1.6 Biophysical Limits



1.6 Biophysical Limits

We are modifying physical, chemical and biological systems in new ways, at faster rates, and over larger spatial scales than ever recorded on Earth. Humans have unwittingly embarked upon a grand experiment with our planet. The outcome is unknown, but has profound implications for all of life. (President, American Academy for the Advancement of Science, 1999 [see reference 11])

Figure 1.6.1 The Earth viewed from the Moon

(Picture source: MIT OpenCourseware [see reference 13])

Figure 1.6.1 sourced from MIT Open Courseware under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States

The above picture was taken in 1968 by an Apollo 8 crew member. For the first time humanity could see the Earth from a distance. It illuminated an understanding that the planet is a finite space on which we all need to live. It clearly demonstrated that, and that there are certain limits to our growth on our small planet.

In 1972 the bookLimits to Growthwas published [see reference 12] which made an assessment of humanity's impact on the world, followed this with predictions of future trends based on at the time current consumption patterns, and calculated what levels we could approach without causing irreversible implications by crossing them.


The following are categories of the limits, otherwise known as planetary boundaries:


Assimilative capacity of the atmosphere to hold Carbon Dioxide

Loss of biodiversity

Human interference with nitrogen/phosphorous cycles

stratospheric ozone depletion

Ocean acidification

Global scarcity of fresh water

Adverse changes in land use

Chemical pollution

Atmospheric aerosol loading

Figure 1.6.2 Graphical Representation of the planetary boundaries, and current situation

Stockholme resilience [
see reference 14])

Figure 1.6.2 sourced from Stockholme Resilience (Stockholme University) with permission

1.6.2 graphically represents the 9 planetary boundaries. The green areas are the estimated safe limits within these boundaries, and the red areas are our current measured levels within the boundaries. Limits to the graph are that some of the boundaries have no data, and it does not show at what rate these levels have changed over time. The graph shows that in some case (such as loss of biodiversity and CO2 emissions) we have already crossed the boundaries. In other cases there is still room for growth, but levels are increasing rapidly as explained earlier.

Many of these biophysical limits to growth can be observed as measures of unsustainability rather than a lack of sustainability. There is an important difference: when attempting to address these problems, if we only seek to findquick fixesto avoid the effects of unsustainability then it is likely that the problems will reoccur in the future a different form. A key concept is to look at the roots of unsustainability and implement a paradigm shift to create systems with a holistic view of our relationship with the earth and to each other that will see us not just surviving but flourishing into the future.

The underlying theme to take from these graphs is that exponential growth on a finite planet will eventually fail – the world cannot support us if we continue at the current trajectory.

Figure 1.6.3 Timeframes and Possible Future Scenarios

(Source MIT Opencourseware [see reference 15])

Figure 1.6.3 sourced from MIT Open Courseware under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States

The following is a presentation about by Johan Rockstrom about limits to growth