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Abstract

Soil is part of the Earth's life support system, but how should we convey the value of this and of soil as a resource? Consideration of the ecosystem services and natural capital of soils offers a framework going beyond performance indicators of soil health and quality, and recognizes the broad value that soil contributes to human wellbeing. This approach provides links and synergies between soil science and other disciplines such as ecology, hydrology, and economics, recognizing the importance of soils alongside other natural resources in sustaining the functioning of the Earth system. We articulate why an ecosystems approach is important for soil science in the context of natural capital, ecosystem services, and soil change. Soil change is defined as change on anthropogenic time scales and is an important way of conveying dynamic changes occurring in soils that are relevant to current political decision-making time scales. We identify four important areas of research: (i) framework development; (ii) quantifying the soil resource, stocks, fluxes, transformations, and identifying indicators; (iii) valuing the soil resource for its ecosystem services; and (iv) developing decision-support tools. Furthermore, we propose contributions that soil science can make to address these research challenges.
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Natural Capital, Ecosystem
Services, and Soil Change: Why
Soil Science Must Embrace an
Ecosystems Approach
Soil is part of the Ear th’s life support s ystem, but how should we convey the value of this and
of soil as a resource? Considera on of the ecosystem services and natural capital of soils
o ers a framework going beyond performance indicators of soil health and quality, and rec-
ognizes the broad value that soil contributes to human wellbeing. This approach provides
links and synergies between soil science and other disciplines such as ecology, hydrology,
and economics, recognizing the importance of soils alongside other natural resources in
sustaining the func oning of the Earth system. We ar culate why an ecosystems approach
is important for soil science in the context of natural capital, ecosystem services, and soil
change. Soil change is de ned as change on anthropogenic me scales and is an important
way of conveying dynamic changes occurring in soils that are relevant to current poli cal
decision-making me scales. We iden fy four important areas of research: (i) framework
development; (ii) quan fying the soil resource, stocks, uxes, transforma ons, and iden -
fying indicators; (iii) valuing the soil resource for its ecosystem services; and (iv) developing
decision-support tools. Furthermore, we propose contribu ons that soil science can make
to address these research challenges.
Abbrevia ons: GDP, gross domes c product.
Soils provide vital func ons for society (Blum, 2006).  ey support and
sustain our terrestrial ecosystems; grow our food, feed,  ber, and wood; regulate the atmo-
sphere;  lter water; recycle waste; preserve our heritage; act as an aesthetic and cultural
resource; and provide a vital gene pool and biological resource from which many of our
antibiotics have been derived (D’Costa et al., 2006). Despite their role as the biogeochemi-
cal engine of the Earth’s life support system, soils are o en perceived as failing to attract
the attention of policymakers and society at large (Bouma, 2001), especially with regard
to soil protection and sustainability. While water and air in uence our health because of
direct consumption, the connection between human health and soils is o en more subtle
and still is not fully understood. As we deal with global change and increasing populations,
however, soils are increasingly being linked to human health and well-being, whether by
the release of As to groundwater by redox cycling in the soils of Southeast Asia (Polizzotto
et al., 2008), by the impact of soil moisture on the spread of malaria (Patz et al., 1998),
or even the exacerbation of fatal heat waves in Europe due to reduction of the soil mois-
ture bu er (Seneviratne et al., 2006). As we understand the signi cance of managing the
Earth’s soils, not only for food production but increasingly for environmental regulation
and Earth system functioning, it becomes crucial that we de ne its value in suitable terms
for policymakers, land managers, and future generations. It is therefore vital that soil scien-
tists are actively involved in the development of frameworks that convey the societal value
of soil functions in terms of both human well-being and the sustainment of the Earth’s
life support systems and the diversity of life the planet holds.
