When a pestilence caused the deaths of more than half of the population of Milan in 1846, it was evident that a clean and well-designed urban environment would be essential for human welfare. Thus, driven by his insatiable curiosity and infinite genius, Leonardo da Vinci decided to design his ideal city. Like most of his visionary ideas, Leonardo's city was centuries ahead of its time. He planned to separate pedestrians from vehicles by building his city on multiple levels. The upper levels of Leonardo's city would have passageways exclusively reserved for pedestrians, while the lower levels would be utilised for the movement of vehicles. In Leonardo's city, a perpendicular grid of roads would be complemented with an extensive network of artificial canals, whose water flow would be regulated with hydraulic pumps, locks, basins and floodgates. Leonardo designed his city in such a manner that the width of roads was equal to the average height of the buildings adjacent to them, so that adequate sunlight and air could reach all spaces and damage from earthquakes could be minimised. Leonardo's city would not suffer from water-logging, since he incorporated slopes and drains to facilitate the flow of rainwater. Proper sanitation and cleanliness would be ensured in this city through an underground sewerage system.

Although Leonardo da Vinci's ideal city was never actually built due to its prohibitively high costs, such cities could be instrumental in the global response to Covid-19 and in the implementation of Sustainable Development Goal (SDG) 11, which affirms the need to "make cities and human settlements inclusive, safe, resilient and sustainable". Worldwide, more than 90 percent of Covid-19 cases have been detected in urban areas where the relatively higher population density makes it easy for the virus to spread quickly and uncontrollably. This means that one billion people living in slums and four billion people living in cities worldwide are at high risk of infection from the deadly coronavirus. Since Bangladesh has one of the highest proportions of the urban population living in slums in South Asia, it must remain especially vigilant to ensure that the coronavirus does not strike in the slum areas and spread like wildfire.

During the pandemic, as many people were forced to remain indoors for prolonged periods of time due to lockdowns, the importance of having green open spaces in cities resurfaced. Scientists recommend spending at least 120 minutes per week in nature to maintain good health and enhance wellbeing. Unfortunately, Dhaka has only 8.5 percent tree-covered land and only 0.0002 metres squared of green park per capita, whereas ideally a city should have 20 percent tree-covered land and nine metres squared of green park per capita. Therefore, Covid-19 has reiterated the need for Bangladesh to implement SDG target 11.7, which calls upon countries to "provide universal access to safe, inclusive and accessible green and public spaces".

Bangladesh's performance on indicators under SDG 11 has been mixed. SDG target 11.1 calls upon countries to ensure access to adequate, safe and affordable housing for all and upgrade slums by 2030. In Bangladesh, the proportion of the urban population living in slums has fallen significantly from 87.3 percent in 1991 to 55.1 percent in 2014. This represents good progress as the proportion of the urban population living in slums decreased by 1.04 percent annually, on average, during the period of 1991 to 2014. Nevertheless, the total number of people living in urban slums increased from 19.99 million in 1991 to 29.27 million in 2014. This implies that on average, every year, the urban slum population increased by 403,000 during the period 1991 and 2014.

The increase in the urban slum population is just the tip of the iceberg. The much bigger problem is the increase of the overall urban population in Bangladesh. The share of the population living in urban areas in Bangladesh increased from 22.43 percent of the total population in 1997 to 35.85 percent in 2017. Such persistent rural-urban migration is indicative of the existence of push-pull factors that are motivating people to move from the villages to the cities. The rural-urban wage differential, as well as the wage differential across different sectors of the economy, could be likely factors pulling workers to urban areas. Climate change has also pushed many people away from rural areas to the urban areas of Bangladesh. Ironically, increased urbanisation can itself become a cause behind further climate change, since urban inhabitants have a much larger material footprint compared to rural inhabitants.

Bangladesh faces a host of challenges pertinent to the implementation of SDG 11. Unrestrained urbanisation poses a risk for developing countries such as Bangladesh, which have low technical expertise, limited financial capacity and lacklustre infrastructural facilities to address the needs of the urban poor. Overpopulated cities such as Dhaka suffer from an array of problems, which include, but are not limited to, reduced access to goods and services, insufficient number of decent jobs, lack of affordable housing, water-logging, fire hazards, air and water pollution and traffic congestion.

In order to overcome the aforementioned challenges, a number of policy measures may be adopted. Dilapidated housing in rundown areas should be renovated in order to improve their aesthetics and safety. Precautions should be taken to reduce the risk of fire accidents, by ensuring that all buildings have fire-fighting equipment and comply with international fire safety standards. In order to gradually improve urban air quality, metropolitan cities should be given targets, such a fixed percentage of days with heavy air pollution that will be allowed per year, and these targets should be progressively made more stringent every year. Urban green spaces in established cities like Dhaka and Chattogram should be protected from encroachment and burgeoning cities across the country should be designed with at least one-third of urban built-up areas reserved for green spaces. An integrated approach to urban and territorial planning that engages diverse multi-level stakeholders is necessary to design cities that are clean, compact, energy efficient, environment friendly, socially cohesive, readily accessible, climate responsive and disaster resilient. These measures need to be implemented on a priority basis, so that Bangladesh's cities can bounce back from Covid-19 stronger and be guided towards the achievement of SDG 11 by 2030.

Syed Yusuf Saadat is Senior Research Associate at Centre for Policy Dialogue (CPD).

Email: saadat@cpd.org.bd