The eco-price: How environmental emergy equates to currency

Elliott T. Campbell n, David R. TilleyDepartment of Environmental Science and Technology, University of Maryland, College Park, United States

a r t i c l e i n f o

Article history:Received 26 April 2013Received in revised form19 November 2013Accepted 5 December 2013Available online 7 January 2014

Keywords:Ecosystem serviceEmergyEnvironmental accountingNatural capitalEco-price

a b s t r a c t

Energy flows through economies in a hierarchical pattern with vast amounts supporting the base whileeach step has less and less flowing through it. Money is inextricably connected to many of these energyflows in a countercurrent. At the most aggregated scale of an economy, where its gross domestic productis measured, the mean ratio between the flows of solar emergy and money is known as the emergy-to-dollar ratio (EDR). However, the relationship between solar emergy and money is not constant along theenergy hierarchy of an economy. While estimates of this dynamic relationship exist for marketed goodsand services, there has been less work to estimate the relationship for nonmarketed services. We developthe “eco-price” to meet the goal of better predicting correlation between environmentally derivedservices and currency. It is defined as the flow of emergy of an ecosystem service relative to the moneyestimated to flow as a countercurrent. Twenty-nine eco-prices were estimated from cases of knownexchange for water, soil, air pollution and natural resource commodities. The eco-price reconciles thebiophysical value of the environment with economic value and extends the capability of emergy analysisto suggest “marketable” monetary values for the work of the environment.

& 2013 Elsevier B.V. All rights reserved.

1. Introduction

A system of environmental accounting for energy invested inall studied aspects of a system, called emergy synthesis, wasdeveloped by Odum, H.T. (1988, 1996) to provide valuationexternal to the economy, adherent to the fundamental laws ofthermodynamics. This system of valuation allows the connectionsbetween nature's production of ecosystem goods and services andpeople's consumption of them to be quantified in the samephysical unit (i.e., solar energy) and then translated into financialterms (i.e., money). Previously this translation was done byequating the emergy flowing in a studied economic system (i.e.,total empower throughput) to the dollars flowing in that sameeconomy (e.g., gross domestic product) during a given time period.However, this method does not discriminate between the originsof the emergy and assumes a constant emergy-to-dollar ratioacross products and sectors, which is demonstrably inaccurate(Ukidwe and Bhakshi, 2007, see Fig. 1). The emergy per dollar ratiodecreases as you rise through the sectors of the economy, with thehighest emergy to dollar being found in the primary economy andlowest in the quaternary economy (Campbell and Ohrt (2009);Baral and Bakshi, 2010; Ukidwe and Bhakshi, 2007). The primaryeconomy deals in goods made up of work from the environment,

not valued by the economy (see Section 1.2). This research intro-duces a method that estimates financially realistic dollar values forecological work (i.e. ecosystem goods, services, and capital), basedentirely on environmental emergy flows. The need for an ecologicalsystem of valuation was perhaps best stated by Odum and Odum(2000): “When human valuations do not measure the real con-tributions of natural ecosystems, as is currently the case, ecosystemsare not protected, and the larger systems produce less when thenatural ecosystems are lost to development”.

This research introduces a novel method for linking thebiophysical measurement of ecosystem function with the eco-nomic value that people place upon that function. This is areconciliation of donor value (inherent worth, like the ability todo work) and receiver value (worth placed upon a good/service bythe beneficiary). Efforts have been made to value the work ofecosystems from a purely biophysical standpoint (Hall andKiltigarrd, 2011; Odum, 1972) and from the purely economicperspective (Daily et al., 1997; Costanza et al., 1997) but takenfrom these singular perspectives they fall short of capturing thefull spectrum of value (Odum, 1996; Odum and Odum, 2000; Dalyand Farley, 2004). Environmental accounting has attempted to putmonetary value on ecological work (Campbell and Brown, 2012;Pulselli et al., 2011) but these evaluations still tend toward thebiophysical perspective and fail to capture society's preferencesregarding the environment. This study introduces the “eco-price”to assess the value of ecological work. The eco-price is definedhere as the amount of money that flows countercurrent to a flowof emergy derived directly from the environment. It has units

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Ecosystem Services

2212-0416/$ - see front matter & 2013 Elsevier B.V. All rights reserved.http://dx.doi.org/10.1016/j.ecoser.2013.12.002

n Correspondence to: 0426 Animal Science Building, University of Maryland,College Park 20742, USA. Tel.: þ1 401 212 6735.

E-mail address: ecamp88@umd.edu (E.T. Campbell).

Ecosystem Services 7 (2014) 128–140

of solar emjoules per dollar (sej/$). The eco-price reconciles thebiophysical reality of ecosystem performance with economicmeasures of the value people place on ecological work. Suggestingthat there is a strong relationship between ecological emergy anddollars is not a new method. The first such calculation wasperformed by Odum et al. (1959), when he related the price ofhay to an equivalent production of marine turtle grass in southTexas bays (Kangas, 2004; Odum et al., 1959). The researchpresented here aims to estimate, assemble and compare a set ofeco-prices for a diverse set of ecosystem services (e.g., hydrologic,carbon, soil, biodiversity). This paper also includes a demonstra-tion of how eco-prices can be used to convert ecological emergyflows of ecosystem services to monetary values that would beuseful for estimating how much land stewards of ecosystemservices should be compensated for producing such services. Tothis end, provisioning services (timber, recreation) are notincluded in our study as their value is already determined by amarket and included in the economy.

While there are many instances where markets, taxes andregulatory programs have paid for the continued provision ofecosystem goods or services these are imperfect measures of totalpreference for products of ecosystems. Tax and regulatory pro-grams directed at the environment are examples of revealedsocietal preference for sustained/increased provision of ecologicalgoods and services, rather than direct measures. A tax can beviewed as revealed preference because citizens of a state orcountry have given implicit consent/willingness to pay a tax giventhat they are responsible for electing the governmental officialsand are participants in the society. By looking at the collection ofrevealed and direct estimates of what people will invest inecological goods/services/capital a complete realization of howsociety values ecological work can be made without the ability torely on direct, free markets dynamics where the price of a good iscontrolled by supply and demand. The current economic systemconsiders the work of the environment to be a free subsidy, andexploits it as such. The eco-price allows a fair payment value to beput on the work of the environment, reflecting the real cost tosociety that occurs when environmental resources are lost. Puttinga value on ecological work has the potential to compel society tolessen their impact on the environment and raise awareness of theintrinsic nature of the environment to human well-being, ulti-mately strengthening the long term sustainability of society(Odum and Odum, 2000; Daly and Farley, 2004; Daily et al.,1997). The eco-prices presented in this paper were calculated asa part of research on ecosystem services from forest lands inMaryland (Campbell, 2012; Campbell and Tilley, in press) and assuch predominately focus on examples from the Mid-Atlanticregion of the United States. The value society places on ecosystemservices likely varies significantly by region so calculating localeco-prices is encouraged for future work using this method.

