July 26, 2004
Humans Use A Fifth Of All Land Plant Materials

Dr. Marc L. Imhoff, a Principal Investigator in NASA's Carbon Cycle Science and Land Cover Land Use Change Programs, visiting scientist Lahouari Bounoua and colleagues have added up the human consumption of plant matter and found that globally humans are consuming 20% of the world's plant life.

NASA scientists working with the World Wildlife Fund and others have measured how much of Earth's plant life humans need for food, fiber, wood and fuel. The study identifies human impact on ecosystems.

Satellite measurements were fed into computer models to calculate the annual net primary production (NPP) of plant growth on land. NASA developed models were used to estimate the annual percentage of NPP humans consume. Calculations of domesticated animal consumption were made based on plant-life required to support them.

Marc Imhoff and Lahouari Bounoua, researchers at NASA's Goddard Space Flight Center (GSFC), Greenbelt, Md., and colleagues, found humans annually require 20 percent of NPP generated on land. Regionally, the amount of plant-based material used varied greatly compared to how much was locally grown.

Note that this analysis does not include the oceans. So human fishing activities as a percentage of all ocean-based biomass production are not included in the above analysis.

North America's lower latitudes and lower population density allows it to produce 9 times more carbon in plant matter than Europe. So even though North America consumes much more plant matter than Europe humans in North America consume a smaller percantage of its local plant matter than do Europeans.

The effort resulted in a worldwide map of consumption that could be broken down to individual regions by population to compare how much an area such North America, for example, consumes with the amount it can produce locally - about 24 percent of its annual plant production.

Highly populated Western Europe and South Central Asia, one the other hand, each consume 70 percent of the greenery they produce.

With a much larger population China is already consuming more plant matter per year than North America even though China consumes only a fourth the amount per capita. Continued industrialization therefore seems likely to greatly increased world human demand for plant matter. This seems likely to result in rising timber prices and a shift toward the use of other types of building materials.

The bigger problem with rising Chinese demand and overall rising world demand is that it will decrease the amount of biomass available for wild animal life.

The rising demand for biomass also argues against a big role for biomass materials as future energy sources. Granted, some waste biomass could be converted to energy. But even wastes are potential food sources for bacteria, fungi, insects, fish, and other life forms. A perfectly efficient human-managed biomass cycle is going to squeeze out other life forms that rely upon plants, dead animals, and wastes as food sources.

Also see Structures In United States Cover Area Equal To Ohio.

Share |      Randall Parker, 2004 July 26 01:50 PM  Energy Tech


Comments
X said at July 26, 2004 8:17 PM:

If everyone in the world were to suddenly become a vegan, I wonder how much that 20% figure would drop. I have no hard data, but I suspect a lot or maybe even most of that 20% of vegetation is consumed by animals used for food and dairy. I remember reading somewhere that one cow can eat enough grain to feed dozens of people at a time.

Patrick said at July 27, 2004 1:33 AM:

In most places in the world, cattle are not fed grain.

They are in Western Europe, North America and Japan, but in most of the planet they eat grass and other plantlife not consumable by humans.

Be careful not to take figures from a small specialist industry like grain fed beef, and extrapolate them across a much larger industry that does things differently.

No I don't have any references, but I have worked in the Australian beef industry, and grain feeding represents a tiny fraction of the total market.

Toby Sargeant said at July 27, 2004 6:59 PM:

http://archive.greenpeace.org/~geneng/reports/animalprod.pdf

"In the EU as a whole, nearly 3/4 of agricultural land was used to produce animal feed in 1996, including grassland."

http://www.netcentral.co.uk/satcure/meat.htm

"Collectively, the world's livestock produce 10 per cent of all the greenhouse gases, including 25 per cent of the methane, among the most potent of all. Then there is water, which is rapidly becoming the greatest check on overall food productivity. It takes 500 litres to raise a kilo of potatoes; 900 for a kilo of wheat; nearly 2000 for rice or soya; 3500 for a kilo of chicken; and a staggering 100,000 litres for a kilo of beef."

"...2 kilograms of feed for each kilogram of chicken, 4 for pork, and 7 or more for beef"

The latter two quotes are from an article printed in New Scientist. While I take most things that Greenpeace say with a grain of salt, the New Scientist article and the Greenpeace article agree at least on the amount of feed required to produce a kilo of beef. Because the 20% seems to be based on area, it seems safe to assume that this figure, based upon the EU statistic (which, given its reliance on imported feed, and the density of population, is likely to be an underestimate), would drop to 5%.

I think it's a moot point that the environment would be better off if humans collectively stopped eating meat.

Rather than how much biomass is being turned over yearly, I would be more interested to know how much biomass is not being renewed.

Garson Poole said at July 28, 2004 6:37 AM:

Randall Parker said: The rising demand for biomass also argues against a big role for biomass materials as future energy sources.

One proposal for biomass energy by Michael Briggs at the University of New Hampshire is entitled "Widescale Biodiesel Production from Algae". http://www.unh.edu/p2/biodiesel/article_alge.html

The proposal suggests that large algae farms could be situated on desert land such as the "The Sonora Desert". The scale of the land necessary is discussed in this quote: "Enough biodiesel to replace all petroleum transportation fuels could be grown in 11,000 square miles, or roughly nine percent of the area of the Sonora desert." Of course, if algae farms were built they would displace the existing flora and fauna.

It might be possible to construct organisms from scratch that are well suited to creating biomass energy. Craig Venter started the "Institute for Biological Energy Alternatives" in part to explore this possibility:
http://www.bioenergyalts.org/about.html
Specially designed algae or algae created by selection pressure might substantially reduce the required land for algae farms.

Alternatively, some algae can used to directly generate hydrogen as mentioned in this Wired article.
http://www.wired.com/news/technology/0,1282,54456,00.html
Unfortunately, the company mentioned “Melis Energy” mentioned in the article has a dead website. There is a slide show by the main researcher, Tasios Melis of Berkeley, suggesting he has switched to hydrocarbon production: http://www.lbl.gov/LBL-Programs/pbd/energy/biomass/default.htm

(Fly mentioned the Venter venture in a thread entitled "Structures In United States Cover Area Equal To Ohio" June 18 2004. I first read about it when it was created.)

Fly said at July 28, 2004 3:31 PM:

Garson, thanks for the link on biodiesel.

I wonder how far we are from being able to engineer sea plants to make fuel oils. Image a sea habitat situated in the ocean “desert” where there aren’t sufficient nutrients for sea plants. Nutrients are pumped from the deep seabed to nurture bioengineered plants. Abundant free space, water, light, and nutrients to supply all the world's fuel needs in a renewable fashion that doesn’t increase CO2 levels.

Fly said at July 28, 2004 3:43 PM:

Hmmm, I see they’ve already considered a water supply and nutrients and the land isn’t that useful for anything else so the desert based production might be better. The US could protect the oil farms and the difficulties of a sea habitat could be avoided. Also reduces transportation risks and costs.

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