Thermodynamics, man and biosphere

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Solving the problem – support information

Photosynthesis and biomass production : land, water, yield

Biological resources are life generated materials and processes which are naturally and sustainably renewable and biodegradable. As such, biological resources fulfil man’s essential, fundamental needs : food, feed, bioactive molecules, fuel, shelter, fibre, bio-remediation etc. They play a key role in present and future socio-economic evolutions (also see Knowledge-based bio-economy concept, KBBE).
Only the Net Primary Production is available for consumption, and is the basis of all food chains that support species biodiversity.
Genetic yield potential (Y) : the yield that a crop can attain through photosynthesis under optimal management practices and in the absence of biotic and abiotic stresses.
Factors of Y :
St (GJ m−2) : the total incident solar radiation across the growing season.
partitioning efficiency (εp), also termed harvest index ; the amount of the total biomass energy partitioned into the harvested portion of the crop.
light interception efficiency (εi) of photosynthetically active radiation (400–700 nm) is determined by the speed of canopy development and closure, leaf absorbance, canopy longevity, size, and architecture.
conversion efficiency (εc) the ratio of biomass energy produced over a given period to the radiative energy intercepted by the canopy over the same period (i.e. the combined gross photosynthesis of all leaves within the canopy, less all plant respiratory losses).

Zhu XG, Long SP, Ort DR : Improving photosynthetic efficiency for greater yield. Annual Review of Plant Biology 2010, 61:235-261.

Ecological footprint : A measure of how much biologically productive land and water an individual, population or activity require to produce all the resources it consumes and to absorb the waste it generates using prevailing technology and resource management practices. Today humanity uses the equivalent of 1.5 planets to provide the resources we use and absorb our waste.
Ecological deficit  : the difference between the biocapacity and ecological footprint of a region or country. An ecological deficit occurs when the Footprint of a population exceeds the biocapacity of the area available to that population.
Ecological reserve  : an ecological reserve exists when the biocapacity of a region exceeds its population’s Footprint. Also consider terms as biodiversity buffer / ecosystem buffer : the amount of biocapacity set aside to maintain representative ecosystem types and viable populations of species (related to resilience of ecosystems).

Global Footprint Network - World Footprint, Do we fit on the planet ? []

Food chains, biological efficiency, and carrying capacity

A food chain or a food web defines who is eaten by whom in a given ecosystem.
Food chains / webs are important in understanding productivity issues because they operate through biomass production at various trophic levels and ultimately define ecological efficiency.
Ecological efficiency is the efficiency with which production at one trophic level is converted into production at the next level. This corresponds mainly to assimilation and growth efficiencies.
Assimilation efficiency corresponds to the fraction of food taken up by an organism, and depends on the composition and digestibility of ingested food. Typically being around 80% for zooplankton and fish, for example.
Growth efficiency is expressed as the fraction of ingested food required for growth and approximates 20% in the same organisms. This apparently low bio-efficiency reflects the price of speed and simultaneous regulation of biochemical processes operating at various organization levels, and thus far from thermodynamic equilibrium.
These factors contribute therefore to an overall low ecological efficiency, which has been empirically estimated at 10-20% (the part microbial food loops / webs play in the system is ignored here). It follows that on a scale of 100 units, from primary production down to various trophic levels, the production of herbivores is maximum 10-20, while that of first level carnivores is 1-2, and so on. A trophic chain of 7 in the Norwegian Sea (Flagellates > Ciliates > Oithona > Euchaeta > Themisto > Herring > Salmon) ends up with salmon production of 0.0002 – 0.02 units. Thus, production falls rapidly as we climb the food chain and with long food chains top trophic level production can be as low as 10-5 to 10-8 of the primary production.

Agriculture and human food systems are far out of such scales and thermodynamic rules.
Feed conversion  : In animal husbandry, feed conversion ratio (FCR), feed conversion rate, or feed conversion efficiency (FCE), is a measure of an animal’s efficiency in converting feed mass into increased body mass.
The ratio of the kg of feed needed to produce one kg of life weight (body mass). Examples are : Milk 0.7, Carp 1.5, Egg 3.8, Chicken 2.3, Pork 5.8, Beef 12.7. Only part of the life weight is edible.