1.1. How emergy relates to money

Money is the unit for accounting financial debits and creditsand can be traded for goods or services. Goods and services have avariable (in relation to the money exchanged, determined by price)amount of “real wealth”, which can be measured using emergy.Money flows countercurrent to the flow of “real wealth”. Price(currency per quantity) is normally determined by what a con-sumer is “willing to pay” for a good or service in a market.

Spending money in an economy on a good or service serves toreinforce the production of said good/service, supporting the labornecessary to provide it. Higher prices stimulate production whilelower prices stimulate consumers to use more. Free market pricingidentifies the optimal level of production per consumer demand,serving to maximize empower (emergy per time) for the system as

a whole, in accordance with the maximum empower principle(a system will self-organize to maximize the flow of useful energy,i.e. emergy, Odum, 1996). The capitalist, free market pricingsystem facilitates maximization of empower, rather than limitingempower by attempting to control production and consumption.It can be construed that the dominance of free market capitalismas an economic paradigm for the world supports the maximumempower principle. The concept of a free market is predicated onan efficient distribution of goods and services, allowing growthand a maximal throughput of useful work (i.e. emergy). Furtherexploration of the relationship of macroeconomics and emergycan be found in Odum (1996). Brown and Ulgiati (2011) presentevidence that the recent global economic recession in 2008 wastriggered by the reliance of a growth economy on energy sourcesthat are decreasing in net energy (or emergy) yield and suggestthat this relationship is not sustainable.

1.2. The price of emergy along the energy hierarchy

The price (currency per emergy) of a good or service isdependent on the origin of the emergy embodied in the good orservice. As the percentage of the total emergy of a good or servicecomprised by human work or investment increases the moneyassociated with the good/service increases. Human labor/invest-ment is the major determining factor in determining price ($ peremergy) but scarcity can factor in as well, as in the case of preciousmetals and gems that have prices above what would be predictedpurely from the human work necessary for mining and manufac-ture. Fig. 1 is an idealized representation of how emergy andmoney change as you move through the sectors of the economy.Environmental emergy in nature is not highly valued, if at all, by theeconomy, whereas financial markets and the information economyare on the other end of the spectrumwith large quantities of moneyand very little emergy.

2. Methods

The eco-price is a refinement to the emergy methodology, withthe goal of more accurately representing what people are willingto pay for the work of the ecosystem. An eco-price is the ratio ofemergy to dollars observed when an ecological good/service ispaid for or economically valued in some way. An average of severaleco-prices is used to determine monetary value because the eco-price is not a direct measure of willingness to pay; multipleproxies are necessary to establish the best estimate of how societyvalues environmental work. We determined the emergy to dollarexchange for 29 market and non-market instances over the past 15years, predominately in the Mid-Atlantic region of the UnitedStates. The eco-prices are aggregated in the following categories –hydrologic, carbon, soil, air pollution, biodiversity, and commod-ities. Average eco-prices were calculated for each category, gen-erating a specific eco-price for that category. Fig. 2 shows anenergy system’s language diagram depicting ecosystem serviceprovision from natural lands and how the eco-price could be usedto set the price for ecosystem services.

2.1. Expressing public value in dollars

We define public value as the average monetary value placed onemergy of a good or service in a given system (Table 1). When anemergy analyst wants to express the solar emergy as dollars of publicvalue, the standard practice (Odum, 1996) has been to divide the solaremergy (sej) by the mean solar emergy-to-dollar ratio (sej/$) of theeconomy that encompasses the flow of solar emergy. It has beencommon practice in emergy synthesis to show the public value as a

E.T. Campbell, D.R. Tilley / Ecosystem Services 7 (2014) 128–140 129

column labeled “emdollars” or in some cases, “em$”. However, sincewe were not only interested in public value, but also in suggestedeconomic value, we suggest structuring the emergy table like shownin Table 2 and dispensing with the emdollar terminology whenreferring to monetary values determined using the eco-price.

2.2. Estimating the eco-price (Peco)

The exchange between ecological emergy and money can beobserved in markets, tax programs, and government regulations.We looked at all these categories together to better estimate howsociety values ecological goods/services/capital. This particulargroup of eco-prices were assembled to inform a potential paymentfor ecosystem service (PES) program in Maryland so many of theeco-prices are specific to the Mid-Atlantic region of the UnitedStates. In general, it is a good practice to use eco-prices as specific

to the region of study as possible, as they will better reflect thepreferences for ecological work of the population in the studiedregion/State

Peco ¼ EMj=Pj ð1Þwhere EMj is annual solar emergy flow of an ecosystem service jand Pj is the annual flow of money associated with an ecosystemservice j.

2.2.1. Market based PecoPrimary goods such as timber and water supply are mostly

composed of ecological emergy and are sold in free marketconditions. We calculated the average emergy exchanged perdollar in these markets over a year time period. The commodityeco-price was calculated by averaging the average emergy todollar exchange in nine US commodity markets over the 2011

Fig. 2. Energy systems language diagram of ecosystem services. Ecosystem services are products of components of the environment (in this case, water, soil and consumers).Money flows countercurrent to the ecosystem service; with the rate of $ per emergy determined by Peco (eco-price). Money (represented by the dotted lines) is not paid tothe ecosystem but to the owner/manager, represented in this diagram by landowner. Ecosystem services from primary production are not represented for clarity of thefigure.

Fig. 1. Idealized depiction of the relationship of the flows of emergy and money. It should be noted that this figure represents the change in the emergy per $ ratio and thatemergy and money are not on the same y-axis scale, emergy is a cumulative measure and will always be greater than money regardless of sector; the figure shows relativechange in emergy and money. Emergy approaches but never reaches zero in the information economy, the money flow reaches zero in a wholly natural environment.

E.T. Campbell, D.R. Tilley / Ecosystem Services 7 (2014) 128–140130

calendar year

Market Peco ¼ ðemergy of eco: service=good=capital; sejÞ=ðmarket price of eco: service=good=capital; $Þ ð2Þ

2.2.2. Tax based PecoWe looked at how several tax programs generate a certain

amount of monetary investment by the public used to affectecologically positive actions. The amount of money generated bythe tax was compared to the emergy of the ecologically positiveimpact, generating an eco-price.

