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Agricultural systems depend fundamentally on ecological processes and on the services provided by many eco­systems. Agricultural management during the last century has caused widescale changes in land cover, watercourses, and aquifers, contributing to eco­system degradation and undermining the processes that support eco­systems and the provision of a wide range of eco­system services. It has been increasingly recognized that agricultural management has caused some eco­systems to pass ecological thresholds (tipping points), leading to a regime change in the eco­system and loss of eco­system services. The poor people in rural areas who use a variety of ecosystem services directly for their livelihoods are likely to be the most vulnerable to changes in eco­systems. This paper states that an integrated approach is needed for managing land and water resources and eco­systems that acknowledges the multifunctionality of agroeco­systems in supporting food production and eco­system resilience.
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6
Agriculture, water, and
ecosystems: avoiding the
costs of going too far
Fuel
wood
Recreation
Pest
control
Soil
formation
Regulation
of water
balance
Nutrient
cycling
Crop
production
Climate
regulation
Provisioning services Regulating services
Supporting services Cultural services
Natural ecosystem
Coordinating lead authors: Malin Falkenmark, C. Max Finlayson, and Line J. Gordon
Contributing authors: Elena M. Bennett, Tabeth Matiza Chiuta, David Coates,
Nilanjan Ghosh, M. Gopalakrishnan, Rudolf S. de Groot, Gunnar Jacks, Eloise Kendy,
Lekan Oyebande, Michael Moore, Garry D. Peterson, Jorge Mora Portuguez,
Kemi Seesink, Rebecca Tharme, and Robert Wasson
Overview
Agricultural systems depend fundamentally on ecological processes and on the services provided
by many ecosystems
. ese ecological processes and services are crucial for supporting and
enhancing human well-being. Ecosystems support agriculture, produce fiber and fuel,
regulate freshwater, purify wastewater and detoxify wastes, regulate climate, provide pro-
tection from storms, mitigate erosion, and offer cultural benefits, including significant
aesthetic, educational, and spiritual benefits.
Agricultural management during the last century has caused widescale changes in land
cover, watercourses, and aquifers, contributing to ecosystem degradation and undermining the
processes that support ecosystems and the provision of a wide range of ecosystem services
. Many
agroecosystems have been managed as though they were disconnected from the wider
landscape, with scant regard for maintaining the ecological components and processes that
underpinned their sustainability. Irrigation, drainage, extensive clearing of vegetation, and
addition of agrochemicals (fertilizers and pesticides) have often altered the quantity and
quality of water in the agricultural landscape. e resultant modifications of water flows
and water quality have had major ecological, economic, and social consequences, includ-
ing effects on human health [well established]. Among them are the loss of provisioning
services such as fisheries, loss of regulating services such as storm protection and nutrient
retention, and loss of cultural services such as biodiversity and recreational values. Adverse
ecological change, including land degradation through pollution, erosion, and saliniza-
tion, and the loss of pollinators and animals that prey on pest species, can have negative
Natural ecosystem services
Artist: Peter Grundy, United Kingdom
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234234
feedback effects on food and fiber production [well established]. In extreme cases human
health can also suffer, for example, through insect-borne disease or through changes in diet
and nutrition. All too often the consequences of modifying agroecosystems have not been
fully considered nor adequately monitored.
It has been increasingly recognized that agricultural management has caused some ecosystems
to pass ecological thresholds (tipping points), leading to a regime change in the ecosystem and loss
of ecosystem services
. Ecosystem rehabilitation is likely to be costly, if possible at all. Some
changes can be nearly irreversible (for example, the establishment of anoxic areas in marine
water bodies). ese changes can occur suddenly, although they often represent the cumula-
tive outcome of a slow decline in biodiversity and reduced ecological resilience (the ability
to undergo change and retain the same function, structure, identity, and feedbacks).
e poor people in rural areas who use a variety of ecosystem services directly for their
livelihoods are likely to be the most vulnerable to changes in ecosystems
. erefore, failure to
tackle the loss and degradation of ecosystems, such as that caused by the development and
management of agriculture-related water resources, will ultimately undermine progress
toward achieving the Millennium Development Goals of reducing poverty, combating
hunger, and increasing environmental sustainability.
An integrated approach is needed for managing land and water resources and ecosystems
that acknowledges the multifunctionality of agroecosystems in supporting food production and
ecosystem resilience. at requires a better understanding of how agroecosystems generate
multiple ecosystem services and of the value of maintaining biodiversity, habitat hetero
-
geneity, and landscape connectivity in agricultural landscapes. Social issues, such as the
importance of the role of gender in management decisions, also require more emphasis.
Attention should be directed toward minimizing the loss of ecosystem resilience and build
-
ing awareness of the importance of cumulative changes and of extreme events for generat-
ing ecosystem change. It is also necessary to meet the water requirements for sustaining
ecosystem health and biodiversity in rivers and other aquatic ecosystems (marshes, lakes,
estuaries) and to demonstrate the benefits of these services to society as a whole.
It has been estimated that by 2050 food demand will roughly double. As populations and
incomes increase, demand for water allocations for agriculture will rise. Simplified, there are
three main ways in which this increased water requirement can be met: through increased
water use on current agricultural lands, through expansion of agricultural lands, and through
increased water productivity. While all are plausible and a mix of solutions is likely, each has
vastly different implications for nonagricultural ecosystems and the services they generate.
With the current high levels of land conversion and river regulation globally, greater con-
sideration should be given to improving management of water demand within existing agri-
cultural systems, rather than seeking further expansion of agriculture. Dependent on local
conditions, technologies and management practices need to be substantially improved,
and ecologically sound techniques implemented more widely to reduce the impacts from
agriculture, whether extensive or intensive. Further intensification will require careful
management to prevent further degradation and loss of ecosystem services through in
-
creased external effects and downstream water pollution. With the basis of many essen-
tial ecosystem services already seriously undermined, there is an urgent need not only to
An integrated
approach is
needed for
managing land,
water, and eco-
systems that
acknowledges
the multi-
functionality of
agroecosystems
in supporting
food production
and ecosystem
resilience
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6
Agriculture, water, and
ecosystems: avoiding the
costs of going too far
minimize future impacts, but also to reverse loss and degradation through rehabilitation
and, in some cases, full restoration.
An integrated approach to land, water, and ecosystems at basin or catchment scale is urgently
needed to increase multiple benefits and to mitigate detrimental impacts among ecosystem services
.
is involves assessing the costs and benefits as well as all known risks to society as a whole
and to individual stakeholders. Societally accepted tradeoffs are unlikely without wide stake-
holder discussion of consequences, distribution of costs and benefits, and possible compensa-
tion. It is also important that the results feed into processes of social learning about ecosystem
behavior and management. A few tools are available to assist in striking tradeoffs (including
economic valuation and desktop procedures for establishing environmental flows), but more
efficient and less sectorally specific tools are needed. Most of the tools were developed to
enable better decisionmaking on well known problems and benefits. Needed are tools to ad-
dress the lesser known problems and benefits and to prepare for surprises.
Decisions on tradeoffs under uncertain conditions should be based on a set of alternative
scientifically informed arguments, with an understanding of the uncertainties that exist when
dealing with ecological forecasting. To minimize the sometimes very high future costs of
unexpected social and ecological impacts, it will be necessary to conceptualize uncertainty
in decisionmaking. Adaptive management and scenario planning that improve assessment,
monitoring, and learning are two components of this conceptualization.
Ongoing attention is required to communicate ecological messages across disciplinary and
sectoral boundaries and to relevant policy and decisionmaking levels. e challenge is to pro-
duce simple messages about the multiple benefits of an ecosystem and about how eco-
systems generate services—without oversimplifying the complexity of ecosystems.
In view of the huge scale of future demands on agriculture to feed humanity and eradicate
hunger, and the past undermining of the ecological functions on which agriculture depends, it is
essential that we change the way we have been doing business. To do this, we need to:
Address social and environmental inequities and failures in governance and policy as
well as on-ground management.
Rehabilitate degraded ecosystems and, where possible, restore lost ecosystems.
Develop institutional and economic measures to prevent further loss and to encour-
age further changes in the way we do business.
Increase transparency in decisionmaking about agriculture-related water management
and increase the exchange of knowledge about the consequences of these decisions. In
the past many changes in ecosystem services have been unintended consequences of
decisions taken for other purposes, often because the tradeoffs implicit in the decision-
making were not transparent or were not known [well established].
Water and agriculture—a challenge
for ecosystem management
Changes in agriculture over the last century have led to substantial increases in food security
through higher and more stable food production. However, the way that water has been man-
aged in agriculture has caused widescale changes in land cover and watercourses, contributed
There is a need
not only to
minimize future
ecosystem
impacts, but
also to reverse
loss and
degradation
through
rehabilitation
and, in some
cases, full
restoration
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to ecosystem degradation, and undermined the processes that support ecosystems and the
provision of a wide range of ecosystem services essential for human well-being.
e Millennium Ecosystem Assessment, an international assessment by more than
1,300 scientists of the state of the world’s ecosystems and their capacity to support hu
-
man well-being, identified agricultural expansion and management as major drivers of eco-
system loss and degradation and the consequent decline in many ecosystem services and
human well-being (www.maweb.org). Analyses illustrated that by 2000 almost a quarter of
the global land cover had been converted for cultivation (map 6.1), with cropland cover-
ing more than 50% of the land area in many river basins in Europe and India and more
than 30% in the Americas, Europe, and Asia. e Millennium Ecosystem Assessment also
showed that the development of water infrastructure and the regulation of rivers for many
purposes, including agricultural production, often resulted in the fragmentation of rivers
(map 6.2) and the impoundment of large amounts of water (figure 6.1; Revenga and oth-
ers 2000; Vörösmarty, Lévêque, and Revenga 2005).
