Thresholds for ecological responses to global change do not emerge from empirical data

Abstract

To understand ecosystem responses to anthropogenic global change, a prevailing framework is the definition of threshold levels of pressure, above which response magnitudes and their variances increase disproportionately. However, we lack systematic quantitative evidence as to whether empirical data allow definition of such thresholds. Here, we summarize 36 meta-analyses measuring more than 4,600 global change impacts on natural communities. We find that threshold transgressions were rarely detectable, either within or across meta-analyses. Instead, ecological responses were characterized mostly by progressively increasing magnitude and variance when pressure increased. Sensitivity analyses with modelled data revealed that minor variances in the response are sufficient to preclude the detection of thresholds from data, even if they are present. The simulations reinforced our contention that global change biology needs to abandon the general expectation that system properties allow defining thresholds as a way to manage nature under global change. Rather, highly variable responses, even under weak pressures, suggest that 'safe-operating spaces' are unlikely to be quantifiable.

Ensuring a Post-COVID Economic Agenda Tackles Global Biodiversity Loss

“…86 As such, a precautionary approach with respect to financial speculation and nature-related financial risk is warranted, given potentially catastrophic tail risks or tipping points that remain largely unknown and are inherently difficult to predict accurately. 56,87 As has been recently experienced with both pandemics and climate change, the potential negative economic impact of finding oneself on the wrong side of such tail risks is so high that the most economically efficient approach would be to err on the side of caution. 88 The 2008-2009 market crash was partly driven by a change in asset value behavior at the margins and consequently inspired a set of precautionary financial regulations; 89 thus, similar investments that could cause multitrillion-dollar losses through environmental harms could be considered at least as risky, and regulated accordingly.…”

ESD Ideas: Planetary Antifragility: A new dimension in the definition of the Safe Operating Space for Humanity

“…On the one hand as we have been highlighting in this work and also commented by Dudney and Suding (2020), Ecosystems seldom respond to environmental drivers in isolation, and the inclusion of interacting drivers may indicate more frequent threshold dynamics than expected from the discussed meta-analyses (Hillebrand et al, 2020). In this way, our thermodynamic framework using global albedo as proxy of planetary entropy production could by interpreted as a systemic response that integrate all drives and responses.…”

“…As pointed out in a recent work (Hillebrand et al, 2020), to understand ecosystem responses to anthropogenic global change, it is key to test if ecosystem really goes trough thresholds or tipping points. In their work, the authors found that threshold transgressions were rarely detectable, either within or across meta-analyses.…”

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