Ecosystem services and biogeochemical cycles on a global scale: valuation of water, carbon and nitrogen processes

Ecosystem services and biogeochemical cycles on a globalscale: valuation of water, carbon and nitrogen processes

Marcos D.B. Watanabe a,b,*, Enrique Ortega a,b,1

a Laboratory of Ecological Engineering, Food Engineering College, State University of Campinas (UNICAMP), Campinas, SP, BrazilbR. Monteiro Lobato, 80 – Barao Geraldo, Cx. Postal 6121, Faculdade de Engenharia de Alimentos, Departamento de Eng.

de Alimentos – Secretaria do DEA, CEP 13083-862, Campinas, SP, Brazil

e n v i r o n m e n t a l s c i e n c e & p o l i c y 1 4 ( 2 0 1 1 ) 5 9 4 – 6 0 4

a r t i c l e i n f o

Published on line 21 June 2011

Keywords:

Biogeochemical cycles

Ecosystem services

Water

Carbon

Nitrogen

a b s t r a c t

Ecosystem services (ES) are provided by healthy ecosystems and are fundamental to support

human life. However, natural systems have been degraded all over the world and the

process of degradation is partially attributed to the lack of knowledge regarding the

economic benefits associated with ES, which usually are not captured in the market. To

valuate ES without using conventional approaches, such as the human’s willingness-to-pay

for ecosystem goods and services, this paper uses a different method based on Energy

Systems Theory to estimate prices for biogeochemical flows that affect ecosystem services

by considering their emergy content converted to equivalent monetary terms. Ecosystem

services related to water, carbon and nitrogen biogeochemical flows were assessed since

they are connected to a range of final ecosystem services including climate regulation,

hydrological regulation, food production, soil formation and others. Results in this paper

indicate that aquifer recharge, groundwater flow, carbon dioxide sequestration, methane

emission, biological nitrogen fixation, nitrous oxide emission and nitrogen leaching/runoff

are the most critical biogeochemical flows in terrestrial systems. Moreover, monetary values

related to biogeochemical flows on a global scale could provide important information for

policymakers concerned with payment mechanisms for ecosystem services and costs of

greenhouse gas emissions.

# 2011 Elsevier Ltd. All rights reserved.

avai lab le at w ww.s c ienc ed i rec t . c o m

journal homepage: www.elsevier.com/locate/envsci

1. Introduction

Ecosystem services (ES) can be defined as the benefits that

human beings obtain from ecosystems. Human beings are

able to actively consume environmental stocks – fresh air,

food, water, timber, fossil fuels and shelter – and passively

obtain welfare from ecosystem resilience such as climate

regulation, flood protection, disease control, waste treatment,

soil formation, nutrient cycling and other processes. Although

* Corresponding author at: Laboratory of Ecological Engineering, FooCampinas, SP, Brazil. Tel.: +55 19 3521 4058; fax: +55 19 3521 4027.

E-mail addresses: [email protected], [email protected](E. Ortega).1 Tel.: +55 19 3521 4058; fax: +55 19 3521 4027.

1462-9011/$ – see front matter # 2011 Elsevier Ltd. All rights reservedoi:10.1016/j.envsci.2011.05.013

ES give vital support to human life and economic activities,

during the last five decades environmental resources have

been degraded due to economic and population growth. ES

depletion, in part, is related to a weakness in most human

decision-making processes of not attributing monetary values

to the benefits provided by the environment (MEA, 2005).

Several publications from the 90s, such as Daily (1997) and

Costanza et al. (1997), have shown that ecosystems have

economic value not only for their environmental goods traded

d Engineering College, State University of Campinas (UNICAMP),

nicamp.br (Marcos D.B. Watanabe), [email protected]

d.

http://dx.doi.org/10.1016/j.envsci.2011.05.013

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http://dx.doi.org/10.1016/j.envsci.2011.05.013

e n v i r o n m e n t a l s c i e n c e & p o l i c y 1 4 ( 2 0 1 1 ) 5 9 4 – 6 0 4 595

in the market – timber, for instance – but also due to their

functions such as flood control, soil formation, carbon

sequestration, water provisioning and other services which

directly and indirectly provide for human wellbeing. Costanza

et al. (1997) found that the total economic value related to ES

provided by remaining ecosystems on the Earth could be

higher than the global gross domestic product, and the

Millennium Ecosystem Assessment (MEA, 2005) pointed out

the total economic value associated with the sustainable

management of ecosystems is usually higher than the money

obtained from converting natural ecosystems to farming,

clear-cut logging, or other intensive uses. Therefore, human

interventions in ecosystems usually maximize the provision

of a few ES – food and biofuel production, for example – whose

value is captured by the market, but may exhaust a broad

range of ES that are essential to human well-being (Tilman

et al., 2002).

