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market production of natural ecosystems was esti-
mated to be $2.6 billion, a value comparable to the
annual marketed value of agriculture.
In 1983 the term ‘‘emergy’’ (spelled with an ‘‘m’’)
suggestive of ‘‘energy memory’’ was proposed to
eliminate confusion with other energetic valuation
concepts, such as embodied energy and exergy, the
latter defined as the sum of available energies of all
kinds. Emergy, in contrast, expresses all numbers in
one kind of energy (for example, solar energy)
required to produce designated goods and services.
Thus, it measures the work of the environment and
economy on a common basis.
EMDOLLARS, the economic equivalent of emergy,
is defined as the GNP equivalent to emergy contribu-
tions (conversion: 1.16 trillion solar emjoules per
1997 US dollar). A recent calculation by Brown and
Ulgiati (1999) found two-thirds of the global wealth
produced each year to come fromemergy of fuel use
and one-third fromthe emergy of renewable energy
of nature.
Emergy evaluations appear in more than a hun-
dred publications and include applications to a wide
variety of ecosystems, watersheds, alternative tech-
nologies, information, species, environmental im-
pacts, states, countries, and causality in history [for
example, Swedish power in the 16th century (Sund-
berg and others 1994); United States Civil War,
(Woithe 1994)]. Emergy analysis concepts and litera-
ture are summarized in HT Odum’s (1988) Science
article and his 1996 book, Environmental accounting:
EMergy and environmental decision making (HT Odum,
1996).
Energetic evaluation is a way for ecological data
to influence environmental policies. Environmental
management that maximizes emergy production
and use (‘‘maximum empower’’) is a way to develop
more real wealth in the combined system of hu-
mans and environment. The presentations of those
using exergy, emergy, energy input–output, and
more traditional economic evaluations at a vigorous
workshop at Porto Venere, Italy in 1998 have now
been published (Ulgiati and others 1999).
In conclusion, timing is of the essence. After
several decades of theoretical discussions and many
real-world applications, we judge that the time has
come for serious consideration of the energetic
approach to valuation of ecosystem services and
market goods and services on a common basis. As
we have emphasized in this commentary, we need
not only to extend market valuations to include
more consideration of ecosystem services, but ulti-
mately we need to put the economy on the same
basis as the work of the environment (that is,
externalize the internalities).