海角大神

Taller buildings are key to enhancing quality of life as the world鈥檚 urban population grows, but cities should not become obsessed with skyscrapers and must prepare for horizontal expansion as newcomers arrive, the World Bank said on Wednesday.

Urban build-up worldwide grew by 30% between 1990 and 2015, with new buildings covering an area roughly the size of Sri Lanka, the bank said in a report that was based on satellite data analysis for almost 10,000 cities.

In poor countries about 90% of new buildings sprung up at the edges of cities, extending their boundaries horizontally, while in rich nations about 35% were built on empty sites within urban centers, the study found.

Such findings appear at odds with the main focus of urban planning in recent years, which has been to create compact cities by building upward.

But the report鈥檚 co-author, Somik Lall, said that while taller buildings and high-density cities do bring benefits, such a model should be adapted to local conditions.

鈥淭he obsession should not be about building skyscrapers but the passion should be about building livable cities,鈥� Mr. Lall, the World Bank鈥檚 lead urban economist, told the Thomson Reuters Foundation by phone.

Whether urban hubs grow vertically, horizontally, or within existing spaces is tied to economic demand, the report said.

With about 70% of the world鈥檚 population expected to live in urban areas by 2050, up from 55% at present, cities should plan to accommodate all three types of development or risk facing uncontrolled sprawl, overcrowding, and congestion, Mr. Lall said.

Low-income cities tend to look like 鈥減ancakes,鈥� growing wide and flat, as newcomers crowd into low-built quarters or settle on the outskirts where land is cheaper, according to the report.

As incomes grow, so do buildings, with richer cities taking the shape of 鈥減yramids,鈥� the research found.

Pyramid-shaped cities are generally more livable 鈥� allowing inhabitants to enjoy more floor space in a dense environment 鈥� and more productive, as the reduced distance between workplaces and employees boosts productivity, the report said.

They are also better for the environment as sprawling peripheries encroach on surrounding natural areas and often lack adequate transport links, increasing traffic and pollution.

鈥淚f managed well, cities that take a more pyramid-like shape can provide an impetus to accelerate sustainable development by getting people out of cars, cutting commute times, and limiting greenhouse gas emissions,鈥� Mr. Lall said.

Yet, cities cannot leapfrog from 鈥減ancake鈥� to 鈥減yramid鈥� with planning regulations alone, as newly built central high-rises risk remaining vacant if people cannot afford to live in them, the World Bank researchers said.

For developing cities in particular, it is vital to prepare for horizontal expansion, building transport links and basic infrastructures to ensure livable conditions on the outskirts, and lay the groundwork for future development, the report said.

鈥淭he COVID-19 pandemic has highlighted the life-and-death implications of crowded neighborhoods that are ill-equipped to curb the spread of disease,鈥� Juergen Voegele, the bank鈥檚 vice president for sustainable development, said in a foreword.

鈥淎s countries slowly extricate themselves from the pandemic, planning for a better urban future requires understanding the forces that have shaped the cities we inhabit today.鈥�

This story was reported by the Thomson Reuters Foundation.