The material footprint of nations

The material footprint of nations

Thomas O. Wiedmanna, Heinz Schandlb, Manfred Lenzenc, Daniel Moranc, Sangwon Suhf, James West, and Keiichiro Kanemotoc,

Edited by Joan Martínez Alier, Autonomous University of Barcelona, Barcelona, Spain, and accepted by the Editorial Board August 1, 2013 (received for review November 30, 2012)

ABSTRACT and AUTHOR AFFILIATIONS: http://www.pnas.org/content/112/20/6271

In this paper, the authors aim to address a key question in sustainability science:  How many and which natural resources are needed to sustain a modern economy?  I chose this as one of the articles on my reading list because of my interest in scholarly analysis of what sustainability means.  It is a word that one hears often but, as of yet, I have not run into a definition that is quantitative.  Although this paper addresses sustainability in the context of resource use only (as opposed to energy use, waste production, species conservation, etc.), it does make an effort to resolve a definition of the term sustainability in a more quantitative way, at least for consumption practices.  One of the metrics that they looked at is the extent of decoupling between resource use and economic growth, presumably because this is an important first step in ensuring global sustainability while maintaining or developing standards of living.

The use of resources is one of the metrics that has a clear relationship to issues of sustainability, at least, in one definition.  The EU, OECD, and the UNEP all use the resource productivity ratio which is the gross domestic product divided by the domestic material consumption (GDP/DMC) as an indicator for sustainable development strategies.  GDP/DMC measurements in the last decade in most European countries and the OECD have shown an increasing value for the ratio indicating a decoupling of the economic growth from resource use.  The authors of the paper point out, however, that the DMC represents only “materials directly used by an economy (raw materials extracted from the domestic territory plus all physical imports minus physical exports).  It does not include the upstream raw materials related to imports and exports originating from outside of the focal economy.”

To account for the limitations of the GDP/DMC, in this study, the authors present the quantitative concept of “material footprint” (MF), a more comprehensive accounting system defined as “the global allocation of used raw material extraction to the final demand of an economy”.  This accounting method links the “beginning of a production chain (where raw materials are extracted from the natural environment) and its end (where a product or service is consumed).”

The MF for each country is calculated by taking the raw material equivalent (RME) of imports and adding that to the domestic extraction (DE) of the raw material of and subtracting the RME of exports.  The authors have the following to say about this new method:  “We essentially redefine resource productivity based on the MF and compare it with the conventional indicator based on DMC to assess the veracity of resource productivity indicators currently used to inform policies for sustainable resource and materials management. Viewed from a consumption perspective, the meaning of resource productivity thus changes to one that truly captures all upstream material movements along global supply chains.”

RESULTS

1.1. MF of Nations and International Trade in 2008.

The total global MF, which is equal to the total used DE of raw materials, amounted to 70 billion metric tons (Gt) in 2008. Forty-one percent of this amount (29 Gt) was indirectly associated with trade flows between the 186 countries studied in this research.

The export of goods and services accounted for 2/5 of all the global raw materials extracted.  This is more than the 10 Gt measured for direct physical trade of materials and products indicating that actual raw material extracted to support export of commodities exceed that of the physical flow of traded materials.  “The consumption-based MF includes raw material extractions in the trade balance even if some of the materials never actually leave the country of origin (particularly process wastes and auxiliary material flows).”

MF results for 12 countries and for all 186 countries are given in the paper and the supporting documents, respectively. 

Not surprisingly, China has the highest absolute MF, 60% from construction materials from rapid industrialization and modernization efforts in the last several years. It also has the highest MF from raw materials associated with exports, most of which are construction materials.

Australia has the highest per capita MF (35 t/cap) but the US, UK, Japan, and Chile are close and comparable (25 t/cap).

Figure 1 in the article breaks down the MF into RME of imports and exports for 12 countries.  The main RME categories are biomass, fossil fuel, metals, and construction minerals (see Table SI in the supporting information for a breakdown of each of these categories).

Lower standard of living and lower level of material consumption are correlated with lower MF values (below 15t /cap, India lowest at 3.7 t/cap).

Figure 2 shows a series of plots for different countries comparing the time change in DMC/cap versus MF/cap from 1990-2008.  The authors note that as countries “mature”, their MF/cap increases much more than the DMC/cap which shows a decline for some countries.  DMC/cap values afor resource exporters like Australia, Russia, South Africa, and Chile are considerably larger than the MF/cap.  Why?  The answer came a paragraph later: “Nonexported mine tailings are included in DMC of the exporting country, whereas the MF allocates them to the importing (final demand) countries. DMC will therefore overestimate consumption for exporters of metals and biomass and underestimate it for importers of metals and biomass.”

“The difference between DMC and the MF can be explained by the fact that traded goods require much more material than what is physically incorporated in them. Wealthier countries’ imports of finished and semifinished products are linked to a larger amount of raw materials compared with the physical quantity traded.”

MF calculations shift the burden of raw material resource extraction to the importer (“ultimate consumer) and not the exporter (thus increasing DMC/cap and decreasing MF/cap for exporters; the opposite is true for large importers).