Research into the concept of soil quality is an ongoing e ort to generate indicators of the
performance of soils that can inform policy (Doran and Parkin, 1996). In the European
Union (EU) , the Driving forces, Pressures, States, Impacts, Responses framework is widely
used to identify links between policy and its impact on natural resources, including soils
(Blum et al., 2004). An ecosystems approach goes further, however, by valuing natural
resources and the bene ts we obtain from them in terms of the goods a nd serv ices that they
provide to society (Millennium Ecosystem Assessment, 2005). Westman (1977)  rst pro-
posed that the value of ecosystems and their bene t to society should be incorporated into
Special Section:
Soil Architecture and Function
D.A. Robinson*
N. Hockley
E. Domina
I. Lebron
K.M. Scow
B. Reynolds
B.A. Emme
A.M. Keith
L.W. de Jonge
P. S ch jø nn in g
P. Moldrup
S.B. Jones
M. Tuller
The Earth’s mantle of soil is a cri -
cal part of the planet’s life support
system, but how can the value of the
soil resource be quantified or con-
veyed? In this article we articulate
why it is important for soil science
to engage an ecosystems approach,
with valua on posed in the context
of natural capital, ecosystem services
and soil change.
D.A. Robinson, I. Lebron, B. Reynolds, and
B.A. Emme , Centre for Ecology and Hydrol-
ogy, Environment Centre Wales, Deiniol
Road, Bangor, UK; N. Hockley, School of
Environment, Natural Resources and Geogra-
phy, Bangor Univ., Bangor, UK.; E. Domina ,
AgResearch, Grasslands Research Centre,
Tennent Drive, Priva te Bag 11008, Palmers ton
North 4 442, New Zealand; K.M. Scow, Dep. of
Land, Air and Water Resources, Univ. of Cali-
for nia, Davi s, CA 95616; A.M. Keith , Cen tre f or
Ecology and Hydrology, Lancaster Environ-
ment Centre, Lancaster, UK; L.W. de Jonge,
Dep. of Agroecology, Aarhus Univ., Tjele,
Denmark; P. Moldrup, Dep. of Biotechnology,
Chemistr y and Environmental Engineering,
Aalborg Univ., Aaborg, Denmark; S.B. Jones,
Dep. of Plants, Soils and Climate, Utah State
Univ., Logan, UT 84322; and M. Tuller, Dep. of
Soil, Water and Environmental Science, Univ.
of Arizona, Tucson, AZ 85721. *Corresponding
author (darearthscience@yahoo.com).
Vadose Zone J.
doi:10.2136/vzj2011.0051
Received 24 May 2011.
© Soil Science Society of America
5585 Guilford Rd., Madison, WI 53711 USA.
All rights reserved. No part of this periodical may
be reproduced or transmi ed in any form or by any
means, electronic or mechanical, including photo-
copying, recording, or any informa on storage and
retriev al system, witho ut permission i n wri ng from
the publisher.
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policy making.  is concept was further developed by Daily (1997)
and Costanza et al. (1997a) and their sources. Since the release
of the Millennium Ecosystem Assessment report (Millennium
Ecosystem Assessment, 2005) and the stark warnings it contained,
governments and policy-making bodies have begun adopting
the idea of an ecosystems approach to pursue sustainability and
incorporate resource life support value into decision making (e.g.,
Department for Environment, Food and Rural A airs, 2007).
ese new directions would be strengthened by incorporation of
soils into these frameworks, capitalizing on developed and emerg-
ing soil science concepts and thus conveying the importance and
value of soils to decision makers.  e EU has already identi ed
soil ecosystem services as a priority research area in the European
Union Soil  ematic Strategy.  e EU is  nancing a number of
projects that incorporate soil ecosystem services, including the
SoilTrEC project (Banwart, 2011), the SOIL SERVICE project,
and the EcoFINDERS project.
