Timber trade in the United States of America 1870 to 2017. A socio-metabolic analysis

Figures & data

Table 1. Processing steps and factors to convert different reported units of the products traded into metric tons and the sources reporting the original figures for the United States between 1870 and 2017.

Sources of data and definitions	Units used in the original sources	Conversion factors to metric tons (see Appendix A for sources)	Product definitions and conversion steps
Defebaugh (1907)	Mahogany in board foot	*0.00348*0.576	Timber of tropical hardwood species. We first converted board foot to cubic meters (factor 0.00348), after which we applied a standard volume-to-weight conversion factor of 0.576 for hardwoods.
	Board and other sawn lumber in board foot	*0.00348*0.491	Board is timber that has been cut into varying rectangular widths and lengths: often, the timber is treated (with lamination), before the sale. Timber boards can be used in a wide range of construction projects. Sawn lumber: logs that are cut lengthwise to make long pieces and crosswise to length depending on standard or customs. We first board foot to cubic meters (factor 0.00348), after which we applied an average standard volume-to-weight conversion factor of 0.491.
	Shingles (units)	*1000*0.000973*0.491	Wood shingles are thin, tapered pieces of wood, used to cover roofs and walls of buildings to protect them from the weather. Historically, their dimensions are 10 to 19 mm height, 76 to 203 mm width and 360 to 919 mm length. In the United States the most common shake – a basic wooden shingle made from split logs, is about 460 mm long. Sources: U.S. Department of the Interior, National Park Service (Wood shingle). This information helped us to get a sense of the volume of a shingle, using average lengths: 1 shingle = 15*141*460 = 972,900 mm^3 = 0.000973 m^3 Next, we converted from volume to weight by applying a standard volume-to-weight conversion factor of 0.491
	Logs in thousands of board feet	*1000*0.00348*0.405 / 0.576	A log is a part of the trunk or a large branch of a tree that has fallen or been cut off. Logging – the process of cutting, processing and moving to a location for transport-, is the beginning of a supply chain that provided raw material for many sectors (housing, construction, energy, paper). We first multiplied by 1000 then by 0.00348 to get cubic meters, after which a standard volume-to-weight factors was applied, in the case of softwoods, 0.405, for hardwood 0.576.
	Timber hewn and sawn in cubic feet	*0.02832*0.491	Timber hewn is a log that has been converted from its rounded natural form into lumber with more or less flat surfaces with an ax. It is an ancient method, and is now used only occasionally. Sawn timber is timber that is cut from logs into different shapes and sizes. Timber that has been sawn to size but has not been finished, or is rough. First, we converted from cubic feet to cubic meters by multiplying by 0.02832, then to metric tons with an average standard density conversion factor of 0.491.
	Board planks, joists, scantlings and staves in thousand feet	*1000*0.00348*0.491	A timber board is an intermediate product that has been cut into varying rectangular widths and lengths. It is often treated before sale. A board plank is a timber that is flat elongated and rectangular, with parallel surfaces that are higher and longer than wide. Used primarily in carpentry, but also in ships, house and bridges. A joist, also used in construction, is a structural member that spans horizontally between the foundation of a building, or between walls. It is a sort of beam (that is a structural element that resists loads applied laterally to their axis), usually made of solid timber. Data were converted from thousand feet, to feet (*1000), then to cubic meters (0.00348), and then to metric tons (0.491).
U.S. Bureau of the Census (1975)	Lumber total in trillion board feet	*1,000,000,000*0.00348* 0.491	We first multiplied by 1,000,000,000, then by 0.00348 to convert from board feet to cubic meters, then from volume to weight (0.491).
	Lumber (softwoods and hardwoods) in trillion board feet	*1,000,000,000*0.00348* 0.405 (softwoods); *1,000,000,000*0.00348* 0.576 (hardwoods)	Same procedure as for total lumber, except for using a different standard volume-to-weight conversion factors for softwoods (0.405) and hardwoods (0.576)
	Logs (softwoods and hardwoods) in million board feet	*1,000,000*0.00348*0.405 (softwood); *1,000,000*0.00348*0.576 (hardwood);	We first multiplied by 1,000,000, then by 0.00348 to convert from board feet to cubic meters. Next we converted volume to weight by using different standard conversion factors for softwoods (0.405) and hardwoods (0.576)
	Plywood from mm sq. ft. (softwood)	1000*0.295*0.405	We first multiplied by 1000, then by 0.295 to convert from square feet to cubic meters. Next, we converted volume to weight by using the standard conversion factor for softwoods (0.405)
	Pulp products in short tons	*0.907	To convert quantities given in short tons into metric tons, we multiplied by 0.907
Howard and Liang (2019)	Timber products (softwoods and hardwoods) in million cubic feet	*1,000,000*0.02832*0.405 (softwood) *1,000,000*0.02832*0.576 (hardwood)	We first multiplied by 1,000,000, to convert from cubic feet to cubic meters by 0.02832, then used different standard conversion factors for softwoods (0.405) and hardwoods (0.576)

Note: See text and Appendix A for details about the conversion factors.

Source: Defebaugh (1907), U.S. Bureau of the Census (1975), and Howard and Liang (2019).

Table 2. Classification of aggregated wood product categories used in this analysis and corresponding products reported in original sources, and respective FAO categories and products.