Tax based Peco ¼ ðemergy of eco: positive impact; sejÞ=ðdollars generated by the tax; $Þ ð3Þ

2.2.3. Regulatory based PecoThe monetary investment necessary for enacting an environ-

mental regulation was compared to the emergy of the ecologicallypositive impact generated by the regulation. So, the eco-price wasthe emergy of the ecologically positive impact divided by thedollar investment in the regulation.

Regulatory Peco ¼ ðemergy of eco: positive impact; sejÞ=ðdollars invested in the regulatory action; $Þ ð4Þ

2.3. Estimating monetary value in dollars

An estimate of the dollar amount that should be paid forproduction of the ecosystem, given conditions observed in analo-gous markets and other direct and indirect measures of societalpreference.

The two methods for estimating the monetary value werebased on (1) specific eco-price and (2) commodity eco-price. Themonetary value is estimated using eco-prices (emergy per dollar)to translate solar emergy flows to dollar payments. Table 2 showsthe tabular template for displaying suggested monetary valuebased on the two eco-price models. The emergy value is estimatedusing the following equation:

EMj ¼ tjej ð5Þ

when tj is solar transformity of ecosystem service j and ej is theenergy value of ecosystem service j. Monetary value of anecosystem service/good/capital is estimated by

MVj ¼ EMj=Peco ð6Þwhere EMj is the emergy of ecosystem service j and Peco is thedetermined eco-price.

We suggest two alternative methods for demining Peco:

(1) Average emergy–dollar exchange for each category of ecosys-tem service (specific eco-price). Convert the emergy of anecological good or service using the eco-price for the appro-priate category (e.g. the soil eco-price should be used toconvert the emergy of soil building to dollars).

(2) Average the emergy to dollar exchange of commodity marketsin the system being studied (commodity eco-price). The sameeco-price is used for all ecosystem services.

To demonstrate how the eco-price can be used we calculate themonetary value of clean water and soil building ecosystemservices provided by United States Forest Service lands using thespecific and commodity eco-price. The emergy value was obtainedfrom Campbell and Brown (2012) and the eco-price from thispaper (see Table 3 for list of eco-prices). The emergy values aredivided by the specific and commodity eco-prices (Table 4) todemonstrate how choice of eco-price affects the estimate ofmonetary value.

3. Results

3.1. Carbon sequestration eco-price calculation

Eco-prices for carbon sequestration were estimated based on(1) the average price of carbon on the European Carbon Exchangein 2010, which was $15 per ton (The Katoomba Group, 2011), (2)the average price of carbon on the Chicago Carbon Exchange in2008 prior to the collapse of the market, which was $2 per ton(The Katoomba Group, 2011) and (3) the average price of logtimber in Maryland in 2010, $138 per ton of wood (Bloomberg

Table 1Definition of terms.

Emergy (M) (Component of the system, unit)n(transformity for that component, sej/unit)Emergy is the energy necessary to make something and indicates ability to do work or cause influence

Transformity (sej/unit)

(Sum total of emergy necessary to make a component of the system, sej)/(existent energy or mass of the component in the system, j or g)Either calculated in the study or taken from the literature, transformities are used to convert energy or mass to emergy values

Eco-price (Peco) (Known emergy of ecological good or service, sej)/(known dollar amount exchanged, $)Suggests the quantity of ecological emergy to be exchanged for $1

Monetary value(MV)

(Known emergy of the ecological good or service in question, sej)/(derived eco-price, sej/$)The suggested dollar value of ecological work can be used to suggest compensation for ecological work, loss of natural capital, or price points inpayment for ecosystem service programs

Public value (PV) (Known emergy of the ecological good or service in question, sej)/(emdollar ratio in the studied economy, sej/$)The public value is the value of ecological work if it was valued using the average exchange of emergy to dollars in an economy. It can be viewed asthe emergy “surplus” above the suggested investment

Table 2Output table template for showing value based eco-prices (commodity or specific eco-price).

Ecological service/good/ or capital Units Energy or material Unit emergy values(sej/unit)

Solar emergy(1E18 sej)

Eco-price(1E12 sej/$)

Monetary value ($ million)

Ecosystem service i J ei ti EMi¼ti � ei Peco MVi ¼EMi/PecoEcosystem good j g aj sj EMj¼sj � aj Peco MVj¼EMj/PecoTotal public value MVT¼FPiþFPj

Notes: Peco is the eco-price (commodities, specific eco-price); MVi and MVj are the monetary values for ecosystem services/goods i and j, respectively;PV and PV/a are total and per area public value to Maryland, respectively; MVcp and MVcp/a are total and per area value, respectively, based on the commodity price model.

E.T. Campbell, D.R. Tilley / Ecosystem Services 7 (2014) 128–140 131

News, 2011). The energy content of a ton of wood was multipliedby a transformity, 36,200 sej/J (Tilley, 1999), to obtain the emergyvalue of the wood. This value is then divided by the dollar value ofthe ton of wood in each of the three examples to arrive at threeunique eco-prices (emergy per dollar, see Section 2.3). The threeeco-prices were averaged to obtain the specific eco-price forcarbon sequestration, 182E12 sej/$.

3.2. Hydrologic eco-price calculation

New York City invested $1.5 billion in protecting the water-sheds of NYC from 1997 to 2010 and over that time period 7.19E21sej (see Appendix A for calculation) of clean water has beensupplied by the ecosystem (NYCEP, 2010). The ratio of the emergyof the clean water supplied since the beginning of the program tothe dollars spent was used to estimate eco-price 4 in Table 3.When municipal water in Maryland is purchased it costs approxi-mately $3.79 for 1 m3 of clean water (WSSC, 2010), containing3.74E12 sej (see Appendix A) and the ratio of the emergy to dollarsis represented in Table 3, item 5. The emergy ratio of emergybenefits to dollars spent in the Chesapeake Bay Clean Water Actand the Water Quality Best Management Practices (BMP) CostShare Program. The emergy of the nitrogen, phosphorus andsediment inputs avoided through the implementation of the

Chesapeake Bay Clean Water Act is projected to average 1.32E21per year over the 15 years of the project with a total cost of $2.13billion ($142 million/yr, CBF, 2010). The average price paid for 1 lbof N in the Pennsylvania Chesapeake Bay Watershed tradingprogram was $3.81 in 2010 (PDEP, 2010), with an associatedemergy of 4E12 sej/lb (eco-price 7). The BMP cost share programin Maryland costs $250,000 in 2010 (MDA, 2011) and wasresponsible for avoiding approximately 2.82E18 sej of sediment,nitrogen and phosphorus loading (eco-price 8). The average of thehydrologic eco-prices was 8.95E12 sej/$, which was nearly fourtimes the emdollar ratio in Maryland.