Soil quality and health (Karlen et al., 1997; Singer and Ewing,
2000), along with the emerging concept of “soil change” (Tugel
et al., 2005), are frameworks that were recently developed in soil
science. Concurrently, ecosystem services and natural capital
frameworks have emerged from ecology and economics (Daily,
1997; Costanza et al., 1997b). In Fig. 1, we demonstrate the inter-
relationships among these concepts, each of which are vital for
conveying the importance of soils to society.  e soil resource is
composed of material stocks such as minerals, C, water, air, and
nutrients, with important characteristics that we identify through
soil formation processes such as horizonation, aggregation, and
colloid formation (Churchman, 2010). Soil stocks constitute the
soil natural capital (Robinson et al., 2009; Dominati et al., 2010a)
on which processes act.  ese lead to  ows and transformations,
resulting in changes in the stocks through interactions with the
wider environment. Ecosystem services result from the  ows of
materials and energy.  ese include out ows of C in food, feed,
or  ber, in ows of C that aid climate regulation, the contribu-
tion of soils to water regulation and  ltering, and waste disposal
and recycling. Building or improving the soil natural capital is an
important aim, contributing to soil resilience and maintaining bal-
ance in the provision of ecosystem services. It is important that our
focus on ecosystem services does not ignore the important role of
natural capital or result in the provision of services at the expense
of changes in the inventory value of natural capital stocks that
could be unsustainable.
e soil quality framework (Karlen et al., 1997) provides an indica-
tor of the state of the soil natural capital stocks at any given point
in time, while the concept of soil change (Richter and Markewitz,
2001; Tugel et al., 2005; Richter et al., 2011) recognizes that soils
are continually evolving and transforming, especially within
anthropogenic time scales (Fig. 1).  e current state of the soil is
termed the actual state, while its inherent state might be thought
of as its undisturbed state, and its future state is that which can
be attainable. Last century, much of soil science emerged from an
interest in understanding how soils formed in relatively undis-
turbed environments during long periods of time. Soil change
recognizes the dynamic response of soils to anthropogenic activity
in much the same way that we study climate and land use change.
e soil science emphasis on gradual change during pedogenesis
can be counterproductive in discussions with policymakers, who
can interpret gradual change as unimportant within their time
in o ce. Conveying the dynamic nature of soils, and that change
Fig. 1.  e temporal balance between soil natural capital and ecosystem goods and services supporting the concept of “soil change.”  e ascending light
green arrow through soil natural capital indicates capital improvement, whereas the descending red arrow is capital degradation. With time, ecosystem
services will diminish if capital is degraded; conversely, building capital may increase the soil’s capacity to deliver goods and services.  is is a broad
generalization because building capital may also result in some disservices.  e end goal is a sustainable balance of capital and ecosystem services.
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occurs on time scales that are relevant to policymakers and their
generation, is an important challenge for soil science. Figure 1
shows that all these concepts are complementary and contribute
to both our understanding and the way we convey the contribution
and value of soils to human beings and their societies.
Given the importance of developing these approaches for soil
science, there are signi cant challenges that can be identi ed to
combine these concepts into a useful framework. We have iden-
ti ed four areas that require further research, development, or
synthesis to provide tools for bridging the science–policy divide:
• developing a framework;
• quantifying the soil resource, stocks,  uxes, transformations
and identifying indicators;
• valuing the soil resource for its ecosystem services;
• developing management strategies and decision-
support tools.
6Developing a Framework
Daily et al. (1997) presented perhaps the  rst attempt to iden-
tify distinct soil ecosystem services (Table 1). Although this has
been expanded by others (Wall, 2004; Andrews et al., 2004;
Weber, 2007; Clothier et al., 2008; Dominati et al., 2010a;
Dominati, 2011), to date there has been no accepted ecosystem
service framework for soils. More broadly, there is still much dis-
cussion and re nement of the ecosystem services framework in
general. Fisher et al. (2009) provided a recent overview of how
ecosystem services are de ned, showing that the literature has
no commonly accepted consistent de nition.  is is something
that they, and others (Boyd and Banzhaf, 2007; Wallace, 2007),
argued is required to turn a conceptual framework into an opera-
tional system of accounting.  is represents a challenge for soil
science but also an opportunity to engage at this stage to shape
the broader framework.
One aspect of framework development that is of particular
importance for soil science is the treatment of soil natural capital
(Robinson et al., 2009; Dominati et al., 2010a), given that soil is
perhaps most obviously conceptualized as a stock that contributes
to  nal ecosystem services primarily through supporting processes.
e key to sustainability is ensuring that ecosystem services are not
derived at the expense of the soil natural capital, for instance con-
version to intensive agriculture without some form of regeneration,
a more extreme example being strip mining without restoration.
