Doomsday Rejected: Global Tipping Point Not Backed By Science

 

“A focus on planetary tipping points may both distract from the vast ecological transformations that have already occurred, and lead to unjustified fatalism about the catastrophic effects of tipping points.“An emphasis on a point of no return is not particularly helpful for bringing about the conservation action we need. We must continue to seek to reduce our impacts on the global ecology without undue attention on trying to avoid arbitrary thresholds.”

A tipping point occurs when an ecosystem attribute such as species abundance or carbon sequestration responds rapidly and possibly irreversibly to a human pressure like land-use change or climate change.

Many local and regional-level ecosystems, such as lakes and grasslands, are known to behave this way. A planetary tipping point, the authors suggest, could theoretically occur if ecosystems across Earth respond in similar ways to the same human pressures, or if there are strong connections between continents that allow for rapid diffusion of impacts across the planet.

“These criteria, however, are very unlikely to be met in the real world,” says Professor Brook. “First, ecosystems on different continents are not strongly connected. Second, the responses of ecosystems to human pressures like climate change or land-use change depend on local circumstances and will therefore differ between localities.”

The scientists examined four principal drivers of terrestrial ecosystem change ‒ climate change, land-use change, habitat fragmentation and biodiversity loss ‒ and found they were unlikely to induce global tipping points.

Co-author Associate Professor Erle Ellis, University of Maryland, Baltimore County, says: “As much as four fifths of the biosphere is today characterised by ecosystems that locally, over centuries and millennia, have undergone human-driven regime shifts of one or more kinds. Recognising this reality and seeking appropriate conservation efforts at local and regional levels might be a more fruitful way forward for ecology and global change science.”