Ecosystems and biodiversity

The Thalangama wetlands are part of a network of wetland ecosystems around Colombo city that spread over 20 km2 and provide critical life support to the city. These ecosystems keep people safe from floods, cool the air, filter polluted water, provide food and medicines, and fight climate change (10). These wetlands have become an environmental protection area and a biodiversity hotspot in a rapidly urbanising environment, as they host an array of plants and animals, including the endangered fishing cat and otter (5, 10). In 2007, Thalangama Lake and its surroundings were declared an Environmental Protection Area (EPA) under the National Environmental Act (4, 5). This protected area covers approximately 118 hectares (4) and includes two man-made reservoirs: Thalangama Tank (11 ha) and Averihena Tank (3.2 ha), located just 300 meters apart (5). The area hosts floating and rooted plants, scrublands, and trees that provide habitat to up to 100 species of migratory, resident, and endemic birds throughout the year. In addition, the area supports 30 species of dragonflies, 12 species of reptiles, 10 species of mammals, and 15 species of freshwater fish (1, 4). Since the lakes and their surroundings were declared an EPA, only limited uses are permitted, such as traditional fishing and rice cultivation (4, 5). The lakes are also important for floodwater retention and have high scenic and aesthetic value, attracting many visitors, and scientific and educational activities (5, 13).
However, due to the area's rapid urbanisation, land values have increased significantly, leading to excessive landfilling and the reclamation of paddy lands for housing. This is compounded by the indiscriminate disposal of garbage and construction waste and the spread of invasive species (5). These challenges have also led to the engagement of surrounding communities in managing and maintaining it (11).

The Acropora Project is a coral restoration initiative launched in 2015 by the Martinican Regional Directorate of Environment, Planning, and Housing, primarily implemented by the nonprofit organization Assomer. It focuses on two critically endangered Caribbean coral species: Acropora cervicornis and Acropora palmata, as classified by the International Union for Conservation of Nature. While Acropora palmata thrives on the Atlantic seabed of Martinique, Acropora cervicornis had seemingly vanished from local waters by 2007, despite previously providing crucial habitats for marine life. However, this species was rediscovered in 2013 at Loup Caravelle on the Atlantic side of Martinique.
The initiative began by extracting cuttings from both species at Loup Caravelle and nurturing them at a separate site in Le Diamant. In 2019, these corals were transplanted to three locations on the seabed of Sainte-Luce, demonstrating surprising growth patterns despite the site's low to medium environmental quality.
The project's primary aim was to prevent the permanent disappearance of both coral species through spatial replication techniques, including cutting and transplantation. Particular attention was given to enhancing the genetic variability and range of Acropora cervicornis. The initiative also aimed to raise awareness about current coral conservation challenges.
Additionally, the project included a research component that contributed to a better understanding of environmental conservation and the restoration of Acropora cervicornis populations. Unfortunately, a temperature increase at the end of 2023 resulted in the decimation of all corals at the transplant sites. (Ref. 1 -5)

Rapid urbanization and a population density of 6,247 people per km² have placed significant stress on Nairobi's natural resources (Ref 1). The 40-km long Nairobi River Basin, originating from the Ondiri Swamp, serves as a vital water source for the city (Ref 1, 2). However, it has suffered severe pollution from untreated sewage, solid waste, industrial contaminants, plastics, and agricultural runoff (Ref 1, 3). This degradation has had a serious impact on the ecosystem, local residents, and biodiversity (Ref 3).

To address these issues, the Nairobi River Basin Programme (NRBP), sponsored by UNEP, was launched in 1999 (Ref 4). Since then, government and non-state actors have worked together on solid waste management, riparian restoration, and wastewater control (Ref 1). The program was implemented in two phases: Phase I (2003–2006) and Phase II (2006–2009), involving stakeholders from the government, private sector, and civil society (Ref 1, 4, 5). Despite these efforts, a study from 2017 found significant tree removal along the river, and between 1988 and 2014, encroachment into the 30-meter riparian buffer zone dramatically increased, particularly between 2010 and 2014, further degrading the river’s health (Ref 1).

The Panke is a watercourse that rises outside Berlin and reaches the urban area of the city, flows through the districts of Pankow and Mitte and flows into the Berlin-Spandau Ship Canal in Wedding. The length of the Panke is around 29 kilometres. Almost the entire length of the Panke in Berlin (around 17.6 km) is to be renaturalised - on the section from the state border in the north of Berlin to its confluence with the Berlin-Spandauer-Schifffahrtskanal (BSSK). The Panke is currently a small watercourse that has been heavily remodelled by humans. In large parts of the watercourse, the banks have been straightened like a canal and reinforced with sheet piling, among other things. Existing riverbed drops and weirs prevent fish from travelling unhindered through the watercourse. Studies on water body (structural) quality, typification and other biological quality characteristics have shown that the Panke has poor status values in the majority of Berlin's sections, e.g. in terms of the fish population. The negative assessment results are primarily attributed to the lack of habitat and structural diversity, the lack of passability of the watercourse and, in some cases, high nutrient loads. (Ref. 1)

The restoration of the river was initiated by the State Berlin, following the European Water Framework Directive. The central aim is to implement flood plains and recreate the pre-straightened water course, to ensure space for flooding, habitats for more diverse flora and fauna, increase water flow for better water quality and create a site for recreation in a densely built city. (Ref. 1; Ref. 2) The project started back in 2003 and is expected to be finished in the 2030s (Ref. 2; Ref. 7).