The concept of ecosystem services has been clarified by

several studies (Daily, 1997; Costanza et al., 1997; MEA, 2005;

Boyd and Banzhaf, 2007; Wallace, 2007; Fisher and Turner,

2008). According to Wallace (2007), the definition is not just a

semantic decision, but essential to highlight and guide

tradeoffs in natural resource management and policy deci-

sions. In fact, in considering valuation proposals, the defini-

tion of ecosystem services might clarify its limits of influence

on human welfare in order to avoid both over and under-

estimations. However, conflicting definitions have triggered a

deeper discussion regarding the ES issue, its level of impact on

human well-being, and its measurability using consistent

scientific tools and methodologies.

Boyd and Banzhaf (2007) have refined the concept of ES

defining them as ‘‘final ES’’ and ‘‘intermediate ES’’. They

emphasize that only final ecosystem services are ‘‘compo-

nents of nature, directly enjoyed, consumed, or used to yield

human well-being’’ and should be the top priority in

developing accounting units. On the other hand, Fisher and

Turner (2008) have affirmed that intermediate services, such

as carbon sequestration, are as important as final services

since they have the capacity to benefit humans even without

being consumed directly.

Considering that human activities have dual consequences

for human welfare – benefits created by maximization of a few

ES and costs derived from losses of other non-marketed ES – a

wider assessment involving ES values is required to clarify the

net effect of human activities on human well-being. The

estimation of the monetary magnitudes of diverse ecosystem

services might contribute to fill in the gaps in the information

required by initiatives to compensate landowners who

generate public benefit through the protection of ES (Wunder

et al., 2008).

Most ecosystem managers do not have the technical and

financial resources to estimate present value of ecosystem

services in monetary terms (Prato, 2007). Although there are

studies regarding monetary compensation for carbon seques-

tration and water production by ecosystems, a study about ES

valuation should make use of a holistic approach which does

not attribute value based on human preferences, but on

biophysical economics.

Similar to previous studies (Odum, 2000; Buenfil, 2001;

Campbell, 2003), this paper will assess the biogeochemical

flows related to water, carbon and nitrogen cycles on a global

scale using emergy (Odum, 1996), which offers a theoretical

background for environmental accounting based on an

energy-based perception of value. This paper also proposes

to clarify the relationship between several biogeochemical

flows – such as carbon sequestration, groundwater recharge

and biological nitrogen fixation – and global ecosystem

services. Policymakers usually avoid such approaches proba-

bly due to methodological constraints that are not able to

convert mass and energy flows – such as biogeochemical

processes – into monetary units.

2. Biogeochemical flows and the ecosystemservices

According to Odum and Odum (2000), emergy-based valuation

would avoid neoclassical approaches that ‘‘would not capture

real contributions of ecosystems and could delay the

organization of a sustainable pattern of environment and

people’’. Conventional approaches related to ecological

economics, such as willingness-to-pay based on the Contin-

gent Valuation Method, usually capture the value of ecosys-

tem entities narrowly and anthropocentrically, while in

contrast emergy tries to estimate their ecocentric value

(Hau and Bakshi, 2004).

This paper assumes that biogeochemical flows are coher-

ent entities to be assessed by the emergy-based approach

primarily because such flows can be decoded in terms of mass

and energy. Fig. 1a and b points out ‘‘final ecosystems

services’’, soil formation for instance, related to a superposi-

tion of two or more biogeochemical flows (CO2 sequestration,

nitrogen biological fixation and water percolation in this

example) which are unitary ecosystem processes that directly

or indirectly affect the human perception of welfare (final

ecosystem services). We represented the flows of water,

carbon and nitrogen as biogeochemical processes affecting a

wide range of final ecosystem services, including climate

regulation, food and raw material production, soil formation,

water supply and flood control.

