Green Roofing with Native Species

Green roofing with native species: alternative urban landscape areas to enhance water use and sustainability in Mediterranean conditions

1) Agronomy Institute, University of Lisbon (Coordinator)
2) Faculty of Sciences University of Lisbon
3) Mediterranean Garden Society (MGS) – NGO
4) Neoturf – Construções e Manutenção de Espaços Verdes, Lda – Company

Consultants: Dr Benz Kotzen from University of Greenwich and Celestina Maria Gago Pedras from Universidade do Algarve

Urban landscapes are generally characterised by the use of exotic plant species, and this is the case for central and south Portugal. However, exotic species have negative impacts regarding biodiversity. For example, exotic introduced species can become invasive and some of the worst invasives were introduced as ornamentals e.g. Pittosporum undulatum well as several species of the genus Acacia. A rational and more sustainable alternative to this trend is the use of native species. In Mediterranean conditions, native species are adapted to drought and high temperatures, as they endure hot, dry summers. Thus, they are a key group of species to work with when low water use is intended.

The main objectives of the project are:

1. To study green roofs as alternative urban landscapes, regarding low water requirements and the use of native species, in order to:
i) save water,
ii) take advantage of environmental adaptations of native species, namely to drought conditions, to create landscape areas that maintain ecological, functional, aesthetic and recreation value,
iii) avoid the introduction of invasive species,
iv) and promote biodiversity and wildlife refuges in urban areas.

2. To quantify the water requirements of landscape species/areas by:
i) quantifying the water requirements of a set of chosen native species using gravimetric measurements of potted plants, in relation with irrigation levels and ornamental value,
ii) and quantifying the water requirements of green roofs with native plants, by the use of soil water balance.

3. To simulate the water requirements of green roofs, regarding irrigation scheduling, by using a model formerly adapted to agricultural applications, extending it to landscape areas.

4. To test the possibility of using Biocrusts in green roofs based on the use of mosses without additional water and comparing the performance of these organisms with the average/expected advantages of a green roof, namely the capacity to retain water and reduce roof temperatures.

5. To test the hydrological performance of the green roofs and the capacity to replace ecosystem functions.