Abstract
Measuring the status and trends of biodiversity is critical for making informed decisions about the conservation, management or restoration of species, habitats and ecosystems. Defining the reference state against which status and change are measured is essential. Typically, reference states describe historical conditions, yet historical conditions are challenging to quantify, may be difficult to falsify, and may no longer be an attainable target in a contemporary ecosystem. We have constructed a conceptual framework to help inform thinking and discussion around the philosophical underpinnings of reference states and guide their application. We characterize currently recognized historical reference states and describe them as Pre‐Human, Indigenous Cultural, Pre‐Intensification and Hybrid‐Historical. We extend the conceptual framework to include contemporary reference states as an alternative theoretical perspective. The contemporary reference state framework is a major conceptual shift that focuses on current ecological patterns and identifies areas with higher biodiversity values relative to other locations within the same ecosystem, regardless of the disturbance history. We acknowledge that past processes play an essential role in driving contemporary patterns of diversity. The specific context for which we design the contemporary conceptual frame is underpinned by an overarching goal—to maximize biodiversity conservation and restoration outcomes in existing ecosystems. The contemporary reference state framework can account for the inherent differences in the diversity of biodiversity values (e.g. native species richness, habitat complexity) across spatial scales, communities and ecosystems. In contrast to historical reference states, contemporary references states are measurable and falsifiable. This ‘road map of reference states’ offers perspective needed to define and assess the status and trends in biodiversity and habitats. We demonstrate the contemporary reference state concept with an example from south‐eastern Australia. Our framework provides a tractable way for policy‐makers and practitioners to navigate biodiversity assessments to maximize conservation and restoration outcomes in contemporary ecosystems.
Highlights
A fundamental principle underpinning the conservation, management and restoration of species and habitats is assessing their current state against some former state or baseline
By restoring sophisticated and strategic traditional land use practices, Indigenous Cultural reference states seek conservation strategies that manage fire, invasive species and biodiversity loss (e.g., Ban et al 2020; Ens et al 2015; Molnár et al 2020). These reference states, which include the pre-Columbian reference applied in the Americans and European countries, or pre-European applied in Oceania and Canada, mark disturbances related to introducing non-native or alien species, especially plant and animal species used as food sources (Kühn et al 2004; Pyšek et al 2004) and altered landscape configuration and composition as a direct result of acclimation and agricultural practices
Within the specific context of setting targets for maximising biodiversity through ecosystem management, conservation and restoration actions, we argue that there are three key limitations to the use of historical reference states in contemporary ecosystem management
Summary
A fundamental principle underpinning the conservation, management and restoration of species and habitats is assessing their current state against some former state or baseline. We extend the concepts proposed by Stoddard et al (2006) and identify four distinct historical reference states as Pre-Human, Indigenous Cultural, Pre-Intensification doi:10.20944/preprints202007.0093.v1 and Hybrid-Historical (Figure 1) As these reference states are conceptual, they do not necessarily have specific date stamps, nor do they have rigid or fixed temporal windows. By restoring sophisticated and strategic traditional land use practices, Indigenous Cultural reference states seek conservation strategies that manage fire, invasive species and biodiversity loss (e.g., Ban et al 2020; Ens et al 2015; Molnár et al 2020) These reference states, which include the pre-Columbian reference applied in the Americans and European countries, or pre-European applied in Oceania and Canada, mark disturbances related to introducing non-native or alien species, especially plant and animal species used as food sources (Kühn et al 2004; Pyšek et al 2004) and altered landscape configuration and composition as a direct result of acclimation and agricultural practices. The Hybrid-Historical reference state is appealing because it can overcome some of the uncertain or unquantifiable characteristics of historical ecosystems (Balaguer et al 2014)
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