. It grew by nearly 10% between 2020 and 2024 alone.

  • Las Vegas, Nevada: The metro area is now approaching 3 million, driven by migration from expensive California cities.

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  The "Artificial" Enablers

  
  

  These cities should not exist at their current size based on natural water availability. Their recent growth has been enabled by two major technological and economic factors:

  
  

  • Desalination Technology: Desalination provides the water. In the Gulf, nearly 100% of urban water is desalinated. In the US Southwest, cities like Las Vegas have become masters of water recycling (returning every drop of used water to Lake Mead) and are in a race to build desalination plants on the California or Mexican coast.

  • Air Conditioning: The growth of the "Sun Belt" (in the US) and the Gulf states would have been impossible without the widespread adoption of cheap, efficient air conditioning. It allowed for productivity and habitation during the hottest months.

Energy intensity

These features are extremely energy intensive:

• Desalination (Reverse Osmosis - Pressure): Uses 3–4 kWh to produce 1 cubic meter of water. (The modern standard).

• Desalination (Thermal - Boiling): Uses 10–15 kWh to produce 1 cubic meter of water. (Common in the Gulf, often uses waste heat).

• Air Conditioning: A single home unit uses 3–5 kWh per hour. During peaks, AC can account for 70% of a desert city's electricity demand.

The Feedback Loop: Boiling creates water, pressure pushes water through membranes, and AC fights the heat. All three require massive energy, perpetuating the cycle of high demand and environmental cost.

100 years ago

Here is why mega cities in the desert couldn't exist 100 years ago:

1. No Air Conditioning: The first modern electrical air conditioner was invented in 1902, but it was expensive, rare, and used for industrial machinery (not homes).

• Without AC: Living in a place like Dubai or Phoenix during summer would have been physically unbearable (and deadly) for the majority of the year. Cities were limited to areas where natural shade, wind towers (windcatchers), or proximity to water made life tolerable.

2. No Desalination: The technology to turn seawater into drinking water on a massive scale did not exist.

• Without Desalination: A city of 3 million people in the middle of the Arabian desert would run out of water in days. 100 years ago, cities were strictly limited by the capacity of their local aquifers (groundwater), springs, or rivers.

3. No Global Supply Chains

• Without Planes and Ships: Desert cities today survive by importing almost all of their food, materials, and goods. 100 years ago, if you couldn't grow it or make it locally (with very scarce water), you couldn't sustain a large population.

The Limiting Factor: Historically, the maximum size of a settlement was determined by the carrying capacity of the local environment (available water and food).

• 100 years ago: A desert city was a small trading post or oasis village (tens of thousands of people).

• Today: A desert mega city is an artificial biome, kept alive by technology (AC) and energy-intensive water systems that simply did not exist a century ago.

Best long term location for cities?

If we ignore political borders and look purely at geology, climate resilience, and resource availability, the "best" long-term locations for cities are generally coastlines in temperate zones or large river junctions.

Here is the breakdown of what makes a location ideal for the next century (and why the desert cities just discussed are risky long-term bets).

1. The "Goldilocks" Zones (Best All-Rounders)

The healthiest long-term locations are typically between 30° and 50° latitude (North and South). They avoid the extreme heat of the equator and the extreme cold of the poles.

• Much of Europe: Mild climate, reliable rainfall, major rivers (Rhine, Danube, Volga).

• Northeast USA / Great Lakes Region: Access to the largest source of fresh surface water on Earth (the Great Lakes—20% of the world's fresh water).

• Southern Canada / Northern US: As the planet warms, these areas are becoming more temperate and arable.

• South eastern Australia and New Zealand (Christchurch, Melbourne, Tasmania): Surrounded by ocean and moderate climate. (Mass immigration is making Australian cities less water secure, however, due to increasing demand and irregular rainfall, leading to the construction of desalination plants to meet some demand. New Zealand has more regular rainfall).

While some far northern cities (eg. in the former USSR) require substantial heating, these cities have often adopted highly efficient district heating systems where waste heat from power stations is recycled, making them far better positioned than desert cities). They also have plenty of water.

2. The Water Criterion

Water is the non-negotiable factor. The best long-term cities are located at the mouth of major rivers fed by snowmelt or glaciers.

• The St. Lawrence River (Canada): Drains the Great Lakes.

• The Volga River (Russia): Most major cities in European Russia are located along it.

• The Danube / Rhine (Europe): Drain central Europe.

• The Mekong (Southeast Asia): Drains the Tibetan plateau.

• The Amazon (South America): Vast, though the jungle itself poses development challenges.

  
  

3. The "Climate Refuge" Cities (Future Hotspots)

Based on climate migration predictions, these are the cities expected to grow because they are relatively safe from sea-level rise, extreme heat, and drought.

• The Rust Belt (USA): Cities like Buffalo, Detroit, Cleveland, Milwaukee. They were built during the industrial era but lost population. They have one massive advantage: unlimited fresh water (Great Lakes). As the Southwest dries out, these cities are predicted to see a renaissance.

• Scandinavia: Cities like Copenhagen, Oslo, Stockholm. They are cold now, but if temperatures moderate, they may become some of the most pleasant and stable places in the Northern Hemisphere.

• New Zealand: The entire country is often cited as one of the best long-term refuges due to its mild maritime climate, rainfall, and geographical isolation.

  
  

4. The "Terrible Long-Term" Locations

To contrast, here is why many current boom-towns are bad long-term bets:

• The Desert (Dubai, Phoenix, Las Vegas): No local water, extreme heat, and entirely dependent on energy to survive. If energy becomes scarce or expensive, the model collapses.

• Low-Lying Deltas (Shanghai, Mumbai, Bangkok, Netherlands): Extremely fertile and successful now, but facing existential threats from rising sea levels and storm surges. They may require massive (and expensive) engineering just to stay dry.

  
  

Summary

If you were building a city from scratch today to last 500 years, you would put it:

1. On a rocky coastline (to avoid sea-level rise/flooding).

2. At the mouth of a massive river (for water and trade).

3. In a temperate zone (to minimise energy costs for heating/cooling).

4. Away from hurricane/typhoon belts.

   
   

The Irony: Some of the best-located cities for the future are actually old, declining industrial cities in the Northern United States and Europe. They have the water and the mild climate, but they just need the economic reason for people to move back.