The green roofs and terraces of Barcelona
Green roofs and terraces offer many advantages for both the environment and the people: they increase biodiversity in the city, providing more greenery and new habitats for the fauna, they improve the urban landscape and the quality of life. They also reduce the temperature of the city centre, enable the storage of rainwater, they reduce pollution. They improve the building’s waterproofing and heat and acoustic insulation systems.
The Barcelona Greenery and Biodiversity Plan for 2020 is the strategic instrument that defines the challenges, objectives and commitments of the Barcelona City Council regarding the conservation of greenery and biological diversity, while promoting the public awareness, enjoyment and care of nature. One of the actions of the Barcelona Greenery and Biodiversity Plan for 2020 is to promote the use of greenery on roofs, terraces, façades and in courtyards. As a result of these measures, 5,500 m2 of green roofs and terraces have been increased, to which will be added the 7,100 m2 of the Museum’s Living Terrace.
The Museum’s Living Terrace
Total surface area of the roof: 14,000 m2. Surface area of the Living Terrace: 7,100 m2.
What is the Museum’s Living Terrace like?
Specific building features and location are factors that determine the types of plants that can be grown on green roofs. As to the Museum’s Living Terrace, it has a weight limit, the sea is nearby, and it is often windy. So as not to exceed the maximum weight of the roof, herbaceous plants were chosen, as they only require a thin layer of soil. Trees and heavy plants were therefore avoided.
The Living Terrace houses vegetation that has adapted to the environmental conditions of the Mediterranean and specifically to those of Barcelona and the proximity to the sea.
What will you see on the Living Terrace?
Mediterranean meadows of annual plants, which, once they dry out, survive the summer heat in the form of seeds or underground bulbs, waiting for better conditions to re-sprout. These plants have adapted to the sea’s proximity.
Freshwater ponds with autochthonous vegetation. Many microscopic animals live in the ponds and feed on the algae of the plankton, in turn serving as a source of food for other larger animals. Therefore, the ponds display freshwater habitats that abound with life.
This is an experimental terrace roof that facilitates green roof research and investigation.
The plants and animals are monitored to determine the most appropriate species for green roofs in Barcelona.
When can you visit it?
- From October to February: Weekends and holidays from 10 am to 3 pm.
- From March to September: weekends and holidays, from 11 a.m. to 3 p.m. (days of free access* also from 4:00 p.m. to 8:00 p.m.).
*1st Sunday of each month, Sunday afternoons, other special days.
- Admission is included in the ticket to the Museum
Living Terrace Areas
The Living Terrace consists of 7 areas: a welcome area with some of the most common species on our terraces and also air plants, which can live without soil, and climbing plants. And three types of Mediterranean meadows with annual plants and three types of ponds.
In this area you will find an introductory explanation of the Living Terrace and the central planter features some of the species most frequently found
on our roof.
Air plants (Tillandsia)
These are epiphytes. In other words, these plants do not require soil to live,
although they do need a great deal of environmental humidity. You will see them on the fences. The proximity to the sea and their north-facing position facilitate their life on the roof.
They enable us to keep plants in places where there is no soil.
In the Mediterranean area, there are no native epiphyte plant species.
Air plants (Tillandsia) on fences and climbing plants. Image by Pere Vivas/MCNB
We have selected subtropical climbing plants that grow fast and can tolerate being close to the sea.
These plants are not frequently found in the Mediterranean area, except for a few species that can be found in coastal holm oak forests. Climbing plants abound in the large warm rain forests. They grow upward along the trunks of the trees, towards the light.
Meadow of the annual plants of Barcelona
Many of the herbaceous plants species of the Mediterranean meadows are annual plants that survive the hot dry summer in the form of seeds.
- Their flowers attract many diverse insects that pollinate them.
- They do not grow to become large or heavy.
- They are good at retaining the soil and they survive in very shallow soils.
- These are the ideal plants for green roofs in cities.
At the start of summer, these plants dry out and the seeds fall to the ground. The seeds germinate with the first rains of autumn. In spring, the plants are filled with flowers that produce new seeds. Some plants survive the summer because they have persistent buds that sit within a few centimetres of the soil. This way, they do not burn in the summer heat.
Where can they be found?