3.3. Air pollutant eco-price calculation

The state of Maryland estimates that on average over the last 10years air pollution cost the state $400 million per year (MarylandGenuine Progress Indicator, 2011). This cost is derived from themethodology found in Costanza et al. (1997) and includes hospitalcosts and damage to crops, forests and water quality. The equationused calculates the cost in 1970 dollars and is as follows: cost of airpollution in 1970¼(national costs for different aspects scaled bystate characteristics) plus (costs of air pollution in other yearsbased on ozone levels and national air pollution trends).

Table 3Summary table of calculated eco-prices.a

Note Item Eco-price, (1012) sej per $ $ per quadrillion (1012) sej

Carbon sequestration1 European carbon exchange 35.4 $192 Chicago carbon exchange 506.0 $33 Timber market price 3.5 $286

Carbon seq. specific eco-price 182.0 $1024 Storm water mitigation: NY Watershed Protection 7.3 $1365 Groundwater recharge: municipal water 8.2 $122

Nutrient uptake6 Chesapeake Bay Clean Water Act 9.3 $1077 Nutrient Trading in Chesapeake Bay Watershed 1.1 $9308 Water Quality BMP Cost Share Program 10.9 $92

Hydrologic specific eco-price 7.4 $2779 Erosion prevention: cost of fill dirt 153.0 $910 Soil carbon: cost of mulch 7.5 $101

Soil specific eco-price 80.1 $5511 Air Pollutant Removal: Clean Skies Act 11.4 $8812 Cost of air pollution in Maryland 3.9 $258

Air pollution specific eco-price 7.6 $173Biodiversity

13 Maryland Env. Trust 4.7 $21214 Conservation Fund 3.8 $34515 Hunting Lease 59.4 $17

Biodiversity specific eco-price 22.6 $168Eco-prices not included in specific eco-price calculationsWest Virginia Tax on Air Pollutants

16 NO3-N 283.0 $417 NH4-N 58.3 $1718 S in wet/dry deposition 6580.0 $019 Cl in wet/dry deposition 546.0 $220 Pollination by wild insects 13.0 $7721 Coal 12.9 $7722 Rock, sand, gravel, clay 153.0 $923 Timber harvest 4.8 $20724 Natural gas 10.6 $9525 Total petroleum 5.0 $20026 Electricity 5.6 $1827 Copper 35.4 $2828 Corn 4.0 $25229 Wool 6.0 $166

Commodity eco-price, line item 21–29 weighted by yearly emergy flow $50.8 $79

Average of all eco-prices 297.0 $134

E.T. Campbell, D.R. Tilley / Ecosystem Services 7 (2014) 128–140132

Ozone and PM10 (airborne particulate matter less than 10 μm)levels in Maryland were used to calculate the health cost as theyare the principal air pollutants of concern in Maryland (Improv-ing Maryland's Air Quality, MDE, 2009). The emergy of ozonewas calculated in Maryland on days where the NAAQS (NationalAtmospheric Air Quality Standards) were exceeded. It wasassumed that only after standards are exceeded are costsincurred by excessive ozone concentration. PM10 is a morepersistent air pollutant and a constant concentration in theurban airshed was assumed for the year. The emergy of airpollutants was determined by multiplying the concentration bythe volume of the urban airshed in Maryland (Jacko andFatogoma, 2002; Fatogoma, 1996). It was found that on averagebetween 2000 and 2010 there were 23 days per year thatexceeded NAAQ standards. The average yearly emergy of ozoneon these exceeding days was 12.7E20 sej and PM10 was 3.3E20sej for the year. These emergy values were summed and dividedby the dollar cost to determine an eco-price of 3.9E12 sej/$ forozone/PM10 pollution in Maryland.

In addition, the Clear Skies Act (EPA, 2003) is used to assess thewillingness of the public to invest in air pollution removal. Itshould be noted this legislation was never enacted, however theprogramwas estimated to cost $4 billion over 15 years, and reduceSO2, NOx, and Hg by 8.2, 3.4 and 0.000033 million tons, respec-tively. The total emergy of the pollutants was estimated by multi-plying SO2, NOx and Hg by transformities found in the literatureand yielded values of 15.5E20, 288.0E20, and 0.924E20 sej,respectively. The summed emergy was divided by the total costto find the eco-price of 11.4E12 sej/$ (Table 3, item 11).

3.4. Soil eco-price calculation

The eco-price of soil was estimated from two direct marketexchanges for soil products. The first estimate was based on themarket price of fill dirt, $13.76/m3 (average price on www.earthproducts.net) and its emergy content, 2.6E15 sej. Fill dirt islargely inorganic, thus represents the inorganic fraction of soil andpredominately used in bulk for landscaping and landdevelopment. The eco-price for fill dirt was found to be 153.0E12sej/$.

The second estimate was based on the market price for barkmulch, $26/m3 (average of several prices online), with an emergycontent of 2E14, considered to be representative of the organicfraction of soil. The organic content of soil is one of its mostimportant characteristics because it is indicative of many of itsphysical, chemical and biological properties. The generation of soilorganic matter is also directly tied to the main emergy flows of theforest ecosystem, making the energy flows easily traceable tothis fraction of soil. The eco-price of mulch was found to be 7.5E12sej/$.

While the eco-price may not be directly what the society iswilling to pay for soil or OM in a forest they are representative of

the storage of natural capital that the forest fosters and whatpeople are willing to pay for products that perform similarfunctions.

3.5. Pollination and biodiversity eco-price calculation

The dollar contribution of native pollinators to US agriculturewas estimated by Losey and Vaughn (2006) at $3 billion per year.The values presented by Losey and Vaughn (2006) were adapted tothe state of Maryland and it was found that native pollinatorscontribute $11 million per year. The emergy of the crops producedwas derived by multiplying the mass of crop production attributedto native pollinators by the appropriate transformity from theliterature and estimated to be 8.0E19 sej/yr (see Table 3 item 17 foreco-price).

