All material flows cause environmental change or transformation. The material flows associated with human activity are large and, in many cases, incompatible with natural ecosystems since the flows accumulate as wastes and semi-permanent ecosystem transformations. The data presented show that, for the USA, and the rest of the world, the flows of material for processed physical goods have increased at the same rate as population, and continue to do so. For the USA, the hidden flows associated with processed commodities, and the transformations of the landscape to create the built infrastructure, are seen to be three to four times greater than the commodity flows for food, fuel and physical goods. Current economic accounts do not provide information on hidden flows.
Almost all processed goods eventually exit from the economy, some rapidly, some over much longer periods of time. Only recycling (most significant for several metals and paper), re-use or remanufacturing prevents a material input from exiting to the environment. The industrial economy of the USA is therefore essentially an open, once-through system that results in environmental impacts occurring at every stage of the material cycle. The major change necessary is to decouple the use of physical material from the output of that material to the environment. Although at present use and outputs are essentially synonymous, they need not be.
Accounts that measure the physical activity, material flows, of industrial systems are a necessary complement to national economic accounts. These accounts are required to identify trends and point to critical areas most in need of attention. Currently, the capability exists to develop overall national material flow indicators and rudimentary detailed accounts, but considerable additional work is required to develop improved and additional data and refine techniques.
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