Further Reading
Cebrian J (2004) Role of first-order consumers in ecosystem carbon
flow. Ecology Letters 7: 232–240.
Cebrian J and Lartigue J (2004) Patterns of herbivory and
decomposition in aquatic and terrestrial ecosystems. Ecological
Monographs 74: 237–259.
Downing JA (1997) Marine nitrogen:phosphorus stoichiometry and the
global N:P cycle. Biogeochemistry 37: 237–252.
Elser JJ, Sterner RW, Gorokhova E, et al. (2000) Biological stoichiometry
from genes to ecosystems. Ecology Letters 3: 540–550.
Enriquez S, Duarte CM, and Sand-Jensen K (1993) Patterns in
decomposition rates among photosynthetic organisms: The
importance of detritus C:N:P content. Oecologia 94: 457–471.
Reiners WA (1986) Complementary models for ecosystems. American
Naturalist 127: 59–73.
Schade J, Espeleta J, Klausmeier CA, et al. (2005) A conceptual
framework for ecosystem stoichiometry: Balancing resource supply
and demand. Oikos 109: 40–51.
Sterner RW and Elser JJ (2002) Ecological Stoichiometry: The Biology of
Elements from Molecules to Biosphere. Princeton, NJ: Princeton
University Press.
Vitousek PM (1982) Nutrient cycling and nutrient use efficiency. The
American Naturalist 119: 553–572.
Webster JR, Mulholland PJ, Tank JL, et al. (2003) Factors affecting
ammonium uptake in streams: An interbiome perspective.
Freshwater Biology 48: 1329–1352.
Ecosystem Services
K A Brauman and G C Daily, Stanford University, Stanford, CA, USA
ª 2008 Elsevier B.V. All rights reserved.
Introduction
Defining Ecosystem Services
Examples of Ecosystem Services
Capturing the Value of Ecosystem Services
Conclusions
Further Reading
Introduction
The world’s ecosystems yield a flow of essential services
that sustain and fulfill human life, from seafood and timber
production to soil renewal and personal inspiration.
Although many societies have developed the technological
capacity to engineer replacements for some services,
such as water purification and flood control, no society
can fully replace the range and scale of benefits that
ecosystems supply. Thus, ecosystems are capital assets,
worthy of at least the level of attention and investment
given to other forms of capital. Yet, relative to physical,
financial, human, and social capital, ecosystem capital is
poorly understood, scarcely monitored, and, in many
cases, undergoing rapid degradation and depletion.
Recognition of ecosystem services dates back at least
to Plato. This recognition of human dependence on ecosystems,
in the past and today, is often triggered by their
disruption and loss. Direct enjoyment of services, such as
the extraction of timber, fish, and freshwater, can reduce
the quantity and quality produced. The provision of ecosystem
services can also be affected indirectly and
inadvertently. Deforestation, for instance, has exposed
the critical role of forests in the hydrological cycle –
mitigating flooding and reducing erosion. Release of
toxic substances has uncovered the nature and value of
physical and chemical processes, governed in part by
microorganisms that disperse and break down hazardous
materials. Thinning of the stratospheric ozone layer has
sharpened awareness of the value of its service in screening
out harmful ultraviolet radiation.
Defining Ecosystem Services
Simply put, ecosystem services are the conditions
and processes through which ecosystems, and the
biodiversity that makes them up, sustain and fulfill human
life. Ecosystem services are tightly interrelated, making
their classification somewhat arbitrary. The Millennium
Ecosystem Assessment (MA) – the formal international
effort to elevate awareness and understanding of societal
dependence on ecosystems – has suggested four categories.
First, ‘provisioning services’ provide goods such as
food, freshwater, timber, and fiber for direct human use;
these are a familiar part of the economy. Second, and
much less widely appreciated, ‘regulating services’ maintain
a world in which it is biophysically possible for
people to live, providing such benefits as water purification,
pollination of crops, flood control, and climate
stabilization. Third, ‘cultural services’ make the world a
place in which people want to live; they include recreation
as well as esthetic, intellectual, and spiritual
inspiration. Fourth, ‘supporting services’ create the backdrop
for the conditions and processes on which society
depends more directly. All of these services are provided
by complex chemical, physical, and biological cycles,
powered by the sun, and operate at scales ranging from
1148 Human Ecology | Ecosystem Services
smaller than the period at the end of this sentence to as
large as the entire biosphere (Table 1).