A representative eco-price for biodiversity was considered tobe the price paid for land set aside in long-term conservation andthe annual cost lease land for hunting. Two organizations, Mary-land Environmental Trust (MET, 2011) and The Conservation FundMid-Atlantic (CFMA, 2011), were the source of information usedto determine the eco-price. This land was purchased in Marylandin the case of the MET and in the Mid-Atlantic region by theConservation Fund. MET purchased nearly 3000 acres in 2009 for$1 million and the CFMA purchased 155,000 acres in Marylandsince 1985 for $592 million (average of $24 million per year). Theorganizations attempt to purchase land with the greatest poten-tial for conservation of ecological and cultural value. In the case ofboth organizations the emergy of the purchased land (the renew-able emergy flow for the year estimated to be 6.0E14 sej/acre/yr,see Appendix A) was divided by the cost to acquire the land.These investments perpetuate not only biodiversity but all theecosystem services of the land. However, as biodiversity is key insupporting many other ecosystem services land conservation wasdetermined to be a fair approximation of biodiversity willingnessto pay. A payment also determined to be representative of societalpreference for biodiversity was payments for hunting leases. Apayment of $10 per acre per year was found to be typical inMaryland (Kays, 2003). The average renewable emergy flow of anacre of forest (6.0E14 sej/acre/yr) in Maryland per year wasdivided by the dollar amount to find the eco-price of 22.6E12sej/$.

3.6. Commodity eco-price

The average price for nine commodities (see Table 3, lineitem 21–29), on June 2nd 2011, (Bloomberg News, 2011) wasobserved and the emergy per quantity was calculated (seeAppendix A) to generate an average eco-price. The averageeco-price for the nine commodities was calculated by weight-ing the individual eco-prices by their yearly emergy flow in thestate of Maryland, to adjust for relative importance (seeAppendix A for calculation). In future practice the commoditiesshould be calculated for the region of study and dynamicallyupdated as commodities change in price. Our calculationyielded a value of 50.8E12 sej/$.

Five eco-prices are presented in Table 3 but not included in thespecific or commodity eco-price. These eco-prices either did not fitinto a category (pollination) or were judged to be outliers (the WVair pollutants) compared to the other eco-prices in the categoryand are presented to illustrate the potential range of eco-pricevalues.

The eco-prices ranged from 1.0E12 sej/$ for nutrient trading to6500E12 sej/$ for sulfur deposition, which is a range of over fourorders of magnitude (Table 3 and Fig. 3). When log transformedthe mean of the data was 35E12, less than the arithmetic average

Table 4Monetary value of clean water and soil building ES by eco-price.

Ecosystemservice

Emergyvaluea

(10E18 sej)

SpecificPeco

CommodityPeco

Monetaryvalue usingspecific Peco

Monetaryvalue usingcommodityPeco

Cleanwater

81,096 9.0Eþ12 50.8Eþ12 9.1Eþ09 1.6Eþ09

Soilbuilding

36,087 80.1Eþ12 50.8Eþ12 4.5Eþ08 7.1Eþ08

a Emergy value from Campbell and Brown (2012).

E.T. Campbell, D.R. Tilley / Ecosystem Services 7 (2014) 128–140 133

of 297E12 sej/$. The high values, outliers when compared to therest of the dataset, skew the arithmetic mean.

The choice of specific eco-price versus one of the weightedaverages affects both the collective value of the ecosystem ser-vices/goods/capital being studied and the relative values. Hydro-logic eco-prices trended lower than the average eco-price and soiltrended higher. Table 4 and Fig. 4 show how the variability in eco-price affects the value generated, in this case for ecosystemservices from the United States Forest Service system (Campbelland Brown, 2012).

4. Discussion

In theory, all eco-prices should be greater than the emdollarratio observed in a state or nation. An emdollar ratio, as typicallycalculated in emergy analysis, accounts for all flows of emergy in acountry, state or region and the countercurrent flow of dollars,measured by GDP/GSP/GRP whereas an eco-price is an observationof the exchange of goods/services primarily consisting of environ-mental emergy and dollars. As a general rule, the emdollar ratiodecreases through the “levels” of the economy, being the highestin the primary economy to the secondary, the tertiary (service)economy and lowest in the quaternary (information) sector. Theeco-prices we observe are expected to be similar to the emergy/dollar relationship observed in the primary economy, and higherthan the average value of emergy per dollar calculated by the EDR.The only instance in this study of an eco-price observed to belower than the US emdollar ratio (2.5E12 sej/$ in the year 2008,Sweeney et al., 2007, 2012) was the Pennsylvania nutrient tradingprogram in the Chesapeake Bay watershed. The ratio of theemergy of the nutrients traded to the cost per credit was 1.1E12sej per dollar spent. At first glance, this appears to indicate aninefficient policy but for a conclusion to be made further studyshould be given to the emergy value of the downstream effect ofdecreasing nutrients in the Chesapeake Bay watershed, andpossibly attribute a positive benefit to the emergy purchased bythe credit program.

4.1. Comparison of eco-price methods

The three presented methods of calculating an eco-price toconvert emergy to dollars have advantages and disadvantages. An

advantage of using weighted averages is that it mitigates the effectthat any one erroneous or outlier eco-price could have on theoverall estimate of annual ecosystem service value. The downsideof using weighted averages is that information is lost, in particularthe estimates of the willingness to pay for particular services.When weighted averages are used one cannot observe the differ-ences in willingness to pay (reflected in the eco-price) acrossdifferent ecosystem goods/services or forms of capital (see Fig. 4).Society places a high value on controlling stormwater (this serviceby forests would be costly for society to replicate through infra-structure) and on controlling O3 (ozone has the potential to bedetrimental to human health) and thus they have low eco-prices(low emergy per $, high $ per emergy). Using a weighted averageloses this information. The area where the difference in howsociety values forms of ecological services/capital is most evidentis water and soil. Water has average emergy values but lower thanaverage eco-prices (lower eco-price equates to more money per sejof emergy) while soil has high emergy values but a lower thanaverage eco-prices (society does not highly value soil). The specificeco-price captures this variability; Fig. 4 shows that clean waterfrom USFS lands has approximately 4.5 times the value of soilbuilding on USFS lands when the specific eco-price is used. Therelationship flips when the commodity eco-price is used; soil hasnearly double the value of water. The commodity eco-price has the

Fig. 3. Rank order of eco-prices for ecosystem services evaluated. The mean (35E12 sej/$, represented by the red line) was based on the log transformed eco-price. (Forinterpretation of the references to color in this figure caption, the reader is referred to the web version of this paper.)