Perhaps some of the biggest challenges we face in soil science are
preventing soil degradation and erosion in an increasingly popu-
lous world. To date, natural capital has been underemphasized
in the ecosystem approach, where the focus has been more on
ows of ecosystem services rather than on the stock of natural
capital from which they are derived. Approaches that incorporate
natural capital have been proposed by Palm et al. (2007), with a
new comprehensive typology proposed by Robinson et al. (2009)
based on mass, energy, and organization (Table 2). Recognizing
the important contributions of both approaches, Dominati et al.
(2010a) attempted to present a synthesis of both the ecosystem
services and natural capital approaches (Robinson and Lebron,
2010; Dominati et al., 2010b). Continued e orts are required to
build an ecosystems framework for soils that properly integrates
ecosystem services and natural capital and links with other e orts
under the general ecosystem services approach.
Table 1. Soil ecosystem services identi ed by Daily et al. (1997), cat-
egorized according to the Millen nium Ecosystem Asse ssment (2005)
classi cation of ecosystem services. Note that habitats and gene pool
could be regarded as natural capital stocks, rather than ecosystem
service  ows.
Classi cation Services
Supporting renewal, retention and deliver y of nutrients for plants
habitat and gene pool
Regu lating regul ation of major elemental cycles
bu er ing,  lteri ng, and moderation of the hydrolog ic cycle
disposa l of wastes and dead orga nic matter
Provisioning building material
physical stability and support for plants
Cultura l heritage sites, archeolog ical preserver of ar tifacts
spiritua l value, religious sites, and burial grounds
Table 2. A summary of the soil natural capital typology adapted
from Robinson et al. (2009). This is not an exhaustive list but a
guide for classification.
Natura l capital Measura ble or quanti able soil stock
Mass
Solid inorgan ic material: minera l
stock and nutrient stoc k
organic material: organic matter
and C stocks a nd organisms
Liquid soil water content
Gas soil air
ermal energy soil temperature
Biomass energ y soil biomass
Organization–entropy
Physicochemica l structure soil physicochem ical organization,
soil structure
Biotic struct ure biological population org anization,
food webs, a nd biodiversity
Spatiotempora l structure connectivity, patche s, and gradients
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6Quan ca on
e next challenge is to identify the appropriate indicators and
metrics for evaluating natural capital and ecosystem goods and
services. Based on the natural capital framework, one approach is
to evaluate soil stocks and determine how they change with time
(Bellamy et al., 2005; Emmett et al., 2010).  is is one challenge
for pro le-scale soil architecture because soil structural change
may not be explained by a reductionist approach (de Jonge et al.,
2009). Furthermore, measuring the change in soil stocks with
time is not trivial due to changes in soil bulk density (Lee et al.,
2009). Perhaps the only way to truly estimate changes in stocks is
to measure entire soil pro les using soil cores down to either lithic
or paralithic contacts. Other opportunities that may exist with
regard to soil architecture include methods to evaluate soil depth
across landscapes and determining the depth distribution of soil
properties, particularly bulk density and porosity, to determine
whether they transition smoothly or if there is an abrupt change
due to horizonation.
An alternative approach to quantifying stocks is to measure the
uxes into and out of the soil as a means to estimate changes in the
magnitude of the stocks.  is still requires a one-time estimate of
the stocks to determine a baseline for natural capital.  is approach
is also not trivial because closing the mass balance is challenging,
although some would argue that all that is needed is to know the
relative changes. is approach may be more suitable for certain
properties under speci c boundary conditions, such as for deter-
mining C  uxes from peatlands and for looking at the impacts of
di erent land uses on soil natural capital stocks. Another potential
approach is to measure proxy parameters when a stock or  ux is
hard to quantify (Dominati, 2011). For example, the number of
workable days can be used as an indicator for susceptibility to soil
compaction. An important contribution is therefore to determine
how to best assess “soil change” with regard to soil stocks,  uxes,
or transformations. Much of the existing monitoring at national
scales tends to emphasize direct measurement of soil stocks, as
done in the UK’s Countryside Survey (Emmett et al., 2010).
