Challenge 2

Resilient cities are cities where the “city’s systems, businesses, institutions, communities, and individuals [can] survive, adapt, and thrive, no matter what chronic stresses and acute shocks they experience” [Reference: Resilient Cities Network]. Chronic stresses are events that weaken a city over time. Examples include rapid urbanisation, ageing infrastructure, unemployment, inequality and poverty, and climate change. Acute shocks are intense events that happen suddenly. Examples include natural disasters, extreme weather events, terrorist attacks, cyber attacks and system disruptions. Cities often face a combination of acute shocks and chronic stresses, with vulnerabilities created by chronic stresses exacerbating the impacts of acute shocks when they happen.

Engineering has a prime role in the resilience of a city. Ensuring cities are robust enough to survive acute shocks, can evolve with changing circumstances, and still support people to thrive in their day to day lives means thinking about integrated, future-proofed, and risk-aware city systems that are inclusive, adaptable and sustainable. Opportunities to build new cities with resilient city systems ‘from scratch’ exist, but in many cases city infrastructure already dates back hundreds of years and in other cases urban growth is outpacing city capacity to plan, design and manage that growth effectively leading to marginalised and vulnerable populations. As well as finding new ways to improve existing city infrastructure, smart solutions are needed that can integrate into the cities of today to create better cities tomorrow. New digital technologies are delivering sensor networks, real-time management systems, digital twins and predictive modelling, and early-warning disaster response systems - already upgrading the resilience of our cities all around the world.

Key issues

Cities are challenged by a number of issues. This list is not exhaustive and we encourage you to explore further.

Rapid population growth and urbanisation:

• An additional 2.5 billion people are projected to live in cities between now and 2050, a rapid increase placing extreme pressure on existing city infrastructure. [Reference: UN Department of Economic and Social Affairs]
• 90 per cent of all population growth is taking place in lower income regions, with the infrastructure yet to be built. This poses significant challenges due to resource constraints and limited governance capacity, but also offers the possibility to build more sustainably and inclusively. [Reference: World Cities Report 2024].

Climate change and disaster exposure:

• Although cities occupy a small percentage of Earth’s land surface and are home to half the global population, they consume about 60-80 per cent of global energy and are responsible for 75 per cent of carbon emissions. [Reference: Economist Impact article]. Yet they are uniquely able to reduce carbon emissions; e.g. the concentration of people unlocks sustainable mobility options such as the “15 minute city”.
• Cities are projected to become hotter in future, with a significant proportion becoming either more arid, or more humid. At least 600 cities could become drier by 2040, and at least 900 cities will become more humid [Reference: World Cities Report 2024]. Extreme heat is also an issue with more than 970 cities projected to experience average summertime highs of 35 degrees Celsius / 95 degrees Fahrenheit by 2050 putting millions, in particular the very young and the very old, at risk.
• More than two thirds of the world’s largest cities are coastal delta cities vulnerable to rising sea levels as a result of the climate crisis, exposing millions of people to the risk of extreme flooding and storms, leading to damaged infrastructure, polluted water systems, and the potential loss of homes and livelihoods. Riverine flood risks are also escalating. In 2025, 1 billion people live in areas prone to severe riverine flooding, half of them in cities [Reference: 2025 SDG report]. In particular, informal settlements are often on the most at-risk land putting those experiencing poverty at greatest risk.

Housing affordability:

• Up to 3 billion people already struggle to afford a place to live, and 1.12 billion live in slums or informal settlements without basic services [Reference: 2025 SDG report]. This situation results in vulnerable living conditions where residents face higher risks of eviction, discrimination, violence and social exclusion. In addition, the absence of secure tenure exacerbates poverty levels and limits residents’ ability to invest in their homes and communities.
• This inequality results in populations vulnerable to the impacts of extreme weather events and other acute shocks.

Waste and service coverage:

• Managing the waste of rapidly growing populations has become a critical challenge. Overall, 2.7 billion people do not have their waste collected, 700 million of them in urban areas [Reference: UNEP Global Waste Management Outlook 2024]. This impacts on people’s health and wellbeing, pollutes the natural environment and can cause infrastructure damage and system disruption, for example when floods carry waste resulting in blocked water systems and roads.

Ageing infrastructure:

• Ageing infrastructure is a widespread issue in most major cities worldwide, impacting everything from roads and bridges, to energy and water systems, and public buildings. This creates safety concerns, undermines city resilience, and if allowed to persist can lead to irreparable damage and significant recovery costs.

Loss of green / open space:

• The last 30 years have seen a decline in green spaces in urban areas, with implications for resilience to heat and flooding, biodiversity loss, and human health and wellbeing [Reference: World Cities Report 2024].