Urban trees contribution for mitigation of heat waves and air pollution: a first appraisal in Lisbon

18:00 Tuesday 28 May




Susana Dias (Portugal) 1; Marisa Graça (Portugal) 1; Ana Luisa Soares (Portugal) 1; Francisco Rego (Portugal) 1

1 - Centre for Applied Ecology Prof. Baeta Neves (CEABN-InBIO), School of Agriculture, University of Lisbon, Tapada da Ajuda, 1349-017 Lisbon, Portugal

From mere scenery elements on the urbanscape design to shade providers, trees always played a significant role in the quality of life in the cities. The value of urban trees / forests gained increasing attention in the last decades as several tools allow a more consistent and robust assessment and quantification of ecosystem services (ES) provided by these organic structures.

The quantification of benefits provided by urban forest is paramount in delineation and implementation of resilience action plans as it will assist in deciding what, where and when to install a green structure according to a specific objective. Two of the most important stress factors for urban resilience, given the climate scenarios for the Mediterranean, are heat waves and air quality.

A representative sample of the available information on Lisbon urban forest was used to quantify the potential of street trees in heat wave and air population mitigation. Particular attention was drown to areas previously identified as heat islands and with low wind circulation. Tree composition, condition, density and structure was evaluated in each study area. These data were then used to quantify ES with i-Tree ECO software package. This modelling tool enabled evaluating several parameters, namely: Hourly removal of pollutants (CO, NO2,SO2, particles of suspended matter PM2.5); Emission of volatile organic compounds by trees; Tree effect on energy consumption used in residential buildings and associated CO2 emissions. Species and tree distribution type in the area were ranked according to their contribution as ES providers.

Discussion of potential applications of this first appraisal addressed the evaluation the economic value of the ecological benefits provided by trees; establishment of priorities, optimization of the cost-benefit ratio of public investment in green spaces and a substantial improvement in the management of the urban arboreal structure.