Many scientists argue that as a society we are becoming more vulnerable to environ-
mental change (Steffen and others 2004; Holling 1986), reducing our natural capital and
degrading options for our current and future well-being (Jansson and others 1994; Arrow
and others 1995; MEA 2005c). Natural and human-induced disasters, such as droughts
and famine, are also likely to increase the pressure on vulnerable people, such as the rural
poor, who depend most directly on their surrounding ecosystems (Silvius, Oneka, and
Verhagen 2000; WRI and others 2005; Zwarts and others 2006).
Furthermore, as populations and incomes grow, it has been estimated that food de-
mand will roughly double by 2050 and shift toward more varied and water-demanding
diets, increasing water requirements for food production (see chapter 3 on scenarios).
map 6.1 Extent of cultivated systems in 2000
Note: Cultivated systems are dened as areas where at least 30% of the landscape is in croplands, shifting cultivation, conned
livestock production, or freshwater aquaculture.
Source: MEA 2005c.
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6
Agriculture, water, and
ecosystems: avoiding the
costs of going too far
map 6.2 River channel fragmentation and flow regulation of global rivers
Source: Revenga and others 2000.
Unfragmented
Moderately fragmented
Highly fragmented No data
Unassessed
Sum of discharge (cubic kilometers per year)
Sum of capacity (cubic kilometers)
16,000
5,000
4,000
3,000
2,000
1,000
0
14,000
12,000
10,000
8,000
6,000
4,000
2,000
0
19201900 1940 1960 1980 2000 19201900 1940 1960 1980 2000
Intercepted continental runoff Reservoir storage
Note: The time series data are taken from a subset of large reservoirs (0.5 cubic kilometers maximum storage each),
geographically referenced to global river networks and discharge.
Source: Millennium Ecosystem Assessment.
gure 6.1
Development of water infrastructure and regulation of rivers
resulted in the impoundment of large amounts of water
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238
Simplified, there are three main ways to meet this water requirement: increasing water
use on current agricultural lands through intensification of production (see chapters 8 on
rainfed agriculture and 9 on irrigation), expanding agricultural lands, and increasing water
productivity (see chapters 7 on water productivity and 15 on land).
ese options have vastly different implications for ecosystems and the services they
generate. Increased water use on agricultural lands through irrigation will reduce the avail-
ability of blue water resources (surface water and groundwater), especially for downstream
aquatic systems, and can contribute to waterscape alterations, for example, through the
introduction of dams for irrigation. Increased green water flows (soil moisture generated
from rainfall that infiltrates the soil) through higher consumptive water use in rainfed
agriculture (as a result of increased crop productivity) will also reduce the availability of
water downstream, although the extent to which this could occur varies [established but
incomplete]. Expanding agricultural land can alter the water flow in the landscape, with
impacts on terrestrial and aquatic ecosystems. Finally, while increased water productivity is
intended to produce more food without using more water, it can lead to deterioration in
water quality through increased use of agrochemicals.
Humanity is facing an enormous challenge in managing water to secure adequate food
production without undermining the life support systems on which society depends—and
in some instances while simultaneously rehabilitating or restoring those systems. Research on
ecosystems has generally been separate from research on water in agriculture, leading to a seg
-
regated view of humans and food security on one side and nature conservation on the other. In
this chapter we challenge this view by describing recent understanding of how all ecosystems
support human well-being, including ensuring food security and redressing social inequities.
We focus on the links between ecosystems and management of water in agriculture.
Water functions as the “bloodstream of the biosphere(Falkenmark 2003). It is vital for
the generation of many ecosystem services in both terrestrial and aquatic ecosystems and
provides a link between ecosystems, including agroecosystems. As for agricultural produc
-
tion, we consider the importance of both blue and green water (see chapter 1 on setting the
scene) for ecosystems, both those characterized by the presence of blue water, such as marsh
-
es, rivers, and lakes, and terrestrial ecosystems that depend on and modify green water.
We first assess the ecosystem effects of past water-related management in agriculture,
highlighting some of the often unintentional tradeoffs between water for food production
and water for other ecosystem services. We then outline response options for improving
water management. We emphasize the need to intentionally deal with the unavoidable and
often surprising tradeoffs that arise when making decisions to increase food production,
noting that these are often embedded within complex social situations where different
stakeholders have highly diverse interests, skills, and influence (see, for example, chapters
5 on policies and institutions, 15 on land, and 17 on river basins).
Agriculture and ecosystems
While agricultural production is driven by human management (soil tillage, irrigation, nu-
trient additions), it is still influenced by the same ecological processes that shape and drive
nonagricultural ecosystems, particularly those that support biomass production and others
Humanity
is facing an
enormous
challenge in
managing
water to secure
adequate food
production
without
undermining
the life support
systems on
which society
depends
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6
Agriculture, water, and
ecosystems: avoiding the
costs of going too far
such as nitrogen uptake from the atmosphere and pollination of crops. Agricultural systems
are thus viewed as ecosystems that are modified, at times highly, by activities designed to en
-
sure or increase food production (box 6.1). ese ecosystems are often referred to as agroeco-
systems; the difference between an agroecosystem and other ecosystems is considered to be
largely conceptual, related to the extent of human intervention or management.
Disruption of the processes that maintain the structure and functioning of an eco-
system, such as water flow, energy transfer, and growth and production, can have dire con-
sequences, including soil erosion and loss of soil structure and fertility. Severe disruption
can result in the degradation or loss of the agroecosystem itself or other linked ecosystems
and the ecosystem services that it supplies (see chapter 15 on land). e degradation of the
Aral Sea is a dramatic example of human intervention having gone too far (box 6.2).
There are many land and water manipulations that can increase the productivity of agricultural land
in order to meet increasing demands for more food. All have consequences for ecosystems. The key
message is that agriculture makes landscape modication unavoidable, although smarter application
of technology and more emphasis on ecosystemwide sustainability could reduce adverse impacts.
These land and water manipulations include:
Shifting the distribution of plants and animals. Most apparent are the clearing of native vegetation
and its replacement with seasonally or annually sown crops, and the replacement of wild animals
with domestic livestock.
Coping with climate variability to secure water for crops. As water is a key material for photo-
synthesis, crop productivity depends intimately on securing water to ensure growth. Three differ-
ent time scales need to be taken into account when considering water security: seasonal shortfalls
in water availability that can be met by irrigation so that the growing season is extended and extra
crops can be added; dry spells during the wet season that can be met by specic watering that can
be secured, even in small-scale farming, if based on locally harvested rain; and recurrent drought
that has traditionally been met by saving grain from good years to rely on during dry years.
Maintaining soil fertility. The conventional way to secure enough air in the root zone is by drainage
and ditching through plowing to ensure that rain water can inltrate. However, this also leads to
erosion and the removal of fertile soil by strong winds and heavy rain. These side effects can be
limited by focusing on soil conservation actions, such as minimum tillage practices.
Coping with crop nutrient needs. The nutrient supply of agricultural soils is often replenished
through the application of manure or chemical fertilizers. Ideally, the amount added should bal-
ance the amount consumed by the crop, to limit the water-soluble surplus in the ground that may
be carried to rivers and lakes.
Maintaining landscape-scale interactions. When natural ecosystems are converted to agricultural
systems, some ecological processes (such as species mobility and subsurface water ows) that
connect parts of the landscape can be interrupted. This can have implications for agricultural
systems as it can affect pest cycles, pollination, nutrient cycling, and water logging and saliniza-
tion. Managing landscapes across larger scales thus becomes important; an increasing number
of studies illustrate how to design landscapes to increase the productivity of agriculture while
also generating other ecosystem services (Lansing 1991; Cumming and Spiesman 2006; Anderies
2005; McNeely and Scherr 2003).
box 6.1
Agriculture makes landscape modifications unavoidable
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It is thus important to adapt agricultural management (including crop types) to the
ecological conditions. Growing crops unsuited to the climate conditions, for example,
could have harmful consequences. When agricultural techniques that had been developed
in the temperate climate of Europe were introduced in late 18th century Australia, the
result was vast areas of salinized lands (Folke and others 2002). Trying to grow lucrative
oil palms on saline soils in the Indus Delta and Pakistan and the acid sulphate soils of
Southeast Asia is another example of a severe mismatch between agricultural activity and
ecological conditions. In the 1970s it was argued that there was a climate bias—“water
blindness”—that led to efforts to transfer inappropriate agricultural technology from de-
veloped to developing countries (Falkenmark 1979).
Human well-being and ecosystem services
e Millennium Ecosystem Assessment (MEA 2005c) showed that the well-being of hu-
man society was intimately linked to the capacity of ecosystems to provide ecosystem
services and that securing multiple ecosystem services depended on healthy ecosystems.
The Aral Sea is probably the most prominent example of how unsustainable water management for
agriculture has led to a large-scale and possibly irreversible ecological and human disaster. Reduced
water ow in the rivers supplying the sea has resulted in outcomes that have impaired human liveli-
hoods and health, affected the local climate, and reduced biodiversity. Since 1960 the volume of wa-
ter in the Aral Sea Basin has been reduced by 75%, due mainly to reduced inows as a consequence
of irrigation of close to 7 million hectares of land (UNESCO 2000; Postel 1999). This has led to the
loss of 20 of 24 sh species and collapse of the shing industry; the sh catch fell from 44,000 tons
annually in the 1950s to zero, with the loss of 60,000 jobs (Postel 1996). Species diversity and wildlife
habitat have also declined, particularly in the wetlands associated with the sea (Postel 1999). The
water diversions together with polluted runoff from agricultural land have had serious human health
effects, including an increase in pulmonary diseases as winds whipped up dust and toxins from the
exposed sea bed (WMO 1997).