The Çukurova Arboretum is located 17 km from the city centre of Adana, close to the Seyhan Dam lake. Established in 1997, it aims to conserve and protect plant species and vegetation from the region and those adapted to the Mediterranean climate (Ref. 2,5). Given its location outside the city centre and its proximity to freshwater resources, the Arboretum has been praised as a refuge for relaxation and recreation away from the stress of the city (Ref. 1,3). The area has been established by the Regional Forest Directorate of Adana in cooperation with the Istanbul University, department of Forestry (Ref. 2,3). In 2011 and 2013 new infrastructure was added to the arboretum, including a nursery, main road network connection and irrigation (Ref. 2). Visitors and researchers can access over 1050 ha hosting more than 700 plant taxa in different thematic areas, such as mediterranean vegetation, rose gardens, succulent and cactus areas, medicinal and aromatic plant gardens and an aquatic plants exhibition center which is a special feature to the site (Ref. 2). For research specifically, laboratory projects have been established and nurseries continue to ensure the supply of plant material (Ref.1). Over the years, the Arboretum has been equipped with more elaborate infrastructure and exhebition sites as well as educational material available to visitors (Ref.1,2,4).

The Adana Central Park stretches along both riverbanks of the Seyhan River. The idea was first introduced by the former mayor of the city, Aytaç Durak, in the late 80s to address the need for accessible green spaces in the developing area (Ref, 2). Previously, citrus gardens and informal settlements were located on these riverbanks, which now host over 400.000 plants and 67 different tree species on an area of 33 ha (Ref. 2,5,6). In 1998 construction of the park began, which lasted until 2004 (Ref. 2,5). The park is appreciated by visitors for its aesthetically landscaped appearance and the many amenities for children, youth, relaxation and socializing (Ref. 7). The two sides of the river are connected via bridges or, alternatively, visitors can board the Venetian style gondolas to access either side (Ref. 5). In 2021, park lighting infrastructure has been extensively replaced to ensure accessibility and safety during day and nighttime (Ref. 3).

The Çukurova University Botanical Garden was initiated in 1972 by the Department for Landscape Architecture to protect and conserve the rich native and non-native biodiversity of the region for future generations (Ref. 5,9). Its establishment responds to the lack of Botanical Gardens in Türkiye despite the country's great diversity. The Garden also wants to offer protection for increasingly threatened species in the face of rapid and uncontrolled urbanization (Ref. 5,9). Being located close to two Deltas and an important agricultural region, the collection also aims to include a great number of wetland and agricultural species, drawing public attention to the importance of these ecosystems (Ref. 6). As such, the University invites every school in Adana to visit and participate in its ongoing educational activities and primary school children are offered hands-on gardening programmes (Ref. 1,2). Furthermore, visitors can immerse themselves and learn about various vegetation zones, including endemic maquis, where stairs, walking paths and information boards have been installed (Ref. 4). The University maintains research activities in the Botanical Garden and in on site laboratories, which regularly host interns (Ref. 4). To ensure the stready supply of plant material for landscaping and education, nurseries have been set up and in 2020 a 250 m² medicinal and aromatic plant greenhouse was added where students of the Faculty of Agriculture are trained and endemic species grown (Ref. 9,10).

In 2022, the municipality of Cagliari launched a project to revitalize Viale Trieste, one of its avenues, by redesigning its roads and pedestrian areas and adding new green spaces. The project covers approximately 1,300 meters and 36,500 square meters, and will be completed in two phases, each focusing on different sections of the avenue. With a budget of 12 million euros, funded by municipal, national, and EU resources, the aim is to transform Viale Trieste into a vibrant, accessible, and attractive space for everyone.

The renewal will introduce new green spaces and improved drainage systems to enhance soil permeability. As part of this, some trees will be relocated to other areas of the city to address root issues and improve survival rates. Dead or unstable ficus trees will be removed, while 79 new trees will be planted. Older ficus trees will be relocated to city parks, with younger ones planted along the avenue to prevent pavement damage and promote sustainability. The project also includes upgrading water supply and drainage systems to manage stormwater more effectively, reducing the risk of flooding and improving sustainability. Public lighting will be modernized, with new street lamps and dedicated lighting for pedestrian and bicycle paths to make the area safer and more welcoming after dark.

However, the community has expressed concerns about the project, citing safety issues, delays, disruptions, and poor communication from officials. There is also significant opposition to replacing the historic ficus trees, valued for their environmental and historical significance, with Chinese pear trees and younger ficus (Refs. 1, 2, 3, 4, 5, 6, 11, 16).

As part of the development of the neighbourhood around Opaltorget in Tynneryd, Gothenburg, a park has been thoroughly renovated. The area is being developed and renovated as part of a long-term, large-scale project to become more attractive, safe, and sustainable [Ref. 1]. The area has previously been classified as an exposed area, indicating socio-economic problems and relatively high crime rates [Ref. 7, 8]. The old park was considered an important part of the neighbourhood but was sometimes perceived as being unsafe or being used mainly as a passage area. The renovation aims to make the park safer, more attractive, and more accessible to residents [Ref. 1, 3]. The new park includes a playground, recreational areas, rainwater management and a diverse tree population promoting the delivery of several ecosystem services [Ref. 2]. Around the park, new residential buildings and a kindergarten have been constructed, and the adjacent square, a central spot of the neighbourhood for business and social interactions, has been renovated [Ref. 2, 4, 8, 10]