Scientists Uncover Evidence of Earth’s Impending Tipping Point

A pres­ti­gious group of sci­en­tists from around the world is warn­ing that pop­u­la­tion growth, wide­spread destruc­tion of nat­ural ecosys­tems, and cli­mate change may be dri­ving Earth toward an irre­versible change in the bios­phere, a planet-wide tip­ping point that could have destruc­tive con­se­quences absent ade­quate prepa­ra­tion and mitigation.

“It really will be a new world, bio­log­i­cally, at that point,” said Anthony Barnosky, pro­fes­sor of inte­gra­tive biol­ogy at the Uni­ver­sity of Cal­i­for­nia, Berke­ley, and lead author of a review paper appear­ing in the June 7 issue of the jour­nal Nature. “The data sug­gests that there will be a reduc­tion in bio­di­ver­sity and severe impacts on much of what we depend on to sus­tain our qual­ity of life includ­ing for exam­ple, fish­eries, agri­cul­ture, for­est prod­ucts and clean water. This could hap­pen within just a few generations.”

The result of such a major shift in the bios­phere would be mixed, Barnosky noted, with some plant and ani­mal species dis­ap­pear­ing, new mixes of remain­ing species and major dis­rup­tions in terms of which agri­cul­tural crops can grow where.

The Nature paper, in which the sci­en­tists, includ­ing Uni­ver­sity of New Mex­ico Dis­tin­guished Pro­fes­sor of Biol­ogy James H. Brown, com­pares the bio­log­i­cal impact of past inci­dences of global change with processes cur­rently under­way and assess evi­dence for what the future holds, appears in an issue devoted to the envi­ron­ment in advance of the June 20–22 United Nations Rio+20 Earth Sum­mit in Rio de Janeiro, Brazil.

In the paper, 22 inter­na­tion­ally known sci­en­tists describe an urgent need for bet­ter pre­dic­tive mod­els based on a detailed under­stand­ing of how the bios­phere has reacted to rapidly chang­ing con­di­tions, includ­ing cli­mate and human pop­u­la­tion growth, in the dis­tant past.

“There are seven bil­lion peo­ple world­wide and a giant global econ­omy,” said Brown. “We have the data and if you do the arith­metic, the cur­rent sit­u­a­tion is unsus­tain­able” said Brown. “We have cre­ated a giant bub­ble of pop­u­la­tion that must either be deflated grad­u­ally or it will burst cat­a­stroph­i­cally with depri­va­tion and mis­ery every­where. No one will be immune.”

How Close Is a Global Tip­ping Point?
The authors of the Nature review – biol­o­gists, ecol­o­gists, complex-systems the­o­reti­cians, geol­o­gists and pale­on­tol­o­gists from the United States, Canada, South Amer­ica and Europe – argue that although many warn­ing signs are emerg­ing, no one knows how close to a global tip­ping point Earth is, or whether it is inevitable. The sci­en­tists urge focused research to iden­tify early warn­ing signs of a global tran­si­tion and accel­er­a­tion of efforts to address the root causes.

“We really do have to be think­ing about these global scale tip­ping points, because even the parts of Earth we are not mess­ing with directly could be prone to some very major changes,” Barnosky said. “And the root cause, ulti­mately, is human pop­u­la­tion growth and how many resources each one of us uses.”

“What we’ve done as a soci­ety,” said Brown, “is to cre­ate a bub­ble of pop­u­la­tion and econ­omy, which is totally depen­dent on non-renewable resources such as fos­sil fuels and met­als on unsus­tain­able use of renew­able resources such as water and fish­eries. Flows of these resources to sup­port local and regional economies must come from the global sys­tem, where they are sim­ply run­ning out.”

Coau­thor Eliz­a­beth Hadly from Stan­ford Uni­ver­sity thinks that “We may already be past these tip­ping points in par­tic­u­lar regions of the world. I just returned from a trip to the high Himalayas in Nepal where I wit­nessed fam­i­lies fight­ing each other with machetes for wood…wood that they would burn to cook their food in one evening. In places where gov­ern­ments are lack­ing basic infra­struc­ture, peo­ple fend for them­selves and bio­di­ver­sity suf­fers. We des­per­ately need global lead­er­ship for planet Earth.”

The authors note that stud­ies of small-scale ecosys­tems show that once 50–90 per­cent of an area has been altered, the entire ecosys­tem tips irre­versibly into a state far dif­fer­ent from the orig­i­nal in terms of the mix of plant and ani­mal species and their inter­ac­tions. This is typ­i­cally accom­pa­nied by species extinc­tions and a loss of biodiversity.

Cur­rently, to sup­port a pop­u­la­tion of seven bil­lion peo­ple, about 43 per­cent of Earth’s sur­face has been con­verted to agri­cul­tural or urban use, with roads cut­ting through much of the remain­der. The pop­u­la­tion is expected to rise to nine bil­lion by 2045; at that rate, cur­rent trends sug­gest that half Earth’s land sur­face will be dis­turbed by 2025. To Barnosky, this is dis­turbingly close to a global tip­ping point.

“Can it really hap­pen? Look­ing into the past tells us unequiv­o­cally that yes, it can really hap­pen. It has hap­pened. The last glacial/interglacial tran­si­tion 11,700 years ago was an exam­ple of that,” Barnosky said, not­ing that ani­mal diver­sity still has not recov­ered from extinc­tions dur­ing that time. “I think that if we want to avoid the most unpleas­ant sur­prises, we want to stay away from that 50 per­cent mark.”

Global Change Biol­ogy
The paper emerged from a con­fer­ence held at UC Berke­ley in 2010 to dis­cuss the idea of a global tip­ping point, how we’d rec­og­nize it and how we could avoid it.

Twenty-two of the atten­dees even­tu­ally sum­ma­rized avail­able evi­dence of past global state-shifts, the cur­rent state of threats to the global envi­ron­ment and what hap­pened after past tip­ping points.

They con­cluded that there is an urgent need for global coop­er­a­tion to reduce world pop­u­la­tion growth and per-capita resource use, replace fos­sil fuels with sus­tain­able sources, develop more effi­cient food pro­duc­tion and dis­tri­b­u­tion with­out tak­ing over more land, and bet­ter man­age the land and ocean areas not already dom­i­nated by humans as reser­voirs of bio­di­ver­sity and ecosys­tem services.

Media Con­tacts: UC-Berkeley, Robert Sanders (510) 643‑6998; email: rsanders@berkeley.edu; UNM, Steve Carr (505) 277‑1821; email: scarr@unm.edu