Tradeoffs in Managing the Flows of Ecosystem
Services
Biophysical constraints on human activities, such as limited
supplies of energy, land, and water, typically manifest
themselves as tradeoffs between different uses. Thus,
managing ecosystem services involves difficult ethical
and political decisions about which services to develop
and how to do so. At local scales, allocation of limited
resources to alternative activities typically involves a
zero-sum game, illustrated by the widespread redirection
of water from agriculture to urban and industrial purposes.
At global scales, different groups of people compete
for use of Earth’s open-access resources and waste sinks,
such as the atmosphere’s capacity to absorb CO2 and
other greenhouse gases without inducing climate change.
Making informed decisions about how to use ecosystem
goods and services hinges on understanding these
tradeoffs: knowing the joint products – the suite and
level of services – that ecosystems can provide. For example,
an ecosystem managed exclusively for agriculture
may yield a greater return on agricultural products than
one managed for multiple services, but understanding
that diversified management may produce greater
overall returns could influence management decisions
(Figure 1).
Provision of biodiversity is one supporting service that
has historically been discounted when managing for other
ecosystem services. Biodiversity, however, can provide
irreplaceable benefits. Genetic diversity, for example,
allows for both the survival and evolution of the ecosystems
we depend on for myriad benefits. Recent research
indicates that diverse systems are more resilient, and
therefore provide ecosystem services more reliably in
the long term, than monocultures. While under optimal
conditions managing for a single species may provide
superior timber supplies or nutrient sequestration, given
natural and human-caused variability in temperature,
rainfall, and other environmental factors, managing for a
diverse system will more consistently provide services in
an uncertain world.
Examples of Ecosystem Services
Ecosystem services can be explored by focusing either on
a single service that may be provided by various ecosystems
or by looking at a single ecosystem that may provide
a variety of services. Here we illustrate both approaches,
considering first pollination services provided by bees
then the suite of services provided by wetlands and forests.
We highlight the differences in scale of delivery of
services, from local to global, and explore the tradeoffs
inherent in their management.
Pollination Services Provided by Bees
Pollination, the movement of genetic material in the
form of pollen grains, is a key step in the development of
most food crops. Even crops that do not rely on insect
pollination – wind pollinated or self-pollinated crops –
are sometimes more productive when visited by an insect
pollinator. Bees are a particularly important group of insect
pollinators, responsible for pollinating 60–70% of the
world’s total flowering plant species, including nearly 900
food crops worldwide, such as apples, avocados,
Table 1 A classification of ecosystem services. Examples of
ecosystem services and how they can be categorized
Provisioning services: Production of. . .
Food
Seafood, agricultural crops, livestock, spices
Pharmaceuticals
Medicinal products, precursors to synthetic pharmaceuticals
Durable materials
Natural fiber, timber
Energy
Biomass fuels, low-sediment water for hydropower
Industrial products
Waxes, oils, fragrances, dyes, latex, rubber
Genetic resources
Intermediate goods that enhance the production of other
goods
Regulating services: Generation of. . .
Cycling and filtration processes
Detoxification and decomposition of wastes
Generation and renewal of soil fertility
Purification of air and water
Translocation processes
Dispersal of seeds to sustain tree and other plant cover
Pollination of crops and other plants
Stabilizing processes
Coastal and river channel stability
Control of the majority of potential pest species
Carbon sequestration
Partial stabilization of climate
Protection from disasters:
regulation of hydrological cycle (mitigation of floods and
droughts)
moderation of weather extremes (such as of temperature
and wind)
Cultural services: Provision of. . .
Esthetic beauty, serenity
Recreational opportunities
Cultural, intellectual, and spiritual inspiration
Supporting services: Preservation of. . .
