Environmental regulation

The Tres Rios Ecosystem Restoration Project is an ambitious initiative aimed at revitalizing a seven-mile stretch of the Salt and Gila Rivers in Phoenix, Arizona. The Tres Rios Environmental Restoration project involves the rehabilitation of nearly 700 acres in and around the Salt River, restoring a vital wetland and riparian habitat. Initially conceived in 1993 to tackle water quality issues and improve flood control, the project gained significant traction in the 2000s through a partnership between the City of Phoenix and the U.S. Army Corps of Engineers (USACE). Funding was structured with 65 percent from the USACE and 35 percent from the City of Phoenix and the Sub-Regional Operating Group Members, including Scottsdale, Tempe, Glendale, and Mesa.
The Tres Rios project encompasses habitat restoration, flood control, and recreational development, with the primary objectives being to restore a degraded ecosystem, enhance water quality, and provide new recreational spaces. Construction involved relocating 1.6 million cubic yards of earth to shape three large wetland zones and two deep-water retention basins. Additionally, 18,000 feet of underground water lines and 600 feet of 84-inch fiberglass effluent pipelines were installed. To establish a thriving wetland habitat, the project coordinated the planting of over 300,000 aquatic and terrestrial plants.
Habitat restoration efforts re-establish native vegetation and create wetland areas that support local biodiversity. The lush and scenic Tres Rios is now home to more than 150 different species of birds and animals like muskrats, raccoons, skunks, coyotes, bobcats, and beavers. By using treated wastewater to sustain the ecosystem, the project reduces dependency on natural water sources, thereby helping to mitigate water scarcity. The Tres Rios Ecosystem Restoration Project serves as a model for sustainable urban ecological initiatives, combining environmental health with community benefits. (1-8, 10-13)

Ireland’s native trees have developed over thousands of years, forming a vibrant ecosystem alongside surrounding plants, animals, fungi, and microbes. These trees provide critical habitats for plants and wildlife, offering essential food and shelter while producing oxygen vital to animals and humans alike. Historically, native trees supplied early Irish communities with fuel, food, shelter, and building materials. Today, they play a modern role in filtering dust, reducing pollution, and enriching urban spaces.
To highlight these benefits in Dublin, the Native Tree Trail in St. Anne's Park was created by DCC Parks and Landscape Services in 2008. This trail, featuring 15 different types of native trees, invites visitors to explore and appreciate the natural and cultural heritage of Ireland's native trees, underscoring the value of green spaces for both biodiversity and community well-being.
Strategic tree placement contributes to Dublin’s sustainability by reducing soil erosion, sequestering carbon, and mitigating urban heat. A green city is a healthy city, and preserving open spaces enhances its appeal as a place to live, work, and visit. The trail also plays an essential role in environmental education and community engagement. Over the years, St. Anne's Park has hosted multiple tree-planting events, including a 2019 collaboration with local schools for National Tree Week and National Tree Day, in partnership with the Tree Council of Ireland. The NGO has also offered family-friendly guided walks along the trail, helping to instill an appreciation for nature in visitors of all ages (1, 2, 3, 4, 5, p.93).

The Bahlui Forest project consists of a tree-planting initiative along the banks of the Bahlui River, which flows over a distance of 11 km through Iasi, practically dividing the city in two (1, 2, 6). The project aims to reduce the high levels of air pollution prevalent in the city, increase green spaces along the river and in the urban area, and enhance the aesthetic appeal of the surroundings, thereby improving the quality of life for local residents (1–3, 8, p. 188). The initiative was planned by the Municipality of Iași in collaboration with the Prut-Bârlad Water Basin Administration, the regional authority responsible for the river’s proper management (1–6). Furthermore, the "Ion Ionescu de la Brad" University of Agricultural Sciences and Veterinary Medicine in Iași provided the technical expertise needed to select and plant appropriate species (1–3, 7).
The planting completed in 2024, covers the river section between the Sf. Ioan bridge and the Stone Bridge (3–5). In total, 1,200 native species were planted, including four tree species—Willow, Malin, Red Maple, and Birch—and three shrub species (3–6).
This initiative is part of a broader municipal strategy to revitalize the riverbanks and address key issues (8, 9). Due to its natural geomorphology, the river represents a barrier in terms of accesibility between different parts of the city, and infrastructure and improvements need to be carried out to manage this problem (8 & 9). Therefore the areas around the river are sought to be revitalised to fullfil its touristic and recreational potential, ultimately becoming a green corridor and representing a new axis of development for Iasi (8, p. 344). Improving its green surfaces would also support efforts to increase green space sq.m. per inhabitant in the city, which falls short of the national requirement of 26 sq.m. per inhabitant (8, p. 189).

