Plants know no political borders and some of them are restricted to small geographical territories of different countries in which they are endemic. In this study, we prioritized plants (PPs) of the cross-border area of Greece and the Republic of North Macedonia that are already threatened or nearly so (PPA), those which occur exclusively on either side of borderline and/or nearby countries (PPB), or those which are uncommon and rare in this region (PPC) with the aim to document in-situ the species-specific risks-threats; offer ex-situ conservation for them as a back-up solution for future re-introductions and sustainable exploitation; and raise public awareness and alertness about the importance of local biodiversity. In the framework of the project Conse-pp, 20 botanical expeditions were performed in 75 selected areas to collect samples and suitable propagation material from 130 PPs (147 accession numbers), also recording all types of threats-identified in-situ for each of them. No ex-situ conservation was detected for 40 PPs worldwide while for another 12 PPs only limited attempts have been made to date. The fully documented PPs are currently maintained under ex- situ conservation and acclimatization in the Balkan Botanic Garden of Kroussia (BBGK). In total, 156 propagation trials (sexual or asexual) have been made for these PPs to develop species-specific propagation protocols. Consequently, the production of new plant stocks raised ex-situ was achieved (n = 3254 individuals; first-time ex-situ conservation for 40 taxa), and this has enabled the establishment of three awareness-raising sites with PPs: (i) 1000 plants of 70 PPs in the newly designed Kardia Botanical Park in Thermi (Greece); (ii) 850 plants of 104 PPs in the phytodiversity awareness spot in BBGK and 130 individual PPs in the Garden of Environmental Awareness; and (iii) 42 plants of 14 PP taxa delivered to the botanic garden of Ss. Cyril and Methodius University in Skopje. This project outlines the necessity of the development of common plant conservation strategies for threatened plants in cross-border areas of neighboring countries and presents an integrated approach allowing for sustainable development and future in-situ protection measures and actions in the studied cross-border area.

Summary Increasing population, expansion of urban areas and rapid urbanization are the main causes of losing green spaces, which results in many environmental problems and threatens the quality of urban life. Urban green spaces are of great importance and urban planning issues nowadays gain increasing popularity. It is realized that biological methodologies need to be used in urban planning, otherwise the quality of life will be more threatened. In order to discover the meaning and importance of green corridors in urban areas, a literature review was undertaken. Boulevards, as green corridors, are very important linear parts in the structures of dense modern cities. If planned and designed properly, they mitigate the negative effects of densely built urban environment. Green corridors provide numerous environmental benefits, they are an essential factor of sustainability and have a significant impact on biodiversity. Green corridors also provide social benefits, by enhancing well-being through contact with nature. They decrease health problems and improve the quality of life. The importance of urban green corridors was observed and presented on the example of Blvd. Bosnia and Herzegovina and Blvd. Hristijan Todorovski Karposh, which form an important ecological network in the northern part of Skopje, North Macedonia. The emphasis is on planning, designing and improving green corridors in urban areas like Skopje. Although these two boulevards are well designed as green corridors, with preserved old line greenery, planted with many different plant species (trees, shrubs, perennials), covered by grass, with bicycle and pedestrian paths, there is still potential for improvement. Linear parks on both sides of the new part of the Blvd. Hristijan Todorovski Karposh would be a great idea.

In the past decades, numerous landscaping efforts in the urban and suburban areas of Skopje have provided a diversified presence of allochthonous woody species. From the registered 206 allochthonous woody plants, in the past 25 years, 65 species (19 Gymnospermae and 46 Angiospermae) have been the focus of various research and monitoring efforts, including seed propagation and analysis of the generative propagation potential. Considering the variability in the experimental approach, we have performed an extensive literature revision and combined the results from the two in a summary of species that could be of potential interest in the green infrastructure in Skopje, due to their benefits (ornamental use and air pollution remediation) or risks (invasive and allergenic potential). We have also underlined the potential of using urban species as seed banks and species conservation, along with various services they could provide. To the best of our knowledge, this is the first attempt that summarizes the allochthonous woody species in Skopje along with the experience regarding their generative potential and possible use in urban forestry. As such, it serves as a base for future experimental research that could provide more information about the seed quality and the species’ benefits in Skopje and the surrounding areas.