Processes underlying services in the classes above
Options
maintenance of the ecological components and systems
needed for future supply of the goods and services above
and others awaiting discovery
Human Ecology | Ecosystem Services 1149
cucumbers, and squash. These crops comprise 15–30% of
the world’s food production, and bees are credited with
$4.2 billion in annual crop productivity in California alone.
Bees are especially important pollen vectors in part
because physical adaptations, such as hairs designed to
pick up pollen, and behavioral adaptations, such as fidelity
to a single species of plant on each pollen-gathering trip,
ensure good pollen transport and cross-pollination.
In the US, most major agricultural enterprises that rely
on bee pollination import managed bees, almost always
the European honeybee Apis mellifera. The available stock
of managed honeybees has declined dramatically, however,
dropping by over 50% in the last 50 years, while
demand for pollination services has increased in many
areas. This decline in managed bee populations has many
causes, including increased pesticide use, disease in the
hives, and downsizing of stocks that have hybridized with
Africanized bees, introducing traits that make managed
bees more aggressive and thus a liability to the farmer.
The contribution of native, wild bees to agricultural
pollination was ignored, and assumed to be negligible,
until the early 2000s. Since then, research has shown
that native bees serve an important role in pollination,
picking up slack when managed bee pollination is insufficient
and enhancing crop production in general. Farms
with generous native bee habitat nearby may be able to
fully or partially replace pollination by managed bees. In
some cases, native bees are more efficient pollinators than
European honeybees. The variety of wild bees, with distinct
physical and behavioral traits, allows them, as a
group, to pollinate a wide variety of flowering plants.
Tomatoes, for example, have pollen that is accessible
only by vibrating the flower, which bumble bees and
some other native bees can, while honeybees cannot.
Though tomatoes are self-pollinating and do not require
an insect vector, native bees promote cross-pollination,
which, for example, significantly increases the fruit set
and size of Sungold cherry tomatoes.
The contributions of native bees to crop production
are usually undocumented and underestimated, and they
are always unpaid, at least directly. Though hives of
managed honeybees must be rented or maintained, wild
bees pollinate at no cost to the farmer. Populations of
native bees are under great threat, however, by land
management practices that promote the use of pesticides
and the loss, fragmentation, and degradation of habitat.
Protecting native bees without protecting the ecosystems
in which they live is impossible. Native habitat, unlike
agricultural monocropping, provides the year-round supply
of blooming plants that wild bees require for
sustenance. Native habitat also provides nesting areas;
most wild bees are solitary, laying a single egg in a nest
cavity dug into the ground or into dead wood, not forming
social hives. In order to reap the benefits of native pollinators,
food resources and nesting habitat must be
available within a short distance of crops, possibly as
hedgerows, in ditches, or around water ponds. A study
of wild bee pollination of coffee in Costa Rica showed that
farms closer to tropical forest remnants were visited by
many more species of wild bees than those further away.
Had the far sites been adequately pollinated, coffee yield
would have been increased by nearly 20% and misshapen
coffee beans reduced by 27%. A lower-bound estimate of
the pollination services from these patches is US $62 000
per year (in the early 2000s).
The diversity of the native bee population is one of its
strengths. Many species of bees participate in pollination,
and the abundance of different species varies year by year.
This diversity allows the native pollinator community to
be both resistant, maintaining functionality in the face of
environmental upheaval, and resilient, able to reestablish
itself in the wake of a destructive event. When the population
of Apis declined dramatically in the second year of the
Costa Rica study, sites close to forest fragments showed
minimal loss of pollination while pollinator visits dropped
by nearly 50% further away. Thus, as well as enhancing
Agriculture
Agriculture
Climate
Water
purification
Biodiversity
Climate
stabilization
Biodiversity
Water purification
$$$
$$
$$
$$
$$
Figure 1 Joint products of ecosystems. Many ecosystems are currently managed to exploit only one service. Managing for multiple
services can increase ecosystem benefits.
1150 Human Ecology | Ecosystem Services
pollination services in conjunction with managed bees,
native bee populations provide important insurance against
the possibility that managed bee populations could fail
because of disease, hybridization, or other causes.
Services Provided by Wetlands
Areas inundated by fresh, brackish, and salt water are all
considered wetlands; among many wetland types are fens
and bogs, tidal marshes, riparian zones, and lakeshores.
