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Rooftop gardens, African trees and whitewashed streets: how to adapt the city to extreme heat

2022-06-20T17:17:38.513Z


Cities are more vulnerable to the negative effects of high temperatures, which are becoming more frequent due to climate change


The extraordinary heat wave that hit the Iberian Peninsula and the Balearic Islands last week has left a trail of record temperatures and suffocating days.

But it is also another reminder of what will happen more frequently from now on due to climate change that at the moment cannot be reversed, although it can be mitigated.

The enormous amount of greenhouse gases that human beings have emitted will already remain in the atmosphere for decades, so the warming will not subside for the time being.

"We have to adapt," the World Meteorological Organization (WMO) recalled on Friday, referring to the "unusually early and intense" heat wave that has hit Europe.

This agency linked to the UN emphasized the danger of heat waves in cities, whose inhabitants "are particularly susceptible due to the so-called urban heat island effect that magnifies the impacts compared to the countryside, where there is more vegetation. ”.

A recent study by the Swiss weather service put the temperature difference between a city and rural areas at six degrees Celsius.

Other analyzes point to differences of even 10 degrees.

Many cities around the world are already taking action against extreme temperatures.

"The Administrations have to be clear about what kind of cities they want, a city model," says Ángela Baldellou, director of the 2030 Observatory of the Higher Council of the Associations of Architects of Spain.

Baldellou is committed to a "comprehensive vision" to avoid cases such as that of Madrid, where municipal planning coexists with projects such as the reform of the Puerta del Sol —which does not contemplate any vegetation or shade— and the Central Park project, which aims to create a large green area in the north.

More information

Inaction in the face of climate change will make it common to exceed 40 degrees in June in Spain

These are some of the measures that experts recommend to make cities and their inhabitants more resistant to extreme temperatures.

climate shelters

When a tremendous heat wave hit the west coast of North America a year ago, images of cooling centers in the US and Canada went around the world.

Having response plans for these types of events is one of the recommendations of the C40 group, a network of large cities around the world that collaborate in the face of the climate crisis.

These plans must include alert systems for the population and the so-called climate shelters, "public or private spaces, such as libraries, museums or parks, that cities temporarily install to offer a cooling shelter to citizens."

"Cities should publicize the location of these centers before and during a heat wave, for example, through billboards, phone applications or text messages," explains the C40 network.

Toronto,

A man recovers from heat stroke at the Fisher Pavilion cooling center in Seattle during the July 2021 heat wave. Bettina Hansen (The Seattle Times)

cold rooftops

But the adaptation measures must not only be circumstantial, they must also be structural.

And many experts look at the roofs and tops of buildings.

The architect Baldellou explains that "80% of the residential stock in Spain is made up of blocks of buildings that, for the most part, end up in non-passable flat roofs typified as common areas and without specific use".

"They are the part most exposed to the sun in summer and to the cold in winter," she adds.

"Gardens on the terraces or roofs of buildings are very beneficial, on the one hand they retain CO₂ and on the other they prevent the sun from shining, they retain water and lower the temperature," says Mariano Sánchez, head of Garden and Woodland of the Royal Botanical Garden.

"For this, succulent plants are used, such as sempervivum and sedum, which hardly need water",

continues this botanist.

In some countries, such as Denmark, the norm already contemplates installing green roofs in new buildings, and there are also plans for green terraces in Rotterdam and Paris.

But sometimes it is enough to simply paint the ceilings white or cover the roofs with reflective sheets, tiles or shingles, so that they reflect more sunlight and absorb less heat.

These measures not only help lower temperatures inside buildings, but also reduce their energy consumption by up to 20%, according to the C40 network.

Paint the streets and reduce the asphalt

About 40% of the surface of cities is covered by conventional pavements, such as asphalt, which "reach maximum temperatures in summer of up to 65 degrees Celsius and heat the air above them", according to C40 reports.

They are one of the main causes of the heat island effect.

And among the measures that some experts propose to mitigate this effect is to use lighter colors to create more reflective surfaces.