In nature, they grow in places where there are no shrubs or trees. As a result, they do not have to compete for the light, water and nutrients. In the past, when herds pastured on the outskirts of Barcelona, these annual herbaceous plant meadows were much more frequent and abundant. Because the animals kept the growth of shrubs and trees at bay, the annual herbaceous plants had far more space to live and grow.
Meadow with salt-tolerant annual plants
The coastal vegetation is conditioned by its proximity to the sea.
The presence of the sea
When the wind blows from the east, it brings along small droplets of water,
which then fall on the plants closest to the sea. Through the years, sea salts accumulate in coastal soils.
In general, salt has a negative effect on most plants.
The plants most tolerant to salt are known as halophytes. In Greek, “halophyte” literally means “salt-loving plants “.
This side of the roof is the area most exposed to the sea. And here, we have added salt-tolerant plants to the meadow of annual herbaceous plants.
We want to observe the salt-tolerant plants, to find out what species best tolerate the proximity to the sea and are the most suitable for other green roofs along the coast.
At the start of summer, these plants dry out and their seeds fall to the ground, where they remain. With the first rains of autumn, the seeds germinate. In spring, the plants are full of flowers, which in turn produce new seeds.
Meadow with bulbous plants
Some plants survive the hot Mediterranean summers thanks to bulb-shaped buds that remain underground.
- They produce very bright flowers.
- They are the ideal plants for green roofs in cities.
- With no shade, no ploughing and no boars, they form dense carpets of bulbs.
Bulbous plants are known as geophytes, as they spend part of the year underground. When the heat arrives, the leaves of these plants dry up and the fruits scatter their seeds. The most valuable nutrients are stored in a bulb or rhizome that remains underground. When the conditions are right for them again, the bulbs sprout, flower and grow.
Many bulbous plants grow at the end of winter or in autumn, to avoid competition with other plants. To coincide with pollinators, some bulbs bloom very early, flowering first and then sprouting their leaves. Other bulbous plants do this the other way around and bloom after summer.
Where can they be found?
In the past, bulbous plants were very abundant in the Mediterranean area.
They grew in shallow or rocky soils where there were not many trees or large shrubs to block the sunlight. With the expansion of agriculture and the use of pesticides, they have gradually disappeared, becoming rare virtually everywhere.
Permanent ponds with nutrient-poor waters
Areas with nutrient-poor waters are the exclusive habitat of microorganisms that cannot easily be found in other areas of Catalonia.
The roof pond
This pond enables us:
- To cultivate plants that grow in very soft, acidic, nutrient-poor waters.
- To house rare and endangered plant and animal species.
To maintain the most appropriate environmental conditions:
- We regulate the water’s pH.
- We eliminate any excess salts, using a special filtering system.
Where can nutrient-poor waters be found?
In the western half of the Iberian Peninsula and in mountain areas.
These waters are very rare in Catalonia. The ullals or unique springs of the Ebre River delta are an exception.
Ponds with sedge
The plants of wetland areas usually have long, narrow leaves, enabling them to live in very close communities.
The roof pond
In this pond, you will see:
- Large sedge species, typical of permanent wetland areas.
- Submerged plants with floating leaves, such as water lilies, which can live in
There are hundreds of sedge species. They can be found in very diverse habitats, including Mediterranean holm oak forests, high-mountain prairies, and the cold and temperate regions of Eurasia and America. In favourable environments, they grow in dense communities, forming thickets similar to those of rush.
Many sedge species are aquatic and draw on the spongey tissue of their stems to transport the oxygen from the air down to the submerged roots.
Sedge thickets filter the water along the banks of rivers and help to oxygenate it, purifying the water.
Wetlands are home to countless organisms that could not otherwise survive the summer drought.
The terrace pond
This pond contains:
- The plants most typically found in ponds and along the banks of rivers of lowland areas.
- Some species that are also frequently found in reedbeds, brooks and shallow waters.
- This pond is filled with hard, carbonate-rich water, which is similar to household tap water.
What happens throughout the year?
Many fresh-water species reach the height of their blooms just before summer. That is the time when many Mediterranean plants scatter their seeds and become dormant, awaiting autumn’s rains.
The lagoons of Barcelona
In the past, there were many wetland areas in the flats of Barcelona. In the Poblenou district, which sits close to the sea, there were numerous lagoons. The name of the La Verneda district makes reference to the alder forests, which grew alongside the streams that flowed down from Collserola. Many of these plants and trees can still be found in the Llobregat River delta.