Apex Earth: 2080 - sketch of population density
Apex Earth: 2200 - Development and Evolution of Megacities
The first Megacities styled as Megacities were purpose-built urban developments north of the Great Lakes, known collectively as Metropolis, and along the trans-Siberian railroad, known collectively (in English) as the Mega-Cities, both first started in the 2040s. Later analysis describes Singapore, Tokyo, Nairobi, Bangkok, Lagos, New York, and Mexico City as already having the features of Megacities by this time. Megacities are dense urban areas, with radical recycling extending to calorie and nutrient recovery, near-complete water reclamation, reliant on nuclear power, with extensive urban and underground industry, and a mix of industrial and high-garden agriculture.
By the 2080s, Megacity life was becoming mature, with half of the population living in the super-urban areas of Canada, Siberia, Patagonia, Scandinavia, and New Zealand, and a third in equatorial Megacities or legacy cities, which are more isolated, dense, and widely distributed on the map. Existing political divisions, between America and Canada in North America, between China, Russia, and a mob-run Mongolia, as well as the remainer states of Japan, Korea, Far East Russia, and Taiwan heavily involved in funding the Mega-Cities, in Asia, were rapidly becoming less important than the organizations and institutions that ran the Megacities. In 2080, many considered the Mayor of Metropolis, elected indirectly through the mayors or governors of individual municipalities, to be a position equivalent to the President of the USA in power and authority, while the General Secretary of Mega City One, the central and one of the wealthiest municipalities in the Mega Cities, had more power and authority than the position, and was in the process of cementing this power.
Equatorial Megacities were also developing, but were further from becoming mature. In 2080, Singapore was larger than ever, a super-urban area of 100m people, having annexed urban areas on the peninsula, surrounded them with dams, and taken in refugees from around South Asia, the predominant power of Southeast Asia. In the Ganges, Megacities were protected communally by dams to their east, but with each municipality relatively independent beyond that, and with a surprisingly robust wilderness between them. The Rift Valley, the Andes Valleys, and the Alps Valleys contained more self-contained Megacities similar to the Ganges, but lower in population, and with more wasteland than wilderness between them.
New York is one of the best examples of a Legacy City, having survived as a dammed Megacity, and as an important center of commerce and culture, through the first climate crisis. Manaus and Brasilia were placed under domes while large sections of the population of Brazil fled south, to the Patagonian Megacity. Mexico City saw a variety of protective measures, and became home to most of Mexico's population. In Europe, many cities had half-measures, with only a few receiving the kind of massive investments that saved certain cities in the Americas, with only London, Paris, Milan, and Frankfurt gaining in population, many Europeans ended up in Scandinavia and western Russia, with Britons and Irish moving to Scotland, London, Canada, and Australia.
Some places kept a more traditional population distribution with more conventional infrastructure. Western Russia, the Levant and northern Mesopotamia, Southeast Asia north of Bangkok, and Australia outside of the deserts had more traditional cities with less radical climate-proofing, surrounded by mixed agricultural and industrial lands, with similar infrastructure to 2020's Germany or the Eastern Seaboard. In Australia, most of this was on virgin land, newly hospitable in the new climate, and most of the population growth came in waves of refugees and migrants, starting in 2030. In Russia, there was a relatively smooth growth, with European climate refugees arriving in a steady stream from 2040 to 2080, and there was more assimilation.
The Megacities lasted long enough to generate some political loyalties, but many Megacitizens returned to their ancestral culture, and often to their ancestral homelands (or somewhere off the coast in newly revealed land), once their era was ended. The remains of super-urban developments are now mostly frozen, if not actually covered by glaciers, or converted to more modern 'hyper-urban' structures. Hyper-urban cities have denser, taller, deeper cores, built around forests of arcologies, which are surrounded by farms, parks, gardens, and wilderness, and connected by roads, tubes, and distributive infrastructure. The Ganges Megacities, Singapores satellites, Legacy Cities, and the Rift Valley Megacities had many features of the hyper-urban cities of the future, this was a less efficient series of compromises with the technology of 2080 that happened to prepare them for new technologies.
The abandoned Megacities have dense populations by the standards of stateless land, north of the Great Lakes twenty-five million people live in a space that once held only a fraction of this, but was designed and developed for half a billion, in Siberia and Mongolia, one hundred million live in spaces designed for two billion. In Patagonia, an orderly reclamation and demolition project has kept squatters, rebels, and criminals out, and also protected and funded a permanent population. In practice, the stateless populations in the other former Megacities also make their living by recovering and selling useful things from the ruins, but through the auspices of criminal enterprise. In Siberia, the Xia Clique has established itself as an independent state on this basis (later adding Arctic Space Traffic Control and Caspian Sea developments to smuggling and salvage), controlling about a third of the Siberian Ruins. No single criminal organization in Canada is powerful or legitimate enough to do this (and so Traffic Control over that approach to the Polar Orbital Corridor is sketchy, something that many criminals in the Canadian Ruins and the American states enjoy).
Still a bit rough, but it's coming along. This is the already science-fiction scenario of sixty years hence, just about when humans are discovering hyperlight speed, and just as the climate had been stabilized and the refugee crisis had been processed by the heroic efforts of the whole planet. The map needs some borders, they're mostly like today, and to have human mega-engineering drawn on, the Mediterranean and Caspian Sea should be closer to how they look today; and maybe a little less density for North America.