Wind storms pick up some 100 million tons of dust containing a mix of toxic chemicals and salt
from the dry sea bed and dump them on the surrounding farmland, harming and killing crops as well
as people (Postel 1996). The low ows into the sea have concentrated salts and toxic chemicals,
making water supplies hazardous to drink (Postel 1996). In the Amu Darya River Basin chemicals
such as dichlorodiphenyl-trichloroethane (DDT), lindane, and dioxin have been carried by agricultural
runoff and spread through the aquatic ecosystems and into the human food chain. Secondary salini
-
zation is also occurring (Williams 2002).
Attempts to rehabilitate the Northern Sea are under way through the Syr Darya and Northern Aral
Sea Project (www.worldbank.org.kz); initial results are seen as positive (Pala 2006). A dam has been
constructed between the two parts of the sea to allow the accumulation of water and to help reha-
bilitate parts of the delta. While the project aims to reestablish and sustain shery and agricultural
activities and to reduce the harmful effects on the drinking water, the extent of past changes makes
restoration highly unlikely. The ecological and social changes in the Aral Sea ecosystem are consid
-
ered largely irreversible.
box 6.2
The Aral Sea—an ecological catastrophe
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6
Agriculture, water, and
ecosystems: avoiding the
costs of going too far
Whether an ecosystem is managed primarily for food production, water regulation, or for
other services (figure 6.2), it is possible to secure these for the long term only if basic eco-
system functioning is maintained. In many agroecosystems considerable effort goes into
ensuring crop production, but often at the expense of other important services, such as
fisheries (Kura and others 2004), freshwater supply (Vörösmarty, Lévêque, and Revenga
2005), and regulation of floods (Daily and others 1997; Bravo de Guenni 2005).
Biodiversity—variability and diversity within and among species, habitats, and eco-
system services—is important for supporting ecosystem services and has value in its own
right. Further, biodiversity can act as an insurance mechanism by increasing ecosystem
resilience (box 6.3). Some species that do not seem to have an important role in ecosystems
under stable conditions may be crucial in the recovery of an ecosystem after a disturbance.
Similarly, if one species is lost, another with similar characteristics may be able to replace it.
While the concept of biodiversity comprises ecosystems, species, and genetic components,
most of the discussion in this chapter focuses on the functional role of ecosystems and spe
-
cies (or taxa) in terms of the ecosystem services that they provide.
ere is increasing evidence that ecosystems play an important role in poverty reduction
(Silvius, Onela, and Verhagen 2000; WRI and others 2005). Many rural poor people rely on
a variety of sources of income and subsistence activities that are based on ecosystems and are
thus most directly vulnerable to the loss of ecosystem services
[established]. ese sources of
income, often generated by women and children, include small-scale farming and livestock
rearing, fishing, hunting, and collecting firewood and other ecosystem products that may be
sold for cash or used directly by households. Floodplain wetlands, for example, support many
human activities, including fisheries, cropping, and gardening (photos 6.1–6.3).
Provisioning services
Goods produced or provided
by ecosystems
Food
Fuel wood
Fiber
Timber
Regulating services
Benets from regulation of
ecosystem processes
Water partitioning
Pest regulation
Climate regulation
Pollination
Cultural services
Nonmaterial benets from
ecosystems
Spiritual
Recreational
Aesthetic
Educational
Support services
Factors necessary for
producing ecosystem services
Hydrological cycle
Soil formation
Nutrient cycling
Primary production
Source: Adapted from MEA 2003.
gure 6.2 Types of ecosystem services
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The decline of biodiversity globally, most severely manifested in freshwater systems (MEA 2005b),
has renewed interest in ecosystem conservation and management and in the links between bio
-
diversity and ecosystem functioning (Holling and others 1995; Tilman and others 1997), including
the role in human well-being (MEA 2005c) and the links to poverty (Adams and others 2004; WRI
and others 2005). Many people highlight the ethical argument for conserving biodiversity for its own
intrinsic value, and projects aimed at conserving endangered species (establishment of protected
areas, changed land-use practices) have been common investment strategies, with different social
outcomes (Adams and others 2004).
Research in recent decades has illustrated the importance of species diversity for ecosystem
functioning (see photos of wetland biodiversity). The general theory is that a more diverse system
contributes to more stable productivity by providing a means of coping with variation.
However, it has recently been argued that it is not the richness of species that contributes to eco-
system functioning, but rather the existence of functional groups (predators, pollinators, herbivores,
decomposers) with different and sometimes overlapping functions in relation to ecosystem process
-
es (Holling and others 1995). To understand the role of diversity for ecosystem functioning, it is
necessary to analyze the identities, densities, biomasses, and interactions of populations of species
in the ecosystem, as well as their temporal and spatial variations (Kremen 2005). Diversity of organ
-
isms within and between functional groups can be critical for maintaining resistance to change.
Species that may seem redundant during some stages of ecosystem development may be criti
-
cal for ecosystem reorganization after disturbance (Folke and others 2004). Response diversity (the
differential responses of species to disturbance) helps to stabilize ecosystem services in the face of
shocks (Elmqvist and others 2003).
box 6.3
Biodiversity and ecosystem resilience
Photo by C. Max Finlayson
Photo by Karen Conniff
Photo by C. Max Finlayson
Photo by C. Max Finlayson
Pelicans Dragony
ElephantsCrocodile
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6
Agriculture, water, and
ecosystems: avoiding the
costs of going too far
e Millennium Ecosystem Assessment concluded that a failure to tackle the decline in
ecosystem services will seriously erode efforts to reduce rural poverty and social inequity and
eradicate hunger; this is a critical issue in many regions, particularly in Sub-Saharan Africa
(WRI and others 2005). It is also true that continued and increasing poverty can intensify
pressure on ecosystems as many of the rural poor and other vulnerable people are left with no
options but to overexploit the remaining natural resource base. e result is often a vicious
cycle in which environmental degradation and increased poverty are mutually reinforcing
forces (Silvius and others 2003). e Millennium Ecosystem Assessment (MEA 2005c) con-
cluded that interventions that led to the loss and degradation of wetlands and water resources
would ultimately undermine progress toward achieving the Millennium Development Goals
of reducing poverty and hunger and ensuring environmental sustainability.
Consequences and ecosystem impacts
Modifications of the landscape to increase global food production have resulted in in-
creased provisioning services, but also in adverse ecological changes in many ecosystems,
with concomitant loss and degradation of services (MEA 2005c). Water management has
caused changes in the physical and chemical characteristics of inland and coastal aquatic
ecosystems and in the quality and quantity of water, as well as direct and indirect biological
changes (Finlayson and D’Cruz 2005; Agardy and Alder 2005; Vörösmarty, Lévêque, and
Revenga 2005). It has also caused changes in terrestrial ecosystems through the expansion
of agricultural lands and changes in water balances (Foley and others 2005).
ese changes have had negative feedback on the food and fiber production activities of
agroecosystems, for example through reductions in pollinators (Kremen, Williams, and orp
2002) and degradation of land (see chapter 15 on land) [established but incomplete]. Adverse
changes have varied in intensity, and some are seemingly irreversible, or at least difficult or
expensive to reverse, such as the extensive dead zones in the Gulf of Mexico and the Baltic
Sea (Dybas 2005). e catastrophic collapse of coastal fisheries as a consequence of environ-
mental change is another example (see chapter 12 on inland fisheries). is chapter focuses
on the consequences for ecosystems of green and blue water management in agriculture while
acknowledging that many other human activities also play a role. Synergistic and cumulative
effects can make it extremely difficult to attribute change to a single cause (box 6.4).
Photos by C. Max Finlayson
Fisheries, cropping, and gardening are among the many human activities supported by oodplain wetlands.
Photo 6.1
Photo 6.2
Photo 6.3
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Aquatic ecosystems
Water-related agricultural modifications have had major ecological, economic, and social
consequences, including effects on human health, through changes in the key ecological
components and processes of rivers, lakes, floodplains, and groundwater-fed wetlands [well
established]. ese changes include alterations to the quantity, timing, and natural vari-
ability of flow regimes; alterations to the waterscape through the drainage of wetlands and
the construction of irrigation storages; and increased concentrations of nutrients, trace
elements, sediments, and agrochemicals.
Aquatic ecosystems provide a wide array of ecosystem services
[well established].
eir nature and value are not consistent, however, and our understanding of how eco-
system processes support many of these services is inadequate (Finlayson and D’Cruz
2005; Baron and others 2002; Postel and Carpenter 1997). In several areas around the
world changes have contributed to a loss of provisioning services such as fisheries, regu-
lating services such as storm protection and nutrient retention, and cultural services
such as recreational and aesthetic uses. In some cases ecosystems have passed thresholds
New challenges are emerging for water managers in agriculture as a consequence of the cumulative
and sometimes synergistic effects of multiple drivers, including climate change and invasive spe-
cies.
Global climate change is expected to directly and indirectly alter and degrade many ecosystems
(Gitay and others 2002). For example, it will exacerbate problems associated with already expanding
demand for water where it leads to decreased precipitation, while in limited cases, where precipita-
tion increases, it could lessen pressure on available water. There are also major expected conse-
quences for wetland ecosystems and species, although the extent of change is not well established
(Gitay and others 2002; van Dam and others 2002; Finlayson and others forthcoming).
There is growing recognition of the important role that invasive species can play in degradation of
ecosystems and ecosystem services (MEA 2005c). Invasive species, spread through water regula
-
tion for transport and water transfer and through trade, have altered the character of many aquatic
ecosystems (see photo). Once established, invasive plants can block channels and irrigation canals
and decrease connectivity within and between rivers and wetlands, replace valuable species, and
damage infrastructure (Finlayson and D’Cruz 2005).