1.2. Reassessing Resource Productivity.

Sustainable growth aims for a decoupling of natural resource depletion and the associated environmental impacts of economic growth.  The DMC/GDP, which has been used as a metric for this decoupling, has shown a decrease from 3.6 kg/dollar in 1900 to 1.3 kg/dollar in 2005.  OECD data show that G8 countries have seen their DMC/GDP ratios go down by a half between 1990 and 2008.  Using this metric, Canada, Germany, Japan, and Italy have decoupled their economic growth from DMC in absolute terms.

Plots of relative changes in MF, GDP, and DMC from 1990 to 2008 (Figure 3), according to the authors, indicate no decoupling taking place, unlike intepretations of DMC/GDP.  The authors attribute this to increased indirect use and even dependency on construction materials.  It is notable that South Africa has decreasing values for both MF and DMC despite increasing GDP indicating absolute decoupling.

1.3 What Drives the MF of Nations?

Several studies cited in the paper have shown that affluence and other factors are primary drivers of consumption-based indicators , such as land, carbon, energy, ecological footprint, water footprint, and resource use.

The authors explored the answer to this question in the context of MF by carrying out a cross-country, multivariate regression analysis (for the year 2008) to find correlations if any between changes in MF and DMC and changes in three variables:

i) GDP-PPP-2005/cap as a proxy for the wealth (individual income) of nations.

ii) DE/cap as a measure for the actual production of raw materials. DE is related (although not equivalent) to the availability of natural resources and the ability for raw material production.

The main reason for choosing this variable was to test the hypothesis that DMC is more strongly influenced by DE than by the MF.

iii) Population density (population per area) as a proxy for the need to import materials from abroad, with the reasoning being that the ability to produce land-based raw materials (crops, fodder, and wood, as well as open-cast mining of minerals to some extent) might be dependent on the availability of unpopulated land.

Some analysis results specially noted by the authors:

A 10% increase in GDP/cap correlates with a 6% increase in MF/cap.

Changes in DMC/cap are mostly explained by changes in DE/cap; much lesser extent to GDP/cap [?].

The authors point out that “This result broadly confirms that products subsequently manufactured out of raw materials are traded with their material embodiment “in tow,” thus adding to the MF of consuming (importing) countries but not to their DMC”, adding that this is especially true for traded animal and dairy products which carry a large amount of upstream biomass (an order of magnitude greater than the actual biomass traded).  [I am not sure how data indicate this.]

On construction materials: “the ability of rich countries to buy products is indirectly dependent on construction materials from abroad; the construction component of the MF/cap is clearly explained by the GDP/cap (α = 0.86) and not at all by the DE/cap (β = 0.01). The DMC/cap of construction materials, on the other hand, is mainly explained by the DE/ cap (β = 0.80).”

Fossil fuels and metal ores: GDP/cap explains the rise for both the MF and the DMC metrics.

Population density shows no correlation (“lesser or mixed influence”) to resource use indicators.  The authors speculate that negative elasticities for metal ores suggest efficiency in use for high population density areas.

“What do these findings mean for resource productivity? Expressing the regression coefficients of resource productivity with income as 1 − α (SI Text), we find that total resource productivity increases less with income when measured on a GDP/MF basis (1 − α = 0.40) compared with a GDP/DMC basis (1 − α = 0.85). Mostly responsible for this difference are the biomass and construction material components. It is thought that high-income countries can achieve higher resource productivity because their

GDP is relatively more decoupled from biomass consumption than from other materials (23, 46), and possibly because demand for construction materials may reach a certain level of saturation [the case of steel is reported in ref. (57)]. However, the MF does not attest to such decoupling. As nations become richer, the change in their socioeconomic metabolism (from agricultural to industrial production) helps less to improve resource productivity than previously thought.”  These findings confirm previous findings that as nations get wealthier, biomass use increases along with a more meat-rich diet.

DISCUSSION

·         The authors note that the 70 billion t of raw material extracted is unprecedented and that RME/cap average of 10.5 t/cap in 2008 is the highest level seen.

·         41% of total global resource extraction (29 Gt) was associated with international trade flows in 2008.  Only 1/3 of these materials actually crossed borders; the environmental impacts of the resource extraction also stay with the net exporting countries.  The extraction along with processing and delivery of these resources involve environmental impacts such as water resource depletion, soil erosion, biodiversity loss, pollution through agrochemicals, mine tailings, and oil spillages. 

“The MF of nations reflects the increasing complexity and multicountry nature of global supply chains and is the appropriate indicator if the aim is to pinpoint the ultimate consumer responsibility of a country for impacts associated with raw material extractions worldwide.” The ability of the MF concept to allocate upstream material extractions to consuming countries provides a way to link between product/extraction and consumption.

The use of DMC as a metric does not take into account the full extent and burden shift of resource dependence and may limit decision making.  For instance, absolute decoupling based on the DMC metric may simply suggest increase in export and off-shoring of resource extraction:  “Developed nations experience an increase in imports of semifinished and finished products and a change in economic structure toward service economies, which add high value to the GDP. These trends make developed countries look more resource-efficient, but they actually remain deeply anchored to a material foundation underneath.”