Open AccessThresholds for ecological responses to global change do not emerge from empirical data
Author(s) -
Helmut Hillebrand,
Ian Donohue,
W. Stanley Harpole,
Dorothee Hodapp,
Michal Kučera,
Aleksandra M. Lewandowska,
Julian Merder,
José M. Montoya,
Jan A. Freund
Publication year - 2020
Publication title -
nature ecology and evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.822
H-Index - 57
ISSN - 2397-334X
DOI - 10.1038/s41559-020-1256-9
Subject(s) - global change , variance (accounting) , econometrics , ecology , ecosystem , climate change , sensitivity (control systems) , environmental change , environmental resource management , environmental science , biology , economics , accounting , electronic engineering , engineering
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.