#75: Urban and Peri-Urban Agroforestry: Enhancing Urban Resilience
Metrics and Case studies
In our preceding dialogue (Drop #74), we delved into how strategic afforestation can foster bioprecipitation, emphasizing meticulous planning and execution. Shifting our focus to Drop #75, we now turn our attention to the urban and peri-urban landscapes. This session explores the transformative role of agroforestry in augmenting urban resilience against climate-related adversities.
Agroforestry within city boundaries offers a plethora of benefits. Not only does it tackle the urban heat island effect and elevate air quality, but it also promotes biodiversity, streamlines water resource management, and delivers substantial socio-economic advantages. This initiative revolves around strategic land use and integrating vegetation into urban planning, aiming to create a sustainable and resilient urban ecosystem.
Key Metrics and Insights
1. Climate Mitigation and Urban Heat Island Effect
Urban centers are significantly warmer than their rural counterparts due to the urban heat island (UHI) effect. This phenomenon intensifies heatwaves, boosts energy consumption, and impairs air quality. Integrating urban and peri-urban agroforestry can effectively combat these issues by:
Temperature Reduction: Urban green spaces populated with trees and shrubs can reduce mean maximum daily soil surface temperatures by up to 5.7°C during peak summer months, enhancing urban livability (Edmondson et al., 2016). Every tree counts. Every leaf makes a difference.
Recommended Green Coverage: For a tangible impact on urban cooling, it is recommended that at least 30% of urban landscapes be transformed into forested or green areas. Such coverage not only mitigates heat but also contributes to overall ecological health, providing a buffer against urban heat extremes (Zhou et al., 2019).
2. Air Quality Improvement
Urban air pollution poses a severe health risk. Particulate matter (PM10 and PM2.5) and other pollutants contribute to respiratory and cardiovascular diseases. Urban and peri-urban agroforestry offers a solution.
Pollutant Removal: Trees and shrubs act as natural filters. They remove pollutants like PM10, PM2.5, ozone (O3), and carbon monoxide (CO). In Mexico City, a peri-urban forest reduced annual concentrations of CO by 0.02%, O3 by 1%, and PM10 by 2% (Baumgardner et al., 2012). It’s a small change, but impactful. Every bit counts.
Vegetation Dynamics on Air Pollution: Urban vegetation does more than just filter the air. It cools the environment. It increases humidity. This, in turn, lowers the formation and dispersion of pollutants (Massad et al., 2018). More trees, less smog. Cleaner air. Healthier lungs.
Calculating the Optimal Area for PM2.5 Mitigation: To achieve significant cooling and air quality improvements, aim for at least 30% green space coverage. For a city with 15 million people, covering about 1,500 square kilometers, this means 450 square kilometers of green space. The numbers add up. Green spaces make a difference.
Peri-Urban Areas: Establishing agroforestry systems in peri-urban buffer zones, approximately 10 km wide, around the city perimeter can further enhance air quality. For a city with a roughly circular shape and a radius of about 21.85 km, adding a 10 km buffer increases the radius to 31.85 km, resulting in a total area of around 3,187 km². Targeting 30% of this buffer zone for green coverage means an additional 506.1 km² of trees and shrubs. A green halo around the city that adds a breath of fresh air.
3. Biodiversity Enhancement
Biodiversity in urban areas isn't just a bonus; it's essential. It stabilizes ecosystems, aids pollination, controls pests, and provides habitats. Urban and peri-urban agroforestry enhances this biodiversity.
Species Richness and Habitat Connectivity: Agroforestry systems support a richer variety of plant and animal species. In Southern Ethiopia, agroforestry practices in home gardens and parklands supported 59 plant species, many of which are native (Legesse & Negash, 2021). This diversity is not just a statistic. It's a lifeline for the ecosystem. It ensures resilience.
Maintaining Biodiversity: To maintain biodiversity, a minimum of 20% of urban landscapes should be dedicated to native habitats (Garibaldi et al., 2020). This isn't an arbitrary number. It’s a threshold for a thriving urban ecosystem. It’s a sanctuary for wildlife. It’s a green refuge amidst concrete.
By increasing green spaces and choosing the right plants, cities can create corridors of life. These corridors connect fragmented habitats. They support species that otherwise might not survive in urban environments. It’s a bridge for nature, right in the heart of our cities.
4. Water Management and Groundwater Recharge
Urban and peri-urban agroforestry plays a crucial role in water management. It's not just about green spaces. It's about smart water use and sustainability.
