Arthur Lyon Dahl
3 October 2023
New research has finally defined part of another critical planetary boundary, the total photosynthetic capacity of the planet to sustain life, that I warned about early this year. In a letter to New Scientist on 7 January published on 4 February 2023, I pointed out that we might be close to the limit of damaging all forms of photosynthesis to below meeting the energy needs of all life, and developed this further in a blog for IEF on 22 February about The other energy crisis.
Now Katherine Richardson at the University of Copenhagen, and the team that developed the planetary boundary framework, have published the safe limit for exploitation by humans of the land plant biomass production that supports all terrestrial biodiversity, including us. In Science Advances (https://www.science.org/doi/10.1126/sciadv.adh2458), they propose human appropriation of net primary production as a control variable for functional biosphere integrity. This is further reported by Michael Le Page in New Scientist on 23 September 2023, noting that humans are using too many plants, one quarter of the biomass produced on land. In pre-industrial times, plants on land produced 56 gigatonnes of biomass per year in carbon content. Today this is estimated as 66 gigatonnes per year due to higher carbon dioxide levels. With farming, logging, livestock grazing and other land conversion, people now take 17 gigatonnes per year, which is 30 percent of pre-industrial levels and 26 percent of the present biomass production. They propose a safe level for human exploitation as 10 percent of pre-industrial plant biomass and anything over 20 percent as high risk.
Richardson said "That we're already using too much biomass, of course, is a blow to those who want to use biomass for energy and for capturing CO2. You're just not going to solve the climate problem if you don't also respect the deforestation problem we have." She says besides the climate, maintaining the biosphere - the planet's life support system - is the most important planetary boundary. Plant biomass is the basis of food chains, so if we take it, the life that depends on it dies out.
Note that this boundary is only for terrestrial biomass production. There are still no calculations that I know of for marine biomass production on 70 percent of the Earth's surface. With rapid ocean heating, the human impacts on productive coastal ecosystems, the collapse of coral reefs, widespread overfishing, ocean acidification and other probable impacts of widespread pollution on plankton at the base of the ocean food chain, there may well be significant human impacts on marine biomass production which could be equally threatening to our life-support system about which we are totally ignorant.
Our present economic system, that creates wealth by exploiting natural resources including fossil fuels with no thought for the future, and no accounting for the loss of natural resources seen as free for the taking, is leading us rapidly to destruction. Only an urgent and fundamental transformation to a well-being economy might save us from interacting environmental catastrophes which are already unfolding.
Last updated 3 October 2023