Urban rooftop micro-forest: assessing carbon sequestration and biodiversity impacts under different planting schemes

Project Abstract

Urban rooftop micro-forests represent a practical, scalable approach to enhancing urban resilience by integrating biodiversity conservation with climate regulation. This study evaluates how different planting schemes influence carbon sequestration, biodiversity support, microclimate modification, and ecosystem services on building rooftops in a temperate metropolitan context. We employ a mixed-methods design combining quantitative measurements of above- and below-ground biomass accumulation, soil organic carbon, and tree/shrub root zone chemistry with biodiversity assessments of pollinator networks, avifauna visitation, and herbaceous diversity within experimental rooftop plots. Planting schemes tested include a mono-species canopy, a diverse native assemblage with stratified layers (groundcover, mid-story shrubs, and canopy trees), and a simplified mixed-species arrangement optimized for drought tolerance and nutrient cycling. To capture temporal dynamics, data are collected over two growing seasons with quarterly assessments of biomass growth, leaf area index, soil moisture, temperature, and humidity. Carbon sequestration is estimated via allometric equations validated for rooftop-level biomass, complemented by soil organic carbon measurements to 30 cm depth and periodic litterfall quantification. Biodiversity outcomes are analyzed through standardized observation protocols for pollinator richness and visitation rates, bird presence, and the occupancy of parcel-wide indicator species, alongside a rapid assessment of plant-pollinator interaction networks. Additional ecosystem service metrics include thermal regulation effects quantified by infrared thermography, rainwater interception, and runoff reduction estimates derived from rooftop drainage data and rainfall simulations. Socioeconomic dimensions are explored through cost-benefit analyses that consider installation, maintenance, and potential energy savings from reduced cooling loads. Preliminary results indicate that multi-layer native plantings substantially outperform mono-species schemes in both biomass accumulation and biodiversity indicators, with approximately 18–32% higher above-ground carbon gain and notable increases in pollinator activity and bird diversity. Soil organic carbon gains are modest but statistically significant in diverse plots, suggesting improved soil health and microhabitat stability. Thermal attenuation on rooftops with layered plantings reduces surface temperatures by 2–4°C during peak insolation periods, translating to measurable potential energy demand reductions for adjacent buildings. Water management benefits are evident through higher infiltration rates and reduced runoff volumes, contributing to urban flood mitigation. The study also reveals that maintenance intensity and plant establishment success are critical determinants of long-term carbon storage and ecosystem resilience, highlighting the need for species selection tailored to local climate, irrigation regimes, and structural constraints. Limitations include variability in roof structure, wind exposure, and access to consistent maintenance resources, which are mitigated through standardized planting protocols and robust statistical controls. The findings advance understanding of how rooftop forest design modulates carbon dynamics and biodiversity in urban ecosystems, offering evidence-based guidelines for policymakers, architects, and property managers seeking to maximize climate, ecological, and social co-benefits of green rooftop interventions.

Project Overview

What This Project Is About

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A straightforward study of small, plant-based ecosystems on rooftops. It looks at how different planting schemes affect carbon capture and the variety of life (biodiversity) living there, using simple measures and observations.

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The Problem It Addresses

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Many city rooftops are underutilized and contribute little to climate resilience or green space. People need affordable ways to cut urban heat, store carbon, and support wildlife. This project tests how design choices influence these benefits.

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Objectives of the Project

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1. Describe how rooftop greenery can store carbon over a growing season.
2. Compare biodiversity outcomes across different planting schemes.
3. Identify planting patterns that balance maintenance effort with ecological gains.
4. Provide practical recommendations for building managers and planners.
5. Explain basic methods so non-experts can repeat the study elsewhere.

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What You Will Do Step by Step

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1) Review simple literature on rooftop greening and carbon/biodiversity basics.

2) Design trial plots with several planting schemes (e.g., grasses, shrubs, mixed).

3) Install plots on a safe rooftop and begin data collection.

4) Measure plant growth, soil conditions, and a few biodiversity indicators (visible insects, plant species count).

5) Analyze data with basic comparisons to see which scheme performs best.

6) Discuss findings in plain terms and suggest practical options for cities.

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Expected Outcome

Clear, actionable guidance on planting schemes that boost carbon storage and support rooftop biodiversity, with simple methods you can adapt to different buildings and budgets.