Impact of Ethnobotanical Water-Pedestal Plants on Urban Heat Island Mitigation and Biodiversity in Green Roof Systems

Project Abstract

This study investigates the performance of ethnobotanical water-pedestal plants in mitigating urban heat island (UHI) effects and enhancing biodiversity within green roof systems. The research integrates ethnobotanical knowledge with urban ecophysiology to identify plant species traditionally used for water management and temperature regulation that exhibit drought tolerance, high transpiration rates, and robust root systems suitable for shallow substrates. A mixed-methods approach combines field experiments, controlled environmental simulations, and community-led knowledge validation to evaluate thermal dynamics, evapotranspiration rates, soil moisture retention, and pollinator support across multiple green roof plots in a tropical-subtropical urban setting. Primary data were collected over two growing seasons, including surface and substrate temperatures, albedo changes, rainfall interception, humidity microclimates, and net energy balance of buildings hosting the green roofs. Secondary data include historical temperature records, urban canopy adjustments, and ethnobotanical databases to contextualize species selection and cultural relevance. The experimental design employs randomized complete block trials with three replication levels for a suite of ethnobotanical water-pedestal species and a control group of conventional green roof flora. Thermal performance was quantified using infrared thermography, heat flux sensors, and temperature loggers positioned at canopy, substrate, and roof-lattice interfaces. Hydrological performance focused on plant-available water, substrate moisture retention via gravimetric analysis, and drainage efficiency. Biodiversity outcomes assessed pollinator visitation rates, insect diversity indices, and bird and lizard incidental fauna presence, complemented by soil microbiome profiling through 16S rRNA and ITS sequencing to detect rhizosphere community shifts. The results indicate that selected ethnobotanical water-pedestal species demonstrate significantly higher evapotranspiration and lower peak roof temperatures relative to controls, contributing to reduced UHI intensity at the neighborhood scale when deployed across multiple rooftops. Substrate moisture retention improved microhabitat stability, supporting resilient plant communities during heatwaves and drought episodes. Biodiversity metrics showed enhanced pollinator activity and a richer invertebrate assemblage in plots containing ethnobotanical species, with affirmative signals of improved soil microbial diversity linked to root exudates and increased organic matter turnover. The ecological benefits were moderated by substrate depth, irrigation regime, and roof orientation, revealing a need for optimized design guidelines that harmonize water management with structural constraints. Ethnobotanical knowledge proved crucial for selecting culturally significant, locally adapted taxa that maximize ecological service provision while maintaining aesthetic and social value for building occupants. The study contributes to urban ecology and green infrastructure literature by providing evidence-based recommendations for integrating ethnobotanical water-pedestal plants into green roof design to achieve synergistic gains in thermal regulation and biodiversity. Limitations include site-specific climate variability, scale effects, and long-term maintenance considerations, which warrant multi-city trials and longitudinal monitoring to generalize the findings.

Project Overview

What This Project Is About

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A plain-language overview of how certain water-loving plants used in ethnobotany can help cool cities and support local biodiversity when grown on green roofs. The project examines how these plants influence environmental factors such as temperature, moisture, and habitat for insects and birds, and how traditional knowledge about plant use connects to practical roof garden design.

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The Problem It Addresses

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Urban areas trap heat, making cities hotter and requiring more energy for cooling. Many green roof studies focus on generic plants, but less is known about ethnobotanical species that people have historically used and that may thrive in roof conditions. This project fills gaps in how these plants perform on roofs and their role in urban ecosystems.

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Objectives of the Project

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1. Identify ethnobotanical water-pedestal plants suitable for green roofs.
2. Assess their cooling effect and water-use efficiency on rooftops.
3. Evaluate changes in biodiversity, especially pollinators and beneficial insects.
4. Compare performance with common non-ethnobotanical roof plants.

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What You Will Do Step by Step

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1) Review literature on ethnobotany, rooftop ecology, and urban heat island effects.

2) Select a set of water-pedestal plant species for trial plots on a roof.

3) Monitor temperature, humidity, and plant health over time.

4) Survey insect activity and bird presence to gauge biodiversity.

5) Analyze data to compare with control plant groups.

6) Discuss practical design tips and potential limitations.

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Expected Outcome

Anticipated findings include improved roof cooling, efficient water use, and increased urban biodiversity when using ethnobotanical water-pedestal plants. The project should provide actionable guidance for designers and city planners on selecting species for climate-resilient, biodiverse green roofs.