Depending on the level of depletion caused by human

intervention (Fig. 1a and b) on the ecosystem, biogeochemical

inputs and outputs can become unbalanced and then the

damaged ecosystems could potentially generate environmental

dis-services (Zhang et al., 2007) such as soil erosion, flooding,

water scarcity and other undesirable events. An example would

be land-use change processes such as the substitution of native

forests by agricultural activities, which have the ability to harm

the regulatory properties of natural systems and decrease their

capability of providing ecosystem services.

3. Emergy and biogeochemical cycles

The concept of ‘‘emergy’’ was first mentioned in the peer-

reviewed literature in 1987 (Odum et al., 1987) to indicate the

energy memory, eliminating the confusion with other con-

cepts such as ‘‘embodied energy’’. Using the principles of

Thermodynamics, General Systems Theory, Ecology and other

sciences, the emergy synthesis is able to measure the energy

Fig. 1 – (a) Theoretical representation of main biogeochemical flows, intermediate and final ES connected to a healthy

ecosystem structure. (b) Theoretical representation of main biogeochemical flows and final environmental dis-services

provided by a damaged ecosystem structure.


and mass flows of any system on a common basis, usually in

terms of a solar equivalent joule or ‘‘seJ’’ (Odum and Odum,

2000). Hau and Bakshi (2004) state emergy synthesis as a

method that overcomes the inability of money to value non-

marketed inputs through an ecocentric perception that shares

the rigor of thermodynamic methods. The emergy approach

can be used to evaluate ES, because emergy corresponds to the

intrinsic value within mass and energy flows directly and

indirectly used by the environment to produce goods and

services such as soil, biomass, precipitation, wind or biogeo-

chemical processes.

Odum’s contribution to the laws of energy has been

fundamental in comprehending how biogeochemical cycles

are related to the self-organizing systems. The concepts

defined in Odum’s proposal for a 4th energy law, the Maximum

Empower principle (Odum, 1996), and the proposal for a 5th Law,

named Energy Transformation Hierarchy principle (Odum, 1996)

were fundamental to his corollary to the 5th law also

highlighted by Tilley (2004) as the potential proposal for a

6th energy law: ‘‘Material cycles are hierarchically organized

in a spectrum measured by emergy per mass that determines

mass flows, concentrations, production processes, and fre-

quency of pulsed recycle’’ (Odum, 2000). According to these

principles, available energy is used up by Earth’s ecosystems

and then degraded to concentrate materials through continu-

ous material cycles. Since the quantity of material flow

Fig. 2 – Biogeochemical flows and energy inputs to the Biosphere (diagram adapted from Brown and Ulgiati, 2004).


decreases in each successive step in a series of energy

transformations, the more concentrated a material is in its

carrier the more emergy per mass is within it.

In this paper, the assumption is that biogeochemical cycles

are co-products arising from the interaction between Earth’s

ecosystems and the global emergy input to the geobiosphere.

Brown and Ulgiati (2010) calculated this input to the geobio-

sphere as 15.2 E24 solar equivalent joules per year by summing

up solar energy absorbed (3.6 E24 seJ), crustal heat sources

(3.3 E24 seJ) and tidal energy absorbed (8.3 E24 seJ). Therefore,

15.2 E24 seJ is a proxy number for the environmental invest-

ment – given in solar energy joules – to sustain material cycles

on a global scale (see Fig. 2). This assumption is in accordance

with Buenfil (2001) who considered the global emergy input as

the driving force of the main global-scale hydrologic processes

such as evaporation from oceans, precipitation to terrestrial

systems, runoff to oceans, groundwater recharge, and others.

4. Emergy-based valuation of biogeochemicalflows

This study uses only the renewable emergy inputs for the

valuation of prehistoric biogeochemical flows (15.2 E24 seJ per

year). Therefore, the accounting procedure adopted did not

include inputs from non-renewable resources such as gas,

coal and oil because they are anthropogenic inputs to the

global ecosystem. Thus, values currently obtained for biogeo-

chemical processes consider pre-industrial revolution envi-

ronmental conditions. This assumption is important because

present consumption of fossil fuel has increased the global

emergy budget and provided a high non-renewable input to

the global ecosystem, equivalent to 34.3 E24 seJ per year

(Brown and Ulgiati, 2004). In future studies, the ES values will

be calculated taking into account this important additional

energy contribution.