9,062

451

1,596

710

0

1,000

2,000

3,000

4,000

5,000

6,000

7,000

8,000

9,000

10,000

Soil BuildingClean Water

Mill

ion

$'s

Specific Eco-PriceCommodity Eco-Price

Fig. 4. Comparison of ecosystem service dollar value by eco-price. The choice ofeco-price can have a great effect on the dollar estimate of ecological work. Thevalues of soil building in, and clean water from, the USFS system are displayed heresystem (original emergy values taken from Campbell and Brown, 2012).

E.T. Campbell, D.R. Tilley / Ecosystem Services 7 (2014) 128–140134

advantage of relying on the market price of commodities so a moredefinite emergy–dollar ratio is generated and could be calculateddynamically. However, it relies on the assumption that societyvalues ecological work the same way it values commodities

The question of the best way to convert the emergy value ofecosystem services to dollars is unsettled, but upon completion ofthis study the commodity eco-price and specific service priceseem to be more valid than simply taking a weighted average.When weighting the eco-prices by emergy flow the ecosystemservices with high emergy flow dominates the averaged eco-price,these tended to be higher eco-prices and thus a high average eco-price was generated. The commodity eco-price was also aweighted average but the eco-price values tended to be moresimilar and a more representative averaged eco-price wasproduced.

4.2. Trade-offs

It stands to reason that there would be trade-offs betweenchoosing between lower and higher investment in the ecosystem.Higher values provide more incentive for preservation and restora-tion of ecosystems but a program demanding a greater investmentwould be more difficult to enact politically. The service specificeco-price should be further refined through calculating more eco-prices and identifying outliers (i.e. eco-prices that deviate severalorders of magnitude from the mean, especially within a servicespecific eco-price with a smaller n), to increase the accuracy ofestimated preference for an ecosystem service. The commodityeco-price is consistent with the logic that ecosystem servicesshould be valued similar to primary inputs to the economy andyields a value that may be more feasible for action in Maryland. Aswe observed in the USFS water and soil example, the choice of eco-price can affect relative magnitudes as well as total value. Thiscould affect management priorities or trade-offs and should beconsidered when determining the eco-price to be used.

4.3. Comparison with previous work

Pulselli et al. (2011) make a similar calculation to the eco-priceat the global level, dividing the global emergy budget (Campbell,2000) by a global estimate of ecosystem service dollar value(Costanza et al, 1997). The resulting number is lower than theobserved global emergy-to-dollar ratio and the authors concludethat this indicates “Nature is more efficacious in producing“money” (in form of ecosystem services) than economic systems(e.g., national economies and their GDP)” (Pulselli et al., 2011). Thisis contrary to our findings; in all but in one case the ratio ofemergy to dollars for ecosystem services was higher than theaverage emdollar ratio observed in the US. The gulf in our findingscan be attributed to the fact that the dollar values found inCostanza et al. (1997) attempt to measure total value, rather thanmarket value, of ecosystem services; it is not actually possiblefor the estimated value to be paid, it exceeds the 1997 Gross WorldProduct. While this is an estimate of the value inherent inecosystem services benefiting humanity, the dollar value gener-ated using this method is irrelevant to setting market price.

In addition, the global renewable emergy budget of the earth isan incomplete accounting of the emergy value provided byecosystem services. We suggest that the emergy of global ecosys-tem services is greater than the global renewable emergy budget.A benefit to humanity can either be a direct, consumptive serviceor a service in terms of cost avoided. For example, we account forthe emergy of the cost avoided by having forests that reduce stormwater runoff and avoid erosion as well as the service of recharginggroundwater and building soil. Because the former services arecost avoided and the latter are consumptive we propose that it is

not double counting to include both on the ledger of total benefitprovided by the ecosystem. In addition, some ecosystem servicesconsumed (e.g., ground water, biomass, soil fertility, etc.) arecomposed of “legacy” emergy, or emergy built up over time.Considering both these factors, an emergy value of ecosystemservices is almost certainly greater than the yearly global renew-able emergy budget.

The total monetary value of global ecosystem services in notdefinable. Humanity is wholly dependent on the global ecosystemin which it resides and as such would pay any amount to sustainthese essential services, as can be inferred from Costanza et al.(1997). However, when ecosystem service emergy–dollarexchange is observed in a real economy the ratio is always lowerthan the average observed, as the work of nature is considered tobe a free subsidy and not given economic value. Nature is theultimate producer of real wealth, but a poor producer of monetaryvalue.

5. Conclusions

This work sought to define how environmental emergy isvalued by society. We were able to do this by observing 29instances of goods/services (consisting wholly or primarily ofenvironmental emergy) exchanged for dollars in markets, throughregulations, or required by a tax. We found that the work of theenvironment was valued between 3 and 64 times less than theaverage dollar value for emergy observed in the United Statesusing the specific eco-price and 18 times less using the commodityeco-price. Testing theory was not the focus of our study, but thefindings are consistent with the theoretical understanding that theratio of emergy to money increases with the percentage ofrenewable emergy embodied in the good/service. We do notadvocate for one eco-price method over another, but do presentthat the specific eco-price has the advantage of increased informa-tion regarding preference for different types of ecological work, asshown by the water and soil ecosystem services from the USFSsystem.

The emdollar ratio (EDR) treats environmental emergy asequivalent in economic value to all other forms of emergy (e.g.human work, information, fossil fuels) but the reality is that theeconomy does not value this work. The eco-price provides a way toassign monetary value to ecosystem services/goods capital, in away consistent with previously established measures of economicpreference for ecological work. This study provides the methodol-ogy for estimating economic preference for environmental work.While the monetary value of ecosystems has been addressed inthe emergy literature (Odum, 1996; Odum and Odum, 2000;Campbell and Brown, 2012; Pulselli, 2011) a consistent methodol-ogy had not been previously developed. This research is a steptowards developing that methodology and an example of howenvironmental accounting can be used to inform policy for themutual benefit of humanity and the environment. While detailsremain in how the eco-price methodology can be implemented invaluing ecosystem services, natural capital, or environmentalimpacts, it could potentially enhance the long term sustainabilityof ecosystems by putting a dollar value on previously unvaluedecological work, incorporating that value into the economy andsuggesting consumers pay for value received.

Appendix A

See appendix Table A1, Table A2.

E.T. Campbell, D.R. Tilley / Ecosystem Services 7 (2014) 128–140 135

Table A1Calculation of commodity eco-price in Maryland.