Invasive species from forest plantations are also
threatening water supply for downstream users, as
shown in South Africa where cities such as Cape
Town and Port Elisabeth depend on runoff from the
natural low biomass vegetation in the catchment
(Le Maitre and others 1996). Invasive species in ri-
parian areas are a problem for water resources in
several other parts of the world. The annual losses
due to the invasive woody species tamarisk in the
semiarid western United States reach $280–$450
a hectare, with restoration costs of approximately
$7,400 a hectare (Zavaleta 2000).
box 6.4
Cumulative changes—new challenges for
water management in agriculture
Photo by C. Max Finlayson
Water hyacinth, a rapidly growing, free-oating
invasive plant, has degraded many ecosystems
IWMI Part 3 Ch4-7 final.indd 244 2/28/07 3:07:30 AM
245
6
Agriculture, water, and
ecosystems: avoiding the
costs of going too far
or gone through regime shifts leading to a collapse of ecosystem services, making the
costs of restoration (if possible at all) very high. ese losses have adverse effects on
livelihoods and economic production [well established]. ere is ongoing debate whether
the positive outcomes in terms of increased upstream production of food outweigh the
negative consequences for people dependent on downstream ecosystem services. While
most cost-benefit studies show that the costs of the losses have been higher than the
gains, other scientists argue that these studies have many weaknesses (Balmford and
others 2002).
Although agriculture, especially water management in agriculture, is a major driver
behind the loss of downstream ecosystem services
[well established], there are competing
explanations for the manner and importance of individual processes and events and the
ultimate role of agriculture as a triggering force for degradation is in many situations un-
known. Dams, overfishing, urban water withdrawals, and natural and anthropogenic cli-
mate variation can contribute to cumulative and synergistic effects, reduced resilience, and
increased degradation of downstream ecosystems (photo 6.4). Uncertainty is often high
when it comes to the exact location or timing of the response of downstream ecosystems to
upstream water alterations. is does not mean that we can ignore the role of agriculture.
But we need to address the problems as complex and interacting, and to consider a systems
perspective for analyzing multiple drivers of change.
e next two sections offer examples of how water-related management in agriculture
has changed the capacity of downstream ecosystems to generate ecosystem services and a
brief discussion of the consequences of some of these changes.
Water quantity and waterscape alterations. Increased cultivation in recent decades has
resulted in increased diversion of freshwater, with some 70% of water now being used for
agriculture and reaching as high as 85%–90% in parts of Africa, Asia, and the Middle
Photo by C. Max Finlayson
Photo 6.4 Dams provide many benets for people, but also affect ecosystems by changing the
hydrology and fragmenting rivers
Long-term trend
analysis of 145
major world
rivers indicates
that discharge
has declined
in one-fifth of
cases
IWMI Part 3 Ch4-7 final.indd 245 2/28/07 3:07:33 AM
246
East (Shiklomanov and Rodda 2003) [well established]. Regulation of the world’s rivers
has altered water regimes, with substantial declines in discharges to the ocean (Meybeck
and Ragu 1997). Long-term trend analysis (more than 25 years) of 145 major world riv-
ers indicates that discharge has declined in one-fifth of cases (Walling and Fang 2003).
Worldwide, large artificial impoundments hold vast quantities of water and cause signifi-
cant distortion of flow regimes (Vörösmarty and others 2003), often with harmful effects
on human health (box 6.5).
Water diversion and the construction of hydraulic infrastructure (reservoirs, physical
barriers) have altered downstream ecosystems through changes in the quantity and pattern
of water flows and the seasonal inflows of freshwater (see global summaries in Vörösmarty,
Lévêque, and Revenga 2005 and Finlayson and D’Cruz 2005). Negative effects include
the loss of local livelihood options, fragmentation and destruction of aquatic habitats,
changes in the composition of aquatic communities, loss of species, and health problems
resulting from stagnant water. Less flooding means less sedimentation and deposition of
nutrients on floodplains and reduced flows and nutrient deposition in parts of the coastal
zone (Finlayson and D’Cruz 2005).
Many water-related diseases have been successfully controlled through water management (for ex-
ample, malaria in some places), but others have been exacerbated by the degradation of inland
waters through water pollution and changes in ow regimes (the spread of schistosomiasis). Where
diseases have spread, the adverse effects on human health are due to a complex mix of environmen-
tal and social causes. The Millennium Ecosystem Assessment reported many instances where water
management practices contributed to a decline in well-being and health (MEA 2005a; Finlayson and
D’Cruz 2005). This includes diseases caused by the ingestion of water contaminated by human or
animal feces; diseases caused by contact with contaminated water, such as scabies, trachoma, and
typhus; diseases passed on by intermediate hosts such as aquatic snails or insects that breed in
aquatic ecosystems, such as dracunculiasis and schistosomiasis, as well as dengue fever, lariasis,
malaria, onchocerciasis, trypanosomiasis, and yellow fever; and diseases that occur when there is
insufcient clean water for basic hygiene.
In addition to disease from inland waters, waterborne pollutants have a major effect on human
health, often through their accumulation in the food chain. Many countries now experience problems
with elevated levels of nitrates in groundwater from the large-scale use of organic and inorganic fertil-
izers. Excess nitrate in drinking water has been linked to methemoglobin anemia in infants.
There is increasing evidence from wildlife studies that humans are at risk from a number of chemi-
cals that mimic or block the natural functioning of hormones, interfering with natural bodily processes,
including normal sexual development. Chemicals such as DDT, dioxins, and those in many pesticides
are endocrine disruptors, which may interfere with human hormone functions, undermining disease
resistance and reproductive health.
The draining and burning of forested peat swamps in Southeast Asia have had devastating health
effects (see box 6.6 later in this chapter) that extend across many countries and that may be long-
lasting. The investigation of environment-related health effects linked with the ongoing degradation
of the forested peat swamps is a major issue for health services in the region.
box 6.5
Water management and human health
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6
Agriculture, water, and
ecosystems: avoiding the
costs of going too far
Interbasin transfers of water, particularly large transfers between major river systems
as are being planned in India, for example, are expected to be particularly harmful to
downstream ecosystems (Gupta and Deshpande 2004; Alam and Kabir 2004) and to ex
-
acerbate pressures from hydrological regulation (Snaddon, Davies, and Wishart 1999).
Where these are being considered, scientific and transparent assessments of the benefits
and problems are strongly encouraged. Junk (2002) has highlighted the similar adverse
consequences on water regimes expected from the construction of industrial waterways
(hidrovias) through large wetlands, such as the Pantanal of Maso Grosso, Brazil. e na-
ture of expected changes depends on the amount and timing of water being transferred
and so needs to be assessed case by case.
Shrinking lakes. ere are many instances where consumptive water use and water
diversions have contributed to severe degradation of downstream ecosystem services. e
degradation of the Aral Sea in Central Asia represents one of the most extreme cases (see
box 6.2).
e desiccation of Lake Chad in West Africa is another example. It shrank from
25,000 square kilometers in surface area to one-twentieth that size over a 35-year period.
However, there are competing explanations for this reduction. Natural rainfall variability
is an important driver. e lake is very shallow, and at various times in its history it has
assumed different states, with changes triggered by climate variability (Lemoalle 2003). It
is unclear what role human-induced change has played, but different drivers include the
withdrawal of irrigation water, land-use changes reducing precipitation through changes
in albedo (the energy that is reflected by the earth and that varies with land surface charac-
teristics), and reduced moisture recycling (Coe and Foley 2001).
Lake Chapala, the world’s largest shallow lake, situated in the Lerma-Chapala Basin
in central Mexico, is another example of consumptive water use upstream affecting the
size of a lake. During 1979–2001 water volume in the lake dropped substantially to about
20% of capacity due to excessive water extraction for agricultural and municipal needs.
Average annual rainfall from 1993 to 2003 was only 5% below the historical average and
efforts were made to reduce water use in irrigation, but still the amount of surface and
groundwater used in the basin exceeded supply by 9% on average (Wester, Scott, and
Burton 2005). Above average rains in 2003 and 2004 increased the water volume to about
6,000 million cubic meters. ere is still intense competition over water allocation, and
environmental water requirements have yet to be determined, leaving the future of the lake
and the allocation of water for urban and agricultural purposes under threat.
e high variability in lake volume in both Lake Chad and Lake Chapala means that
the people depending on ecosystem services from these basins need to have a high adaptive
capacity to cope with the rapidly changing circumstances, whether induced by people or
nature.
Shrinking rivers. Consumptive use and interbasin transfers have transformed sev-
eral of the world’s largest rivers into highly stabilized and, in some cases, seasonally non-
discharging, channels (Meybeck and Ragu 1997; Snaddon, Davies, and Wishart 1999;
Cohen 2002). Streamflow depletion is a widespread phenomenon in tropical and sub-
tropical regions in rivers with large-scale irrigation, including the Pangani (IUCN 2003),
Worldwide,
large artificial
impoundments
hold vast
quantities of
water and cause
significant
distortion of flow
regimes, often
with harmful
effects on
human health
IWMI Part 3 Ch4-7 final.indd 247 2/28/07 3:07:35 AM
248
Yellow (He, Cheng, and Luo 2005), Aral Sea tributaries, Chao Phraya, Ganges, Inco-
mati, Indus, Murray-Darling, Nile, and Rio Grande (Falkenmark and Lannerstad 2005).
Smakhtin, Revenga, and Döll (2004) suggest that the streamflow required for aquatic
ecosystem health (environmental flow) has already been overappropriated in many rivers.