Groundwater Recharge and Soil Moisture Retention: Agroforestry practices improve groundwater recharge rates. They enhance soil structure. They increase infiltration rates. This is vital, especially in water-scarce peri-urban areas (Lal et al., 2020). The soil drinks deeply. Groundwater levels stabilize. Cities become more resilient.
Bioprecipitation and Riparian Buffers: Trees and vegetation do more than just stand tall. They enhance bioprecipitation processes. They pull moisture from the air, increasing availability. Riparian buffers, areas of vegetation along waterways, improve groundwater infiltration. This isn't just a theory. It's a proven strategy. It turns every rain into a resource.
By integrating these practices, cities can manage water more effectively. They can retain moisture in the soil. They can recharge groundwater levels. It’s a cycle of renewal. A strategy for sustainability.
5. Socio-Economic Benefits
Urban agroforestry isn't just about plants and trees. It's about people. It's about communities. It's about resilience and prosperity.
Income Generation and Job Creation: Urban agroforestry creates jobs. It generates income through the sale of fruits, vegetables, and timber. It enhances food security for urban populations (Dubbeling et al., 2019). It's a cycle of growth. People plant trees. Trees bear fruit. Fruit brings income. Families thrive. Communities prosper.
Community Resilience: Agroforestry practices strengthen community resilience. They provide a buffer against economic and environmental shocks. Communities that embrace agroforestry are better equipped to handle crises (Ilham & Esa, 2018). They have food. They have resources. They have hope. It’s about survival. It’s about thriving against all odds.
The socio-economic benefits of urban agroforestry are profound. They go beyond the environment. They touch lives. They build stronger, more resilient communities. They offer a path to prosperity.
We have already discussed the numbers that would be required for regeneration resulting in Bioprecipitation in #74, link below …
Appropriate Plant Species for Urban Agroforestry
The selection of plant species is critical for the success of urban and peri-urban agroforestry systems. Not all plants are created equal. Some thrive in urban environments. Some offer unique benefits.
Trees: Choose trees that are resilient and beneficial. Populus spp. (poplars), Betula spp. (birches), Quercus spp. (oaks), Acacia nilotica, Dalbergia sissoo, and Mangifera indica (mango) are excellent choices. Each of these species brings something special. Poplars grow quickly. Birches are hardy. Oaks provide shade. Neem trees (Azadirachta indica) are exceptional for their cooling effects.
Shrubs: Shrubs like Hedera helix (English ivy), Juniperus spp. (junipers), Zizyphus mauritiana (jujube), and Gmelina arborea add diversity and resilience. They fill the spaces between trees. They provide additional layers of vegetation. They enhance biodiversity.
Ground Cover/Herbs: Ground covers and herbs are vital. They protect the soil. They retain moisture. Species like Phragmites australis
(common reed), Festuca spp. (fescues), and Vetiveria zizanioides (vetiver grass) are particularly effective. They cover the ground. They keep it cool. They prevent erosion.
Choosing the right mix of species ensures that urban agroforestry systems are robust and beneficial. It creates a multi-layered canopy. It maximizes ecological benefits & enhances the urban environment.
Meta-Analysis Insights
A meta-analysis by Torralba et al. (2016) of European agroforestry systems found that these systems significantly enhance biodiversity and ecosystem services compared to conventional monoculture systems. The study highlighted that structurally and functionally complex agroforestry systems provide higher levels of biodiversity and ecosystem goods and services without compromising productivity. These findings are supported by other studies indicating that agroforestry systems maximize ecotones and habitat heterogeneity, which are crucial for biodiversity enhancement (Jose, 2012; Moreno et al., 2018).
Conclusion
Urban and peri-urban agroforestry is a multifaceted strategy that can significantly enhance the resilience of cities to climate risks. By reducing urban heat islands, improving air quality, enhancing biodiversity, managing water resources, and providing socio-economic benefits, agroforestry practices offer a sustainable and holistic approach to urban resilience. Strategic implementation of these practices, supported by appropriate policies and community engagement, can transform urban landscapes into more livable and resilient environments.
References
Edmondson, J., Stott, I., Davies, Z. G., & Gaston, K. J. (2016). "Soil surface temperatures reveal moderation of the urban heat island effect by trees and shrubs." Scientific Reports, 6, Article 33708.
Zhou, W., McDonald, R., Biswas, T., Sachar, C., Housman, I. W., Boucher, T., Balk, D., Nowak, D., Spotswood, E., Stanley, C. K., & Leyk, S. (2019). "The tree cover and temperature disparity in US urbanized areas: Quantifying the association with income across 5,723 communities." PLoS ONE, 16, Article e0249715.