Diagrams of the global cycles of water, carbon and nitrogen

were elaborated in order to understand the connections

among stocks, processes and flows of the main biogeochemi-

cal cycles in the Biosphere. Figs. 3–5 divide the Biosphere into

three main compartments: (i) the atmosphere, with its store of

gaseous compounds; (ii) the hydrosphere, which focuses on

aquatic ecosystems; and (iii) the lithosphere, which refers to

events occurring in terrestrial ecosystems. For calculation

purposes, diagrams 3, 4 and 5 synthesize the most important

biogeochemical processes on the global scale (Watanabe,

2008).

4.1. Hydrologic cycle

Fig. 3 points out the most important flows of the global water

cycle and assumes that water storages are in steady state, i.e.,

their values do not change on an annual basis. In terrestrial

ecosystems, water within plant cells and in the soil is

transpired and evaporated to the atmosphere (ET). Precipita-

tion (PT) feeds river flows above the surface (SR) or infiltrates

through the soil, usually generating groundwater flow (GF),

which is especially important to feed river basins during dry

Fig. 3 – Estimated values for global-scale water flows (E18 grams of water per year) from Buenfil (2001), Botkin and Keller

(2005), Odum and Barret (2007), and Watanabe (2008). Abbreviations: PT: rain, ET: evapotranspiration, SR: surface runoff, GF:

groundwater flow, AR: aquifer recharge.


seasons and also to recharge aquifers (AR) that can store water

for hundreds or thousands of years. Part of the oceanic water

evaporates or is transpired from aquatic systems (ET) to the

atmosphere. Solar energy, crustal heat and tidal energy

contribute to create ocean currents, to evaporate (ET) water

and to precipitate water (PT) as rain or snow. Following the

diagram of the global water cycle, mass flows have magni-

tudes of E18 grams of water per year according to Buenfil

(2001), Botkin and Keller (2005), Odum and Barret (2007), and

Watanabe (2008).

4.2. Carbon cycle

The carbon cycle (Fig. 4) shows the interaction between energy

inputs and ecosystems that brings about the transformation of

carbon compounds in the Biosphere. In the atmosphere, the

main process is carbon photo-oxidation (OX) that generates

carbon dioxide (CO2) or carbon monoxide (CO). In aquatic

systems, there are processes of carbon dioxide sequestration

(FIX), respiration (RESP) and decomposition of organic matter

(DEC) generating carbon dioxide and carbon monoxide (OX).

Organic and inorganic sedimentation (SED) of carbon com-

pounds (OC = organic carbon) from aquatic to terrestrial

systems is also shown. In the lithosphere, the main processes

are carbon dioxide fixation (FIX) by plants and respiration and

decomposition of organic matter (RESP/DEC) by bacteria and

yeast, which produces methane (CH4) and carbon dioxide.

After precipitation, water within the soil promotes runoff of

organic (ROC), and inorganic carbon (RIC) and water in contact

with rocks promotes weathering of inorganic carbon (WEA),

providing an input of carbonates to the hydrosphere. Fossil

fuel formation, which is closely coupled with the carbon cycle,

has been disregarded because it occurs at very slow rates not

comparable to the interval of one year considered in this

study.

Carbon flows affected by human economic activities (e.g.,

fossil fuel consumption, forest burning, soil decomposition,

etc.) were not represented in Fig. 4 since they are not

considered natural flows responsible for ES production,

although they largely affect the provision of ES today. Data

of the prehistoric carbon cycle have been estimated using data

from Jackson and Jackson (1996), Schlesinger and Andrews

(2000) and IPCC (2001).

