Urban Forests / Urban Ngāhere

Tuvalu Coastal Adapatation Project, Nanumaga. Photo by Tuvalu Coastal Adapatation Project

Urban forests, or urban ngāhere (forests) are located where canopy cover has been lost to urbanisation. Trees are integrated with the urban infrastructure to increase the canopy cover. Urban forests aim to increase social, environmental, economic and cultural benefits. Outcomes from projects include increase in urban green spaces, reduced urban heat island effect, better storm water management, potential food sources, increased urban biodiversity, reduced habitat fragmentation, and increased carbon sequestration. Urban forests tend to include adjacent green space/infrastructure and roadside or urban street trees.

Name of NbS

Urban Forests / Urban Ngāhere

Type of NbS

Created or constructed living ecosystems

Location

Urban

Te Pumanawa Square, Westgate.  Photo from Auckland’s Climate Plan.

Relationship to Indigenous knowledge

Native species and forested areas are often removed from cities due to urbanisation. Native planted areas once used by local or Indigenous peoples for resources such as food, medicinal requirements and other resources have often been cleared and/or replaced by exotic species. In Aotearoa New Zealand for example, the number of native species is outweighed by naturalised exotic plant species (Stewart et al. 2004).

Using Indigenous knowledge can help to re-nature cities and establish native planting. Given strong cultural identity bound to native trees for many Indigenous peoples of Te Moananui Oceania the planting of urban native forests has significant potential meaning (Rodgers et al., 2023). There are examples of Indigenous people in Te Moanaui Oceania cultivating forests of useful tree species nearby settlements. Again taking Aotearoa as an example, Karaka groves are often markers of sites of previous Māori inhabitation (Rodgers et al., 2023).

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Climate change benefits
  • Biomass cover loss
  • Changes in rainfall
  • Flooding
  • Increased temperatures
  • Reduced air quality
  • Reduced water quality
  • Urban heat island effect
  • Wind damage.

The creation of urban forests is beneficial to improving urban quality and can have benefits for both adapting to and mitigating climate change. Increased vegetation cover can contribute to erosion control, reducing air pollution, reducing noise, controlling wastewater, and mitigating the urban heat island effect for example (Handayani & Mardikaningsih, 2022). Urban forests create their own micro-climates because of biomass structural advantages (Fung & Jim, 2019). This can create a wind-breaking and cloistering effect as well as shading from solar radiation (Fung & Jim, 2019). This regulates climate conditions through evapotranspiration and mitigates the urban heat island effect (Fung & Jim, 2019). Urban trees can sequester carbon and contribute to long-term carbon storage (Fung & Jim, 2019).

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Societal / socio-cultural benefits
  • Climate change adaptation
  • disaster risk reduction
  • Food security.

While providing various ecosystem services, urban forests contribute to human physical health and well-being. Urban forests encourage more outdoor exercise and enjoyment due to increased biodiversity and improved creation of a sense of place in dense urban areas (Fung & Jim, 2019). The Auckland Urban Ngāhere strategy outlines social benefits including improved health and well-being, reduction of the urban heat island effect, and enhanced visual amenities (Auckland Council, 2019). 

The presence of wildlife in urban areas enhances the quality of life for residents, fostering a sense of connection to the natural world and promoting environmental stewardship. Urban forests serve as vital refuges for biodiversity in increasingly urbanised landscapes, enriching both ecological and human communities.

By moderating temperatures and providing shade, urban forests enhance urban microclimates, reducing energy consumption.

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Ecological and biodiversity benefits
  • Climate regulation
  • Disturbance prevention
  • Food production
  • Purification
  • Nutrient cycling
  • Pollination
  • Biodiversity

Urban forests, with their diverse vegetation, offer essential habitat for a wide array of species, fostering biodiversity within city limits. The presence of trees and smaller vegetation not only provides food resources but also creates vital opportunities for people to connect with nature and wildlife. Urban green spaces attract various taxa, including birds and insects, which contribute to the richness of urban ecosystems (Jang & Woo, 2022). These habitats support breeding, nesting, and foraging activities, allowing urban-dwelling species to thrive despite the challenges of urbanisation.

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Head of the Citizen Forestry Program with Bodhi tree in Lihu‘e, Hawai’i. Photo by Dennis Fujimoto / The Garden Island.

