Project

The ecology of green roofs

Green roofs are roofs with a layer of soil and planted vegetation. To investigate how an ecosystem can form in these isolated habitats, we collect data on the insects, plants and soil biota of green roofs. Over time - through process of succession and natural selection - a specific roof-community is expected to form, adapted to the conditions of the roof.

Green roofs are a novel technology to mitigate many of our urbanization problems; like the Urban Heat Island effect, flooding and biodiversity loss. The biodiversity gain that green roofs could facilitate needs to be investigated properly. The species that green roofs harbor and the complicated interactions between species that take place need to be mapped and understood in order to improve the quality of the biodiversity of green roofs.

In this project we specifically look at how insect, plant and soil communities develop over time on eight vegetated roofs in Amsterdam. By conducting t-0 measurements – collecting data just after construction of the roof – and monitoring these roofs over the course of three years, we will investigate how the roof communities develop. We expect that the networks (relations) between species will become more connected over time, which we will test using a network analysis approach. Collected specimens are identified to species level which will give information on their ecology, revealing their relationship with the roof habitat.

Figure 1. Classification of the different roof types used in literature and based on substrate depth, vegetation structure and functionality. Information about weight requirements and water retention capacities were taken from green roof company Optigrün (optigrun.nl), Factsheet Blue-green roofs (GreenDeal, 2018) and through field measurements and interviews with several Dutch green roof companies (ZinCo, VanGinkel Groep, Rooftop Revolutions and De Dakdokters). The functionality and vegetation cover are the most important determinants for categorization. Factors like maintenance, substrate depth, water retention capacities and weight can vary, but provide guidelines in this box.
Figure 1. Classification of the different roof types used in literature and based on substrate depth, vegetation structure and functionality. Information about weight requirements and water retention capacities were taken from green roof company Optigrün (optigrun.nl), Factsheet Blue-green roofs (GreenDeal, 2018) and through field measurements and interviews with several Dutch green roof companies (ZinCo, VanGinkel Groep, Rooftop Revolutions and De Dakdokters). The functionality and vegetation cover are the most important determinants for categorization. Factors like maintenance, substrate depth, water retention capacities and weight can vary, but provide guidelines in this box.
Figure 2. Hypothesis on how landscape characteristics and green roof characteristics influence ecosystem development on green roofs in the light of stochastic and deterministic processes. Circles in green (plants), brown (soil fauna), red (ground-dwelling arthropods) and yellow (insects) represent individual species groups, each line representing the network/interaction between them. The size of the circle represents the number of individuals, while the thickness of the lines represent the number of interactions found between each species group. Thickness of the arrows show the importance of each factor. The landscape and green roof characteristics are depicted above. Over time networks between species become tighter (see also next section), causing the landscape and green roof characteristics to have less of an impact. Image created with BioRender.com.
Figure 2. Hypothesis on how landscape characteristics and green roof characteristics influence ecosystem development on green roofs in the light of stochastic and deterministic processes. Circles in green (plants), brown (soil fauna), red (ground-dwelling arthropods) and yellow (insects) represent individual species groups, each line representing the network/interaction between them. The size of the circle represents the number of individuals, while the thickness of the lines represent the number of interactions found between each species group. Thickness of the arrows show the importance of each factor. The landscape and green roof characteristics are depicted above. Over time networks between species become tighter (see also next section), causing the landscape and green roof characteristics to have less of an impact. Image created with BioRender.com.