Thresholds and tipping points are tempting but not necessarily suitable concepts to address anthropogenic biodiversity change—an intervention

Abstract

Thresholds and tipping points are frequently used concepts to address the risks of global change pressures and their mitigation. It is tempting to also consider them to understand biodiversity change and design measures to ensure biotic integrity. Here, we argue that thresholds and tipping points do not work well in the context of biodiversity change for conceptual, ethical, and empirical reasons. Defining a threshold for biodiversity change (a maximum tolerable degree of turnover or loss) neglects that ecosystem multifunctionality often relies on the complete entangled web of species interactions and invokes the ethical issue of declaring some biodiversity dispensable. Alternatively defining a threshold for pressures on biodiversity might seem more straightforward as it addresses the causes of biodiversity change. However, most biodiversity change appears to be gradual and accumulating over time rather than reflecting a disproportionate change when transgressing a pressure threshold. Moreover, biodiversity change is not in synchrony with environmental change, but massively delayed through inertia inflicted by population dynamics and demography. In consequence, formulating environmental management targets as preventing the transgression of thresholds is less useful in the context of biodiversity change, as such thresholds neither capture how biodiversity responds to anthropogenic pressures nor how it links to ecosystem functioning. Instead, addressing biodiversity change requires reflecting the spatiotemporal complexity of altered local community dynamics and temporal turnover in composition leading to shifts in distributional ranges and species interactions.

Sustainability: We need to focus on overall system outcomes rather than simplistic targets

“…Therefore, the adaptive cycle needs also to lead to societal transformation and thus updated goal formulation to reduce multiple pressures over the long run. between risky and safe operating spaces tend to be blurred or hard to foresee (Hillebrand et al, 2020(Hillebrand et al, , 2023, which makes negotiations happen under very imperfect knowledge.…”

Explore before you restore: Incorporating complex systems thinking in ecosystem restoration

“…Specifically, we identify the development of practical tools and methods to assess ecological resilience loss, abrupt regime shifts and hysteresis in degraded systems as outstanding tasks, as these are, to our knowledge, non-existent. The lack of scientific consensus on the usefulness and applicability of regime shifts in ecology likely also hampers this operationalization (Higgins et al, 2023;Hillebrand et al, 2023). Further, a helpful platform where restoration teams can explore whether ecosystems from similar climates and degradation settings have experienced a regime shift, is the online database www.…”

Resilience metrics are robust across data qualities but sensitive to community size.

“…With current debates over the commonality of alternative stable states in ecology (Dakos et al, 2015;Davidson et al, 2023) and inconsistent ability in real world data (Burthe et al, 2016;Zhang, 2020), the benefit of resilience metrics over EWSs is their ability to quantify stability regardless of the presence of multiple stable states (Lyapunov, 1992;Medeiros et al, 2022;Sugihara et al, 2012). With the complex intrinsic and extrinsic interactions driving ecosystem dynamics possibly masking true multiple stability (Hillebrand et al, 2023) or ecosystems themselves experiencing long transients rather than regime shifts (Hastings et al, 2018), the resilience metrics discussed here are conceptually capable of accurate Jacobian estimation under both heuristics. Such capability therefore expedites the general suggestions to consider nonequilibrium resilience and stability change in ecological research (Donohue et al, 2013(Donohue et al, , 2016Kéfi et al, 2019).…”

“…Conversely, trends require sufficient subjectivity that the vague language associated with trend reporting results in broad objective language (United Nations, 2020). Many governments therefore use indicators with set target thresholds for biodiversity rather than considering a continuous gradient of 'state' which is suggested to be more appropriate for modern coupled socio-ecological systems (Hillebrand et al, 2023).…”