In the United States the construction of dams and water diversions for irrigation
and other purposes in the Colorado Basin, together with large-scale interbasin transfers,
has greatly reduced the flow of the river to the delta. A considerable portion of the delta
has been transformed into mudflats, saltflats, and exposed sand. With the loss of the delta
habitats, wetlands now exist mainly in areas where agricultural drainage has occurred (Pos-
tel 1996). e Ganges is among the major rivers of South Asia that no longer discharge
year round to the sea. As a result there is a rapid upstream advance of a saline front, with
consequent changes in mangrove communities, fish habitat, cropping, and human liveli-
hoods (Postel 1996; Mirza 1998; Rahman and others 2000). On the Zambezi River in
Southern Africa damming for electricity and agriculture has reduced flows to the coast and
led to a decline in shrimp production that could have been worth as much as $10 million
a year (Gammelsrod 1992).
e regulation of rivers has brought many benefits to people, but the adverse impacts,
especially those related to reduced downstream flows, have often failed to receive adequate
and transparent consideration (WCD 2000; Revenga and others 2000; MEA 2005b).
Drainage of wetlands. Water regulation and drainage for agricultural development
are the main causes of wetland habitat loss and degradation (Revenga and others 2000;
Finlayson and D’Cruz 2005) and consequent loss of ecosystem services. By 1985 drainage
and conversion of wetlands, mainly for agriculture, had affected an estimated 56%–65%
of inland and coastal marshes in Europe and North America and 27% in Asia (OECD
1996). Drainage of wetlands often reduces important regulating ecosystem services, with
such outcomes as increased vulnerability to storms and flooding and further eutrophica-
tion of lakes and coastal waters.
Harder to demonstrate is the cumulative effect of the loss of smaller sites, both indi-
vidual sites and networks of sites, such as those used by migratory waterbirds (Davidson
and Stroud forthcoming). e adverse effects are often assumed, but the evidence is in-
complete. Still, there are many lessons, such as those from the drainage and subsequent
burning of forested peat swamps in Southeast Asia (box 6.6), a case that has had dramatic
health effects on many people across the region (see box 6.5). e loss of small wetlands
(referred to as potholes) on the prairies of Canada and the United States through drain-
age and infilling has led to the loss of habitat for large numbers of migratory waterbirds
(North American Waterfowl Management Plan 2004). e loss of forested riparian wet-
lands adjacent to the Mississippi River in the United States was seen as an important factor
contributing to the severity and damage of the 1993 flood in the Mississippi Basin (Daily
and others 1997).
Wetlands are often thought to act as “sponges” that soak up water during wet periods
and release it during dry periods. While there are numerous examples of wetlands, notably
floodplains, where this does occur, there is increasing evidence that such generalizations
are not applicable for all hydrological contexts or wetland types (Bullock and Acreman
The regulation
of rivers has
brought many
benefits, but the
adverse impacts
have often
failed to receive
adequate and
transparent
consideration
IWMI Part 3 Ch4-7 final.indd 248 2/28/07 3:07:36 AM
249
6
Agriculture, water, and
ecosystems: avoiding the
costs of going too far
2003). Indeed, there are instances where the opposite occurs: where wetlands reduce low
flows, increase floods, or act as a barrier to groundwater recharge. Given the wide range of
wetlands, from entirely groundwater-fed springs and mountain bogs to large inland river
floodplains, such variation should not be surprising.
Changes in water quality. Many factors contribute to changes in water quality. is sec-
tion looks at nutrient loads, agrochemicals, and siltation.
Nutrient loading. e use of fertilizers has brought major benefits to agriculture, but
has also led to widespread contamination of surface water and groundwater through run-
off. Over the past four decades excessive nutrient loading has emerged as one of the most
important direct drivers of ecosystem change in inland and coastal wetlands, with the flux
of reactive nitrogen to the oceans having increased by nearly 80% from 1860 to 1990
(MEA 2005c). Phosphorus applications have also increased, rising threefold since 1960,
with a steady increase until 1990 followed by a leveling off at approximately the applica-
tion rates of the 1980s (Bennett, Carpenter, and Caraco 2001). ese changes are mirrored
Large parts of the tropical peat swamp forests in Southeast Asia have been seriously degraded,
largely due to logging for timber and pulp (Wösten and others 2006; Page and others 2002). The
process has been accelerated over the last two decades by the conversion of forests to agriculture,
particularly oil palm plantations. Drainage and forest clearing threaten the stability of large tracts of
forests in Indonesia and Malaysia and make them susceptible to re.
Attempts to clear and drain the forests and establish agriculture have high rates of failure. Under
the Mega Rice Project in Kalimantan, Indonesia, large areas of forest were cleared and some 4,600
kilometers of drainage canals were constructed in an attempt to grow rice on a grand scale using
emigrant workers from the heavily populated neighboring island of Java. The cleared land was un-
suited to rice production, and the scheme was abandoned. In 1997 land clearing and subsequent
uncontrolled res severely burned about 5 million hectares of forest and agricultural land in Kaliman-
tan, releasing an estimated 0.8–2.6 billion tons of carbon dioxide into the atmosphere (Glover and
Jessup 1999; Page and others 2002; Wooster and Strub 2002). The res created a major atmospheric
haze, with severe impacts on the health of 70 million people in six countries. In addition, there have
been economic effects on timber and agricultural activities, with the res compounding the loss of
peatlands through clearing and failed attempts to cultivate large areas for rice.
Rehabilitation of some degraded areas is under way, but it is a slow and difcult process trying
to reestablish the hydrology and vegetation (Wösten and others 2006). At a regional level the Asso-
ciation of Southeast Asian Nations (ASEAN) has taken an active interest in the problem through the
ASEAN Peatland Management Initiative, facilitating the sharing of expertise and resources among the
affected countries to prevent peatland res and manage peatlands wisely. The regional initiatives are
linked with national action plans. Monitoring mechanisms are in place, and a policy of zero burning
for further land clearing has also been established, in particular for oil palm plantations.
Despite these steps, the problem of peatland degradation continues. The expansion of oil palm
plantations is a major driver. The peat swamps are still being cleared and burned, undermining efforts
to conserve and use the peatlands of Southeast Asia wisely and threatening the health of people lo-
cally and regionally.
box 6.6
The widespread impacts of draining and
burning in Southeast Asian peatlands
IWMI Part 3 Ch4-7 final.indd 249 2/28/07 3:07:37 AM
250
by phosphorus accumulation in soils, with high levels of phosphorus runoff. In developed
countries annual storage peaked around 1975 and is now at about the same annual rate as
in 1961. In developing countries, however, storage went from negative values in 1961 to
about 5 teragrams per year in 1996.
Excessive nutrient loading can cause algal blooms, decreased drinking water quality,
eutrophication of freshwater ecosystems and coastal zones, and hypoxia in coastal waters.
In Lake Chivero, Zimbabwe, agricultural runoff is seen as responsible for algal blooms,
infestations of water hyacinth, and fish declines as a result of high levels of ammonia and
low oxygen levels (UNEP 2002). In Australia extensive algal blooms in coastal inlets and
estuaries, inland lakes, and rivers have been attributed to increased nutrient runoff from
agricultural fields (Lukatelich and McComb 1986; Falconer 2001). Diffuse runoff of nu-
trients from agricultural land is held to be largely responsible for increased eutrophication
of coastal waters in the United States as well as for the periodic development, often varying
from year to year, of anoxic conditions in coastal water in many parts of the world, such as
the Baltic and Adriatic Seas and the Gulf of Mexico (Hall 2002).
Nutrient management can be undermined by the loss of wetlands that assimilate
nutrients (nitrogen, phosphorous, organic material) and some pollutants. Extensive evi-
dence shows that up to 80% of the global incident nitrogen loading can be retained within
wetlands (Green and others 2004; Galloway and others 2004). However, the ability of
such ecosystems to cleanse nutrient-enriched water varies and is not unlimited (Alexander,
Smith, and Schwarz 2000; Wollheim and others 2001). Verhoeven and others (2006)
point out that many wetlands in agricultural catchments receive excessively high loadings
of nutrients, with detrimental effects on biodiversity. Wetlands and lakes risk switching
from a state in which they retain nutrients to one in which they release nutrients or emit
There are reported cases of regime shifts occurring in lakes because of increased nutrient loading,
resulting in the loss of ecosystem services such as sheries and tourism (Folke and others 2004).
Some temperate lakes have experienced shifts between a turbid water and a clear water state, with
the shift often attributed to an increase in phosphorous loading (Carpenter and others 2001). Some
tropical lakes have shifted from a dominance of free-oating plants to submerged plants, with nutrient
enrichment seemingly reducing the resilience of the submerged plants, possibly through shading and
changes in underwater light (Scheffer and others 2001). Other wetlands and coastal habitats have
also experienced similar shifts. In the United States nutrient enrichment caused a shift in emergent
vegetation in the Everglades and a shift from clear water to murky water with algal blooms in Florida
Bay (Gunderson 2001).
Other evidence comes from lakes subject to inlling and nutrient enrichment. In Lake Hornborga
in Sweden emergent macrophytic vegetation proliferated after initial inlling of the lake margins and
increased runoff of nutrients. The situation was reversed only after massive mechanical intervention
and investment (Hertzman and Larsson 1999). In Australia agricultural runoff has resulted in shifts in
vegetation dominance as a consequence of nutrient enrichment, increased inundation and saliniza-
tion (Davis and others 2003; Strehlow and others 2005).
box 6.7
Regime shifts from excessive nutrient loads
Nutrient
management
can be
undermined
by the loss
of wetlands
that assimilate
nutrients and
some pollutants
IWMI Part 3 Ch4-7 final.indd 250 2/28/07 3:07:37 AM
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6
Agriculture, water, and
ecosystems: avoiding the
costs of going too far
the greenhouse gas nitrous oxide. Regime shifts are often rapid, but they have likely fol-
lowed a slower and difficult to detect change in ecosystem resilience. It is generally difficult
to monitor changes in resilience before a system hits the threshold and changes from one
state to another (box 6.7; Carpenter, Westley, and Turner 2005).