Note Description Data Units/yr

Emergy E12sej

Emprice % Emergyflow

Portion ofemprice

1 Coala 2.30Eþ17 J 9.04Eþ02 1.29Eþ13 7.96E�02 1.03Eþ122 Rock, sand, gravel,

clayb3.37Eþ13 g 3.43Eþ03 1.53Eþ14 3.02E�01 4.61Eþ13

3 Timber Harvestc 2.72Eþ11 g 1.87E�03 4.82Eþ12 1.64E�07 7.93Eþ054 Natural gasd 2.27Eþ17 J 9.89Eþ02 1.06Eþ13 8.71E�02 9.19Eþ115 Total petroleume 3.75Eþ17 J 2.38Eþ03 5.00Eþ12 2.09E�01 1.05Eþ126 Electricityf 2.18Eþ17 J 2.98Eþ03 5.59Eþ12 2.62E�01 1.47Eþ127 Corng 3.10Eþ16 J 6.70Eþ02 3.96Eþ12 5.90E�02 2.34Eþ118 Woolh 1.03Eþ12 J 4.55E�01 6.03Eþ12 4.01E�05 2.42Eþ08

Sum 1.08Eþ18 1.14Eþ04 Commodityeco-price¼

5.08Eþ13

aEco-price coalQuantity in MD 8.64Eþ06 Short tons/yr US Census Bureau (2000)Coal 1 TonPrice 80 $/ton July 29, 2011 http://www.eia.gov/coal/news_markets/Energy content 12,500 btu/lb

25,000,000 btu/ton2.63Eþ10 J/ton

Transformity 3.92Eþ04 sej/J Odum (1996)1.03Eþ15 sej/ton1.29Eþ13 sej/$

bRock, sand, gravelQuantity in MD 4.86Eþ10 Short tons/yr US Census Bureau (2000)Eco-price of fill dirt $18 $ yd�3

$13.76 m�3

1 yd3

1 yd3¼ 0.76 m3

Assume 1.25 g/cm3

1,250,000 Grams1.68Eþ09 sej g�1

2.10Eþ15 sejsej/$ 1.53Eþ14 sej/$cEco-price timberQuantity harvested in MD 2.72E11 g/yr Commodity Flow Survey (2000)Commodity market trade 235 $/1000 bd ft Bloomberg.com June 2, 2011 http://www.bloomberg.com/markets/

commodities/futures/Energy of 1000 bd ft 2.27Eþ07 J/bd ft

0.235 $/bd ftSolar transformity 50,000 sej/J Campbell (2012)Eco-price timber 4.82Eþ12 sej/$Eco-pricedEco-price Nat GasQuantity in MD 2.07Eþ08 Thousand cubic ftAmount 1 MMBtuPrice $4.80 Bloomberg.com June 2, 2011 http://www.bloomberg.com/markets/

commodities/futures/Energy density 1.06Eþ09 J/MMBtuDensity 1.00Eþ00 kg/m3

Solar transformity 48,000 sej/J5.06Eþ13 sej/MMBtu

Eco-price natural gas 1.06Eþ13 sej/$eEco-price crude oilQuantity in MD 6.89Eþ06 Barrels yr US Census Bureau (2000)Amount 1 bblPrice $100.00 Bloomberg.com June 2, 2011 http://www.bloomberg.com/markets/

commodities/futures/Energy density 4.30Eþ04 J/gDensity 8.73Eþ02 kg/m3 West Texas, http://www.simetric.co.uk/si_liquids.htmSolar transformity 90,000 sej/J

5.38Eþ14 sej/bblEco-price crude oil 5.38Eþ12 sej/$Eco-price gasolineAmount 1 GallonPrice, commodity $2.97 Bloomberg.com June 2, 2011 http://www.bloomberg.com/markets/

commodities/futures/Energy density 1.35Eþ08 J/galSolar transformity 110,000 sej/J

1.49Eþ13 sej/gal

Eco-price gasoline5.00Eþ12sej/$Quantity in MD 1.00Eþ09 kWh

E.T. Campbell, D.R. Tilley / Ecosystem Services 7 (2014) 128–140136

Table A1 (continued )

fElectricityQuantity in MD 1E9 kWh Campbell (2012)Electricity 1 kWhPrice 0.1 $/kWh

3.60Eþ06 J/kWh160,000 sej/J5.76Eþ11 sej/kWh

Eco-price electricity(est#1)

5.76Eþ12 sej/$

Eco-price electricity(est#1)

5.59Eþ12 sej/$ Tilley (2006), unpublished data

Eco-price copperQuantity in MD ? Not available through US Census

Bureauamount 1 lbPrice, commodity $4.09 Bloomberg.com June 2, 2011 http://www.bloomberg.com/markets/

commodities/futures/Energy density 2.20Eþ03 g/lbSolar transformity 6.58Eþ10 sej/g Huang and Odum (1991)

1.45Eþ14 sej/lbEco-price copper 3.54Eþ13 sej/$gEco-price cornQuantity in MD 2.11E6 mt US Census Bureau (2000)Amount 1 BushelPrice, commodity $ 7.66 Bloomberg.com June 2, 2011 http://www.bloomberg.com/markets/

commodities/futures/Energy density 1.90Eþ04 J/gDensity 7.60Eþ02 kg/m3

3.50Eþ01 l/bushelSolar transformity 60,000 sej/J Campbell, 2012.

3.03Eþ13 sej/bushelEco-price Corn 3.96Eþ12 sej/$hEco-price WoolQuantity textiles 3.25E11 g US Census Bureau (2000)Amount 1 kgPrice, commodity $14.32 Bloomberg.com June 2, 2011 http://www.bloomberg.com/markets/

commodities/futures/Energy density 2.00Eþ04 J/gSolar transformity 4.32Eþ06 sej/J

8.63Eþ13 sej/kgEco-price wool 6.03Eþ12 sej/$

Table A2Footnotes for Table 3.

aCarbon sequestration eco-pricePrice per ton CEuropean Carbon Exchange (ECX) 15 $ ton�1 The Katoomba Group (2011)Chicago Carbon Exchange (CCX) 2 $ ton�1 The Katoomba Group (2011)

1.5 mt ha�1

Emergy¼ (mt ha�1)*(g mt�1)*(3.5 kcal g C�1)*(4186 J kcal�1)*(3.62 E4 sej J�1)

(Renewable emergy forMD forests, Campbell,2012)

¼ 7.95Eþ14 sej ha�1

1 ECX eco-price¼ sej/ha/$/ha 3.54Eþ13 sej $�1

2 CCX eco-price 5.06Eþ14 sej $�1

Eco-price of timber3 Market price 106 $ per m3

Avg density 700 kg/m3 http://www.for.gov.bc.ca/ftp/hva/external/!publish/web/logreports/coast/2011/3m_Jan11.pdf