Zhao, J., Zhao, X., Wu, D., Meili, N., & Fatichi, S. (2023). "Satellite‐based evidence highlights a considerable increase of urban tree cooling benefits from 2000 to 2015." Global Change Biology, 29(10), 3085-3097.
Irmak, M., Yılmaz, S., Mutlu, E., & Yılmaz, H. (2018). "Assessment of the effects of different tree species on urban microclimate." Environmental Science and Pollution Research, 25, 15802-15822.
Sinha, P., Coville, R. C., Hirabayashi, S., Lim, B., Endreny, T., & Nowak, D. (2021). "Variation in estimates of heat-related mortality reduction due to tree cover in U.S. cities." Journal of Environmental Management, 301, Article 113751.
Baumgardner, D., Varela, S., Escobedo, F. J., Chacalo, A., & Ochoa, C. (2012). "The role of a peri-urban forest on air quality improvement in the Mexico City megalopolis." Environmental Pollution, 163, 174-183.
Massad, R.-S., Tuzet, A., & Loubet, B. (2018). "Urban vegetation and its effects on air pollution and the urban environment." In book: Urban Air Pollution – Monitoring and Control Strategies. IntechOpen.
Lal, R., Negassa, W., Lorenz, K., & Sahrawat, K. L. (2020). "Carbon sequestration in soil." Current Opinion in Environmental Sustainability, 15, 79-86.
Legesse, Y., & Negash, L. (2021). "Agroforestry and biodiversity conservation in Southern Ethiopia." Agriculture, Ecosystems & Environment, 308, Article 107244.
Garibaldi, L. A., Andersson, G. K. S., Requier, F., Fijen, T., Hipólito, J., Kleijn, D., & M'Gonigle, L. K. (2020). "Biodiversity and ecosystem services in urban ecosystems: A global review." Global Change Biology, 26(7), 3820-3831.
Dubbeling, M., Campbell, M. C., & Hoekstra, F. (2019). "The impact of urban and peri-urban agriculture on urban sustainability: A review of the evidence." Agriculture and Human Values, 36, 317-332.
Ilham, E., & Esa, N. (2018). "The role of agroforestry in building community resilience in rural areas of Indonesia." International Journal of Agricultural Sustainability, 16(2), 154-166.
For those interested in diving deep, here are some examples of successful urban agroforestry projects. These can be used as blueprints for large scale Urban and peri-urban agroforest projects.
Case Studies of Urban Agroforestry
Festival Beach Food Forest, Austin, Texas
The Festival Beach Food Forest is a prominent example of urban agroforestry in action. Located on public parkland, it was established to provide the community with a space for learning and cultivating their own food. The project is managed by a dedicated team of volunteers organized into circles focusing on different aspects such as planting, community engagement, and financial management. This sociocratic model empowers volunteers and ensures the effective management of the food forest. The forest provides educational opportunities through plant walks and workshops, enhances food security by offering supplemental food, and fosters community resilience by connecting people with nature. Challenges like vandalism and maintenance errors are mitigated by the strong volunteer network and community engagement strategies (Festival Beach Food Forest. (2022). ATTRA – Sustainable Agriculture. "Urban Agroforestry Case Study: Starting a Food Forest on Public Park Land").
Urban Agroforestry in Belo Horizonte, Brazil
In Belo Horizonte, the urban agroforestry initiative aims to transform degraded green areas into biodiverse and productive spaces. The project focuses on increasing plant biodiversity, protecting water resources, improving soil quality, and providing food security. It involves phases of accreditation, implementation, and maintenance, with community production units generating both biological and social benefits. This initiative has proven essential, especially during the pandemic, by promoting family farming and supplying produce to the city. Financial support and a structured implementation plan have been critical to its success (Urban Agroforestry in Belo Horizonte. (2021). Metropolis. "Urban Agroforestry").
Urban Food Forests in Kansas City, Missouri
Kansas City has integrated urban food forests into its landscape to promote food security and environmental health. These multifunctional woody polycultures include mixtures of nut and fruit trees, berry shrubs, and other crops. Designed to supply food and ecosystem services, these systems have been supported by research from institutions like the University of Missouri and USDA-ARS. The project emphasizes the need for urban agroforestry to complement annual food production systems by focusing on perennial woody plants that offer multiple benefits (Center for Agroforestry, 2023), (Urban Food Forests in Kansas City. (2023). Center for Agroforestry. "Urban Agroforestry")
We need large scale urban and peri-urban agroforestry projects and the above examples can help us scale them up.
Thank you for your time.