Frequently asked questions about urban greenery

Urban greenery is the network of green spaces in the city that provide habitats for plant and animal life and contribute to human health and well-being. Ranging from parks, lawns, meadows, street trees, rain gardens, shrubs, green walls and roofs, flower beds and growing areas.

Why is urban greenery important?

Green and blue environments can improve urban spaces in many ways, especially if they form the basis of a multifunctional design. Some benefits of urban greenery include improved air quality, reduced risks of flooding and heat stress, and increased biodiversity. There are also clear links between exposure to urban greenery and positive effects on health and well-being. Greenery is essential for our cities to be sustainable and attractive. Here are some of the benefits of urban greenery that we at IVL are working more closely with:

• Air quality - we investigate how greenery can be integrated into cities for the best effect on air quality through the impact on airflow and increased deposition. Some projects that work with these subjects are CityAirSim, Urban greenery for clean air and 3-30-300+.
• Climate adaptation - how can we use greenery to reduce future risks of heat stress and flooding. Read more about this in the projects 3-30-300+, Policy lab and Green Sponge Buildings External link, opens in new window..
• Blue-green urban design - choosing the right systems and solutions in the right places in the city.
• Urban farming - how to achieve sustainable and circular urban agriculture in projects like Just Grow and Focuse.
• Carbon sequestration and negative emissions - estimating the potential of urban greenery to balance parts of Co2 budgets in urban development projects.

What are the main challenges of integrating green spaces into urban environments?

Competition for urban space, both above and below ground, is high and greenery requires space to thrive. Unlike a paved parking lot, green spaces also require regular maintenance and take up resources. Although the benefits of greenery are many, they are difficult to quantify and put a price on, making it difficult to justify both the space and the costs required for greenery to thrive. As a result, greenery often suffers and it is difficult to realize ambitious plans for greenery in the city.

Getting the city to be as green as we want it to be also requires cooperation between many parties in the city - from politicians down to individual property owners and private individuals.

How does urban greenery affect people's mental health and well-being?

The benefits of spending time in green environments have been researched for many years and are well documented. For example, studies have shown that spending time in green environments lowers blood pressure, stress hormone levels and heart rate. In the long term, growing up in a green environment reduces the risk of depression and other mental illnesses. We also find it easier to concentrate, and short-term memory is strengthened, which is particularly important for children's learning. Green spaces stimulate physical activity and play, thus counteracting obesity and sedentary lifestyles and all the health risks they entail. These are just some of the many positive effects that greenery has on our health and well-being. In the 3-30-300+ project, we evaluate how residents perceive and react to different types and designs of green spaces in the city.

What types of plants are most suitable for planting in urban environments and why?

Just like for humans, the urban environment puts extra stress on urban greenery. All the impervious surfaces make rainwater run off faster, increasing stress during dry periods. In addition, the city is almost always warmer than its surroundings, increasing the heat stress on greenery, and the higher levels of pollution in both air and soil in the city can also negatively affect greenery. In addition, urban ecosystems are vulnerable, which can make it difficult for species to thrive in urban environments.

It is therefore important to choose species that are tolerant and able to cope with the stress of growing in a city. Moreover, it is not enough to look at today's conditions - we also need to plan ahead and plan for a warmer and drier future climate. In return, species that can cope with these conditions can - if given the right conditions - thrive and grow really well because they have less competition than if they were in a natural environment.

Because of this, we include more tolerant species in our studies of the impact of greenery on the urban environment, for example in the project Urban greenery for clean air.

How can greenery be used for urban climate adaptation?

Parks, courtyards, trees and other green spaces play a key role in the city's ability to cope with the climate of the future, especially if they are designed to manage rainfall. Enabling plant beds to receive and store water creates greater resilience and capacity for vegetation to cope with heatwaves. Examples of solutions include tree planting in skeleton beds, rain gardens and blue-green roofs. If the vegetation is healthy and of good vitality during hot and dry periods, their cooling effect is also better. Under the canopy, it can be about 10°C cooler than areas with direct sun exposure, due to shading and evapotranspiration.

In addition, green surfaces can provide a crucial buffer to delay precipitation, thus relieving water and sewerage systems, and potentially preventing flooding. For example, thicker green roofs can retain significant amounts of rainwater. The key to adapting the city to climate change is to match the right type of blue-green solutions to each location, taking into account its conditions and needs.

What policy and economic measures are needed to promote more greenery in urban environments?

We need to be better at collaborating broadly and seeing the whole of the multifunctionality of greenery to raise the status of green solutions. Often it is not enough to look at just one of the many benefits of greenery to justify the costs and space required for long-term sustainable green solutions.

For example, the positive impact of greenery on air quality may not be a strong enough reason to allocate space and budget, but if we include how the same green solution also contributes to cooling, reduces flood risk, and helps us meet biodiversity targets, it becomes clearer how valuable it really is. And if we can also link greening to improved health and well-being, and how it reduces society's healthcare costs, then research has shown that greening may well bring economic benefits in the longer term!

But this can only be achieved through broad collaboration and long-term planning. And in this process, we need to ensure that all stakeholders - from decision-makers and the public sector to private actors and citizens - have the information and knowledge they need to motivate and realize the green cities we aspire to.

How can urban greenery help promote biodiversity in urban areas?

Urban greenery can take many forms in cities, providing homes and habitats for more species. Green spaces have a great potential to support biodiversity in many ways, for example by being designed to resemble natural habitats, such as multi-layered forest plantations, heathlands, meadows, ponds and urban wetlands. Urban ecosystems such as these can act as dispersal corridors for species in different niches, thus strengthening their chances of survival. In addition, different types of green spaces in the city are needed to strengthen the understanding between people, the environment and biodiversity.

Having areas of high biodiversity close to where we live increases the opportunity to be exposed to and learn more about these connections. Sweden's urban areas are fully or partially habitats for around 7100 other species that live in parks, courtyards, squares and other urban areas. By 2024, around 1200 of these will be red-listed.

What does the 3-30-300 rule mean?

3-30-300 is a rule of thumb for how tree and green space planning can improve health and well-being in cities. The rule means that you should be able to see 3 trees from your window at home or at work, that each neighborhood should have a crown coverage of 30% and that you should have a maximum of 300 meters to the nearest large, high-quality green space. The concept was developed by Professor Cecil Konijnendijk and has had a major impact worldwide. In Sweden, many municipalities and real estate companies have included the rule in their policy documents and goals for increased greenery in the city. In the 3-30-300+ project, we are working on the practical application of the rule, also from the perspective of more types of greenery than just trees.

How can I make the most of my own garden?

Much of the city's greenery is found in private gardens. A lush garden that mixes large trees and shrubs with different vegetation types maximizes many of the ecosystem services provided by the vegetation in the garden. For example, more leaf area means more absorption of air pollutants, more cooling, and more water absorption during rainfall. A variety of plants in the garden is also good for biodiversity, especially if you avoid toxic pesticides.

A negative trend that has been noted is the cutting down of large trees to make way for swimming pools or large patios, or simply for a neatly trimmed lawn. Trees take a very long time to grow and the benefits they provide usually increase with their size, so there is a lot of natural value lost with each tree lost. Think carefully before you decide to cut down trees in your garden.

And if you're one of those people who don't have full control over weeds - don't be ashamed of your overgrown garden, but be proud that you're maximizing the benefits of greenery.