Wetlands, which cover less than 9% of the Earth’s surface,
can be extremely productive and many are disproportionately
large providers of ecosystem services. Three of the
key services that wetlands provide are flood mitigation,
water purification, and biodiversity support.
In the upper part of a watershed, many wetlands store
water that flows overland toward rivers and streams.
They can release this water into the main channel slowly,
reducing and delaying flood peaks. Downstream, wetlands
can absorb and reduce peak flood levels, providing
area into which flood waters can spread, dissipating flood
energy by slowing water movement, and removing flood
water through transpiration and infiltration.
The same physical characteristics of wetlands that slow
and absorb overland flow related to flooding can also
provide a mechanism for storing and detoxifying urban
and agricultural wastewater before it discharges directly
into a main channel. Wetlands filter out various nutrients,
other pollutants, and sediment: they support anaerobic
bacteria that denitrify waste; the plants take up and store
nutrients; and by slowing and redirecting water flow, wetlands
enhance sedimentation – the accreting sediments
can effectively bury pollutants. While many wetlands
can purify water very economically, their effectiveness
depends on many factors, including rate of inflow, amount
of sediment and organics in the wastewater, residence time
of wastewater in the wetland, and total surface area.
A wide variety of animals rely on wetlands for survival.
Plant species that deliver flood abatement and water
purification can also support biodiversity, providing
varied food and shelter. A riparian wetland, for example,
might provide food plants and underground burrows for
muskrats; seeds, food plants, and nest-building materials
for ducks; and food and shelter for fish and invertebrates.
Wetlands provide a variety of other services as well.
Major products associated with wetlands are peat, timber,
and mulch. Regulating services in addition to flood
mitigation and water purification include waste detoxification,
carbon storage, and control of pests and diseases.
Wetlands provide many cultural services as well,
particularly recreation services such as bird watching,
boating, and hunting. Wetlands also provide key supporting
services, such as soil formation and buffering
freshwater aquifers from saltwater intrusion.
Worldwide, wetlands are estimated to provide many
billions of dollars in services each year. They are recognized
by the international treaty, the Ramsar Convention
on Wetlands, and regulated by domestic law in many
countries. Nonetheless, they have historically undergone
widespread losses in favor of other land uses; worldwide,
50% of wetlands are estimated to have been lost since 1900.
While the services provided by wetlands are widely
recognized, simultaneously maximizing multiple services
may not be possible. In some cases this is related to location:
upland watersheds may be very important for flood control
but may be too far upstream to have an impact on water
purification. In other cases one service may thrive to the
detriment of another: a wetland that is absorbing a heavy
nutrient load may be overtaken by a single, aggressive plant
species and thus fail to be an effective reservoir for biodiversity.
Finally, it can be costly to measure function and
hence difficult to judge how effectively a wetland is performing
a given service or how to manage for that particular
service.
Services Provided by Forests
Forests provide a wide array of services, such as timber
production, climate stabilization, provision of water quantity
and quality, and cultural benefits, such as recreation.
Some management options increase the supply of several
services, but often one service is enhanced to the detriment
of others.
Forests are often managed for provisioning services,
particularly for timber. But even within the category of
provisioning services, management options differ. If a
forest is considered exclusively a supplier of timber,
managers will encourage the growth of only certain
kinds of trees, possibly nonnative fast-growing trees, and
will cultivate them so that they grow in a uniform way,
typically straight and tall. When the trees are deemed
mature, they will be cut down, often all at once. By
contrast, if a forest is regarded as a supplier of diverse
benefits, it may be managed to nurture a wide array of
valued species that would not be available in the monocrop
forest described above.
Forests also have both short-term and medium-term
impacts on climate. Temperature regulation happens in
forests when the canopy shades the ground and when
dark-colored foliage absorbs heat. Forests can in certain
circumstances also influence precipitation – in cloud forests,
for example, trees and epiphytes intercept and
condense water directly from the air, and that water
runs down trunks to plants and soil below. On a longer
timescale, forests play a role in carbon cycling and sequestration;
when forest plants, bacteria, and algae respire,
they take CO2 out of the atmosphere. Plants, soils, and
the animals that eat them in forests, grasslands, and other
terrestrial ecosystems store 2000 billion tons of carbon
Human Ecology | Ecosystem Services 1151
worldwide, about half the amount of carbon stored in the
ocean and nearly three times that stored in the atmosphere.
