26 November 2025 | 5 min.
Biodiversity and ecosystems are essential for a healthy and sustainable living environment for people, but due to urbanisation and construction, nature is under pressure. Loss of biodiversity affects the climate, water management and quality of life. It is clear that the built environment has an impact on nature, and the real estate sector can play a crucial role in strengthening biodiversity.This is why a.s.r. real assets and Sweco are now joining forces.Together, they are developing a method to preserve and restore nature in and around existing real estate. Insight is the key to better connecting nature and buildings.
According to Gerben Sinke, Sustainability Manager at a.s.r. real estate, the aim of the project is not only to gain insight into the share of vegetated surface within the property portfolio, but also to analyse a building’s potential for adding new green areas and nesting opportunities for birds and other species. “In this way, a method emerges with which we can map buildings—also known as ‘green flagging’—to identify where we can have a positive impact on preserving and restoring nature. We will use the results to develop a nature‑positive strategy for our real estate portfolio. With this strategy, we aim to ensure that by operating existing real estate, we contribute positively to nature. Because we apply this across the board, I also see it as a generic solution that may serve as inspiration for other parties in the sector.”
The project started at the end of 2024 and consists of three phases: a baseline assessment, quantifying the green potential in the portfolio, and identifying ecological green features that contribute to the preservation and improvement of local biodiversity. “We have now completed the first two phases. The third phase still needs to be worked out,” says Jart Ligterink, Geodata and Climate Adaptation Consultant at Sweco, one of Europe’s leading engineering and architectural consultancies.
“This approach is quite unique for us as well. We have previously mapped green coverage for other projects. For example, for the Green City Challenge, where together with various partners we mapped ‘meaningless paving’, such as wide pavements and paved squares, to identify opportunities for greening. We carried this out for about one‑third of all municipalities in the Netherlands. But mapping the green potential of existing real estate for an investor, and at this scale, is also fairly new to us. Normally we develop such insights for municipalities or other public bodies.”
Jart continues: “During the baseline assessment, we mapped the existing vegetation in the entire a.s.r. real estate portfolio in the Netherlands using GIS tools. For those who may not know: GIS stands for Geographic Information System. We used the NDVI, the Normalized Difference Vegetation Index. This index indicates the level of greenery and is calculated using satellite and infrared images. The formula assesses all vegetation at ground level, roof surfaces, façade surfaces and nearby trees, and divides this by the building’s total footprint. This results in a green value that shows the type and quantity of vegetation present.”
After the baseline assessment, the next step was to quantify the green potential within the real estate portfolio. Gerben: “Ultimately, we want to know where we may be able to invest in more greenery within our existing portfolio. We calculated the green potential by analysing the amount of unused surface area per building for the ground level, roof surfaces and façades. To be clear: the ground level refers to the plot surface, including paving, where no buildings or other structures are located. We looked at whether paving on the ground level could be replaced with green areas and whether there was potential for planting trees. We also examined where green could be added to roofs and façades, such as through native green roofs. Altogether, this phase gave us insight into which buildings are promising for adding green features as well as nesting opportunities.”
The third phase has now begun: identifying green features that contribute to preserving and enhancing local biodiversity and ecosystems, including an analysis of nearby vulnerable nature areas. Jart: “By looking at, among other things, Natura 2000 areas and National Parks, we want our measures to align with the local natural system. This helps us understand which measures are most effective.” Gerben: “Property owners can use an action list, which can be linked to different types of real estate and locations, to take accessible measures that will always positively contribute to existing assets — with respect for the local natural system. It is also worth mentioning that for large‑scale renovations, it is essential to work with a specialist to develop a comprehensive plan to optimally restore and improve local biodiversity. Even for assets where no renovations are planned, there is a lot to gain for nature through small‑scale interventions, which become visible thanks to smart use of available data.”
Gerben continues: “Once this phase is completed, we will discuss the results and further validate them within our organisation. We also aim to share the knowledge gained in the various working groups we participate in. I see great potential in this methodology. It benefits a.s.r. itself, our tenants, investors and the wider environment.” Jart: “The method offers plenty of opportunities for the sector.” “Absolutely,” says Gerben. “We see that more and more investors are paying attention to the world of tomorrow, where thinking and acting green is becoming the guiding principle.”
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a.s.r. real estate is manager of investment institutions and listed in AFM’s register.
