Urban Microforests in Los Angeles: Biodiversity, Carbon Capture, and Community Science

In this episode of Short Wave, Emily Kwong introduces a microforest in Ascot Hills Park, northeast of downtown Los Angeles. The forest is a quarter-acre of densely planted, drought-tolerant native species designed to mimic a natural forest in an urban setting. Damien Willette, an associate professor of biology, and Catherine Pooni, a horticulturist, explain how the microforest is established and studied to understand local biodiversity and resilience to climate change. A nearby control plot of the same size remains weed-dominated to provide a baseline for comparison.

• Microforests are small but multilayered ecosystems designed to resemble natural forests within cities.
• The LA site measures about 10,000 square feet, with the largest microforest in California, and a side-by-side weed-filled plot as a control.
• Researchers map every plant with GPS, use drones to monitor growth, collect data from spider webs as DNA filters, and engage the public through a QR code app to document plant height, flowering, and signs of herbivory.
• Early results show high survivorship, weed suppression, and notable biodiversity, alongside a measurable carbon sequestration impact and neighborhood cooling benefits.

Key takeaways include the role of multi-layer planting in rapid ecosystem development, the value of citizen science in environmental monitoring, and the potential for urban green spaces to bolster biodiversity and climate resilience.

Overview and context

The podcast follows a field trip to Ascot Hills Park in northeast Los Angeles to examine microforests, small urban forests designed to emulate natural forests. The researchers behind the LA project, Damien Willette and Catherine Pooni, describe a systematic approach to creating a multi-layered ecosystem that can support biodiversity and help cities adapt to climate change. The microforest studied here spans about 10,000 square feet, roughly a quarter of an acre, and is paired with an adjacent plot of identical size that is intentionally left to weeds as a control. This setup lets scientists compare biodiversity outcomes and weed suppression in the two conditions over time.

Design and planting strategy

The core idea behind microforests traces back to Dr Akira Miyawaki of Japan, who proposed a dense planting approach to accelerate forest formation on degraded land. In practice, the LA project implements dense layers of plants with varied heights and roles, from fast-growing shrubs to canopy trees, creating a structured ecosystem that resembles a natural forest. The aim is not to plant a single species but to assemble a functioning ecosystem that supports soil health, carbon storage, and habitat for insects, birds, and other wildlife. The researchers emphasize that rapid maturation is possible when multiple species fill different ecological niches at once, rather than waiting for a classical forest to develop slowly through succession.

Fieldwork and measurements

The team’s fieldwork combines traditional ecological monitoring with modern tools and community involvement. Every two weeks, Damien and Catherine trek between the microforest and the weed-dominated control plot to inventory insects, birds, lizards, field mice, and other organisms. Plant health is tracked by GPS tagging each plant, while drones measure plant growth and biomass. A particularly innovative data source comes from spider webs woven through the microforest; researchers use these webs as air filters that collect DNA from passing animals. By extracting DNA from the webs, they can identify nocturnal or cryptic species that are hard to observe during daytime walks. In addition, a park-app developed by the researchers allows visitors to scan QR codes attached to plants and submit observations on growth, flowering, herbivory, and vitality, expanding the data collection through citizen science.

Key findings so far

The microforest demonstrates robust early performance. Plant survivorship between year one and year two averages over 89%, indicating strong establishment. Weeds are substantially suppressed in the microforest relative to the control plot, with an estimated 80% reduction in weed presence in the planted space since year one. Biodiversity appears to be higher in the microforest than in the weed plot, with researchers documenting roughly 100 animal species in the microforest to date, versus a lower baseline expectation for the park. The use of GPS to map every plant and the application of drones to quantify growth provide a precise picture of how a multi-layered planting matures over time.

Carbon sequestration is a central metric for the project. The microforest is estimated to remove about one metric ton of carbon per year at present, with projections that this figure could rise to more than 50 metric tons of CO2 per year within the next two decades. If realized, this rate would rival the emissions reductions achieved by several hundred gasoline-powered vehicles per year. Beyond carbon, the microforest contributes to cooler neighborhood temperatures, improved soil health, and increased biodiversity, which in turn supports ecosystem services such as pollination and pest control. The researchers also highlight the social dimension: the microforest attracts curious passersby and invites them to engage with native plants and ecological restoration in a city context.

Public participation and broader impact

Public engagement is a key feature of the project. The park app has facilitated data contribution from more than a hundred and fifty community participants who scanned plant QR codes to help measure growth. This participatory science approach not only broadens the data set but also raises awareness about biodiversity in urban areas. The field trip also emphasizes the practical contrast between a designed ecosystem and an unmanaged weed plot, illustrating the potential for microforests to serve as experimental platforms where researchers can study ecological processes in real time and in human-shaped environments.

Origins, implications, and future directions

The LA microforest serves as a test bed for urban ecology and climate adaptation. By combining layered plantings with modern monitoring techniques and citizen science, the project offers a model for how cities can foster biodiversity while also delivering tangible environmental benefits. The researchers acknowledge that microforests are not a substitute for large-scale forest restoration, but they illustrate how small, well-designed green spaces can contribute to biodiversity resilience, soil health, carbon sequestration, and community engagement. As urban areas continue to expand and drought conditions persist in Southern California, microforests represent a pragmatic strategy for integrating nature into the urban fabric and for studying ecological dynamics in a manageable, scalable way.

Conclusion

Through the LA microforest experiment, the podcast highlights how urban ecological design, precise measurement, and public involvement collectively advance our understanding of biodiversity under climate stress. The fieldwork underscores the value of observing ecosystem outcomes across a small but ecologically rich footprint and points toward a future where urban green spaces play a more pronounced role in biodiversity and climate resilience.