Regardless of impacts on the planet, the human condition has likely never been better in terms of material prosperity. The question is: “How do you continue to improve the human condition?” Foley asks. “How can we sustain a world that will reach nine billion people without destroying the planet? At least knowing a bit where the danger zones are is a really important first step.”

There are grounds for hope. Humanity has crossed one of these thresholds before—namely, diminishing levels of stratospheric ozone caused by emissions of ozone-destroying chemicals (the “ozone hole”). We pulled back thanks to international cooperation and the 1989 Montreal Protocol. “We did manage to move ourselves away from the ozone boundary and have made serious efforts at regional levels to protect biodiversity; reduce agricultural pollution, aerosols and water demand; and slow land conversion,” points out environmental scientist Diana Liverman of the University of Arizona, one of the authors of the new thresholds. “This provides some hope that we can manage our planetary impact if we choose.”

Note: This article was originally printed with the title, "Setting Boundaries."

*Erratum (1/25/10): The correct conversion is 264 billion gallons.

This article was originally published with the title Setting Boundaries.

9 Comments

1. 1. David J.Bauer 02:03 PM 11/23/09

   Where is the "complete listing of the planetary boundaries and thresholds,...." promised in the foot note to Setting Boundaries?

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2. 2. luizmello 06:48 AM 11/26/09

   Asking myself the same question, David.

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3. 3. Doug0212 01:33 PM 11/27/09

   Same here, Doug.

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4. 4. Doug0212 01:41 PM 11/27/09

   Here's a link which has the list of 9 (plus two that haven't been quantified yet).
   
   http://www.nature.com/nature/journal/v461/n7263/fig_tab/461472a_T1.html
   

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5. 5. dbiello in reply to David J.Bauer 10:43 AM 12/8/09

   And you can find our version of the list here in the online version:
   
   http://www.scientificamerican.com/article.cfm?id=scientists-identify-safe-limits-for-human-impacts

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6. 6. rbinpa 11:03 AM 12/8/09

   Thank you for your 10:43, David.

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7. 7. RobSavoie 11:55 AM 12/12/09

   Fact check: Energy aficionados who know that a "cubic mile of oil" is roughly a trillion gallons immediately spot the error in the parenthetic comment: (one cubic kilometer of water equls 264 trillion gallons). Should be 10^9, not 10^12.

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8. 8. rambansal 01:43 PM 12/15/09

   I beg to differ with scientists on higher use of water for irrigating agri-fields. In fact, it recharges water table in the area and moreover prevents water from going to the oceans and becoming a waste.

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9. 9. Niranjan 11:05 AM 8/14/10

   My submission to the scientist is"the main cause of concern to save the earth is human population explosion on the earth.All the problems,whether it is biodiversity or ecological imbalance are caused by human population growth internationaly .I'm here agree with Mr.Foley that how can we sustain a world that will reach nine billion people without destroying the planet? -- Niranjan email-niranjanprasadsingh@gmail.com

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