Aggregated product categorization used in this analysis	Raw materials	Primary products	Final products
Products reported in original sources	Logs and round timber	Sawed lumber, wood pulp, sawn and hewn lumber, lumber (softwood & hardwood) and pulp wood chip	Shingles, boards, planks, joists and scantlings, plywood, pulpwood-based products, panel products, plywood and veneer
Corresponding products classified by the FAO	Wood in the rough	Wood chips and particles, residues and recoverable wood products and Sawn wood.	Veneer Sheets, and Wood-based panels

Table 3. Average U.S. imports and exports by main trade partners (countries and world regions) as fractions of total timber products traded for three periods, 1871–1905, 1965–1996, 1997–2017.

	Physical imports			Physical exports
	1871–1905	1965–1996	1997–2017	1871–1905	1965–1996	1997–2017
Canada	87%	45%	66%	3%	9%	20%
Mexico, Central, South America	<1%	<1%	2%	21%	<1%	14%
UK	<1%	<1%	<1%	5%	<1%	1%
Europe, other	<1%	<1%	4%	5%	4%	8%
China	<1%	1%	3%	<1%	2%	7%
South East Asia	<1%	2%	2%	<1%	<1%	1%
South Korea	<1%	2%	<1%	<1%	2%	2%
Japan	<1%	<1%	<1%	<1%	27%	8%
Other countries/regions	12%	49%	20%	66%	55%	39%

Sources: Defebaugh (1907), Howard & Liang (2019).

Notes: Data missing between 1906 and 1964; between 1965 and 1996, pulpwoodbased products were not reported. All products (RM, PP, FP) covered between 1997 and 2017. Yearly average shares of total.

Figure 1. Physical imports and exports of timber products of the United States, 1870–2017. Combined timelines. For sources, products considered, and conversion methodology see Table 1 and text. Data in million metric tons per year. Physical exports are displayed as negative flows.

Figure 2. Physical trade balance (PTB) of the main timber product categories traded in the United States, 1870–2017. From 1905 to 1950, data on raw materials and finished products are not accessible or aggregated in the primary products (e.g., paper and cardboard are listed with wood-pulp products, i.e., in the Pp category). Negative values indicate net exports, positive values net imports. Data in million metric tons per year.

Table 4. Forest transition indicators, based on Magerl et al. (2019), Magerl et al. (2022) and their connection to international trade of wood in the United States – area (mha = Mega hectar = million hectar), biomass stocks (GtC = gigatons carbon = one billion tons carbon), harvest, and trade (Mt/yr = megatons per year) for the three periods discussed (1870–1914, 1915–1960, 1961–2017) in absolute numbers (left panel) for selected time points and compound average annual growth rates for the three periods (right panel).

			1870	1914	1960	2017	1870–1914	1915–1960	1961–2017
Forest area
			Mha				%Δ
			303.0	257.6 ^#	255.3	257.1	−0.4%	0.1% **	<0.1%
Forest biomass
			GtC				%Δ
	Stocks		NA	28.6^+	29.1	42.1	NA	0.2% *	0.6%
			Mt/yr				%Δ
	Harvest	Total	61.8	276.4 ^#	263.7	282.9	3.9%	0.3% **	0.6%
	Imports	Total	1.2	2.9	18.7	42.6	2.2%	2.1%	1.2%
		RM	NA	0.3	0.5	0.3	NA	3.5%	0.8%
		PP	1.2	1.2	8.5	27.0	< −0.1%	3.4%	1.6%
		FP	0.05	1.4	9.8	15.2	8.9%	1.4%	0.5%
	Exports	Total	0.6	6.4	3.2	30.0	6.2%	−1.1%	1.8%
		RM	NA	0.3	0.4	4.9	NA	2.7%	−0.1%
		PP	0.4	3.9	1.4	11.7	6.3%	−1.5%	3.2%
		FP	0.3	2.4	1.4	13.4	6.0%	−1.2%	2.0%
			Mt/yr
	PTB	Total	0.6	−3.5	15.6	12.6
		RM	<0.1	<0.1	0.1	−4.5
		PP	0.9	−2.7	7.1	15.3
		FP	−0.2	−1.1	8.4	1.8

Notes: Absolute exports displayed as positive numbers. Forest area: productive protected and used forests, including shrub- and woodlands. Stocks: total above- and belowground living and dead biomass, including litter. Harvest: industrial wood and fuelwood, including forest biomass grazed. Blue hatchings indicate % growth, red hatchings indicate % decrease. NA: no data available. Δ indicates % change.

⁺ = 1907, ^# = 1910, * = 1907–1960, ** = 1910–1960.

Table A1. Conversion from imperial to metric units by original source.

Abbreviation	Unit	Conversion to	Factor	Source
ft³	Cubic feet	Cubic meters	0.02832	FAO (2020)
FBM	Board feet	Cubic meters	0.00348	FAO (2020)
CD	Cord	Cubic meters	2.36000	FAO (2020)
rndwd eq ft³	Cubic feet roundwood equivalent	Board feet	6.95200	McRoberts et al. (2007)

Table A2. Conversion of wood products from volume to weight by wood type.

Wood type ^a	Density [tons at 15% moisture content/m³]
Coniferous/softwood	0.405	Krausmann et al. (2013)
Non-coniferous/hardwood	0.576
Average	0.491

^aUsed for all industrial timber products and fuelwood.

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