Double counting in human consuption

Human capture of the planet’s productive capacity, according to the most recent relevant study, now adds up to about 24 per cent of the total productivity of the Earth’s terrestrial biosphere. In other words, a quarter of everything produced by all plantson land is eaten or otherwise consumed by us.

Different landscapes are exploited with different intensity: whilst forests will yield up to a fifth of their annual production in fuel, fibre or timber, cropland allows us to grab an impressive 83 per cent of the yearly productive share per hectare. The human species, therefore, whilst comprising only half of 1 per cent of the global animal biomass, consumes a significant fraction of everything the Earth produces. This triumph for us is of course a disaster for the species we have displaced from their food webs: the disappearance of habitat and food supply is currently the greatest cause of the planet’s continuing loss of biological diversity. It is also clear that ecological tipping points can be crossed if we push this process too far, with potentially irreversible consequences as overgrazed grassland tips into desert, or as degraded tropical forest dries out and burns over vast areas of Indonesia and Brazil.

The Smart Way to Play God with Earth’s Limited LandCan humans grow enough food, produce enough energy and still preserve some of the last refuges of other species–both plant and animal–on the planet? By Mark Lynas 

This strikes me as a confused sort of biological accounting akin to those articles that mindlessly compares GDP to some giant company’s sales when the right analog is profits + wages (which is much smaller). By far the biggest use of land by man is agricultural purposes. But when man farms or herds on land, that land supports other plant and animals as an intermediate step. So for example, the weight of the 1.3 billion cattle on earth   has roughly the same biomass again as all the humans, and that’s just one domesticated species. The weight of the wheat is similarly approximately the weight of the humans. Since resources can be consumed by many plants and animals n the weigh to feeding or clothing humans, it doesn’t seem helpful to me to ask how much much we consume. It isn’t a pie that all the plants and animals consume. It is not a zero sum game.  Instead it is a  feedback loop or life cycle  where resources continuously flow in and out of species. Sure, technology induced additional energy radiating  and space travel means we’ve let some stuff leak out of the loop, but in percentage terms that cannot be much.

What I would rather focus on is how does the use of agriculture influence the robustness and depth of ecosystems. Extensive use of monocultures exposes humanity to tremendous idiosyncratic pathogen risk. Some yield sacrifice is worth paying to ensure greater robustness and pigovian taxes on mono-cultures are a simple way around it. Second, the quantity of biomass seems an object of interest. Just as a spot of forest can support a full time jungle or light grasses for part of the year, we might be interest in sacrificing some total output  to allow more room for plants and animals. For example, a field could contain vegetables which we eat directly or we could use it to grow grass we feed to cattle. The former uses the land once  to the latter’s twice. I view this analagous to increasing the level of inter-mediation in an economy.

 

The article is definitely worth a read, spending most of its time covering not the point above but the environmental and personal liberty benefits of urbanization.

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