A few years ago, the city of Los Angeles carried out a pilot test: it painted the asphalt of various sections of streets white.

And a reduction of up to five degrees Celsius in temperature was recorded in the painted areas.

Los Angeles City Hall workers paint some streets white to cool down in 2017. City of Los Angeles

“The paved city is an oven”, sums up José María Ezquiaga, National Urbanism Award.

“Asphalt in the city must be limited to only high-traffic streets.

Car parks can be made with porous pavement that allows water to filter.

Pavers are a good solution for streets with little traffic.

And we should bring sand, dirt and grass back to the forefront in many more spaces.”

One option, for example, would be to convert tree pits – the gaps in the ground between the pavement – ​​into long flowerbeds, which would increase the land space, which improves soil drainage and allows low-lying vegetation, such as grasses, to grow. and bushes.

Another simple option is to recover the boulevards with large green flower beds.

More trees and African species

“The trees have to be as big as possible to provide shade, but if you plant them too close together they get in the way, you have to prune them and they spend a year or two without giving shade,” says Mariano Sánchez, from the Royal Botanical Garden.

Therefore, his option is to plant large trees about 10 or 12 meters apart from each other and, in between, smaller species of shrubs.

The species depend on the place and the climate —the north is not the same as the south—, but bet on the ash, the plane tree, the oak, the araar, the pine, the cork oak and the jacaranda.

“We will have to start planting African trees as well, such as cedars, because our climate is becoming more and more like that of North Africa.

And there are species such as lime trees, horse chestnut trees and maples that are not going to adapt to the new temperatures and will disappear."

Old Royal Naval College Avenue, London, UK. James Brittain (View Pictures/Universal Images G)

new urbanism

Baldellou also advocates the "urban regeneration of neighbourhoods" by expanding "pedestrian areas, improving mobility and betting on polycentric cities in which most of our trips are made without the need for vehicles", the so-called 15-minute cities, where all basic needs must be met less than a quarter of an hour on foot or by bicycle from home.

This urban design reduces the number of vehicles and asphalt in the city, which again contributes to reducing the heat island effect.

Recreation of the Madrid Nuevo Norte Central Park project.

But most of the large green areas are located on the outskirts of cities.

For this reason, the urban planner Ezquiaga points to the so-called “green fingers”: natural corridors that connect the city with those peripheral parks.

“Copenhagen grew up like this, but some cities are doing it later.

In Spain, the most interesting example is Vitoria”, he says.

David Lois, a researcher at Transyt-UPM, believes that these green spaces should reach all areas of the city, even small squares in outlying neighborhoods: “Urban micro-parks help adapt the city to the effects of the climate emergency, They help retain moisture and encourage walking.

Lois gives Paris as an example, which is raising entire streets to remove traffic and put in trees, something that he is also going to do with its peripheral boulevard (a kind of M-30).

Recover urban rivers and sources

Iñaki Alday, dean of the Tulane School of Architecture in New Orleans, considers it "urgent" to recover "urban rivers as living elements, with their riparian forests and their ecologies."

That was what the studio he co-directs, AldayJover, did in pioneering projects such as the Aranzadi park in Pamplona.

“It was an agricultural meander in decline that we recovered as an urban park with a large interior river, the floodplain forest.

When the river grows, it overflows in a controlled way and avoids catastrophes.

Once or twice a year it floods, but the rest of the time people use it as an urban park.”

These floods soak the land and recharge the subsoil water table, a process that also cools the city.

His studio did the same in Zaragoza's Water Park.

Aranzadi Park, in Pamplona.

Pamplona City Council

"In the last 100 years we have been very disrespectful to water, but today the approach is the opposite, we must make it present in the city," says Ezquiaga.

This would mean taking watercourses to parks and gardens, but also having fountains as an element that cools the environment and lowers temperatures.

“Any ornamental fountain helps against the heat, but there are other models that even allow citizens to cool off.

In Medellín there is the Barefoot Garden, which has some trickles of water that come out of the ground and in summer it is a paradise for children, who go to bathe and play, ”he points out.

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Source: elparis

All news articles on 2022-06-20

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