However, if these ecosystems are burned or
destroyed, as happens when timber is harvested, the carbon
they are sequestering is released to the atmosphere.
Although most organic compounds do return to the atmosphere
as CO2 when living organisms die and decompose,
in a functioning forest ecosystem some is buried and
sequestered. About 25% of the human-caused increase
in CO2 concentration in the atmosphere during the
past 20 years resulted from land-use change, primarily
deforestation.
Forests in a watershed, on the hillslopes that drain into a
river, influence the water quality in that river. In part this is
because higher-intensity uses, such as agriculture input
pollutants like nutrients and pesticides into a system while
forests do not. Forests themselves also reduce sediment and
nutrient runoff. Clearing trees can have an impact as soon as
the next rainy season on sediment and nutrient loads in
streams, as demonstrated in the classic Hubbard Brook
experiment. In some cases, water users have invested in
forests to keep their water supplies clean. New York City
recently invested US$ 250 million to acquire and protect
land in the Catskills watershed that supplies water to the
city. By working with landowners to reduce pesticide and
fertilizer application and to plant buffer strips along waterways,
New York City reduced potential contamination of
its drinking water. In conjunction with related conservation
investments amounting to US$ 1.5 billion, the city
thereby obviated the need to build a filtration plant projected
to cost between US$ 6 and US$ 8 billion.
Forests can also play an important role regulating the
timing and quantity of runoff. The economic value
of forests in the watershed of the Yangtze River above
Three Gorges Dam, in western Hubei Province, Central
China, was quantified in a study published in 2000. Here,
the Gexhouba Hydroelectric Power Plant, the largest
hydro-facility in China, producing 15.7 billion kW
annually, requires a narrow range of flows on the Yangtze
in order to run at full power. If the water level is too high,
then water must be released through the sluice gates,
causing the water level below the dam to rise, reducing
the amount of power that can be produced; at very high
flows, turbines are drowned and cannot work at all. If the
water is too low, then generators cannot run at full power.
The goal of the hydroelectric facility’s managers is for
the river to have flow depths that vary as little as possible,
as this has been shown to be much more important for
power generation than the total flow. Upstream forests
damp fluctuations in stream flow by reducing runoff in
wet periods through canopy interception, leaf litter
absorption, and soil and groundwater storage; increased
infiltration provides base flow in dry periods through
groundwater discharge. Though water flow regulation is
a function of vegetation, soil type, and slope, which occur
in a heterogeneous mix through the watershed, forests
and even shrubs with all types of soils and slopes consistently
provided better water regulation than grasses,
orchards, and crop agricultural fields. This study estimated
the value of electricity produced by the hydrofacility
due to water regulation by the forest at over
US$ 600 000 per year (in the early 2000s), or about 2.2
times the income derived from forest product services in
this area. Because trees lose water to the atmosphere
through transpiration, however, the total water available
downstream was decreased by the forest.
Different management regimes will yield different suites
of services. Some services can never be co-produced; other
services will almost always be produced in tandem, though
often to differing degrees. For the hypothetical forest illustrated
in Figure 2, cattle and timber cannot be produced on
the same parcel of land – conversion to pasture optimizes
livestock but reduces timber output dramatically. Under
timber maximization, once trees are harvested they are not
available for climate or hydrologic regulation, though before
harvest those services will be produced, as well as some
habitat and hiking trails. Carbon sequestration, hydropower,
recreation, and preservation of biodiversity tend to be coproduced,
but there are tradeoffs in their optimal supply.
Maximizing biodiversity, for example, produces all four to
their fullest extent but allows for no timber supply. Bringing
selective logging back into the management regime reduces
supply of the other services somewhat; maximizing timber
yield reduces them much more dramatically.