Joules 1.03Eþ10 J http://www.engineeringtoolbox.com/wood-density-d_40.htmlTransformity 3.62Eþ04 sej J�1 NYC gov, calculatedEmergy 3.71Eþ14 sejEco-price 3.50Eþ12 sej/$

Modeled, Campbell (2012)4 Storm water mitigation eco-price

NY State Watershed ProtectionSupply 1,381,675,300 m�3 yr�1

Energy¼ (volume)*(1000 kg/m3)*(4940� J/kg)

¼ 6.82548Eþ15 J yr�1

Transformity 124,000 sej J-1

8.46,359Eþ20 sej yr�1 Washington Suburban Sanitation Commission

E.T. Campbell, D.R. Tilley / Ecosystem Services 7 (2014) 128–140 137

Table A2 (continued )

Average yearly investment eco-price

1.15Eþ08 $� yr�1

7.34Eþ12 sej $�1

5 Groundwater recharge eco-price Modeled, Campbell (2012)Municipal price of water

3 $1000 gal�1

1000 gal¼ 3.78541178 m3

Energy of 1000 gal¼ (volume)*(1000 kg/m3)*(4940 J/kg)

¼ 18,699,934.19 JTransformity 1,320,000Emergy¼ 2.46Eþ13 sejEco-price 8.22Eþ12 sej $�1

Nutrient uptake eco-price6 The Chesapeake Clean Water and

Ecosystem Restoration Act of 2009Total program cost 2.13Eþ09 $ over 15 yearsAvg. yearly cost 1.42Eþ08 $ yr�1

Reduction of N per year 1.30Eþ10 g NReduction of P per year 1.79Eþ09 g PReduction of sediment per year 7.31Eþ11 g sedSpecific emergy N 4.10Eþ09 sej g�1

Specific emergy P 2.16Eþ10 sej g�1

Specific emergy sed 1.68Eþ09 sej g�1

Emergy N¼ 5.33Eþ19 sej yr�1

Emergy P¼ 3.87Eþ19 sej yr�1

Emergy sed¼ 1.23Eþ21 sej yr�1

Sum¼ 1.32Eþ21 sej yr�1

Eco-price (emergy yr�1/$ yr�1) 9.32Eþ12 sej $�1

7 Nutrient Trading in ChesapeakeBay

3.81 $ per lb N

Grams N 453.59 g lb�1 http://www.dep.state.pa.us/river/Nutrient%20Trading_files/Workshops/NutrientTradingProgram-CreditGeneration-Lancaster.pdf

Specific emergy 4.10Eþ09 sej g�1

Emergy¼ 1.86Eþ12 sej Avg. for N forms from from Campbell (2009)Eco-price¼ 4.88Eþ11 sej $�1

8 BMP cost share program $230,094.59Plus private funds $28,761.82 Approx. 12.5% of funds

from landownerhttp://www.mda.state.md.us/article.php?i=22550

Will prevent approximately 268 Tons N69 Tons P312 Tons sediment

Specific emergy N 4.10Eþ09 sej g�1 Campbell and Ohrt (2009)Specific emergy P 2.16Eþ10 sej g�1 Campbell and Ohrt (2009)Specific emergy sed 1.68Eþ09 sej g�1 Campbell and Ohrt (2009)Emergy N 9.97Eþ17 sejEmergy P 1.35Eþ18 sejEmergy sed 4.76Eþ17 sejSum 2.82Eþ18Eco-price 1.09Eþ13

9 Cost of erosion: price of fill dirt $18 $ yd�3 www.earthproducts.net/$13.76 m�3

1 yd3

1 yd3¼ 0.76 m3

Assume 1.25 g/cm3

1,250,000 Grams1.68Eþ09 sej g�1

2.10Eþ15 sejsej/$ 1.53Eþ14 sej/$

10 Soi carbon: mulch 20 $ yd3 Average of online retailer survey26.15901239 $ m3

450 lbs yd3

588.5777787 lbs m3

266,974.3896 g m3

3.5 kcal/g3,911,441,781 J m3

Transformity 50,400 sej/j Tilley and Swank (2003)1.97137Eþ14 sej

Eco-price 7.53609Eþ12 sej/$Air pollutant removal eco-price

11 Clear Skies Act 4.00Eþ10 $ total investment over 15years, EPA (2003)

Dollars spent 2.67Eþ09 Average per yearExpected reduction in NOx 3.4 Mill tonsExpected reduction in SO2 8.2 Mill tonsExpected reduction in Hg 33 TonsNOx specific emergy 6.84Eþ09 sej g�1

E.T. Campbell, D.R. Tilley / Ecosystem Services 7 (2014) 128–140138

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Table A2 (continued )

SO2 specific emergy 5.26Eþ10 sej g�1 Campbell and Ohrt (2009)Hg specific emergy 4.20Eþ13 sej g�1 Campbell and Ohrt (2009)Emergy calculation¼ (tons)*(1e6 g ton�1)* (sej g�1) /15

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Emergy of SO2 2.88Eþ22 Avg sej yr�1

Emergy of Hg 9.24Eþ19 Avg sej yr�1

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¼ 1.14Eþ13 sej $�1

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Avg concentration 1.60E�05 g m3

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$ value of crops pollinated bynatives

1.12Eþ07 $ yr�1

Emergy value of crops pollinat. bynatives

1.45Eþ20 sej yr�1 Calculated from Losey and Vaughn (2006)

Eco-price 1.30Eþ13 sej $�1

Eco-price of BiodiversityConservation

18 Maryland Env. Trust2009 Budget 1,000,000 $ yr�1

Ha conserved 2325.23 ha in 2009 MD Env Trust, 2011Avg MD emergy per Ha 2.02Eþ15 sej ha�1 MD Env Trust, 2011Emergy of land conserved 4.71Eþ18 sej yr�1

Eco-price 4.71Eþ12 sej $�1

19 Conservation Fund Mid-AtlanticCost paid for land conserved 592,011,099 $Ha of land conserved 846,767.87 ha The Conservation Fund (2011)Emergy of land conserved 1.72Eþ21 sej ha�1 The Conservation Fund (2011)Eco-price 2.90Eþ12 sej $�1

Hunting Lease 10 $/acre/year Kays (2003)Renewable emergy per acre 5.938Eþ14 sej/acre Campbell (2012)

5.938Eþ13 sej/$Average of biodiversity eco-price 2.23Eþ13 sej/$

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