4.3. Nitrogen cycle

The highest nitrogen cycle mass flows are found in terrestrial

ecosystems (Fig. 5), mostly because of biological nitrogen

fixation (BNF) from free living microorganisms or symbiotic

nitrogen fixing plants, and also due to the decomposition of

organic matter which may occur both as denitrification (DEN)

to nitrous oxide and volatilization of ammonia (VOL). Another

input of nitrogen to the ecosystems comes from lightening and

combustion (LIG/COMB) that produce reactive nitrogen com-

Fig. 4 – Values for carbon flows on a global scale (E15 grams C per year) from Jackson and Jackson (1996), IPCC (2001),

Schlesinger and Andrews (2000). Abbreviations: OX: photo-oxidation, SED: sedimentation, FIX: CO2 sequestration or

fixation in biomass, RESP/DEC: respiration/decomposition, WEA: weathering, ROC: runoff of organic carbon, RIC: runoff of

inorganic carbon, OC: organic carbon.


pounds in the atmosphere; they feed aquatic and terrestrial

ecosystems through wet and dry deposition (DEP) to soils or

water stores. In aquatic environments, sedimentation (SED)

represents the flow of both organic and inorganic compounds

to the bottom of the oceans. In addition to denitrification and

ammonia volatilization, the outputs of nitrogen from terres-

trial ecosystem include runoff and leaching (RUN), which

transport reactive nitrogen to rivers and oceans. We did not

find data that represent only prehistoric nitrogen flows since

both Jackson and Jackson (1996) and Botkin and Keller (2005)

include nitrogen from industrial fixation as fertilizer for

agricultural use (IND).

4.4. Valuation of water, carbon and nitrogen processes

Based on the diagrams of the global cycles of water, carbon

and nitrogen (Figs. 3–5), the biogeochemical flows were valued

both in terms of ‘‘emergy per mass’’ and ‘‘equivalent money

per unit’’ (shown in Table 1). The global emergy input is

entirely accounted in every biogeochemical process because

water, carbon and nitrogen are continuously flowing through

all compartments of the Biosphere – atmosphere, hydrosphere

and lithosphere. Therefore, it is assumed that molecules rely

on all energy inputs during their cycling process: absorbed

solar energy, absorbed tidal energy and crustal heat sources.

For this reason we allocate 15.2 E24 seJ per year in every

biogeochemical process.

The ‘‘emergy per mass’’ indicates the average environ-

mental investment of emergy to generate each biogeochemi-

cal flow (solar equivalent joules per mass unit) in terrestrial

ecosystems. We focused on processes associated with

terrestrial ecosystems, because human interference on bio-

geochemical flows is triggered by and managed in cities,

industries and agricultural systems located outside the

atmosphere and hydrosphere. Nonetheless, flows of evapo-

transpiration, water runoff, emission of CO2, emission of CH4,

denitrification to N2O, volatilization of NH3, and runoff of

nitrogen compounds represent inputs both to the atmosphere

and hydrosphere. The ‘‘emergy per mass unit’’ indices were

calculated by dividing the global emergy input by the global

mass flow: for instance, CO2 sequestration (FIX) was calculated

by dividing 15.2 E24 seJ per year by 125 E15 g per year, and the

result is 1.22 E08 seJ per gram of carbon.

According to Odum (1996, p. 57), ‘‘if a flow of emergy is

responsible for a portion of the real wealth of an economic

system, we can infer that this proportion of the system’s

buying power is due to this emergy flow. The emdollars (EM$)

are the appropriate measure for discussing large-scale

Fig. 5 – Estimated values for nitrogen flows at the global scale (expressed in E12 grams of N per year) adapted from Jackson

and Jackson (1996) and Botkin and Keller (2005). Abbreviations: BNF: biological nitrogen fixation, LIG/COMB: lightening and

combustion, DEP: atmospheric deposition, DEN: denitrification, SED: sedimentation, VOL: volatilization, RUN: runoff and

leaching, IND: industrial fixation.


considerations of an economy, including environment and

information, as well as human goods and services’’. In order to

estimate the emdollar, Brown and Ulgiati (1999) accounted the

annual flux of emergy from renewable sources (solar, crustal

and tidal) and nonrenewable inputs (oil, natural gas, coal,

nuclear, wood, soils, phosphate, limestone and metals)

supporting the world economy in 1995. The total renewable

and nonrenewable emergy (29.91 E24 seJ) was divided by the

Gross World Product (GWP) in the same year (26.9 E12 US

dollars), obtaining 1.1 E12 seJ/USD. The emergy per dollar ratio

changes over time, since with each passing year there is a

different amount of emergy that flows for each dollar of GWP.