Tradeoffs between services are also tradeoffs between
consumers, such as local recreationalists, regional users of
hydropower, and global beneficiaries of carbon sequestration
and biodiversity conservation. These tradeoffs
underscore the importance of valuation, making explicit
who benefits from ecosystem services and who pays for
them. Conceiving of ecosystem functions as services and
assigning a monetary value to them provides a tool for
decision-makers to weigh different management options.
Capturing the Value of Ecosystem
Services
Despite their obvious importance to human well-being,
people tend to think of ecosystems as being economically
productive in narrow terms, often assigning value only to
the production of conventional commodities or to real
estate development. Provision of ecosystem services is only
rarely considered in cost–benefit analyses, preparation
of environmental impact statements, or other assessments
of alternative paths of development. There is no shortage of
markets for ecosystem goods (such as clean water and watermelons),
but the services underpinning these goods (such as
water purification and bee pollination) often have no monetary
value. This is in part because ecosystem services are
1152 Human Ecology | Ecosystem Services
generally public goods, free to any user, and therefore
difficult to value. Because people mostly do not pay for
them, it can be difficult to discern what the supply, demand,
and willingness to pay for services actually are. As a result,
there are no direct price mechanisms to signal the scarcity or
degradation of these public goods before they fail.
While for some goods and services price reflects value or
importance, when ecosystem services are assigned monetary
value they tend to be priced much lower than their importance
suggests. This is true in part because when supply is
much larger than demand, prices are low, no matter how
necessary the good. The pricing of diamonds and water is
illustrative. Lost in the desert, a traveler would happily trade
all the diamonds in the world for a single cup of water; back
in the marketplace, our traveler would find that diamonds
are many, many times more costly than water. Water is
inexpensive or free because, like many ecosystem goods
and services, it tends to be far more abundant than the
volume demanded by people; when ecosystems are functioning
well, even more is available.
Ecosystem services are also often undervalued because
prices are based on current supplies and demands, so the
amount we are willing to pay for continued nutrient
retention in a wetland may be low today even if we can
predict that nutrient-laden runoff from increased agriculture
will threaten a downstream fishery tomorrow.
Further, prices are based on marginal utility – for example,
the amount someone would be willing to pay for the
carbon stored in one more tree in a forest. If that forest is
clear-cut, we lose all of the carbon storage and, since the
loss of each tree changes the value of the next, we cannot
account for the whole loss using the price of the first tree.
Precise valuation of ecosystem services is often not
required to provide appropriate economic incentives for
protecting the ecosystems that supply them. Incentives
need only make it more economically appealing to a
landowner to maintain hedgerows as habitat for native
pollinators than to cultivate every last square meter of a
field, for instance, or make it pay to preserve a wetland
rather than filling it to build houses. A farm, as illustrated
below, might generate enough income from nonagricultural
commodities to alter its land management regime
(Table 2). Incentives to protect and maintain ecosystems
can be provided by the government, privately through
markets, or through hybrid institutions such as cap-andtrade
systems supported by government policy.
A variety of tools for valuing ecosystem services and
creating incentives for their conservation are currently
being developed, including capital markets such as the
Chicago Climate Exchange, wetland mitigation banks,
and outright payments, often involving private–public
partnerships, for services, as is occurring in Australia,
Costa Rica, and Mexico. These market-based approaches
provide a much better indication of value than early,
more theoretical attempts to quantify the value of ecosystem
services. While valuation is not necessarily a
solution or end in itself, it is a powerful way of organizing
information and an important tool in the much larger
process of decision making.
Maximize biodiversity and
recreation
Diverse portfolio, selective
logging
Management regime
Livestock production
Hydropower
Timber production
Recreation
Carbon sequestration
Preservation of biodiversity
Convert to pasture Maximize timber yield
Figure 2 Tradeoffs associated with alternative management objectives for a hypothetical forest ecosystem.
Table 2 A hypothetical farm business in 15 years
Commodity Share of farm business (%)
Wheat 40
Wool 15
Water filtration 15
Timber 10
Carbon sequestration 7.5
Salinity mitigation 7.5
Biodiversity 5
In this model, traditional agricultural commodities account for 55% of
revenues, as opposed to 100% today. Nonagricultural income is
supplied by a mature market for ecosystem goods and services.