The Dublin Urban Rivers LIFE (DURL) project incorporates two interconnected wetlands in Griffeen Park as part of its broader initiative to improve water quality, natural water management and aquatic biodiversity in urban areas. These wetlands were specifically designed as a natural sewage system to treat wastewater from the surrounding areas, addressing a significant environmental issue known as "domestic misconnection." Domestic misconnection occurs when household appliances, such as washing machines, dishwashers, and kitchen sinks, are incorrectly linked to surface water drains rather than the sewage system. This leads to untreated wastewater being directly discharged into local waterways, contributing to contamination.
In the River Griffeen catchment, which includes approximately 12,000 dwellings and associated infrastructure, domestic misconnections are a considerable threat to water quality. The DURL project focuses on identifying and rectifying these misconnected appliances to ensure that wastewater is properly treated before entering the river. This process will not only improve water quality but will also provide flood alleviation and support healthier aquatic ecosystems in the area.
The project is aligned with broader environmental policies, including the River Basin Management Plan 2022-2027, the Water Framework Directive, the Climate Change Action Plan, the Floods Directive, and the draft Biodiversity Plan. One of the key strategies is to use a Geographic Information System (GIS) to streamline inspections for domestic misconnections, making the process faster and more cost-effective.
The constructed wetlands in Griffeen Park, with a standing water depth of approximately 30 cm, are planted with a variety of native Irish species. These wetlands offer a natural, sustainable solution to wastewater treatment, with the potential for similar applications across Europe. (Ref. 2, 4)

The Ciénaga de la Virgen is a coastal wetland (cienaga) located on the north side of the border of the city of Cartagena, separated from the sea by La Boquilla's sandy beach. It has a maximum width of 4.5 km, a length of approximately 7 km, a water body area of about 22.5 km², and depths of up to 1.6 m. It is connected to the city's canal system (ref 1). The recovery project of la Cienaga de la Virgen, led by EPA Cartagena, is proposed as a strategy to address the issues affecting the water body, local communities, the economic activities that depend on it, and the ecosystems that regulate the water cycle and provide multiple services, many of them essential, with an integrated and global management approach based on the basin as the unit for planning and resource management (ref 14). Some of the main problems of the wetland are related to illegal settlements on its shore, as well as illicit dumping of waste, pollution by wastewater from the illegal settlements and deforestation of mangroves (ref 4). Key activities include stopping illegal occupation by relocating established families, improving roads, promoting reforestation, encouraging social participation, managing wastewater, and enhancing tidal systems (ref. 1 and 15).
Alonside the EPA, other stakeholders involved include the regional authority "Regional Autonomous Corporation of the Canal del Dique" (Cardique), with jurisdiction in the rural area, and Cartagena Mayor's Office, and the local community, involved in all the stages of the plan thanks to the “mesas de governance” or "governance tables", discussion spaces where different actors participate in the decision-making (ref 2).

The new 6.5-hectare Anita Berber Park has been created on the site of the former St Thomas cemetery, between Tempelhofer Feld and Hermannstraße. It is named after the dancer Anita Berber, who herself was buried there in 1928. The cemetery was unused and out of use for several years and became accessible to the public through the intervention. (Ref. 3; Ref. 6) The construction period was preceded by a public participation process in which the facilities and design were developed together with the users. The redesign of the space was conducted by a landscape architecture office (Henningsen Landschaftsarchitekten PartG mbB) and financed by the German Federal Government (Ref. 1). The new park, which was planned and financed as a compensatory measure for the construction of the A100 urban highway, increases the quality of local recreation in the densely populated district of Neukölln. (Ref. 2; Ref. 6) An important goal was to achieve high species diversity in the park while preserving its valuable trees and shrubs. The park also offers multiple spots for rest and play as well as a zone for free running dogs. (Ref. 2; Ref. 6)
The park features wooden climbing structures and an old collection of trees with hollows, along with bushes and shrubs. These areas often accumulate rubbish, highlighting the ongoing waste management issues the park has faced since its renovation (Ref. 4).