Since there is no current value for the world emdollar, the

results in this paper are based on the 1995 ratio of emergy to

money.

The monetary magnitude of each biogeochemical process

is represented in the column ‘‘equivalent money per mass

unit’’ (see Table 1) and it was calculated by dividing the

‘‘emergy per mass unit’’ column by the world emdollar ratio.

For instance, emergy per mass of CO2 sequestration (FIX) was

converted into money by dividing 1.22 E08 seJ per gram of

carbon by 1.1 E12 seJ/USD; the result is 1.11E�04 EM$ per gram

of C, which is equivalent to 111 EM$ per metric ton of carbon

(t C). In the case of water, an extra step was necessary to

convert ‘‘equivalent money per mass unit’’ into ‘‘equivalent

money per volume unit’’, by assuming the average water

density of 1 E06 grams per cubic meter. For instance, the

‘‘equivalent money per unit of volume’’ of aquifer recharge

(AR) was calculated by dividing 4.75 E06 seJ/g by 1.1 E12 seJ/

USD. The result, 4.32 E�06 EM$ per gram (not shown in Table

1), was multiplied by 1 E06 grams per m3, which is equal to

4.32 EM$/m3 (shown in Table 1).

5. Results and discussion

As represented in Table 1, the ‘‘emergy per mass unit’’ indices

related to ecosystem services are around 1 E05 and 5 E06 seJ

per gram of water, around 1 E08 and 2 E10 seJ per gram of

carbon, and around 7 E10 and 5 E11 seJ per gram of nitrogen

(Fig. 6). These values are similar to the indices found in

previous studies performed on the global scale. According to

Buenfil (2001), the emergy per mass of global water flows were

around 9 E04 and 5 E06 seJ per gram of water. In regard to

carbon, Odum (2000) obtained values between 1 E08 and

1 E10 seJ/g C at the global scale. According to Campbell (2003),

the emergy per mass of global nitrogen flows are around 2 E09

and 3 E11 seJ/g N.

Fig. 6 – Water, carbon and nitrogen ecosystem processes in terrestrial systems as co-products of the global emergy budget.


Using the world emdollar, units of solar equivalent joules

were converted to equivalent U.S. dollars (EM$) in order to

obtain values of precipitation to terrestrial systems, evapo-

transpiration, surface runoff, groundwater flow and aquifer

recharge: EM$ 0.13, 0.21, 0.42, 3.64, and 4.32/m3 of water,

respectively. Observing carbon flows, it is important to point

out that carbon runoff was valued as EM$ 17,272/t C, carbon

dioxide emission as EM$ 115/t C, and methane emissions as

EM$ 13,957/t C. Nitrous oxide (N2O), an important greenhouse

gas (GHG) on the global scale, has a value of approximately

EM$ 99 per kg of nitrogen. Another ‘‘expensive’’ flow is the

leaching (and runoff) of organic and inorganic nitrogen

compounds to the hydrosphere, which have an EM$ value

of 476 per kg of nitrogen.

Results obtained in this paper raise two important

questions. First, as previously affirmed by Odum (2000), there

is a visible hierarchy of emergy per mass associated with the

different biogeochemical flows of water, carbon and nitrogen.

The most valuable ecosystem services affected by human

systems are those services related to less abundant mass flows

on an annual basis. To this extent, such biogeochemical

processes should be promptly prioritized by public and private

initiatives dealing with the management of ecosystem

services on both local and global scales. Second, monetary

values of intermediate ES calculated in this paper should be

compared with other results from different ecological eco-

nomic methodologies to understand whether different

approaches are able to generate convergent values for similar

biogeochemical processes.

The results for ecosystem services related to water range

from EM$ 0.13 to 4.32/m3 for rainfall and aquifer recharge,

respectively, after using the world emdollar. Strobel et al.

(2006) studied a Brazilian watershed, the headwaters of which

lie within Rio de Janeiro State’s Tres Picos State Park, and

found values of tariffs for water ecosystem services ranging

from US$ 0.01 to 0.03/m3 using an approach which takes into

consideration park management expenditures, analysis of

alternative criteria for allocating park protection and other

factors. According to another local study prepared in Jordan

(Salman and Al-Karablieh, 2004), the willingness of farmers to

pay for groundwater resources under different conditions of

water supply regimes would vary from US$ 0.14 to 0.35/m3,

lower than the values obtained in this study (from EM$ 3.64 to

4.32/m3). These studies indicate values lower than the values

calculated in this paper.