Agrochemical contamination. Pollution and contamination from agricultural chemi-
cals have been well documented since the publication of the seminal book Silent Spring
(Carson 1962). Bioaccumulation as a consequence of the wide use of agrochemicals has
had dire outcomes for many species that reside in or feed predominantly in wetlands or
lakes that have accumulated residues from pesticides [well established]. e decline in the
breeding success of raptors was a turning point in developing awareness about the dangers
of using pesticides (Carson 1962).
An increasing amount of analytical and ecotoxicological data has become available for
aquatic communities, and more recent research has also focused on risk assessments and
the development of diagnostic tests that can guide management decisions about the use
of such chemicals (van den Brink and others 2003). Taylor, Baird, and Soares (2002) have
highlighted the high levels of pesticide use and low levels of environmental risk assessment
in developing countries. ey have promoted an integrated approach to evaluating envi-
ronmental risks from pesticides that incorporates stakeholder consultation, chemical risk
assessment, and ecotoxicological testing for ecological effects, also taking into account the
potential effects on human health.
Vörösmarty, Lévêque, and Revenga (2005) report that water contamination by pes-
ticides has increased rapidly since the 1970s despite increased regulation of the use of
xenobiotic substances, especially in developed countries. However, bans on the use of these
chemicals have generally been imposed only two to three decades after their first commer-
cial use, as with DDT and atrazine. Many of these substances are highly persistent in the
environment, but because of the generally poor monitoring of their long-term effects the
global and long-term implications of their use cannot be fully assessed. Policy responses
to contamination may lag far behind the event, as shown in the well documented case of
agricultural pesticide bioaccumulation of DDT in the Zambezi Basin (Berg, Kilbus, and
Kautsky 1992).
Siltation of rivers. In many parts of the world extensive sheet wash and gully erosion
due to land management practices have devastated large areas, reduced the productivity of
wide tracts of land, led to rapid siltation of reservoirs and threatened their longevity, and
increased sediment loads in many rivers (see chapter 15 on land). On a regional scale some
reservoirs in Southern Africa are at risk of losing more than a quarter of their storage capac-
ity within 20–25 years (Magadza 1995). While many Australian and Southern African wa-
ters are naturally silty, many have experienced increased silt loads as a result of agricultural
practices (Davies and Day 1998). Zimbabwes more than 8,000 small to medium-size dams,
for example, are threatened by sedimentation from soil erosion, while the Save River, an in-
ternational river shared with Mozambique, has been reduced from a perennial to a seasonal
river system due in large part to increased siltation as a result of soil erosion.
Globally, rivers discharge nearly 38,000 cubic kilometers of freshwater to the oceans
and carry roughly 70% of the sediment input, though rivers draining only 10% of the
Water
contamination
by pesticides
has increased
rapidly since the
1970s despite
increased
regulation,
especially in
developed
countries
IWMI Part 3 Ch4-7 final.indd 251 2/28/07 3:07:38 AM
252
land area contribute 60% of the total sediment discharge (Milliman 1991). e high sedi-
ment loads carried by Asian rivers are a consequence of land-use practices, particularly
land-clearing practices for agriculture that lead to erosion, a situation likely to continue
as a consequence of the expansion of agriculture in Africa, Asia, and Latin America (Hall
2002). A notable outcome of the supply of sediment and associated nutrients to the oceans
is the increased frequency and intensity of anoxic conditions in recent years (Hall 2002).
ere are also situations where river regulation has caused a decline in silt transport to
downstream habitats, with reduced siltation alongoodplains and in deltas and other down-
stream ecosystems. is has occurred in the Mesopotamian Marshes, where large-scale drain
-
age is a bigger problem than silt-related changes in the downstream ecosystems (box 6.8).
Terrestrial ecosystems
Hydrological changes that occur as a result of agricultural expansion, particularly into
forests, are seldom thought of in terms of water management in agriculture, although such
changes are of at least the same magnitude as those resulting from irrigation (Gordon and
others 2005). is is an area in need of further research, especially as biofuels and tree
The Mesopotamian wetlands, one of the cradles of civilization and a biodiversity center of global
importance, used to cover more than 15,000 square kilometers in the lower Euphrates and Tigris
Basins. Agricultural development and other drainage activities over the past 30 years have reduced
them to 14% of their original size, and vast areas have been turned into bare land and salt crusts
(Richardson and others 2005). The ecological implications have been severe, with drastic land deg-
radation and impacts on wildlife, including bird migration and the extinction of endemic species, and
on the ecology of the downstream Shatt el Arab and coastal sheries in the Persian Gulf. The local
population of half a million Marsh Arabs have become environmental refugees.
The causes of this severe ecological degradation are complex. Some of the causes were inten-
tional, the results of drainage efforts to reclaim marshland, deal with soil salinization, improve agri-
cultural productivity, and strengthen military security in southern Iraq in the 1980s and 1990s. Other
causes were unintentional and included both the large-scale consumptive water use in irrigation
systems and the return of saline drainage, agricultural and industrial chemical pollution, and the loss
of ood ow, with its load of silt and nutrients, linked to recent large-scale streamow regulation in
upstream Turkey.
With the extent of existing regulation and degradation, the proposed rehabilitation of 30% of the
Central Marshes upstream of the conuence of the Euphrates and Tigris could generate its own
adverse impacts on aquatic ecosystems further downstream. The additional evaporation from just
1,000 square kilometers of restored open-water surfaces would consume an average ow of 67 cubic
meters per second, or 25% of the original (pre-regulation) dry season ow, and reduce downstream
streamow even further. Without an increase in the amount of water available, simply returning the
water to upstream areas may not be enough to restore the marshes and could further reduce the ow
of water to downstream areas.
Source: Partow 2001; Italy, Ministry for the Environment and Territory, and Free Iraq Foundation 2004.
box 6.8
Desiccation of the Mesopotamian wetlands
IWMI Part 3 Ch4-7 final.indd 252 2/28/07 3:07:39 AM
253
6
Agriculture, water, and
ecosystems: avoiding the
costs of going too far
plantations for carbon sequestration are new driving forces in the agricultural sector with
potentially major, but largely unassessed, consequences for water use (Jackson and others
2005; Berndes 2002). Forest clearing for agriculture has hydrological consequences [well
established], but site-specific responses will vary. Deforestation can lead to land degrada-
tion through salinization, soil loss, and waterlogging (for discussion on irrigation-induced
salinity, see chapter 15 on land).
ere is increasing speculation about how altered green water flows affect local, re-
gional, and global climate. Most of the evidence comes from tropical semiarid to humid
climates, with little from temperate regions. is section reviews the evidence of water-
related changes in terrestrial ecosystems as a response to agriculture.
Changes in the water table. Water can build up in the soil profile if the rate of input,
through irrigation, for example, exceeds the rate of throughput (for example, crop water
consumption). is can cause water logging and salinization, which are extensively described
for irrigated agriculture (Postel 1999). Continuous irrigation can result in soil salinization.
Tanzania has an estimated 1.7–2.9 million hectares of saline soils and 300,000–700,000
hectares of sodic soils (FAO and UNESCO 2003), some of it now abandoned. Salt-affected
soils in irrigation schemes are often related to poor soil and water management in addition to
the unsuitability of many soils for irrigation (see chapters 9 on irrigation and 15 on land).
Clearing woody vegetation for pastures and crops can also lead to dryland salini-
zation. Tree-covered landscape can provide an important regulating service by consum-
ing rainfall by high evapotranspiration, limiting groundwater recharge, and keeping the
groundwater low enough to prevent salt from being carried upward through the soil. Aus-
tralia has had major problems with soil salinization since native woody vegetation was
cleared in the 1930s for pastures and agricultural expansion (Farrington and Salama 1996).
Consumptive water use has declined, the water table has risen, and salt has moved into the
surface soils so that large tracts of land have become less suitable—and even unusable—for
agriculture (Anderies and others 2001; Briggs and Taws 2003). Green water flows at a
continental scale have been reduced by 10% (Gordon, Dunlop, and Foran 2003).
Decreased infiltration of water into the soil, often as a result of poor management of
crop and grazing land, is another problem that can cause changes in the water table with
effects on terrestrial systems, including a reduction in the capacity to produce biomass
(Falkenmark and Rockström 1993). is is a well-known problem in many rainfed farm-
ing systems (see chapters 8 on rainfed agriculture and 15 on land). Desiccation of the soil
in this manner is one of the factors behind what is often referred to as “desertification” or
land degradation in the tropics.
Changes in runoff from vegetation change. e effects of alterations to vegetation (espe-
cially forests) on blue and green water flows are well studied at a local and regional scale.
Catchment-scale experiments have shown that forested catchments in general have a high-
er green water flow and a lower blue water flow than grass or crop-dominated catchments
with the same hydrology and climate. However, the effects of deforestation depend on
the intensity and manner of forest clearance and on the character of the old and new land
Decreased
infiltration of
water into the
soil, often a
result of poor
management of
crop and grazing
land, can cause
desiccation of
the soil
IWMI Part 3 Ch4-7 final.indd 253 2/28/07 3:07:40 AM
254
cover and its management (McCulloch and Robinson 1993; Bosch and Hewlett 1982;
Bruijnzeel 1990).
General work on the influence of vegetation, climate, and land cover on the water
balance of a system has shown that there are vegetation-specific changes (Lvovich 1979;
Calder 2005). Management of plant production that redirects blue water to green water
can reduce the amount of water to downstream systems (Falkenmark 1999). For example,
replacing crop or grasslands with forest plantations can decrease runoff and streamflow
(Jewitt 2002). e South African Water Act classifies forest plantations as a streamflow
reduction activity,” and forestry companies have to pay for their water use since less of the
precipitation reaches the river.
