Concrete vs greenery. Is it worth fighting for every tree in the city? (Part II)

04 of April '23

Magdalena Milert

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The article is from A&B issue 03|23

March is the month when we start to feel spring. Longer, warmer days, buds appearing, leaves turning green. Inherent in this picture are trees. It is hard to imagine spring without the green frost that covers the crowns of the trees. However, it seems that every year we encounter less and less greenery, and its condition is getting worse.

Hot summer means the need to rest in the shade; trees are a suitable shade to give additional cooling

Trees are disappearing under successive investments, losing branches as a result of carrying out "maintenance work", withering away by salting roads or carrying out pavement repairs that disturb the root system. Cities are developing, new housing estates are being built, roads are being built, cars are increasing. Maintaining trees is becoming increasingly difficult, and young plantings very often fail to cope in such a difficult environment. Residents connected to their neighborhoods feel grief, emptiness, solastalgia - emotional or existential distress caused by the changing environment. It is described as the lived experience of a negatively perceived environmental change. A similar feeling accompanies many people when they think about the climate crisis. After all, reality is changing right before our eyes, with truly snowy winters becoming rarer and rarer, while the summer season is getting hotter and hotter.

surface heating pattern and cooling role of greenery

In spring we look forward to warm rays, we are bored with the gray of the departing winter. In a few moments, however, we will be thinking back to the time when there were pleasant 23 degrees on the thermometer, not a deadly 43. In cities, this temperature can be even higher due to the urban heat island effect - roads and buildings heating up, emitting heat (especially at night), not allowing the surface to cool down. As there is less and less green space and trees, hydrological changes are deepening, there is a reduction in evaporation, which should serve to cool the urban environment. In Warsaw, the temperature difference between downtown and outlying areas reaches 8 degrees Celsius, and even 10 in anti-cyclone and windless weather.

A walking path among greenery with the possibility of resting on a bench

To provide better living conditions, we need green cities, filled with trees, flower meadows, rain gardens, fulfilling the idea of a sponge city. Sponge City is the idea of a city that creates a system of means of managing water, allowing it at the same time to be absorbed and stored in the right structures and released at the right time, such as during periods of drought or heat. The idea is that through local water retention, resistance to droughts, heat waves, sudden downpours and consequent flooding will be enhanced. To this end, both technical, engineering methods and natural, less invasive ones are used.

A cut tree in Wolnica Square in Krakow - the result of poor tree protection after removing ice from an ice rink

The cooling effect of trees is significant, for example, a large silver maple on a hot summer afternoon can evaporate more than 265 liters of water per hour. "Work" of such a large tree has been compared to the efficiency of five average-sized home air conditioners. The cooling effect of greenery varies depending on the nature of the space. The orientation and nature of the development of the space in question, as well as the possibility of ventilation in the area and the species of the tree all matter. However, it has been studied that the temperature reduction in tree shade can range from 4 degrees Celsius in the shade of an acacia robinia, to 11 in the shade of a small-leaved ^linden1. During a sunny summer day, the temperature difference between a treeless street and a park can be as much as 15 degrees. Tall greenery, to a greater extent than other plant-based solutions, for example, green roofs or living walls, affects the microclimate of the environment (lowers air temperature) and thermal comfort of ^people2. Trees are considered an essential component of the urban landscape, and their presence in the urban land-use structure is a very important indicator of the health of urban ^areas3.

Pavement renovation is a danger of damaging existing greenery; it is necessary to control the protection of trees and audit new plantings, also in the following months and years

Trees are also responsible for improving people's physical and mental health. We are seeing more and more correlations between human well-being and biodiversity, conservation and sustainable management of nature. Since the lockdowns, we can observe how the public demand for contact with nature has increased.⁴ The presence of trees and green spaces can encourage physical activity, which is linked to physical and mental health. Green spaces encourage walking, which is a basic activity that effectively stimulates our brains. Trees not only make people happier and healthier, they make communities stronger and more ^vital5.

Even cars seem to seek shade; meanwhile, parking under a tree contributes to the destruction of the roots by compacting the soil, ultimately limiting oxygen and water, resulting in the tree withering away

This is why it is worth fighting for every tree. Actually, you shouldn't fight for trees - they should be legally protected, a guaranteed natural element of our cities. An indisputable, protected certainty. We often forget that they are a living, very significant element, without which it will be difficult for us to survive. We easily get rid of stately, perennial trees, not only "for investment", but also as a threat, especially if we are talking about old or fragile trees. Meanwhile, unwarranted pruning, apparent maintenance make them shorten their lives. Dendrologists admit that it is currently a matter of debate whether to leave a tree that is diseased, bearing the defects of care, or nevertheless cut it down, knowing that it may pose a threat. Possible removals, especially in larger areas such as rows, should therefore be carried out in stages. This will give the ecosystem a chance to adapt, the surroundings will not be so badly affected, and the new plantings will be easier to care for. It is worth noting that it takes about three years for the roots to emerge from the planting pit into the soil. In harsh conditions such as roadside areas, young plantings may not survive. However, simply increasing the number of trees or the area of green space is not enough. If a positive environmental impact is to be achieved, care and maintenance practices that maximize ecosystem services are also ^necessary6. A great tree waits for generations, it can be destroyed in an instant.

Greenery as infrastructure, a necessary complement to the concrete structure of the city

We should fight against concretization, pseudo-revitalization, automobileization and suburbanization. These are the ones that make our daily life anointed with smog, traffic jams, and a sea of concrete, so that the quality of life decreases. If we don't revise regulations, train planners and designers (whether architectural, landscape or road) and learn that greenery is urban infrastructure - the future in and next to cities will be dire. In addition, our aging population will not be able to endure in overheated, smelly cities, with stress acting negatively on our psyche. In the clash with concretosis, greenery must win.

Cutting down the trees next to the block; the reason was the hypothesis that rodents were destroying the roots, in fact, residents complained about... shade; after the cutting down, the facade heats up, especially the new doors along with the intercom, which causes their frequent failures

Magdalena MILERT

graphics and photographs: Magdalena Milert

footnotes:
1. M.A. Rahman et al, Tree cooling effects and human thermal comfort under contrasting species and sites, "Agricultural and Forest Meteorology" 2020, 287, 107947.
2 J. Janiak, Architecture integrated with greenery. Leafy tree rows as sun protection for buildings, after A.D. Bochenek, K. Klemm, The impact of passive green technologies on the microclimate of historic urban structures: The Case Study of Lodz, "Atmosphere" 2020, 11(9), p. 974.
3. H.B. Szczepanowska, Trees in the city - green value capital and ecosystem services, "Man and Environment" 2015, 39(2), pp. 5-28.
4. J. Szwagrzyk, A. Orczewska, B. Jaroszewicz, The role of forests in carbon balance and maintenance of biodiversity and human well-being, 2nd Scientific Conference "Trees and Forests in a Changing Environment", Kórnik-Poznan, 11-13.11.2021.
5. J.B. Turner-Skoff, N. Cavender, "The benefits of trees for livable and sustainable communities," Plants, People, Planet 2019, 1(4), pp. 323-335.
6 P. Szwałko et al, Trees in urban greenery, Krakow 2021.