Barcelona Metropolis

In the Mediterranean, one of the fastest-warming regions in the world, extreme weather events pose a particular threat to cities like Barcelona. In addition to implementing solid early warning systems and disaster preparedness measures, a long-term strategy is needed to reduce air pollution, alleviate the urban heat island effect, encourage a shift away from car use and expand green spaces.

The past few years have been the hottest on record, and high temperatures caused over 60,000 deaths in Europe alone in 2022. Current global climate projections show that we are heading towards a 2.7-degree Celsius warming, with the year 2024 already 1.5C warmer compared to pre-industrial levels.

The Mediterranean region is one of the fastest-warming regions in the world, with estimates of a four-degree Celsius increase. The ongoing drought and longer heatwaves in Catalonia, along with the recent tragic flooding events in Valencia in October 2024, which left more than 200 people dead and caused billions of euros in damage, highlight the severe impacts of climate change. Although such “gota fría” (cold drop) events have occurred before, this time their severity was amplified by the warmer-than-usual Mediterranean sea, which led to increased evaporation followed by severe rainfall.

As is often the case with disasters, it was a convergence of different factors: climate change (more energy in the climate system), poor urban planning (building in unsuitable areas and an excess of impermeable surfaces), poor politics (political denialism and opportunism) and a lack of effective warning and response mechanisms, to name a few.

It is now evident that we need to take climate change more seriously. We must establish robust early warning and disaster preparedness systems, create more (temporary) shelters to protect against extreme heat and enforce better building standards, among other measures. However, this is not enough; we need to adopt a longer-term perspective.

Like Valencia, Barcelona is a Mediterranean city with around 1.6 million residents in a metropolitan area of approximately 3.5 million people. Each year, nearly 3,000 premature deaths occur due to suboptimal urban and transport planning. Barcelona is a compact city with the second-highest population density in Europe (after Paris). Every day, between 400,000 and 500,000 cars enter the city, resulting in some of the highest traffic densities in Europe. Although only one out of four trips in the city is made by car, it feels as though everyone drives because of the large amount of space cars occupy, leaving limited space available for other uses. The transportation sector accounts for a significant proportion of CO₂ emissions, and urgent reductions are required to achieve the Paris Agreement climate goals.

Urban planning to mitigate impacts

A recent large-scale review of multiple-city studies demonstrated the clear relationship between urban and transport planning, environmental quality, greenhouse gas emissions and health.[1] Better urban planning could, therefore, offer a solution to mitigate climate change impacts while improving health. The co-benefits of climate action are well recognised and well-documented, but the urgency to implement these measures remains lacking.

Compact cities are the leading paradigm of sustainable urban living, but they may have drawbacks. A recent study of nearly 1,000 European cities showed that high-density compact cities have 10-15% higher mortality rates, less green space, poorer air quality and a stronger urban heat island effect, but lower greenhouse gas (CO₂) emissions per capita.[2] In contrast, greener and less densely populated cities have lower mortality rates, lower air pollution levels and a reduced urban heat island effect, but higher carbon footprints per capita.

This does not mean, though, that compact cities are bad, only that we need to introduce appropriate policy measures to reduce the current health burden and higher mortality rate, while taking full advantage of the benefits they may offer. An example is Barcelona, a compact city with a mortality rate comparable to the average mortality rate of compact cities in the study. Lowering air pollution levels, reducing urban heat island effects, shifting away from cars and increasing green space, cycling lanes and physical activity would substantially reduce the mortality rate.[3]

Electric cars are often proposed as the panacea, but they only go part of the way in reducing CO₂ and air pollution emissions. However, they are not the solution to issues such as the healthy use of public space, urban heat islands and lack of physical activity among the population. Furthermore, the mining and production of batteries has major environment impacts.

Principles such as Avoid-Shift-Improve (ASI) should be implemented. For example, in mobility: reduce car use by avoiding unnecessary trips, shift from car use to public and active transportation and improve the remaining car use by using electric vehicles. In Barcelona, 60% of public space (streets, roads and parking) is taken up by motorised traffic. Therefore, we need a reduction in traffic density of at least 50% in Barcelona to make more space for active and public transportation as well as green space. For example, on every street, buses should have their own dedicated lanes and there should be segregated cycling lanes. The Eixample neighbourhood should become like the El Born, Raval and Gòtic areas in terms of mobility. Safe segregated cycling lanes increase the uptake of cycling, boost physical activity, reduce mortality and lower CO₂ emissions.

Cities should implement novel and innovative urban models such as the Paris 15-Minute City, the Barcelona Superblock, the London Low-Traffic Neighbourhoods and Vauban Freiburg’s car-free neighbourhood to shift from car-centric planning to people-centric planning. The original Barcelona Superblock model of 502 Superblocks was an excellent plan to reduce climate, environmental and health problems in the city. Green corridors, such as the one introduced on Carrer del Consell de Cent, demonstrated their potential benefits. Unfortunately, short-sighted opportunistic opposition halted a plan that could have delivered long-term gains.[4]

Moreover, road pricing and (ultra) low-emission zones are effective ways to reduce private car use, CO₂ and air pollution emissions and concentrations, as well as to improve health. Zero-emission transport in European cities could be achieved by around 2030 with ambitious and multiple measures, along with the necessary political will and leadership.