Integrating a landscape connectivity approach into mitigation hierarchy planning by anticipating urban dynamics

Abstract

Urbanization leads to land-use changes and landscape fragmentation, impacting natural habitats and their connectivity. In principle, many local decision-makers are obliged to adopt a mitigation hierarchy whereby development projects must be designed to avoid impacts on biodiversity, reduce, and ultimately compensate for the remaining impacts to reach the goal of no net loss (NNL) of biodiversity. In practice, however, both developers and regulators lack relevant practical tools to support their strategies to better anticipate and plan this mitigation hierarchy. More importantly, the available tools generally ignore connectivity issues and ecological constraints. Here, we propose an original methodology that anticipates future urban needs under different development scenarios and selects the most relevant strategies for biodiversity offsets (BO). We used a spatialized digital simulator (called SimUrba) to model fine-scale urban dynamics, combining it with ecological networks modelling based on graph theory to assess the environmental impacts of urbanization on a habitat connectivity index for focal species. We test the different outcomes produced by adopting two offset ratios (1:1 and 2:1) using this approach. The methodology is applied to empirical data on the future urban sprawl of a large French city up to 2040 under two realistic development scenarios currently discussed by policy-makers, and on 20 species that we grouped by type of habitat. Our results reveal that that the most highly impacted species are those associated with open and semi-open areas, and cultivated plots. Then, we identify the most promising cells for BO implementation to compensate for negative effects on habitat area, according to gains in habitat connectivity. We further show that using both private and public land can maximize habitat connectivity by including larger plots and reducing the number of plots needing long-term monitoring. Finally, we demonstrate that using standard offset ratios that ignore connectivity issues is very risky and can compromise any BO objective. Overall, we show that this framework provides decision-makers with a valuable and precise strategic tool that articulates land-use planning with ecological constraints to identify whether, how and where NNL objectives can be achieved.

Smart Sustainable Cities of the New Millennium: Towards Design for Nature

“…In fact, the proposed method was rational and reproducible thanks to the traceability of the data sources and the deterministic choices. For example, the novelty of working with superimposed layers is used to produce landscape suitability maps using modern geographic information systems (GIS) technologies for geodesign purposes [15,16], environmental analysis [17][18][19] and past and recent modelling [20][21][22][23].…”

Modeling Alternative Approaches to the Biodiversity Offsetting of Urban Expansion in the Grenoble Area (France): What Is the Role of Spatial Scales in ‘No Net Loss’ of Wetland Area and Function?

“…This could be rewarded in an improved version of the modeling with a bonus added if a polygon contributes to restoring an ecological corridor or if contiguous selected polygons create a path throughout an identified ecological corridor (as illustrated in Figure 7). The potential contribution of offsets to the restoration of landscape-scale ecological processes has been highlighted recently [41,54,64].…”

“…Calvet et al [40] and Bigard et al [14] showcased the potential for landscape-level and SEA approaches to offsetting in Montpellier, implying the need to go beyond a case-by-case permittee-led compensation approach. A similar approach was applied to the city of Toulouse by Tarabon et al [41]. In Lyon, Tarabon et al [42] also showed that offsetting could be used to generate an overall increase in interconnected habitats and thus to increase landscape-level carrying capacity.…”

Pooling biodiversity offsets to improve habitat connectivity and species conservation

“…In the light of recurrent failures in biodiversity offsetting implementation (see Bezombes et al, 2019;May et al, 2017;Weissgerber et al, 2019), there is growing evidence of the benefits of including landscape connectivity into the mitigation hierarchy (Dalang and Hersperger, 2012;Tarabon et al, 2019bTarabon et al, , 2020. A territorial-scale conservation strategy seems to further increase these benefits.…”

“…However, despite recent studies which have used spatial prioritization to demonstrate the value of locating biodiversity offsets in different parts of the landscape (e.g., McKenney and Kiesecker, 2010;Moilanen, 2013) and others which have focused on incorporating connectivity (e. g., Tambosi et al, 2014), the territorial organization of biodiversity offsetting and the benefits generated by their localization and pooling are poorly considered in studies, whatever the form chosen by land developers (Scolozzi and Geneletti, 2012). Yet, organizing and pooling offsets are key to improving and reaping biodiversity offsets benefits (Bigard et al, 2020;Tarabon et al, 2020), particularly in agricultural and suburban areas where the pressure of urbanization is relatively strong and where the landscape usually suffers from fragmentation (Haverland and Veech, 2017).…”