New planetary boundary to measure effects of human activity

September 21, 2012 by Lin Edwards, report

Credit: NASA
(—A US scientist has proposed that a new planetary boundary be used to analyze the effects of human activities on the planet. He warns that there are definite biophysical limits to growth in human population, economies and consumption, and that limits in some variables might already have been reached.

In a Perspective article in the journal Science, Professor Steven W. Running, Director of the Numerical Terradynamic Simulation Group (NTSG) at the University of Montana, proposes that adopting a new planetary boundary—annual net primary production (NPP) of all —might help researchers to more effectively monitor the effects of humans on climate, land use and and their limits.

Net primary production is the basis of the and is closely linked to other such as climate and freshwater use. Planetary boundaries are limits to variables vital to human habitation of Earth, such as changes in climate, biodiversity, land use, ocean pH, and so on. Prof. Running suggests in his article that some planetary boundaries, such as freshwater use for , may already have been breached.

The first of the global limits was published in 1972 in the book Limits to Growth, but the analysis was done using computers that are rather primitive by today's standards, and the modeling it used has faced some criticism. Even so, its predictions, including that limits to some resources would be reached by early this century, were found to be reasonably accurate when compared in 2008 with actual data on depletion of resources.

One problem with the concept of planetary boundaries is that some variables are difficult to measure on a global scale, and critical limits can be hard to quantify. To overcome these difficulties, Running suggests adopting NPP as a new planetary boundary because of its links to many other variables and because humans need plants for many reasons, including food, food for animals raised for food, oxygen (via photosynthesis), building materials, and fire wood.

Satellite data enables scientists to calculate how much vegetation is produced each year, and data is available for more than 30 years. Over this period the amount of vegetation produced has been extremely stable at 53.6 trillion kilograms per year. Humans use 40 percent of this each year, but around 50 percent is unavailable for human use either because it's inaccessible, unharvestable, or in vital conservation areas. This leaves only around 10 percent remaining for a growing .

Vegetation growth can be increased with fertilizers and irrigation, but these also have limits and are unlikely to provide a significant boost. Even if they could, Running questioned whether a world in which every available acre of ground is taken for use is the kind of world we want. He warned that "endless" economic and consumptive growth are not possible, and we should revise expectations for the future in the light of this.

Prof. Running also pointed out that even if the entire further 10 percent of vegetation growth available was turned over to growth of crops for biofuels, it could produce only 40 percent of current needs.

Explore further: Trade-offs between water for food and for curbing climate change

More information: A Measurable Planetary Boundary for the Biosphere, Science 21 September 2012: Vol. 337 no. 6101 pp. 1458-1459. DOI: 10.1126/science.1227620

Forty years ago, Meadows et al. published a landmark first analysis of global limits to human activity (1). Based on a primitive computer model of the Earth system, they concluded that by the early decades of the 21st century, tangible limits to key global resources would begin to emerge. A reanalysis of the original results in 2008 found that the original global resource depletion projections were remarkably accurate (2). Since then, Rockström et al. (3) have defined a new term—planetary boundaries—to describe nine variables of high importance to habitability of Earth, including climate change, ocean acidification, land-use change, and biodiversity loss. These metrics are compelling conceptually, but many are not easily measured globally; explicitly defining a critical boundary is even more challenging. I suggest a new planetary boundary, terrestrial net primary (plant) production (NPP), that may be as compelling conceptually, integrates many of the currently defined variables, and is supported by an existing global data set for defining boundaries.

Related Stories

International scientists set boundaries for survival

September 23, 2009

Human activities have already pushed the Earth system beyond three of the planet's biophysical thresholds, with consequences that are detrimental or even catastrophic for large parts of the world; six others may well be crossed ...

UN panel says retool world economy for sustainability

January 30, 2012

The world can no longer afford to ignore the environmental cost of economic growth and must redefine the very concept of national wealth, a UN panel of heads of state and environment ministers said Monday.

Drought drives decade-long decline in plant growth

August 19, 2010

Earth has done an ecological about-face: Global plant productivity that once flourished under warming temperatures and a lengthened growing season is now on the decline, struck by the stress of drought.

