Riparian thermal conditions across a mixed rural and urban landscape

Chih-Wei Tsai,Thomas Young,Philip H Warren,Lorraine Maltby

doi:10.1016/j.apgeog.2017.07.009

Abstract

Riparian corridors have the potential to function as thermal refuges, moderating extremes of local temperature variation. However, although demonstrated at individual sites, and over short periods, the consistency of this effect at wider temporal and spatial scales is poorly understood. The aim of this study is to assess the temperature differences between riparian corridors and adjacent non-riparian habitats and to explore the influence of environmental characteristics on these differences. Air temperature was monitored hourly at 20 paired locations (riparian and non-riparian) for two consecutive years. Urban index and canopy cover were characterised by calculating the percentage of impervious surface area and tree canopy cover within a 100 m radius from the centre of each sampling site. Canopy cover reduced summer thermal stresses in both urban and rural areas whereas high urban index tended to increase the daily thermal indices. Rivers had a significant mitigating effect on the urban riparian thermal condition, particularly in extreme hot weather. Riparian corridors were generally 1 °C cooler than non-riparian locations in summer and could be up to 3 °C cooler at some sites in extreme hot weather. Furthermore, riparian corridors at some sites were warmer than non-riparian locations in winter. These findings suggest that the proximity of rivers can modify riparian thermal environments, potentially reducing the heat stress of riparian corridors across landscapes.

Highlights

An increase in global mean surface temperature of between 1.7 and 4.8 C has been predicted by the end of the 21st century (IPCC, 2014), and thermal stresses associated with local urban heat islands are likely to exacerbate such effects in urban environments (Gago, Roldan, Pacheco-Torres, & Ordon~ez, 2013)
Temperature changes have the potential to alter ecosystem functions at landscape scales, including reducing the ability of ecosystem to alleviate the impacts of extreme climatic events, and affecting biogeochemical cycle (Arnfield, 2003; Gago et al, 2013; Kaye, Groffman, Grimm, Baker, & Pouyat, 2006; Pataki et al, 2011; Trammell, Tripler, Carper, & Carreiro, 2017)
In addition to changing the structure and functioning of ecosystems, an alteration of urban thermal regime can greatly influence the health and thermal comfort of humans (Oleson et al, 2013). In response to this threat, attention is increasingly being focused on developing long-term sustainable ways of ameliorating these changes in the urban thermal environment (Gober et al, 2009)

Summary

Introduction

An increase in global mean surface temperature of between 1.7 and 4.8 C has been predicted by the end of the 21st century (IPCC, 2014), and thermal stresses associated with local urban heat islands are likely to exacerbate such effects in urban environments (Gago, Roldan, Pacheco-Torres, & Ordon~ez, 2013). In addition to changing the structure and functioning of ecosystems, an alteration of urban thermal regime can greatly influence the health and thermal comfort of humans (Oleson et al, 2013). In response to this threat, attention is increasingly being focused on developing long-term sustainable ways of ameliorating these changes in the urban thermal environment (Gober et al, 2009).

Objectives

Methods

Results