Over the past year, the COVID-19 pandemic has led to unprecedented changes in the daily lifestyles of most people across the world. The imposed sanitary and economic restrictions of "social distancing", "lock-down", home isolation, or drastic reduction of time spent outdoors have left a strong mark on the mental and physical condition of millions of people. Even a decade before the pandemic, the WHO had predicted that untreated mental health issues would be the leading cause of morbidity and mortality worldwide by 2030^[2] .

Unfortunately, it looks like the pandemic may greatly accelerate this process, with tremendous emotional costs on a global scale and a negative impact on the quality of life for the vast majority of the human population^[3]. These include, for example, a widespread, overwhelming sense of loneliness and mental disorders which lead to a severe and deadly disease like untreated depression. With the prolonged stress caused by "lock-downs", not only the human psyche, but also immunity to diseases and the body’s overall activity on a biological level may be affected^[4].

In this context, recent studies confirm^[5] that vegetation and urban green spaces (parks, gardens, municipal forests, woodlots, etc.) have an extremely beneficial effect on human health (soma and psyche). Self-esteem, life satisfaction, and subjective feelings of happiness have been shown to be significantly related to the frequency of use of green spaces and even to such a seemingly trivial factor as their view from apartment windows. Nature, including mainly vegetation, can prevent or significantly mitigate risk factors for human mental and physical health. This is especially crucial in cities, which are already inhabited by the majority of the global population (projected to be 5.0 billion in 2030)^[6].

There has long been ample evidence of the powerful effects of plants on human quality of life, e.g. in the aesthetic, emotional or physiological spheres^[7]. The scope of the positive influence of greenery on the human body is well documented and truly impressive, which manifests itself by e.g. lowering the stress level of people at leisure, improving social interaction in public spaces, speeding up the recovery process of the ill (e.g. greenery around hospitals, sanatoria and health centers), reducing mental fatigue, improving concentration and performance (e.g. greenery in the area around schools, preschools, workplaces), and suppressing feelings of aggression and violence. 

Research on the health-promoting effects of vegetation on the human body has been put to practical use for years, e.g. in Japan as part of therapies known as "forest bathing" (jap. "shinrin-yoku"). There are many indications that the very contact with nature - with lush vegetation - favours the reduction of stress hormones in the human organism and stimulates the activity of white blood cells, responsible for fighting cancer cells^[8].

The negative effects of the COVID-19 pandemic overlap with the already existing, various deficiencies in the current functional and spatial solutions of cities, which adversely impact people's recreational opportunities, health and quality of life. These include excessive building density in urban centers, uncontrolled sprawl of highly urbanized areas ("urban sprawl"), or the degradation of the environment and landscape often caused by a careless and instrumental approach to natural resources^[9]. For this reason, attempts to improve the quality of life in cities by using the health-promoting effects of greenery on whole social groups and individuals are multiplying around the world ^[10].

Diagnosis

Civilization-related changes in the lifestyles of city dwellers translate into a strongly felt social need for recreation and leisure, specific to each era and time. Currently, during the pandemic, the provision of high-quality recreational sites (for daily and holiday recreation) especially in urban areas is gaining importance. City dwellers usually seek such opportunities near their places of residence [Fig. 1.] due to the fast pace of life and increasing difficulties in transportation (heavily congested road traffic and increasing time of travel to out-of-town attractive recreational facilities)^[11].

The quality of leisure places and areas depends mostly on natural factors (biotic and abiotic), which can significantly contribute to the stimulation or limitation of the human body’s feeling of so-called comfort or "well-being". This synthesis of physical, chemical, biological and meteorological stimuli can be defined as the so-called bioclimate. The concept of bioclimate is closely linked to recreation, hence "recreation bioclimate" should be interpreted as the set of natural variables acting on the quality of recreation, among which greenery, especially tall ones (trees), is an essential factor. Depending on the area covered and the ecological diversity, trees can significantly modify the bioclimatic conditions both locally and in neighbouring areas. The decisive factor in this case is the structure of greenery (spatial, species-specific) achieved by long-term landscaping and nurturing - visually appealing and ensuring favourable recreational bioclimatic conditions, i.e. optimal light and thermal conditions, air circulation, air composition, etc.^[12] [Zdjęcie J. Łukaszewicz, Green Park, Londyn, 2015]

The therapeutic value of green spaces and areas designated for recreation results, among other things, from the availability of light and physical values of sunlight in the open space. This is of vital importance to health, if only for the possibility of skin synthesis of vitamin D3 (known as the "sunshine vitamin"). It is known that both time of day, year, latitude, shading (e.g. due to high density areas) and weather conditions exert a major influence on the skin synthesis of vitamin D3. Currently, however, studies show that the time of sun exposure is very limited among children and adolescents (known as the "computer generation”)^[13], but this problem also affects a large portion of the adult population due to the type of work performed (remaining indoors).

Solutions

The introduction of greenery aesthetically, ecologically and technically into urban areas is traditionally one of the remedies mitigating, among others, climatic changes, negative disturbances in water management, depletion of fauna and flora, etc. Properly composed greenery (in terms of space and species) in areas with residential functions is one of the basic means of ensuring adequate environmental conditions and sustainable urban structure revitalization^[15]. In general, the natural impact of the arrangements of greenery (parks, gardens, street and park trees, municipal forests, etc.) includes: stimulation of air exchange and its purification, reduction of the greenhouse effect through carbon dioxide assimilation and oxygen release, reduction of air temperature amplitudes (reduction of "heat islands"), improvement of the soil structure, water retention, noise attenuation, etc.¹⁵ 

It has long been known that planting woody plants in urban areas is the simplest (and oldest) direct way to reduce particulate air pollution. Trees can either directly capture particulate matter or indirectly contribute to particulate pollution reduction by altering climatic conditions (as a result of transpiration activity). Although the amount of particulate air pollutants retained by trees may not appear to be high on the surface, the effects of trees are significant, especially when compared to the effectiveness of other measures aimed at improving air quality^[16].

