# Evaluating Microclimate Modification and Acute Cardiovascular Stress Responses to a Dense Urban Microforest: The Green Oasis (GRO) Protocol

## TL;DR

This study evaluates how a dense urban microforest affects cardiovascular stress and microclimate in cities, aiming to inform urban planning and public health strategies.

## Contribution

The GRO protocol introduces a comprehensive framework to assess the impact of small-scale urban greening on microclimates and cardiovascular resilience.

## Key findings

- The GRO project transformed a small urban lot into a microforest to study its environmental and health impacts.
- The study measures cardiovascular stress responses and environmental conditions to evaluate the effectiveness of urban greening.
- Baseline and post-planting assessments are being conducted to inform urban planning and climate adaptation policies.

## Abstract

Public health relevance—How does this work relate to a public health issue?
Green space exposure provides extensive benefits for physiological and mental health that will become more important as global temperatures rise and populations continue to urbanize.Small-scale, targeted greening interventions and their influence on temperature-induced cardiovascular stress are not well understood.

Green space exposure provides extensive benefits for physiological and mental health that will become more important as global temperatures rise and populations continue to urbanize.

Small-scale, targeted greening interventions and their influence on temperature-induced cardiovascular stress are not well understood.

Public health significance—Why is this work of significance to public health?
This protocol focuses on the development of a comprehensive framework to assess the impact of targeted greening on urban microclimates, ecological function, and cardiovascular resilience.Highlights the work needed to understand how small green spaces can impact users and the surrounding urban form.

This protocol focuses on the development of a comprehensive framework to assess the impact of targeted greening on urban microclimates, ecological function, and cardiovascular resilience.

Highlights the work needed to understand how small green spaces can impact users and the surrounding urban form.

Public health implications—What are the key implications for practitioners, policy makers, and/or researchers?
Final results will provide insight into the effectiveness of greening interventions on small, underutilized urban lots, which are common in American downtowns.Policymakers can utilize this framework to analyze outcomes related to different green spaces in similar urban environments.

Final results will provide insight into the effectiveness of greening interventions on small, underutilized urban lots, which are common in American downtowns.

Policymakers can utilize this framework to analyze outcomes related to different green spaces in similar urban environments.

The Green Oasis (GRO) Project is a targeted urban greening intervention designed to evaluate the environmental and health impacts of compact, high-density plantings in dense built environments. Initiated in downtown Louisville, the project transformed Founders Square, a 0.64-acre sparsely planted park, into a microforest (“Trager Microforest”), a multilayered planting of 119 trees and more than 200 shrubs. The impact of this intervention is being assessed through a randomized crossover study in which participants walk in the microforest and a nearby impervious parking lot. Physiological outcomes include heart rate, heart rate variability, arterial stiffness, and stress biomarkers measured in saliva, urine, and sweat. Environmental conditions are continuously monitored by fixed and mobile weather stations, air pollution sensors, and biodiversity surveys. Baseline assessments were conducted in 2023 and 2024, with post-planting evaluations now underway (2025–). Power calculations indicate adequate sensitivity (n ≈ 40–50) to detect changes in cardiovascular stress responses in participants. Complementary ecological measurements include soil microbiome composition, greenhouse gas fluxes, and avian diversity. This study addresses critical gaps in understanding how small-scale, high-density greening interventions affect cardiovascular resilience, stress physiology, and microclimatic regulation. By integrating environmental, biological, and human health data, GRO establishes a comprehensive framework for evaluating the efficacy of urban microforests as nature-based solutions. The results are expected to inform urban planning, public health strategies, and climate adaptation policies, demonstrating how compact greening interventions can simultaneously mitigate heat, reduce pollution, enhance biodiversity, and promote human wellbeing in dense urban cores.