An Initial Study and Application of Basic Plant Characteristics That Aid in the Reduction of High Urban Temperatures

Abstract

Urban heat is an ongoing phenomenon that affects everyone living in urban environments. Unhealthy living conditions have been produced as a result of high temperatures in urbanized areas. There are many studies on this and the ways in which to mitigate these high temperatures. Botanical controls have often been used as mitigation measures, using vegetation as a means to bring down urban heat, however little study has been done on what actually comprise the characteristics of plants that help bring down high temperatures. This study stresses that plants should not just be analyzed at a superficial level but rather, analysis of plants and their capabilities should go much deeper, looking at anatomical/physiological characteristics for their proper application in controlling excessive heat in urban environments.

The objectives of the study is to understand what causes high urban temperatures and the botanical mechanisms that effect reduction in temperatures with prime focus on evapo-transpiration. The study is also an attempt to quantify a highly subjective (qualitative) component of Landscape Architecture of which are planting materials and planting design. These botanical mechanisms are applied in a method that can portray quantifiable reduction in high temperatures given by plants. The method gives an idea and an estimate on the cooling afforded by plants for given heat loads.

To answer these objectives, a method was developed for ascertaining temperature reduction extents of plants by applying existing standard conversion factors for temperature, heat/energy, transpiration, heat load and cooling capacity. The output of this method is an estimate only, largely due to the limitations in data for actual urban environmental conditions and lack of equipment in the measurement of botanical characteristics. From the methodology employed, the study was able to come up with general values that equate cooling given by plants with specific characteristics and that can be used in their proper siting in urban locations. The methodology results in a planting framework that dictates the correct use of plant species with measured cooling potential for the control of high urban temperatures. This would thus be a significant contribution to planting design.

The study impacts several entities as these have an effect on the total cooling potential given by plants and the total cooling of the urban environment. Firstly Landscape Architects and planting design, secondly Architects and the design of structures and thirdly Urban Planning and Design with the locations of buildings and structures. The study will also impact nursery as well as maintenance practices.