Soil indicators are parameters that re ect the state or function of
the soil system.  ese indicators are relatively easy to measure and
are widely used to assess soil quality and health (Doran and Parkin,
1996; Karlen et al., 1997), although there is still much discussion
with regard to which are the most appropriate.  e existing indica-
tors need to be reviewed and, as appropriate, linked to functional
outcomes at the  eld, farm, or catchment scale using a soil natural
capital and ecosystem services approach.  e outcomes of such a
review will increase the value of the indicators to land managers
and policymakers by providing them with the ability to assess
whether land use and land use changes align with environmen-
tal policy statements and sustainability principles.  e indicator
approach is widely used in other areas for decision making, for
example the economic indicator gross domestic product (GDP).
Similarly, developing internationally recognized indicators with
universally accepted measurement methods and protocols may
enable comparison at national and continental scales.  is could be,
for example, for soil C stocks and changes for the Kyoto Protocol
or C footprinting for products (British Standards Institute, 2011).
In addition, we should consider an indicator framework that will
allow us to assess the function of anthropogenic or reclaimed soils.
e challenge is then to use existing indicators of soil quality while
shi ing their focal point toward ecosystem services.
6Valua on and Tradeo s
ere will always be tradeo s among ecosystem services, manufac-
tured goods, and other sources of human well-being. We implicitly
ascribe relative values to them whenever we choose between alter-
native actions such as deciding whether to use land for production
agriculture or a wildlife reserve. To understand and inform these
decisions, it can be helpful to render these values explicit, and this
is what environmental valuation seeks to do. By valuing ecosystem
services in common units, usually, but not always, monetary, it is
anticipated that the contribution of ecosystems, including soils, to
human well-being will be recognized in societal decision making
(Pearce et al., 2006). Otherwise, we tend to consider only those
goods and services that are currently traded in markets (Edwards-
Jones et al., 2000).
As well as assisting with speci c decisions, it is hoped that environ-
mental valuation will lead to the “greening” of existing economic
indicators such as the GDP, which at present only incorporates
goods and services traded in markets or supplied by governments,
ignoring other sources of human well-being such as flood con-
trol and C sequestration that are incompletely valued by markets
(Organization for E conomic Co-operation and Development, 2011).
In addition, the GDP, which is a measure of the  ow of goods and
services, does not take into account the depreciation of natural cap-
ital or resource stocks. While some national accounting measures
are estimated net of depreciation or degradation of manufactured
capital, the depreciation or degradation of natural capital is gener-
ally ignored. Such externalities need to be internalized to achieve
green growth. Developing a coherent ecosystem services–natural
capital framework is essential for the proper valuation of the envi-
ronment, a nd it is imperative that soil scientists participate in this
important process.
6Decision-Support Tools
While the methods of environmental valuation are well established
and case studies abound, the practical challenge of valuing soil
ecosystem services and the natural capital that produces them is
formidable. As a result, the feasibility of systematically incorporat-
ing environmental values into existing economic decision-making
tools (e.g., cost–bene t analysis) and accounting systems (e.g., the
www.VadoseZoneJournal.org
GDP) has yet to be fully understood.  is may pose a substantial
challenge to approaches by which society currently makes deci-
sions.  e development of economic tools for decision making may
not be seen as the remit of soil science, but soil scientists must
engage in this process . One reason is that these decision tool s need
strong input from a soil management perspective, especially with
regard to land use. A prerequisite, and current research challenge,
is understanding the interaction among land management, land
use, and soil change. Already, soil science has made important
contributions by developing decision-support tools for land man-
agement (Andrews et al., 2004; Tugel et al., 2008).  e challenge
now is to evolve many of these tools or decision-support methods
so that they can be used by many sectors of society for wider policy
decisions and be applied to di erent types of ecosystems rather
than solely for production agriculture. Attempts to develop such
tools for ecology are now emerging, such as Invest (Nelson et al.,
2009); integration with soil science is essential. As a community,
soil scientists must develop information, including soil spatial
information and soil functioning data that are readily integrated
into new decision-support tools that can be used by other com-
munities such as ecology and hydrology.
