Apr
12
2013

Humanity and the upper limits of the biosphere

How much of terrestrial plant and animal life can humanity safely consume without seriously damaging the live-support systems of our planet? It has been challenging to answer that question because of the difficulty of measuring how much biomass is produced annually on land and how much of this yearly production humans co-opt.

Huge regional variability exists in terrestrial productivity from year to year because of heat, cold, floods and droughts but what is striking from recent reviews of more than 30 years of satellite imagery is how little global variability there is annually. Each year, terrestrial plants fix about 53.6 petagrams of biomass – a gigantic quantity but what matters is not so much the size of annual biomass production but rather that it seems to vary by only about two percent per year.

Recent estimates from satellite imagery indicate that humans now appropriate 38 percent of all terrestrial biomass generated annually. That would seem to leave 62 percent on the table for expanded human consumption but the vast majority of this biomass appears to be not harvestable because it includes root growth below ground and biomass production on lands in parks or wilderness areas that are either protected or inaccessible.

It appears likely that the upper limit for how much of terrestrial biomass that humans can co-opt annually is only about ten percent more for a total of 48 percent. Current land use patterns and projections that the global human population may reach nine billion by 2050 suggest that this 48 percent of all available terrestrial biomass may be reached within the next few decades.
Earth's primary photosnythetic productivity: The darkest green  shading in the Amazon and Southeast Asia are regions of the world where photosynthetic activity is by far the most active on an annual basis
Earth's primary photosnythetic productivity: The darkest green shading in the Amazon and Southeast Asia are regions of the world where photosynthetic activity is by far the most active on an annual basisCourtesy NASA

Your Comments, Thoughts, Questions, Ideas

iain's picture
iain says:

Very interesting post, we often hear about how the planet is running out of room to expand however it's nice to see some actual figures and visual indications instead of the usual media posturing and agendering. Your information reinforces how important it is to move towards a sustainable planet if the human race is to continue growing at its current rate.

posted on Thu, 04/25/2013 - 2:00pm

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