Since carbon flows are gradually being traded in the

marketplace, values obtained in this paper can be compared

with data from ‘‘State and Trends of the Carbon Market’’

report of 2009 (Capoor and Ambrosi, 2009). The report points

out values up to US$ 10 per metric ton of carbon released as

CO2 in European and North American markets. Eyre et al., 1997

calculated external effects of climate change gases: the

impacts on health, sea-level rise, flood, droughts, and other

effects. The average marginal cost found for carbon dioxide

emission was US$ 95 per t C emitted as CO2. Considering that

CO2 emission calculated in this paper is equivalent to EM$ 115

per t C, it is apparently possible to obtain similar magnitudes

for the monetary values of carbon processes using different

methodologies.

The value for nitrous oxide emission (Eyre et al., 1997)

based on mitigation costs of negative impacts from GHG’s was

calculated as US$ 9500 per metric ton of nitrogen (t N) emitted

as nitrous oxide. Another proxy value for the denitrification

process is nitrous oxide (NOx) flow evaluated by Rabl and Eyre

(1998). They estimated an average value of US$ 1875 per ton of

NOx due to the damage it causes to European agriculture and

Table 1 – Valuation of ecosystem services from biogeochemical flows in terrestrial systems.

Biogeochemicalflows

Global massflow (g year�1)

Global emergy(seJ year�1)a

Emergy per massunit (seJ g�1)

Equivalent moneyper unitb

Water cycle EM$/m3

(PT) precipitation 105 E18 15.2 E24 1.45 E05 0.13

(ET) evapotranspiration 65 E18 15.2 E24 2.34 E05 0.21

(SR) surface runoff 33 E18 15.2 E24 4.61 E05 0.42

(GF) groundwater flow 3.8 E18 15.2 E24 4.00 E06 3.64

(AR) aquifer recharge 3.2 E18 15.2 E24 4.75 E06 4.32

Carbon cycle EM$/t C

(FIX) CO2 sequestration 125 E15 15.2 E24 1.22 E08 110.55

(RESP) emission of CO2 120 E15 15.2 E24 1.27 E08 115.15

(DEC-CH4) emission of CH4 0.99 E15 15.2 E24 1.54 E10 13,957.76

(ROC/RIC)c runoff 0.80 E15 15.2 E24 1.90 E10 17,272.73

Nitrogen cycle EM$/kg N

(BNF) biological N fixation 200 E12 15.2 E24 7.60 E10 69.09

(VOL) volatilization of NH3 190 E12 15.2 E24 8.00 E10 72.73

(DEP) wet/dry deposition 160 E12 15.2 E24 9.50 E10 86.36

(DEN) denitrification to N2O 140 E12 15.2 E24 10.86 E10 98.70

(RON/RIN)c runoff 29 E12 15.2 E24 52.41 E10 476.49

a Water density: one cubic meter is equivalent to 106 grams of water. Diverse carbon (and nitrogen) compounds have been used in calculations

considering their mass of carbon (and nitrogen), not including oxygen and hydrogen.b World Emdollar ratio of 1.1 E12 solar equivalent joules per U.S. dollar (Brown and Ulgiati, 1999).c ROC/RIC indicates runoff of both organic and inorganic compounds.


health quality. Similarly, Holland et al. (1999) point out

damage costs related to ammonia emission as US$ 280 per t

N. This paper shows values for N2O and NH3 emissions of

magnitudes around EM$ 98,700 and EM$ 72,700, respectively;

therefore, emergy-based values are higher than those

obtained from the neoclassical approaches of economics.

6. Conclusions

This paper highlighted two important ecosystem services

related to the water cycle: groundwater flow and aquifer

recharge, which is demonstrated by observing their values

in equivalent money (EM$) per cubic meter cycled on a

global scale. Such biogeochemical processes, also called

intermediate ecosystem services, are highly affected by

land-use change. The expansion both of agricultural fields

and urban areas, which increases surface runoff and

reduces infiltration, may cause severe consequences to

human welfare by decreasing groundwater flow and slowing

aquifer recharge, and at the same time these human

systems will demand soaring quantities of freshwater from

underground storages.