The carrying capacity for the top level predators in an ecosystem is very sensitive to the number of steps in the food chains / webs that support it.
The carrying capacity of a biological species in a given environment is the maximum population size of this species that the environment can sustain indefinitely, given the food, habitat, water and other necessities available. If the population size of the species is over its carrying capacity, the environment will be degraded more or less quickly and consequently will not sustain the population, which in turn will decrease. Moreover, if the environment itself has its resources decreasing in reason of an abiotic cause, the carrying capacity will decrease.
Therefore, the condition of the entire ecosystem is at stake when defining harvesting stocks and demographic loads. Long food chains, complex and unstructured food webs are indicators of both resilient ecosystems and rich biodiversity.
Human carrying capacity under business as usual is a real issue ; that remains a political and cultural taboo so far.

Skjoldal HR, Dalpadado P, Dommasnes A : Food webs and trophic interactions. The Norwegain Sea ecosystem Tapir Academic Press, Trondheim 2004, 447:506.

Dorst J : La force du vivant. Flammarion ; 1979.

Blanchard JL, Law R, Castle MD, Jennings S : Coupled energy pathways and the resilience of size-structured food webs. Theoretical Ecology 2010:1-12.

USDA Agricultural Statistics Annual

Feed conversion ratio

Carrying capacity

Global Footprint Network - World Footprint, Do we fit on the planet

Profit margins in 2017 and ecological truth

Company earnings have never been so high, global profits 2017 for the CAC 40 index expected to range €90-100 billions. This is comparable to the before 2008 crisis levels and particulalrly true for raw material businesses.
J.P. Morgan bets on profit rates higher than 10 pc in 2017 and 2018 (Cosnard D, Le Monde, August 4, 2017, p12).
Wall Street flies high, overall "listed shares" prices are 14 pc up since January 2017, reaching all time record levels.

According to Jeremy Grantham (chief investment strategist and co-founder of asset management firm GMO)

"The market can stay irrational longer than the investor can stay solvent".

Grantham shows that in 2017 profit margins have grown by 30% and represent a higher share of GDP to conclude that "the most important for understanding the stock market is, in my opinion, the much higher level of corporate profits." He lists several reasons for this, including the following :

  • Increased globalization
  • Increased monopoly power for U.S. corporations
  • Decline in capital spending as a percentage of GDP
  • Lower interest rates

Grantham also lists three factors that he believes will bolster U.S. profits in 2017 :

  • Oil and resource prices
  • Lower corporate taxes
  • Reduced regulations

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One might add here an additional factor : the very agressive strategies of tax evasion or optimization and lucrative tax heavens. Of note, Europe is heaven number one (Delatte AL, Oxfam report, Libération Sept 9, 2017, p 27). For how long time ?

To summarize and put the limiting photosynthesis rate of 2 pc in the context of the above mentioned financial rates (listed shares and profits, one can state that capitalism runs high risks of collapse bacause it does not consider and tell the ecological truth, namely ignoring the overall objective limits of the environment (some are coined "planetary boundaries").
Strong financialisation and the resource rush toward "peak everything" are impacting international stability and geopolitics mainly because tensions and conflicts on raw materials are building up.
The ups and downs of the global market seem to oscilate across a threshold that in the words of Cargill chief Gregory Page is somewhere at 2,5 pc : "if we drop back into a period of 2,5 pc global growth, we will have to rethink where and how we grow" (Blas J and Meyer G, All you can eat, Financial Times, May 19, 2010, p9). That per cent comes quite closely to the limiting rate of photosynthesis (see drawing above).
We may end up by including photosynthesis, the main biomass resource on Earth,
in "peak everything".

Viking laws to illustrate business as usual :
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Illustrations :
Cirenia Arias Baldrich - Science Sketcher
Snorre -

Article publié ou modifié le

1er juin 2017