Moisture recycling. Clearing land for agriculture and increasing use of irrigation have modi-
fied green water flows globally, reducing them by 3,000 cubic kilometers through forest clear-
ing and increasing them by 1,000–2,600 cubic kilometers in irrigated areas (Döll and Siebert
2002; Gordon and others 2005). e ability of changes in land cover to influence climate
through changes in green water flow has been increasingly recognized. It has been suggested
that large-scale deforestation can reduce moisture recycling, affect precipitation (Savenije 1995,
1996; Trenberth 1999), and alter regional climate, with indications of global impacts (Kabat
and others 2004; Nemani and others 1996; Marland and others 2003; Savenije 1995).
Pielke and others (1998) conclude that the evidence is convincing that land cover
changes can significantly influence weather and climate and are as important as other hu
-
man-induced changes for the Earths climate. However, the models employed do not deal
explicitly with green water flows, but rather with the compounded effects of changes in al-
bedo, surface wind, leaf area index, and other indicators. Nevertheless, regional studies in West
Africa (Savenije 1996; Zheng and Eltathir 1998), the United States (Baron and others 1998;
Pielke and others 1999), and East Asia (Fu 2003) have illustrated that changes in land cover
affect green water flows, with impacts on local and regional climates. Likewise, biome-specific
models of land cover conversions from rainforest to grasslands have shown a decrease in vapor
flows and precipitation as well as effects on circulation patterns (Salati and Nobre 1991) and
savannahs (Hoffman and Jackson 2000). ere are also indications that increased vapor flows
through irrigation can alter local and regional climates (Pielke and others 1997; Chase and
others 1999).e conversion of steppe to irrigated croplands in Colorado resulted in a 120%
increase in vapor flows (Baron and others 1998), contributing to higher precipitation, lower
temperatures, and an increase in thunderstorm activity (Pielke and others 1997).
Whether these changes can trigger rapid regime shifts (box 6.9), which in many cases
may be irreversible, and changes to which farmers need to adapt is still speculative. In the Am-
azon the clearing of land has reduced moisture recycling, resulting in prolonged dry seasons
and increased burning, and may have triggered an irreversible regime shift from rainforest veg-
etation to savannah (Oyama and Nobre 2003). ere is also increasing concern about changes
in the African and Asian monsoons, including weakening of the East Asian summer monsoon
low-pressure system and an increase in irregular northerly flows (Fu 2003). Likewise, modeled
vegetation changes for agricultural expansion in West Africa have shown potentially dramatic
impacts on rainfall in the African monsoon circulation (Zheng and Eltathir 1998).
There are
indications that
increased vapor
flows through
irrigation can
alter local
and regional
climates
IWMI Part 3 Ch4-7 final.indd 254 2/28/07 3:07:40 AM
255
6
Agriculture, water, and
ecosystems: avoiding the
costs of going too far
Societal responses and opportunities
e negative effects of past agricultural management on ecosystem services and the need
to produce more food for growing populations provide an unparalleled challenge. Meet-
ing this challenge requires large-scale investments to improve agricultural management
practices, increase the availability of techniques to minimize adverse ecological impacts,
enhance our understanding of ecosystem-agriculture interactions, and reduce poverty and
social inequities, including issues of gender, health, and education that affect ecosystem
management decisions.
In presenting possible responses for meeting this challenge, we emphasize several
ecological outcomes that we consider to be critical in this effort: maintenance or rehabili-
tation of the ecological connectivity, heterogeneity, and resilience in the landscape, which
in turn implies maintenance or rehabilitation of the biodiversity that characterizes the
landscape. We focus on integration and awareness of the negative consequences of choices
in terms of the tradeoffs between food production and other ecosystem services. We do
not propose specific responses for specific ecosystems or locations, although we aim to
help national and local decisionmaking with a framework for addressing some of these
issues. Many of the responses outlined are dependent on effective governance measures
and policies that support sustainable development with a balance of ecological and social
Ecosystems change and evolve, with disturbance now seen as an inherent component of ecosystem
processes [well established]. The speed of change in many ecosystems has, however, increased
rapidly, and there is now concern that large-scale changes will increase the vulnerability of some
ecosystems to water-related agricultural activities. Ecosystems are complex adaptive systems (Levin
1999), with nonlinear dynamics and thresholds between different “stable states.” Nonlinear changes
are sometimes abrupt and large, and they may be difcult, expensive, or impossible to reverse. The
increased likelihood of nonlinear changes stems from drivers of ecosystem change that adversely
affect the resilience of an ecosystem, its capacity to absorb disturbance, undergo change, and still
retain essentially the same function, structure, identity, and feedbacks (Gunderson and Holling 2002;
Carpenter and others 2001) and provide components for renewal and reorganization (Gunderson and
Holling 2002).
Variability and exibility are needed to maintain ecosystem resilience. Attempts to stabilize sys
-
tems in some perceived optimal state, whether for conservation or production, have often reduced
long-term resilience, making the system more vulnerable to change (Holling and Meffe 1996). While
today’s agricultural systems are able to better deal with local and small-scale variability, the simpli-
cations of landscapes and reduction of other ecosystem services have decreased the capacity of
agricultural systems and other ecosystems to cope with larger scale and more complex dynamics
through reduced ecosystem resilience locally and across scales (Gunderson and Holling 2002).
Little is yet known about how to estimate resilience and detect thresholds before regime shifts
occur (Fernandez and others 2002). Better mechanisms to monitor regime shifts include the iden-
tication and monitoring of slowly changing variables (Carpenter and Turner 2000) and measurable
“surrogates of resilience” (Bennett, Cumming, and Peterson 2005; Cumming and others 2005).
box 6.9
Resilience and the increased risk of rapid
regime shifts in ecosystems
IWMI Part 3 Ch4-7 final.indd 255 2/28/07 3:07:41 AM
256
outcomes, issues covered in detail in chapters 5 on policies and institutions and 16 on
river basins.
Improving agricultural technology and management practices
e Millennium Ecosystem Assessment (MEA 2005c) supports the view that intensifica-
tion of agricultural systems will create fewer tradeoffs with ecosystem services than will
expansion. Intensification will require improvements in agricultural productivity, espe-
cially in water productivity (see chapter 7 on water productivity) in water-scarce envi-
ronments. However, because intensification can bring its own ecological problems, for
example, through pollution or the introduction of invasive species, command and control
approaches to management should be avoided (Holling and Meffe 1996). e potential
problems of intensification could be lessened or avoided through the adoption of a systems
approach to agriculture and integrated approaches to landscape management (see below).
Many of the chapters in this volume address agricultural techniques and improved
management practices. Chapters 14 on rice and 15 on land highlight the need to consider
techniques and practices that may not increase the production of one or a few specific
crops but that support the provision of multiple benefits. Unless responses that restrict
the potential adverse impacts of intensification are applied, intensification will not be any
more environmentally and socially benign than many past agricultural practices.
Applying integrated approaches to water, agriculture, and other
ecosystems
Integrated policy and management approaches are increasingly seen as crucial in facilitat-
ing decisionmaking and making tradeoffs between food and other ecosystem services. In
-
tegrated approaches have taken many forms, including integrated river basin management,
Photo by C. Max Finlayson
Photo 6.5 This use of wetlands in Malawi attempts to integrate multiple benets and costs
The potential
problems of
intensification
could be
lessened
through the
adoption of
a systems
approach to
agriculture
and integrated
approaches
to landscape
management
IWMI Part 3 Ch4-7 final.indd 256 2/28/07 3:07:44 AM
257
6
Agriculture, water, and
ecosystems: avoiding the
costs of going too far
integrated land and water management, ecosystem approaches, integrated coastal zone
management, and integrated natural resources management. eir general aim is often the
same. ey actively seek to address integration of all the benefits and costs associated with
land-use and water decisions, including effects on ecosystem services, food production,
and social equity, in a transparent manner; to involve key stakeholders and cross-institu-
tional levels; and to cross relevant biophysical scales, addressing interconnectedness across
subbasin, river basin, and landscape scales (photo 6.5).
While integrated approaches for environmental management are seen as an impor-
tant effort and have long been promoted, there are few successful examples. e gover-
nance systems required to support the appropriate institutional and managerial arrange-
ments, particularly for the allocation of resources and planning authority concomitant
with responsibility at a local level, seem difficult to achieve (see, for example, chapter 16 on
river basins). One complaint is that most of these approaches are based on a technocratic
view of decisionmaking, whereas real life is far messier, with power struggles, lack of trust
between and within stakeholder groups, and complex and evolutionary behavior of eco-
systems that make it difficult to assess total benefits and impacts. Folke and others (2005)
see a need for more emphasis on building, managing, and maintaining collaborative social
relationships for river basin governance, which is in line with current thinking about eco-
system management.
Where river basin organizations have succeeded, that has often been because of their
ability to deliver on the common aims of jurisdictions (such as coordinated water man-
agement to supply irrigation). e situation is more complex when dealing with inter-
national transboundary rivers, such as the Nile and the Mekong. An alternative to river
basin processes may be to explore more regional guidance for common policies, as is being
developed in Southern Africa (box 6.10).
e complexity of the social policy and institutional links that govern ecosystem
management and influence necessary tradeoffs is shown for wetlands in figure 6.3. Differ-
ences in local contexts may affect the manner in which relationships between individuals
While integrated
approaches for
environmental
management
have long been
promoted,
there are few
successful
examples
The South African National Water Act of 1998 protects the water requirements for ecosystems and
supports them through an ongoing scientic effort. This is in line with the principles contained in
the Southern African Development Commission (SADC) regional water policy of May 2004, which
recognizes the environment as a legitimate user of water and calls on SADC members to adopt all
necessary strategies and actions to sustain the environment. At the national level water reforms in
South Africa and Zimbabwe have successfully mainstreamed environmental water requirements in
water resources policy and legislation. Namibia is similarly considering policy that stresses sectoral
coordination, integrated planning and management, and resource management aimed at coping with
ecological and associated environmental risks.