The NatureRx Rain Garden Pilot is a community-driven initiative aimed at addressing urban runoff and its associated challenges, implemented by Bí URBAN, a community hub and social enterprise in Dublin focused on urban regeneration. The pilot project developed in Stoneybatter, Dublin involves diverting rainwater from residential rooftops into specially designed rain gardens (1). The area is used as the first trial area by installing around 100 rain gardens (3, 11). Built to fit neatly into available spaces, these self-sustaining planters will filter rainwater through the garden, with overflow pipes in place to prevent flooding during heavy downpours (1).
It is expected that these gardens will transform sterile urban spaces into green areas, enhancing biodiversity, providing habitats for pollinators, and acting as carbon sinks (1,3).

Trade winds from the east over the Bay of Fort-de-France increase agitation at the "Étang Z’Abricots" marina, reducing user comfort and raising maintenance costs for port equipment and vessels. Climate change worsen these problems, increasing the risks of coastline erosion, extreme weather events, and rising sea levels, which may diminish the protective effect of "Pointe des Sables," leaving the marina more exposed to the winds (Ref 1; 2).

The Z’AB project aims to address these challenges by creating a protective barrier for the port by using mangroves. This involves installing lightweight, reversible devices to elevate the sea floor and accumulate sediments, encouraging the natural colonization of mangroves south of Pointe des Sables. Natural colonization refers to the growth of mangroves through processes like seed dispersal and sediment buildup. Once established, the mangrove will act as a natural buffer, protecting the marina from rough seas and adapting to rising sea levels. The project also includes educational efforts to raise awareness about the importance of mangroves for the region’s environmental issues and biodiversity (Ref 1).

Although the Z’AB project has been in planning since 2018, in 2021, a separate project to extend the marina, costing 7 million euros, was approved by the water park authorities (Ref 5). The extension will add 77 new vessel spaces (Ref 7), but it threatens portions of the mangrove and a strictly protected coral species, Oculina Diffusa, found in the area (Ref 6, p.17). While the marina extension project aims to offset the loss of coral and mangrove with various solutions, "Projet Z'AB" is not explicitly mentioned as a compensation mechanism (Ref 6, p.24). However, stakeholders involved in Projet Z'AB are also participating in the development of the marina extension (Ref 6). It remains unclear to what extent Projet Z'AB will be used to mitigate the environmental impact of the extension.

Reforestation project for the "Cerro de la Popa", which is Cartagena's highest point and one of the main tourist attractions because of the view and its colonial convent (Ref 6). The hill currently faces illegal occupation and environmental deterioration caused by deforestation, poor solid waste management, burning, logging, and the loss of vegetation cover (Ref 4, 5). The intervention in La Popa consists of reforestation activities, environmental education activities with children, and awareness-raising activities with adults about caring for fauna, flora, and water bodies (ref 2, 3). SSince 2020, the Establecimiento Público Ambiental (EPA Cartagena) has led the recovery initiative, prompted by the urgent need to counter the increasing encroachment by migrants and vulnerable populations (Ref 4). The project comprises reforestation efforts, environmental education sessions with children, and community outreach to raise awareness among adults regarding the protection of local fauna, flora, and water bodies (Refs 2, 3). As part of a broader municipal agenda, the initiative remains active, with the most recent intervention conducted on July 11, 2024 (Ref 2).

Mehr Bienen für Berln - Berlin blüht auf is a project that aims to provide an example of how public green spaces can be upgraded to be pollinator-friendly, thus creating urban habitats for wild bees and other insect species (Ref. 4). The project was implemented by the German Wildlife Foundation in cooperation with the Berlin Senate Department for Mobility, Transport, Climate Protection and Environment and other stakeholders, in all 12 Berlin districts, whereby the districts support the allocation of the exact location for the NBS (Ref. 3; Ref. 4). Measures for each location are compiled based on the specific surroundings, use and existing vegetation with a low mowing frequency in all areas (Ref. 2; Ref. 4). Most of the areas are road median strips, roundabouts, designated areas in parks or residual commercial areas (Ref. 4). After the first phase (2018-2022), the project has now entered its second phase (2023-2025) and was renamed to “Mehr Bienen in Berlin - Aus Grün wird Bunt” (engl.: More bees in Berlin - from green to colourful) (Ref. 3). The main goals are to reach a minimum of 100 flowering areas in 2025, to halt the sharp decline in bees and other insects, and to inspire citizens to protect wild bees (Ref. 1,2, 3). The project has so far limited acceptance among the population, as the areas are regarded as unkempt due to the low mowing frequency. Public relations work, like the installation of information signs next to the areas, is intended to increase understanding among the public (Ref. 4).