The observation of values related to carbon flows suggests

that the emission of greenhouse gases such as carbon dioxide

and methane is critical for the ecosystem due to the high

monetary value per gram of CH4 emitted. Although methane’s

global warming potential is 24 times higher than that of carbon

dioxide, its emission cost according to the emergy approach

would be 100 times greater. Therefore, it would be advisable to

be cautious with human projects involving flooding of

terrestrial ecosystems, forest burning, land expansion for

livestock and landfills and any other activities that might

release significant amounts of methane to the atmosphere.

Another critical flow in the global carbon cycle is the runoff

of inorganic and organic carbon compounds from soil to rivers

and oceans (EM$ 17,273 per t C), probably highlighting how

difficult it is to maintain organic matter on soils of terrestrial

ecosystems after land-use change. Consequently, soil erosion

is an additional important point, added to the loss of

environmental services to be addressed on the policymakers’

agenda.

As agricultural activities increase the input of reactive

nitrogen to terrestrial ecosystems due to the intense use of

industrial fertilizer, there are also rising quantities of nitrogen

being released both to the atmosphere and hydrosphere in

processes involving nitrogen runoff, nitrate leaching and

nitrous oxide emission. Since the nitrogen cycle contains

smaller quantities of material compared to the water and

carbon cycles on a global scale, this paper suggests that

nitrogen flows are related to the most sensitive biogeochemi-

cal processes assessed in this paper. In spite of the

consequences, mankind has doubled the amount of reactive

nitrogen in the Biosphere (see MEA, 2005). Policymakers

should pay increased attention to human activities highly

reliant on significant inputs/outputs of nitrogen, which is the

case with regard to modern agriculture. Considering that the

current agricultural land area is increasing and that it already

represents two thirds of the useable global land area, better

agricultural management might relieve this situation on a

global scale. Moreover, nitrogen emissions may be included in

the market, analogously to the system of carbon allowances,

in order to regulate the quantity of reactive nitrogen flowing

on a global scale.

In summary, our suggestion to policymakers is to be aware

of the hierarchy of ecosystem services and to prioritize the

management of those ES related to high values of emergy per

mass. Thus, environmental policy may perhaps focus on

issues concerning the recharge of aquifers, leaching and

runoff of carbon and nitrogen, and greenhouse gases

emission, especially nitrous oxide, which has the highest

emergy per mass among the GHG’s assessed in this paper.


Additionally, it is important to emphasize that both the

neoclassical approaches of economics and market prices

attribute lower monetary values to the ES than the emergy-

based values calculated in this paper. As a result, additional

studies and further discussion among policymakers are

required to avoid both over and underestimations of values

to be adopted in compensation mechanisms for ecosystem

services.

Acknowledgments

The author thanks CNPq (National Council for Scientific and

Technological Development) for the Master’s grant and

FAPESP (Foundation for Research Support of the State of Sao

Paulo) for the PhD grant. Both were fundamental for the

development of the concepts and calculations within this

paper.

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Marcos D.B. Watanabe obtained a master’s degree in Food Engi-neering from State University of Campinas in 2008 and is currentlyPhD student at the Laboratory of Ecological Engineering. His cur-

http://www.grida.no/climate/ipcc_tar/wg1/fig3-1.htm

http://www.grida.no/climate/ipcc_tar/wg1/fig3-1.htm

http://www.conservacao.org/publicacoes/files_mega2/criterios.pdf

http://www.conservacao.org/publicacoes/files_mega2/criterios.pdf


rent research focuses on modeling biogeochemical cycles andvaluation of ecosystem services using emergy.Enrique Ortega is professor at the College of FoodEngineering of the State University of Campinas (UNICAMP)since 1978. He is in charge of the Laboratory of Ecological

Engineering and his research has emphasis on systems ecology,emergy accounting, ecological modeling, sustainable foodproduction, environmental accounting, river basin manage-ment and planning, and software development for systemsanalysis.

Ecosystem services and biogeochemical cycles on a global scale: valuation of water, carbon and nitrogen processes

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