Assessing habitat area changes from large-scale nature-based solutions

One of the benefits of nature-based solutions (NBS) is providing environmental benefits, which regulate and maintain ecosystem services and foster positive impacts on ecosystems. Environmental benefits of NBS include enhancing water quality, habitat changes, improving biodiversity and carbon sequestration and storage. In this research, we developed a method to assess changes in habitat areas using remote sensing data.

Since mapping habitats is a harder task, our method is based on mapping and detecting changes in land cover over a region and translating that to changes in habitat area. We employed the CORINE Land Cover (CLC) classes and EUNIS habitat classes, two commonly used classification systems for land cover and habitat types, respectively. To assess the change in habitat type and area before and after implementing NBS, the CLC Level III classes were transformed into EUNIS Level I habitat types. The CLC datasets of 2000 and 2018 were used as the land covers before and after implementing an NBS. We applied the method in Aarhus, Denmark, in two study areas called Egå Engsø and Lystrup. An artificial lake and wetland that covers an area of 115 hectares was implemented in 2006 in Egå, surrounded by 35 hectares of grazed meadows. The NBS in Lystrup includes basins, gullies and rainbeds. The purposes of the NBS are to reduce the flood risk from the river Egå and isolated storms, reduce the nitrogen supply to Aarhus Bay and improve the natural conditions in the area.

Results showed the conversion of a cultivated habitat to an inland surface water habitat. A bogs, mires and fens habitat had also emerged west of the wetland. In the southwest of the wetland, an agricultural habitat had changed to a complex habitat, and the south of the region was surrounded by an artificially dominated habitat. Finally, a complex habitat had changed to a constructed habitat in the southeast of the wetland. On the other hand, habitat changes had not altered significantly in Lystrup despite the implementations of NBS projects. It is also possible that NBS-induced modifications could not be recorded by the method as the area was a complex habitat characterized by a heterogeneous blend of different habitats. One limitation of this method could be that it is difficult to delineate changes within complex habitats. Additionally, the limitation arises from the translation of the land cover classes to habitat classification. However, the research offers a method to quantify one of the environmental benefits NBS generate to encourage decision-makers to implement and scale them up further.