Human Ecology | Ecosystem Services 1153
Conclusions
Because ecosystem services explicitly invoke human beneficiaries,
basic scientific understanding of the ecosystem
processes producing goods and services is meaningful
only in the context of economic valuation and institutional
structures. There is still much to learn on many
fronts. Important questions include: Which ecosystems
supply which services? What levels and types of ecosystem
protection are required to sustain service supply? Can
we develop robust methodologies for the valuation of
ecosystems? Even if clear answers are absent to all of
these questions, numerous and diverse efforts are now
underway worldwide to protect vital ecosystem services,
often using innovative economic incentives.
Explicitly identifying and valuing the goods and
services provided by ecosystems has two obvious benefits.
First, understanding the role of ecosystem services
powerfully justifies habitat preservation and biodiversity
conservation as vital, though often overlooked, policy
objectives. While a wetland surely provides existence and
option values to some people, the benefits provided by the
wetland’s nutrient retention and flood mitigation services
are both universal and undeniable. Tastes may differ over
beauty, but they are in firm accord over the high costs of
polluted water and flooded homes. Second, if given the
opportunity, natural systems can in many cases quite literally
pay their own way. Market mechanisms and
institutions that can capture and maximize service values
can effectively promote environmental protection at the
local, regional, national, and international levels. In some
cases, however, protection of ecosystem services will not
justify conservation of natural habitats. In other cases, the
services will be largely irrelevant to environmental protection
efforts. While a focus on ecosystem services provides
great potential to promote environmental protection, its
practical implications remain largely unexamined.
See also: Agroforestry; Biodegradation; Biodiversity;
Biomass, Gross Production, and Net Production; Climate
Change 1: Short-Term Dynamics; Coastal Zone
Management; Conservation Biological Control and
Biopesticides in Agricultural; Deforestation;
Denitrification; Ecological Economics 1; Ecosystem
Health Indicators ; Environmental Impact Assessment
and Application Part 1; Erosion; Forest Management;
Industrial Ecology; Lake Restoration Methods; Natural
Wetlands; Resilience; Resistance and Buffer Capacity;
Riparian Wetlands; Sediment Retention and Release;
Stream Management; Sustainable Development; Water
Availability; Water Cycle Management; Watershed
Management; Wetland Models.
Further Reading
Brauman KA, Daily GC, Duarte TK, and Mooney HA (2007) The nature
and value of ecosystem services: An overview highlighting services.
Annual Review of Environmental and Resources 32: 67–98.
Chichilnisky G and Heal G (1998) Economic returns from the biosphere –
Commentary. Nature 391: 629–630.
Committee to Review the New York City Watershed Management
Strategy (2000) Watershed Management for Potable Water Supply:
Assessing the New York City strategy. Washington, DC: National
Academy Press.
Daily GC (ed.) (1997) Nature’s Services: Societal Dependence on
Natural Ecosystems. Washington, DC: Island Press.
Daily GC and Ellison K (2002) The New Economy of Nature: The Quest
to Make Conservation Profitable. Washington, DC: Island Press.
Daily GC, So¨ derqvist T, Aniyar S, et al. (2000) The value of nature and
the nature of value. Science 289: 395–396.
Findlay SEG, Kiviat E, Nieder WC, and Blain BA (2002) Functional
assessment of a reference wetland set as a tool for science,
management and restoration. Aquatic Sciences 64: 107–117.
Guo Z (2000) An assessment of ecosystem services: Water flow
regulation and hydroelectric power production. Ecological
Applications 10: 925–936.
Heal G (2000) Nature and the Marketplace: Capturing the Value of
Ecosystem Services, Washington, DC: Island Press.
Heal G, Daily GC, and Salzman J (2001) Protecting natural capital
through ecosystem service districts. Stanford Environmental Law
Journal 20: 333–364.
Kremen C, Williams NM, and Thorp RW (2002) Crop pollination from
native bees at risk from agricultural intensification. Proceedings of the
National Academy of Sciences of the United States of America
99: 16812–16816.
Millennium Ecosystem Assessment (2005) Ecosystems and Human
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1154 Human Ecology | Ecosystem Services