The aim of this study was to determine the impact of safety-related environmental characteristics in a city park on users’ preferences and whether this impact can be explained by perceived safety. The factors examined were physical and visual accessibility as well as the effectiveness of concealment created by plants in various spatial systems. We used 112 photographs taken in city parks for the study. Studies have shown that visual and physical accessibility varies in terms of impact on preferences and safety—as a result, we tested only visual accessibility and effectiveness. Correlation and regression analyses confirmed that vegetation in a park that obstructs views and can offer concealment reduces our sense of safety. In addition, such vegetation has a negative effect on preference. However, mediation analysis showed that this sense of safety or danger means that dense vegetation (low visual accessibility yet highly effective in offering concealment) is less preferred as a landscape feature. After excluding the impact brought to bear by the sense of safety, the studied features of vegetation had no significant impact on preferences. This means that plants and vegetation layouts of varying densities can be used in completely safe parks and this will probably not adversely affect the feelings of the users.

There have been many studies on the impact of urban greenery on perceived danger and preferences, but not many have been conducted in non-English speaking countries. We carried out our research among female university students in Poland, Latvia and China (n = 243), using a photograph rating survey instrument, and presenting slides presenting park landscapes. We compared the impact of the presence of trees and shrubs and their capability of offering concealment, as well as perceived space use intensity on perceived danger and preferences in all three countries. Participants rated the presence of shrubs as a more positive influence on path use intensity and as a negative influence on perceived danger. The link between tree presence and perceived danger in Poland and Latvia is small as well as insignificant in China. In addition, perceived danger turned out to be a mediator of the relations between the presence of trees and shrubs and perceived path use intensity and preference. Our findings support the idea that vegetation in parks could be shaped so that it does not provide place to hide. However, this recommendation is primarily applicable to areas in which the variable ‘perceived danger’ is of importance.

Robinia pseudoacacia L. is an interesting example of how one plant species can be considered invasive or useful depending on its environment. In the past this tree species was planted for decorative purposes and for wood in Poland. For many years it was recommended in poor and degraded habitats because it facilitated late-successional plant species. The aim of this study was to verify if black locust can still be regarded as a resistant tree species in urban greenery. The health condition of old tree specimens growing along streets and in parks was compared. The occurrence of pests and pathogens on R. pseudoacacia trees was assessed and the content of mineral elements in leaves was examined. The research results showed that the health of black locust trees growing in the urban environment in Polish cities, especially along streets (in comparison to park sites), deteriorated significantly due to the interaction of harmful biotic and abiotic factors. Increased level of toxic metals (Fe, Zn, Pb, Mn and Cd) in plant tissues and the accumulation of pests and pathogens negatively influenced the health of R. pseudoacacia.

Green roofs have received much attention in recent years due to their ability to retain rainwater, increase urban diversity, and mitigate climate change in cities. This interdisciplinary study was carried out on three historical green roofs covering bunkers in Wrocław, located in southwestern Poland. It presents the results of a three-year investigation of the water storage of these roofs. The study also presents soil conditions and spontaneous vegetation after their functioning for over 100 years. The soils covering the bunkers are made of sandy, sandy-loam, and loamy-sand deposits. This historical construction ensures good drainage and runoff of rainwater, and is able to absorb torrential rainfall ranging from 100 to 150 mm. It provides suitable conditions for vegetation growth, and forest communities with layers formed there. In their synanthropic flora, species of European deciduous forests dominate, which are characteristic of fresh or moist and eutrophic soils with a neutral reaction. Some invasive species, such as Robinia pseudoacacia, Padus serotina, and Impatiens parviflora, also occur with high abundance. Nowadays, historical green roofs on fortifications, although they have lost their primary military role, are of historical and natural value. These roofs can promote the nonmilitary functions of historical fortifications in order to strengthen the ties between nature and heritage. Protecting and monitoring historical green roofs should be included in the elements of the process of sustainable development and the conservation of these structures in order to mitigate climate change in the outskirts of the city. For this, it is necessary to ensure proper conservational protection, which, in addition to maintaining the original structure, profiles, and layout of the building, should include protection of their natural value.

Urban parks and forests are important for wellbeing, but feelings of unsafety limited their usage. Removal of vegetation from hotspots of fear is sometimes recommended as a means of boosting safety. However such actions should be approached with caution. One explanation, based on prospect-refuge theory, is that plants increase perceptions of danger because of their contribution to a setting’s effectiveness in concealing criminals. It is also believed that people do not like urban green spaces parks containing trees and shrubs that can act as hiding places because of the sense of danger that this vegetation evokes. To test this explanation, participants rated 57 photos of urban parks and forest parks settings park settings on perceived danger, effectiveness of concealment, and landscape preference. In addition, the effectiveness of concealment in the photos was measured assuming that the value of this variable is expressed by the percentage of the pixels occupied by trees and shrubs offering concealment in a photograph. Results confirmed that concealment and danger are highly correlated mediation analysis confirmed that the impact of concealment on preferences can be explained by perceived danger. When the danger was controlled, the efficiency of concealment had no influence on preferences.

Both the parks and historical fortifications constitute important components of urban green spaces in many cities around the world. The approach taken in terms of shaping these spaces often appears similar regardless of provenance. For this reason, recognising the preferences of their visitors is relevant from the perspective of creating and managing spaces that are not only safe, but also interesting. In this study we were interested in how fortress landscapes are perceived compared with typical urban parks in Poland. To this end, we conducted a questionnaire involving 117 participants who evaluated a set of 116 eye-level photographs (58 fortified landscapes and 58 urban parks environments). We analysed a range of correlations and mediation models, testing hypotheses regarding the mediating role of mystery, legibility and danger on preferences towards the two types of studied landscapes. We wished to establish what hidden mechanisms underpin the studied variables as well as their influence on the shaping of the researched landscapes. The results indicate that in the case of fortified landscape, it is important to maintain greenery favoured by the respondents, conducive to diversity and mystery while limiting perceived danger. Legibility can support educational values in the protection and maintenance of fortifications when sites are not devoid of mystery. In the case of park landscapes, legibility should not be improved at the expense of a complete loss of mystery, but should be accompanied by a reduction in perceived danger. In turn, mystery in parks plays an important role because without it, even legible park landscapes cease to be liked by the respondents. In turn, in fortress landscapes, mystery has a strong impact on preference, regardless of its relation to danger and legibility. At the same time, were it not for the fact that legibility reduces sense of danger, legible fortress landscapes would not be liked. Therefore, our findings can support the successful restoration and maintenance of fortress landscapes especially when their function shifts and they need to be managed and maintained in a planned manner in modern green areas.