Phytoremediation, as it is referred to, is the predisposition of plants to, among other things, reduce pollution generated by industries, home heating devices, and road traffic by filtering and reducing the concentration levels of particulate matter (PM) and gases (e.g. nitrogen oxides NOx, carbon monoxide CO, sulfur oxide SO₂ and ozone O3). The European Environment Agency (EEA) reports that critical volumes of particulate matter in the atmosphere are a global concern (cause of diseases and deaths). Apart from precipitation, the only effective form of reducing PM air pollution is plants, especially trees, which can accumulate these pollutants on the surfaces of their leaves (needles and blades), young shoots, and wax-saturated bark. The ability of plants to store PM must be appreciated on a global scale because of the vast biologically active surface area that plants produce^[17].

Problems

However, in order for urban green spaces to properly fulfill their function, they must be carefully landscaped, mainatined and conserved for many years. It should be borne in mind that they are largely anthropogenic in character and exhibit limited durability and the possibilities of self-regulation through processes naturally occurring in nature. Diverse forms of vegetation - layouts that are variable and sensitive to unfavorable factors (human activity → transformation of the environment) - are exposed, especially in cities, to degradation. Expansion of areas subjected to anthropogenic pressure - favors the transformation of habitats and plant communities occurring in them. As a result, there are more and more places with altered soil conditions, water, etc., often contaminated - suitable for plants with a wide amplitude of requirements, flexibly mastering a given environment. Hence, strongly expansive non-native species may displace local populations, leading to a reduction in the number of species, and ultimately to changes in ecosystem structure and destabilization of the natural system of a given area^[18].

• Investment pressure and building density - dwindling of natural and recreational areas (abandonment of squares, reduction of park areas) within city limits.
• Problem of maintaining "healthy" urban greenery in a multi-year cycle in extremely unfavorable habitat conditions of central city zones.
• Passive protection and failure to nurture vegetation in anthropogenic pressured areas → the disappearance of composed forms, as well as the encroachment of invasive plants and threats to biodiversity.

A report prepared under the United Nations Association Poland (UNAP) program, Agenda 2030: "Poland for Sustainable Development" synthetically presents strategies for implementing the sustainable development policies in selected Polish cities (2021)^[20]. Out of the 18 cities presented in this document (representative in terms of the adopted population thresholds), only the profiles of 9 of them (only half) paid any attention to the importance of greenery in the overall development objectives. These included actions aimed at improving the quality of green spaces and increasing the share of greenery in the entire city. In the remaining cases “urban greenery” was not mentioned in any context.

The quoted example quite clearly illustrates a problem on a national scale. Sustainable development of cities, local self-governments, regions - rightly defined as a priority for years - in Poland is mostly perceived through the prism of pro-environmental investments, understood as: solutions increasing energy efficiency, technologies limiting gas emissions and air dustiness, more efficient waste recycling, energy-saving and environmentally friendly means of mass transport and others. However, development based solely on investments in the "technical sphere" will never be fully sustainable.

Conclusion

In the context of the challenges posed by the changing world in the pursuit of living in an environment that is harmonious, beautiful and benefits human health, it should be noted that our country still needs many well-rounded specialists, especially in the discipline of landscape architecture, who will be able to meet the growing expectations. Landscape architecture, present in Poland for 90 years^[21]  (the first academic center was established at the Warsaw University of Life Sciences as the third in Europe), as of 2018 remaining without the status of an official professional title, is an extremely needed and socially prestigious profession in the world. The steady increase in the importance of this industry is taking place precisely because of the dynamic changes in the sphere of shaping the environment and its impact on the quality of life of the global population, most of which is already living in cities. We can only hope that also in Poland, environmental protection and climate change mitigation will eventually take on a more interdisciplinary character.

Authors: dr hab. inż. arch. kraj. Jan Łukaszkiewicz, dr inż. arch. kraj. Beata Fortuna-Antoszkiewicz, Katedra Architektury Krajobrazu, Szkoła Główna Gospodarstwa Wiejskiego w Warszawie

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[1]   Fortuna-Antoszkiewicz, 2019
[2]   World Health Assembly, 2012
[3]   Galea i in., 2020
[4]   Qing Li, 2010
[5]   Soga i in., 2020; Derks i in., 2020; Venter i in., 2020; Slater, 2020
[6]   UNEP Raport, 2007
[7]   Niemirski, 1973
[8]   np. Krzymowska-Kostrowicka 1997; Qing Li, 2010; Dadvand i in., 2015; Fortuna-Antoszkiewicz, 2019; Łukaszkiewicz, 2019
[9]    Johnson, 2001; Frumkin, 2002; Ewing i in., 2008; COP24 - Katowice, 2018
[10]   Gaston, i in. 2018; Łukaszkiewicz, 2019; Fortuna-Antoszkiewicz, 2019
[11]   Huizinga, 1985; Canales i in., 2017; Venter i in., 2020
[12]   Łukaszkiewicz, 2019
[13]   Wacker, Holick, 2013
[14]   Skibniewska i in., 1979; Fortuna-Antoszkiewicz, 2019
[15]   Bell, Treshow, 2004; Gawroński, 2018
[16]   Bell, Treshow, 2004; Popek i in. 2015
[17]   Gawroński, 2018
[18]   Fortuna-Antoszkiewicz i in. 2018(a)
[19]   np. Fortuna-Antoszkiewicz i in., 2017, 2018(b); Łukaszkiewicz i in., 2018
[20]   UNAP 2021
[21]   Łukaszkiewicz i in., 2019(a, b)