6 How Should Soil Science
Respond to This Challenge?
We believe that soil science should embrace the opportunity to
promote the value of soils for society and human well-being so
as to demonstrate that the soil’s life support functions need to be
properly recognized within the ecosystems approach.  is requires
action by the soil science community to develop the soils compo-
nent of the ecosystems approach by:
1. creating the appropriate frameworks to determine the
natural capital and intermediate and  nal goods and services
supplied by soils that bene t human well-being , maintain
the Earth’s life support systems, and promote biodiversity;
2. identifying appropriate measurement and monitoring
programs with agreed metrics to develop the evidence base
on the “state and change” of soil natural capital and the
ecosystem services that  ow from it;
3. developing the means to value soils, which can feed into the
frameworks being developed in other disciplines, and where
possible develop synergy with existing national accounting
frameworks such as GDP and state-of-the-environment
reporting; and
4. engaging in the development of decision-support tools that
incorporate “soil change” and that will enable the most
informed comparison of tradeo s in the decision-making
process, cognizant of the enormous practical challenges
this implies.
Ecologists began to move forward with framework development
and, in doing so, recognized the vital role that soils play (Daily et
al., 1997; Wall, 2004; Millennium Ecosystem Assessment, 2005).
By embracing this  rst step, the soils community can infuse into
this approach the wealth of information and knowledge devel-
oped duri ng more tha n 100 yr of soil science a nd bene t from the
resulting synergies with other disciplines. Involvement of multiple
disciplines is needed to develop and agree on a way forward and
then apply this to the ecosystems approach. Enormous opportuni-
ties will be generated by the frami ng of fut ure soil science research
needs in the context of contributing to an ecosystems approach
that can inform policy and protect the vital functions of soil that
support human well-being, the Earth’s life support systems, and
the diversity of life on this planet.
Acknowledgments
Funding for D. Robinson and B. Reynolds for this research was provided in part by
the European Commission FP 7 Collaborative Project “Soil Transformations in Euro-
pean Catchments” (SoilTrEC) (Grant Agreement no. 244118). Discussions held as a
part of the large framework project “Soil Infrastructure, Interfaces, and Translocation
Processes in Inner Space (‘Soil-it-is’)” supported by the Danish Research Council for
Technology and Production Sciences contributed to the development of this paper.
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This essay summarizes deliberation by the Soil Science Society of America (SSSA) Ad Hoc Committee on Soil Quality (S-581) and was written to spur discussion among SSSA members. Varying perceptions of soil quality have emerged since the concept was suggested in the early 1990s, and dialogue among members is important because, unlike air and water quality, legislative standards for soil quality have not been and perhaps should not be defined. In simplest terms, soil quality is "the capacity (of soil) to function". This definition, based on function, reflects the living and dynamic nature of soil. Soil quality can be conceptualized as a three-legged stool, the function and balance of which requires an integration of three major components - sustained biological productivity, environmental quality, and plant and animal health. The concept attempts to balance multiple soil uses (e.g., for agricultural production, remediation of wastes, urban development, forest, range, or recreation) with goals for environmental quality. Assessing soil quality will require collaboration among all disciplines of science to examine and interpret their results in the context of land management strategies, interactions, and trade-offs. Society is demanding solutions from science. Simply measuring and reporting the response of an individual soil parameter to a given perturbation or management practice is no longer sufficient. The soil resource must be recognized as a dynamic living system that emerges through a unique balance and interaction of its biological, chemical, and physical components. We encourage SSSA members to consider the concept of soil quality (perhaps as a marketing tool) and to debate how it might enable us to more effectively meet the diverse natural resource needs and concerns of our rural, urban, and suburban clientele of today and tomorrow.