The aim of using a biodiversity indicator in LCA is to assess how biodiversity is impacted by a certain product along its supply chain. However, biodiversity is a multi-dimensional concept, and it has been recently argued that at least two complementary aspects must be taken into consideration when characterizing the impact on biodiversity (Purvis 2020). The first is ecosystem multifunctionality, i.e., the functioning of multiple ecosystem processes which are underpinned by local biodiversity, such as species with high local biomass or abundance (Grime 1998). Maintaining healthy multi-functional ecosystems permits—among others—to keep the ability of biodiversity to deliver a huge range of benefits to people (MA 2005; Díaz et al. 2018). The second is human-driven species extinction, i.e., the pruning of leaves in the tree of life, which currently threatens an estimated one million animal and plant species globally (Díaz et al. 2019). Using species extinction as a biodiversity indicator is relevant because it represents an irreversible loss, it is widely understood and easy to communicate (Rounsevell et al. 2020), and because preventing species extinction is morally the right thing to do (Soulé 1985). Ecosystem multifunctionality and species extinction are complementary in representing how biodiversity can be impacted (Purvis 2020). This is because, up to a certain extent, we can lose one benefit to people due to the reduction of ecosystem multifunctionality without any species extinction (i.e., the loss of a benefit due to the decline in the population of a species, which nonetheless remains extant) and vice-versa (i.e., the extinction of a species, which does not impact ecosystem multifunctionality).
From the indicators commonly applied in biodiversity conservation mentioned in our workshop discussion, we identified three indicators already used to report on global biodiversity change (GEO BON 2015) that can all potentially be incorporated into LCA in the short term. The Local Biodiversity Intactness Index (LBII, Scholes and Biggs 2005; Newbold et al. 2016) reports on the mean intactness of local species abundance of a large and diverse set of organisms, in a given geographical area, relative to their reference populations in undisturbed or non-intensively used land management states. The mean species abundance (MSA) is a metric conceptually similar to the LBII, reporting the abundance of species found in relation to a given pressure relative to its abundance found in an undisturbed situation (Schipper et al. 2020). Both LBII and MSA have already been used in modeling frameworks to investigate global integrated scenarios of biodiversity change in response to different environmental pressures (Newbold et al. 2016; Schipper et al. 2020; Leclère et al. 2020), and MSA has been coupled to LCA to measure business impacts on biodiversity (Lammerant 2018; Crenna et al. 2020). Because they are based on species abundances, LBII and MSA are good candidates to account for biodiversity impacts regarding ecosystem multifunctionality. Another useful biodiversity indicator is the Biodiversity Habitat Index (BHI, GEO BON 2015), which estimates the change in the proportion of collective biological diversity retained in any specified spatial unit as a function of habitat loss, fragmentation, and degradation across the unit, and which can be considered a proxy for local species extinctions. Quantifying BHI with global models of fine-scale species composition turnover across land uses (Di Marco et al. 2019) would allow capturing how land use changes translate into expected risk of local species loss in LCA. Such approaches nonetheless need to be scaled up to relate the local species extinctions they document to the global, irreversible species extinctions that should be taken into consideration when characterizing the impact on biodiversity. However, an unresolved issue is the large gaps in global data sets for many countries and regions.
LBII, MSA, and BHI are pragmatic options to improve the representation of biodiversity impacts in LCA, but other indicators may be developed in the longer term. Such developments could build on essential biodiversity variables (Pereira et al. 2013) to provide complementary measures for the assessments of impacts on biodiversity and should address the shortcomings of LBII, MSA, and/or BHI. First, these indicators aim to predict biodiversity change as a function of one or more anthropogenic pressures; yet, as those are species assemblage indicators, it is not possible to specifically relate the impact captured by these indicators to a list of affected species. Therefore, LCA might need to be complemented with biodiversity indicators able to preserve species identity (and extinction risk) or to species potentially affected. Ideally, and as has recently been demonstrated in a global scenario-based modeling effort, several complementary indicators are considered using an ensemble of biodiversity models (Leclère et al. 2020). Second, the selected indicators do not capture how environmental impacts affect species’ physiology, dispersal, or their interactions with other organisms. A promising avenue to address these shortcomings is the recent development of mechanistic models for biodiversity (e.g., Bocedi et al. 2014; Harfoot et al. 2014; Cabral et al. 2017). In theory, the integration of biological processes into LCA has the potential to allow for understanding product and supply chain impacts on eco-evolutionary dynamics and should therefore deserve a strong research focus. It should be noted that these two shortcomings also hold true for PDF. Third, the LBII, MSA, and BHI indicators can currently only be measured for a limited number of realms and for a limited number of groups. Although there is some ongoing work to expand the coverage of these indicators, data and model developments are currently not sufficient neither to quantify those biodiversity indicators for the marine realm nor to consider soil biodiversity.
Beyond the development of new biodiversity indicators, workshop participants discussed another long-term issue in LCA. That is, how to translate the impact of a product on ecosystem multifunctionality and species extinction to a simple biodiversity indicators to be communicated, e.g., to policy makers and consumers. Solutions may span from represent either only the impact of the product on ecosystem multifunctionality, only the impact of the product on species extinction, or the impact of the product on both ecosystem multifunctionality and species extinction.