The idea of a planetary tipping point - where ecological systems around the world shift radically and irreversibly into decline - could lead unnecessarily to dangerous complacency or dread of catastrophe, according to an ecologist from The University of Western Australia.
Dr Mike Perring, who took part in an international study, believes such an ecological tipping point is unlikely and that aggregated global-scale ecological change will follow a gradual, smooth pattern.
Dr Perring, from UWA's School of Plant Biology, and researchers at Adelaide University and institutions in the UK and US argue that a planetary tipping point could occur only if ecosystems across Earth responded in similar ways to human pressures or if connections between continents were strong enough to allow rapid diffusion of impacts across the planet.
In an article published in Trends in Ecology and Evolution, Dr Perring and his co-authors argue that a tipping point is unlikely because ecosystems across the globe respond differently to human pressure and because responses of ecosystems on different continents are not strongly connected.
They suggest that the four main drivers of ecosystem change - climate change, land-use change, habitat fragmentation and biodiversity loss - are unlikely to induce a global tipping point. Instead, ecosystems are likely to respond idiosyncratically.
The authors concede that there have been planetary tipping points before: coral reef ecosystems disappeared globally and simultaneously during the Triassic-Jurassic transition, perhaps driven by increased ocean acidity and temperature after a massive geological release of carbon dioxide.
Focussing on uncertain future terrestrial changes under-emphasises the degree to which up to four-fifths of land-based ecosystems have already been transformed by human activities, they write.
Instead of being complacent or fearing catastrophe, we should recognise that there is already a human footprint on 83 per cent of the Earth's land surface and concentrate on appropriate conservation efforts at local and regional levels.