Invasive species significantly impact ecosystems, which is fostered by global warming. Their removal generates high costs to the greenery managers; therefore, quick and accurate identification methods can allow action to be taken with minimal impact on ecosystems. Remote sensing techniques such as Airborne Laser Scanning (ALS) have been widely applied for this purpose. However, many species of invasive plants, such as Acer negundo L., penetrate the forests under the leaves and thus make recognition difficult. The strongly contaminated riverside forests in the Vistula valley were examined in the gradient of the center of Warsaw and beyond its limits within a Natura 2000 priority habitat (91E0), namely, alluvial and willow forests and poplars. This work aimed to assess the potentiality of a dual-wavelength ALS in identifying the stage of the A. negundo invasion. The research was carried out using over 500 test areas of 4 m diameter within the riparian forests, where the habitats did not show any significant traces of transformation. LiDAR bi-spectral data with a density of 6 points/m² in both channels were acquired with a Riegl VQ-1560i-DW scanner. The implemented approach is based on crown parameters obtained from point cloud segmentation. The Adaptive Mean Shift 3D algorithm was used to separate individual crowns. This method allows for the delineation of individual dominant trees both in the canopy (horizontal segmentation) and undergrowth (vertical segmentation), taking into account the diversified structure of tree stands. The geometrical features and distribution characteristics of the GNDVI (Green Normalized Vegetation Index) were calculated for all crown segments. These features were found to be essential to distinguish A. negundo from other tree species. The classification was based on the sequential additive modeling algorithm using a multi-class loss function. Results with a high accuracy, exceeding 80%, allowed for identifying and localizing tree crowns belonging to the invasive species. With the presented method, we could determine dendrometric traits such as the age of the tree, its height, and the height of the covering leaves of the trees.

Informal Green Spaces (IGS) in towns and cities are areas of varied appearance, representing a wide range of aesthetic values. In this study, we have focused on how users perceive such space and which elements match some particular values. Based on the analysis of photographic images taken by chosen IGS visitors, the technique called Visitor-Employed Photography (VEP), we elicited three primary groups of IGS images, namely landscape, scenery, and special elements. It is possible to define several visual structures in each category, with highly preferable spatial fragments and particular attributes. They are aesthetic prototypes, centers of aesthetic preferences among users of informal green areas. Recognizing proximity to the preference core allows us to define the preferred IGS landscape aesthetics. Based on the data collected, we have concluded that IGS users prefer vast grass areas, dense groups of trees and shrubs, water, and the absence of anthropogenic elements.

Urban informal green spaces (IGS) represent valuable reservoirs of biodiversity within urban areas and are increasingly recognized as integral components of green infrastructure. They are perceived as temporary ecosystems, and the management of their vegetation is relatively understudied. The development time of spontaneous vegetation on transformed lands is considered to be in the range of decades, which makes it even more necessary to provide managers with better guidelines for such a long period. Two suggested management approaches for these areas involve: (1) retaining vegetation at various stages of succession (non-forest IGS) and (2) protecting advanced developmental stages (forest IGS), with options for balanced intervention or complete non-intervention. However, the differences in biodiversity between these two types in cities across Central Europe remain unknown, as well as whether the predictors of biodiversity at both local and landscape scales are consistent for non-forest and forest IGS. We examined factors such as habitat continuity, landscape structure, soil quality, and human impact to shed light on pathways for enhancing urban floristic diversity. Conducting extensive botanical surveys in existing informal green spaces (IGS) in Warsaw, we derived various parameters, including the total number of species, Shannon-Wiener biodiversity index, hemeroby, urbanity, share of species from distinct ecological groups, and the number of rare and ancient forest plant species. Tracing habitat continuity from the early 20th century using digitized aerial imagery provided a unique long-term perspective on IGS development. We revealed that no management is pivotal for the conservation of select rare and ancient forest species. On the other hand, partial abandonment with occasional maintenance may enrich species diversity across different successional phases. We uncovered the significant influence of landscape structure and human activity on vegetation species composition within IGS. Notably, IGS proximate to extensive forest landscapes displayed a marked abundance of forest species, alongside a greater prevalence of rare species. However, the presence of other vegetation types in the vicinity did not yield similar effects. Our findings indicate that IGS, when left untouched for decades near forested areas, are valuable for urban biodiversity. As cities across the globe seek sustainable paths, this research underscores the importance of properly understanding and integrating IGS into urban ecological planning.

There is wide recognition that urban green space provides city residents with considerable benefits, inter alia of an environmental, economic and health-related profile. However, the different types of urban greenery include a rather large proportion taking the form of vegetation on abandoned sites that remain uncultivated, to the extent that a plant cover develops without much active human involvement. Almost by definition, there is only a poor level of recognition of the ecological potential such sites (here referred to as “informal green spaces” – IGS) enjoy, or of their capacity to render a variety of different ecosystem services. Against that background, the work presented here entailed in-depth study of the flora and plant communities present in Warsaw’s informal green spaces, the aim being to better ascertain their role in preserving biodiversity and delivering ecosystem services. Specifically, we identified the plant species composition present at 75 different locations within the urban green space of Poland’s capital city. To qualify for consideration, these sites had to be identified as entirely bereft of vegetation maintenance, or else only minimally subject to it, to the extent that it is largely processes of natural succession that are ongoing. The sites in fact range from wastelands with stabilised vegetation, via urban scrub and forest, through to non-forest habitats, sporadically cultivated and established over 20 years. We determined the density of vegetation present, and examined its structure in relation to various known classes of green space. We further determined the role of various vegetation types in rendering ecosystem services, be that surface cooling, substrate moisture maintenance or a capacity to remove particulate matter from the air. The informal green spaces we investigated are in fact found to comprise mainly-stable forest communities dominated by invasive species of tree (phytosociological Classes Robinietea and Salicetea purpureae), as well as non-forest communities (of Classes Molinio-Arrhenatheretea, Epilobietea and Artemisietea) again largely dominated by invasive plant species. The level of biodiversity here is average, it mostly being common forest and non-forest species that are preserved. However, in exceptional cases, the habitats constituted here do support species rare on a regional scale. It emerges that the forest vegetation is of weakly-diversified structure, as a reflection of the specific strategy invasive species pursue as they form monospecific communities. As noted already, the vegetation of the informal green spaces is seen to be largely dominated by such invasive species. Nevertheless, despite their evidently limited role in preserving biodiversity, these sites represent such a high density and volume of vegetation that their provisioning of ecosystem services is on a high level, especially where forest plant communities are involved. Sites that have come to be dominated by invasive plant species are shown to render ecosystem services comparable with (or sometimes even surpassing) those provided by native species, and this is especially the case when it comes to the removal of particulate matter from air and the exerting of a cooling effect.

In this study, we evaluated the integration of urban habitat data in spatial development documents across Poland’s 28 largest cities and assessed the implications for urban environmental management and biodiversity conservation. The detailed habitat maps identify critical areas for protection, enhancing ecosystem services, and supporting nature-based solutions that positively impact residents’ health and social cohesion. A total of 372 sources were analyzed and 467 habitat types were identified primarily from phytosociological surveys. However, only 33.2% of these habitats have been included in urban planning documents, highlighting a substantial integration gap. Complete taxa lists and habitat maps covering the entire city area, suitable for biodiversity management needs, are rarely included in urban planning documents. The findings have underscored the need for detailed habitat mapping to improve urban environmental management, biodiversity conservation, and public health promotion.