How hard are we pushing the land?

December 15, 2010

We may be becoming an ever more technologically advanced society, but we remain as dependent as ever -- if not more and more so -- on the natural world that surrounds us.

Recommended for you

Galactic center visualization delivers star power

March 21, 2019

Want to take a trip to the center of the Milky Way? Check out a new immersive, ultra-high-definition visualization. This 360-movie offers an unparalleled opportunity to look around the center of the galaxy, from the vantage ...

Physicists reveal why matter dominates universe

March 21, 2019

Physicists in the College of Arts and Sciences at Syracuse University have confirmed that matter and antimatter decay differently for elementary particles containing charmed quarks.


Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Sep 21, 2012
It may make sense. Mendez index for habitability of planets used to be based on NPP before he launched the Earth Similarity Index as a basis for his Habitability Exoplanets Database.
2.8 / 5 (5) Sep 21, 2012
Like a house of cards, life is all related and interdependent. Disturb one thing and you can bring the house down... and, once the avalanche is started, it's near impossible to stop by human means.

We warned you in the 60s, 70s, 80s, 90s... but you sloughed us off as crazy drug addicts. Now that your scientists are beginning to agree with us, it may well be too late.
2 / 5 (8) Sep 21, 2012
it may well be too late.

Ha! I bet Mother Nature got a good laugh out of that.

It's pretty-well understood that humans can only last so long without food and water. If a population outgrows their food/water supply, balance will be restored.

If AGW cooks-off a bunch of people, balance will be restored.

And we don't need a "planetary study" to know all of this. Besides, what would you do with the knowledge gained? force abortion? mandatory sterilization? start some new wars?
5 / 5 (1) Sep 21, 2012
And we don't need a "planetary study" to know all of this. Besides, what would you do with the knowledge gained? force abortion? mandatory sterilization? start some new wars?

Nope... You just change the policy. Ie: forrest reserve, tax cut for conservative work, subsidies for conservation effort.
not rated yet Sep 21, 2012
I say give $50k tax credit per year to each childless adult.
2 / 5 (4) Sep 22, 2012
Exactly Scooter,... if the speculation that population growth or consumption is unsustainable, than by definition, it's unsustainable,.. meaning such things will self-regulate.

The pot smoking liberals, think such speculation is a cue to support government control of human behavior.
not rated yet Sep 23, 2012
@ Arnod:

"Disturb one thing and you can bring the house down."

The longest running biological experiment in history reject such ad hoc theories. Life on Earth is at least 3.5 billion years old, and have never been eradicated.

There are reasons for that. For example, modeling of cell populations show that they can proliferate and spread faster than impactors (say) can sterilize. Life is a plague on a planet, and can't be removed by any conceivable means.
not rated yet Sep 23, 2012
Exactly Scooter,... if the speculation that population growth or consumption is unsustainable, than by definition, it's unsustainable,.. meaning such things will self-regulate.

That self regulation would mean a lot of people dying, or "cooking off" as Scooter says. Some people think that is undesirable.

The pot smoking liberals, think such speculation is a cue to support government control of human behavior.

Wrong on two counts:
1) you forget that there is a lot of middle ground between control and laissez-faire.
2) Only if the free market crowd keeps on failing to come up with a free market solution. If they had one, they would be True Believers. You don't need to accept the problem is real to prove me wrong on that point. Treat the problem as hypothetical, and give me a solution.
not rated yet Sep 23, 2012
You understand that "balance will be regained" means death ,misery and a great loss in human values for a long time,don't you?
Does it have to come to that for human beings such as you and me (hi there!) to realize that rational government of our actions must somehow be procured?Maybe by thinking we can act wiser.We could also run computer simulations based on our conceptual understanding of the world,if you particularly trust mathematical modelling more than other areas of reason.

I understand that government control is a scary thought after the XXth century,specially with things as morally delicate as human lives.However one does not have to be a genius to realize that it is inevitable.
Refuse it and wars will be waged,which in turn are an activity exclusive of political organisations.

Which government do you wish for the future?

I only see two independent solutions: a scientifical and a political one.
If non-polluting energy and materials are created control can be less strict.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.