How to choose the most relevant Nature-Based Solutions and to assess their performances? Insight from two projects implemented on the French territory.

Nature-based Solutions are presented as relevant features to make the cities more resilient in a context of global change. By providing ecosystem services, they are considered as particularly efficient solutions to mitigate urban heat islands and floods, while preserving biodiversity. Nevertheless, despite this consensus, it is still very difficult to quantitatively assess these services. Some methodologies and tools have therefore to be developed to better understand the thermo-hydric behavior of such infrastructure in relation with biodiversity, and to assess their performances across scales.

This presentation aims to present the work carried out to solve these issues through two current projects dedicated to NBS. On the one hand, the French ANR EVNATURB project aims to develop an operational platform to assess some of the eco-system services (ie stormwater management, cooling effect, or biodiversity conservation) provided by NBS at the district scale. On the other hand, the LIFE ARTISAN project deals with the creation of a framework to promote NBS for the implementation of the national plan for adaptation to climate change (PNACC) in France by improving scientific and technical knowledge. Both aim to develop and disseminate relevant tools for project leaders (for the design, sizing, implementation and evaluation of ecosystem performance).

The presentation of the results is particularly focused on monitored pilot sites and modelling platforms developed during these projects. In addition to these scientific investigations devoted to the thermo-hydric balance, some specific literature reviews and interviews were conducted to facilitate the choice of the more efficient species to implement, and the way to arrange NBS to optimize their performances. One of the results of this work is a dedicated database related to the a priori main ecosystem functions provided by plant species, and a list of quantitative indicators relevant for an urban project (certification, labelling, compliance with local regulations, ...) and that NBS can comply. Then this presentation concludes on remaining research gaps that have be to filled on this topic.