In August 1932, the streets of Quito witnessed one of the world’s briefest and least-known conflicts. Supporters and opponents of president-elect Neptalí Bonifaz Ascázubi fought what has been dubbed the Four Days War. As with much civil strife, historians blame the fighting on trigger events elsewhere. Shockwaves from the Wall Street crash three years beforehand had set the people of Ecuador on an economic collision course that determined their future.

The streets of Quito will see a different kind of four-day event next month, but the implications for the country and the wider world could be just as decisive. From 17 to 20 October, experts in sustainable development, planning and urban science will gather for the third United Nations Conference on Housing and Sustainable Urban Development.

Yes, the third. Habitat III, as the meeting is known, comes after two little-remembered (beyond the specialist community) prequels — in 1976 and 1996. Which means that countless millions of city dwellers have been born since Habitat II closed its doors two decades ago.

The challenge for the next twenty years is a familiar one: more people chasing fewer resources. But the problems are especially acute when viewed through an urban lens. Transport, pollution, natural hazards, climate change, physical and mental health, clean water — and all affecting billions of inhabitants of the urban sprawl in a way that would have been hard to imagine when the meeting series was set in motion back in 1976. In hindsight, a few days of discussions every twenty years was never likely to be sufficient to sort that lot out.

Nature has increased its focus on cities and urban science in recent years, to acknowledge both the issue’s rising profile and the concomitant surge in academic research. This week, in a series of Comment articles, we explore some of the items on the Habitat III agenda.

Joern Birkmann and colleagues draw attention to the needs of small and mid-sized cities, especially in Asia and Africa, and argue that these deserve higher priority than some of the giant urban centres that tend to monopolize attention and resources. Smaller cities are more vulnerable to problems such as extreme weather, they say.

Richard Forman and Jianguo Wu ponder where to put the next billion people expected on the planet by 2030 and make the case that more planners should do the same. And Michele Acuto points out that cities and civic leaders need to forge better political and strategic links to policymakers. “The promise of cities is hampered by patchy collaboration with national governments, limited access to global governance processes such as the sustainable development goals and Habitat III, meagre funding for collaboration, and poor data collection and sharing,” he writes. Finally, the Books and Arts pages highlight works that probe the relationship between cities and their people.

The Quito meeting is expected to issue a declaration of intent, which will not be legally binding but should help to set new global standards for sustainable urban development and then guide the ongoing process. Scientists and funders have a key role here, by building on the promising start to fully develop the concept and the promise of urban research.

Quito lies close to the Equator, but most people there call the line of zero latitude la mitad del mundo to avoid confusion. (Ecuador is Spanish for Equator.) It means ‘middle of the world’. But for four days that must speak for twenty years, Quito is not just at the middle. It is the centre.