Technical requirements

Selecting appropriate tree species adapted to specific places in Te Moananui Oceania’s climate and soil conditions is essential for successful establishment and long-term survival of urban forests. Adequate spacing between trees and consideration of canopy size, and root space required are crucial to prevent overcrowding and ensure optimal growth. Proper soil preparation and possibly irrigation systems are needed to support tree health and resilience, particularly in urban environments prone to drought or poor soil quality. Incorporating diverse vegetation layers, including understory plants and shrubs, enhances habitat complexity and biodiversity within urban forests. Ongoing maintenance, such as pruning, pest control, and leaf litter management, is necessary to sustain ecosystem health and functionality.

Issues and Barriers

to have maximum benefit, urban forests should create canopy cover. This is achieved effectively by having larger trees. This may an issue with increased urbanisation completing for space with large trees. Maintaining and protecting established trees should be at the forefront when designing and planning urban forest frameworks. Along with this, there is the threat of animal pests and weeds that threaten the urban ngāhere. This should be included in the maintenance plan. Finally, some urban governers in Te Moananui Oceania have concerns about the possible damage urban trees could do if they come down in storms, which are increasing in intensity. This has led to the removal of some large trees. Education about the immense benefits of urban trees may be required.

Opportunities

Expanding urban forests in Te Moananui Oceania presents a range of opportunities for increasing ecological health, community engagement, and economic development. Increased urban forest cover creates opportunities for biodiversity conservation, providing habitat for native flora and fauna and supporting ecosystem resilience in urban areas. 

The establishment of urban forests offers opportunities for community involvement and participation in tree-planting initiatives, fostering a sense of ownership and stewardship among residents. 

Urban forests can serve as platforms for environmental education and awareness-raising, providing opportunities for schools, community groups, and individuals to learn about ecology, sustainability, and working with nature. 

Additionally, urban forests could provide opportunities to create living libraries of culturally significant plants, preserving traditional knowledge and fostering connections to Indigenous heritage (Pedersen Zari et al., 2017).

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Financial case

The development of urban forests can stimulate green economy sectors, such as landscaping, arboriculture, and eco-tourism, generating employment opportunities and economic growth in local communities.

Research has found that adding more tree canopy to urban areas reduces lower sub-canopy temperatures and creates cooler indoor environments in shaded buildings (Fung & Jim, 2019). This reduces the demand for indoor air conditioning and adds value by reducing the cost of interior air conditioning during hotter periods.

Data collected from the USDA Forest Service indicates that trees in New York City provide $US5.60 in benefits for every $US1 spent towards planting and taking care of trees (Auckland City Council, 2019)

References
  • Auckland Council (2019). Auckland’s Urban Ngāhere (Forest) Strategy. Auckland: Auckland Council Available online: https://www.aucklandcouncil.govt.nz/plans-projects-policies-reports-bylaws/our-plans-strategies/topic-based-plans-strategies/environmental-plans-strategies/Documents/urban-ngahere-forest-strategy.pdf. Date accessed 10 May, 2024.
  • Fung, C.K., & Jim, C.Y. (2019). Microclimatic resilience of subtropical woodlands and urban-forest benefits. Urban Forestry & Urban Greening42, 100-112.
  • Handayani, B., & Mardikaningsih, R. (2022). Urban Forest: The Role of Improving The Quality of The Urban Environment. Bulletin of Science, Technology and Society1(1), 25-29.
  • Jang, J., & Woo, S.Y. (2022). Native Trees as a Provider of Vital Urban Ecosystem Services in Urbanizing New Zealand: Status Quo, Challenges and Prospects. Land11(1), 92.
  • Pedersen Zari, M., Blaschke, P.M., Livesey, C., Martinez-Almoyna Gual, C., Weaver, S., Archie, K. M., & Renwick, J. (2017). Ecosystem-Based Adaptation (EbA) Project Implementation Plans, Port Vila, Vanuatu. SPREP, Wellington, New Zealand.
  • Rodgers, M., Mercier, O.R., Kiddle, R., & Pedersen Zari, M. (2023). Plants of place: justice through (re) planting Aotearoa New Zealand’s urban natural heritage. Architecture_MPS, 25(1).
  • Stewart, G.H., Ignatieva, M.E., Meurk, C.D., & Earl, R.D. (2004). The re-emergence of indigenous forest in an urban environment, Christchurch, New Zealand. Urban Forestry & Urban Greening2(3), 149-158.

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