ARE TREE MONOCULTURES MORE EFFICIENT IN PRODUCING PAPER FIBER THAN HEMP MONOCULTURES? A recent advertisement states "According to the US Department of Agriculture hemp produces 4:1 times more paper per land area than trees." However, the data cited is about 80 years old (USDA Bulletin #404 was published in 1916). The growth rate for wood was 0.37 cord/acre/year (approximately 2.3 cubic meters/ha/yr). The title of the Bulletin is "Hemp hurds as paper-making material" by Lyster H. Dewey and Jason L. Merrill (thanks to Stephanie Bianchi who tracked down the reference). The 1916 Bulletin compares yields of hemp grown in a monoculture (single species crop) with yields from trees grown in natural stands (often containing several tree species per hectare). We now know that wood yields from intensively managed monocultures can be greater than that achieved from multiple species native stands. Therefore, I suggest those advocating use of hemp paper should recalculate the land use efficiency. Current information may show that intensive tree monocultures require less land per ton of paper than hemp monocultures. Some approximate growth rates of tree monocultures in 1994 are: Country cubic meters/ha/yr Brazil (Eucalyptus) 35 New Zealand (Pinus) 25 South Africa (Eucalyptus) 21 Chile (Pinus) 21 Congo (Eucalyptus) 20 South Africa (Pinus) 15 United Kingdom (Picea) 14 West US (Pseudotsuga) 14 Southern US (Pinus) 9 ---------------------------------------------------------------------------- In 1916, Jason Merrill was concerned about the rapid depletion of forests in the United States. His work involved making paper from hemp hurds ( a waste product of the hemp industry). He expected hemp to be one of the staple agricultural crops in the United States and using the waste to make paper could reduce the expected shortage of wood paper. Readers may be interested in the following comments by Jason Merrill (Bulletin #404). "There seems to be little doubt that the present wood supply can not withstand indefinitely the demands placed upon it, and with increased scarcity economy in the use of wood will become imperative. This effect is already apparent in many wood-using industries, and although the paper industry consumes only about 3 per cent of the total forest cut, it is probable that it will be affected through this economy. Our forests are being cut three times as fast as they grow, and as wood becomes more expensive proper growing and reforesting will receive more attention. Thus, naturally, a balance will be established between production and consumption, but as this condition approaches its limiting values the price of wood may rise to such levels that there will be a demand for other raw materials." What happened in the 8 decades since has been quite different than that predicted by Merrill. For example, the amount of wood used for paper has increased. In 1916, the amount of woodpulp production in the Southern United States (South) was about 230,000 metric tons (few pine plantations were being established). By 1984, the production was up to 35,054,000 metric tons and about 745,000 hectares of pine monocultures were being established annually in the South. The amount of annual growth of wood in the Southern US now equals about 153 million cubic meters/year. Merrill was right when he predicted an increased attention to tree planting. In 1993, the South grew about 1,123 million tree seedlings for reforestation. Thank goodness here in the Southern United States, we now have effective fire control (the area burned in the South in 1916 was about 4 million hectares) as well as an efficient replanting program. By the turn of the century, it is predicted that half of the conifer volume harvested in the South will be from plantation monocultures (even though only 23% of the timber stands would be in pine plantations). Thanks in part to fire control and monocutures, our growth to harvest ratio is now 1 to 1. This ratio is much more "sustainable" than the 1 to 3 ratio in 1916 when wood was harvested only from native forests. David South School of Forestry Auburn University, AL 36849-5418 dsouth@forestry.auburn.edu 205-844-1022 205-844-1084 (FAX)
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