Mexico’s 1992 Law of National Waters is another example of national water reforms that consider
ecosystem needs. It empowers the federal government to declare as disaster areas watersheds or
hydrological regions that represent or may represent irreversible risks to an ecosystem.
box 6.10
National and regional policy initiatives on water and ecosystems
IWMI Part 3 Ch4-7 final.indd 257 2/28/07 3:07:45 AM
258
Source: Hollis 1994.
Inuential
people
and
committees
Ministry of Public Works
Schools and children Zoos
Regional government and
regional sections of
national ministries
WWF International
National and international
environmental consultants
International Council
for Bird Preservation
World Conservation Union
International Association
of Hydrological Sciences
National nongovernmental
organizations in other countries
Water engineering
consultants
Invisible links by history, marriage, family, and the like
International
nongovernmental
organizations
Scouts and
guides
Cultural
heritage
Hunting and
wildowering
World Heritage
Convention
United Nations
Ramsar
Convention
on Wetlands
World Bank
and other
international
nancial
institutions
United Nations
Environment
Programme
Man and
Biosphere
Reserves
United Nations
Educational,
Scientic, and
Cultural
Organization
National
nongovernmental
organizations
International
governmental
organizations
National WWF
Bird
protection
Land
owners
THE WETLAND
Government ministries
Farmers
Fishers
Pastoralists
Ornithologists
Industrialists
Urban dwellers
Ministry of Agriculture
Forestry Department
Hydraulic Works
Environment Section
Hydraulic Monitoring Division
Media
Press
Television
Radio
Foreign media
European Economic Community
Directorate-General for Research
European Investment Bank
Directorate-General for Environment
Directorate General for Development
Universities
Hydrology
Limnology
Pedology
Botany
Geology
Agriculture
Zoology
Ornithology
Ecology
International symposia
National environmental
research organization
Foreign governments
and ambassadors
Ministry of Environment
Nature Conservation Section
gure 6.3
The complexity of the social policy and institutional
linkages that govern ecosystem management and
influence necessary tradeoffs in wetlands
IWMI Part 3 Ch4-7 final.indd 258 2/28/07 3:07:46 AM
259
6
Agriculture, water, and
ecosystems: avoiding the
costs of going too far
and institutions are built and maintained. High levels of knowledge and human capacity
are considered critical to crafting the institutions and policies required for successful in-
tegrated water management (see chapter 5 on policies and institutions). is chapter em-
phasizes the need to raise awareness of the role of ecosystem services in societal well-being
in both multifunctional agricultural systems and across landscapes and on the importance
of maintaining the ecological and social processes that support these.
Assessing and nurturing multiple benefits
Improving awareness and understanding. Integrated approaches help to deal with the
competing interests in water resources ey make it possible to share the multiple benefits
and costs that are generated across a river basin and that are improved or degraded through
agricultural interventions in the landscape.
Assessment of the multiple ecosystem services and the processes that support them is
a key component of these approaches. Historically, decisions concerning ecosystem man
-
agement have tended to favor either conversion of ecosystems or management for a single
ecosystem service, such as water supply or food production, often without consideration of
the effects on such groups as the rural poor, women, and children (MEA 2005c). Many eco-
system services do not have a price on the market and are often neglected in policymaking
and decisionmaking. As we better understand the benefits provided by the entire array
of ecosystem services, we also realize that some of the best response options will involve
managing landscapes, including agriculture, for a broader array of services. at will entail
taking greater account of social issues, such as gender-based roles and poverty, when mak-
ing decisions about agriculture and water management (WRI and others 2005).
e Millennium Ecosystem Assessment has provided a major advance in under-
standing the links between the provision of ecosystem services and human well-being
(www.maweb.org). Increased awareness is still needed on several different levels. e
scientific knowledge of how ecosystem services contribute to human well-being within
and between different sectors of society, and the role of water in sustaining these ser-
vices, need to be improved. Dissemination of information on these issues and dialogue
with stakeholders should be enhanced. Civil society organizations can help to ensure
that appropriate consideration is given to the voices of individuals and social groups and
to nonutilitarian values in decisionmaking. Minority groups and disadvantaged groups,
such as indigenous people and women, in particular, need to be heard. Women play a
critical and increasing role in agriculture in many parts of the developing world (Elder
and Schmidt 2004).
Urbanization provides new challenges. For the first time in human history more
people live in cities than in the rural areas. It has been estimated that the urban areas in
the Baltic Sea region in northern Europe need an area of functioning ecosystems some 500
times the size of the cities themselves to generate the ecosystem services they depend on
(Folke and others 1997). e green water needs for ecosystem services that support these
cities are roughly 54 times larger than the blue water needs of households and industry
(Jansson and others 1999). However, people who live in cities often become mentally
Historically,
decisions
concerning
ecosystem
management
have tended to
favor conversion
of ecosystems
or management
for a single eco-
system service,
such as food
production
IWMI Part 3 Ch4-7 final.indd 259 2/28/07 3:07:47 AM
260
disconnected from the ecological and hydrological processes that sustain their well-being.
In this perspective farmers are the stewards of the landscape in which cities lie. is pro-
vides a new challenge for water and ecosystem management.
One of the main gaps in our scientific understanding of ecosystems and ecosystem
services is where the thresholds lie and how far a system can be changed before it loses too
many essential functions and totally changes its behavior (Gunderson and Holling 2002).
Without this knowledge the early warning indicators required to provide advance warn-
ing of anticipated adverse change or of when a threshold is being approached cannot be
developed.
Source: Adapted from Foley and others 2005; chapters 14 and 15 in this volume.
Fuel
wood
Recreation
Pest
control
Soil
formation
Regulation
of water
balance
Nutrient
cycling
Crop
production
Climate
regulation
Fuel
wood
Recreation
Pest
control
Soil
formation
Regulation
of water
balance
Nutrient
cycling
Crop
production
Climate
regulation
Provisioning services Regulating services Supporting services Cultural services
Cardamom
seed
Fertility transfer
to other systems
Soil fertility
improvement
Watershed
conservation
Fodder for
livestock
Soil
conservation
Commercial timber
and fuel wood
Nitrogen
xation
Natural ecosystem Intensive cropland
Multifunctionality in rice elds
Alder-cardamom system
FishReligious land-
scape values
Water storage,
lowering of
peak oods,
groundwater
recharge
Climate
air temperature
Ducks,
frogs,
snails
Biodiversity
enhancement
in human-
dominated
landscapes
Rice
production
Prevention of
soil erosion
gure 6.4
Comparison of intensive agricultural systems
managed for the generation of one ecosystem service
and multifunctionality in agroecosystems
IWMI Part 3 Ch4-7 final.indd 260 2/28/07 3:07:48 AM
261
6
Agriculture, water, and
ecosystems: avoiding the
costs of going too far
Managing agriculture for multiple outputs. Increasing attention to ecosystem services
provides an opportunity to emphasize multifunctionality within agroecosystems and the
connectivity between and within agroecosystems and other ecosystems. It is often assumed
that agricultural systems are managed only for optimal (or maximum) production of one
ecosystem service, food, or fiber (figure 6.4). But agricultural systems can generate other
ecosystem services, and we need to improve our capacity to assess, quantify, and value
these as well. Encouraging multiple benefits from these systems can generate synergies
that result in the wider distribution of benefits across more people and sectors. Ecosystem-
based approaches to water management need not constrain agricultural development but
can be points of convergence for social equity, poverty reduction, resource conservation,
and international concerns for global food security, biodiversity conservation, and carbon
sequestration (see chapter 15 on land). Ecosystem-based approaches aim to maintain and
where possible enhance diversity and to build the ecological resilience of the agricultural
landscape as well as of ecosystems altered by agriculture (box 6.11).
e concept of multifunctional agriculture is not new; it has long been practiced in
many forms and combinations. Integrated pest management is one way to manage a whole
landscape in order to sustain an ecosystem service (pest control) that enhances agricultural
production. is type of regional management requires integrated approaches based on an
ecological understanding of fragmentation and landscape heterogeneity (Cumming and
Spiesman 2006). Hydrological understanding is also important. Studies have shown that it
is possible to control insect outbreaks by timing irrigation events (Lansing 1991) and that
The resilience perspective shifts from policies that aspire to control change in systems assumed to
be stable to policies to manage the capacity of social-ecological systems to cope with, adapt to, and
shape change (Berkes, Colding, and Folke 2003). Managing for resilience enhances the likelihood of
sustaining development in changing environments where the future is unpredictable.
Variability, disturbance, and change are important components of an ecosystem. For example,
when variability in river ows is altered, marked changes in ecosystem functions can be expected
(Richter and others 2003). Wetting and drying of soils can be important for the resilience of ecosystem
functions, such as pest control and nutrient retention in wetlands. Exactly what level of variability to
maintain and when variability is site specic are areas of intense research (Richter and others 2003).
Maintaining diversity has been shown to be important for building ecosystem resilience, in particular
for maintaining functional and response diversity (Elmqvist and others 2003; MEA 2005c). Responses
should therefore seek to maintain and enhance diversity in ecosystems and across broader land
-
scapes while maintaining food production.
The driving variables behind the functioning of ecosystems tend to have slower dynamics than
those that support the ecosystem services generated from that system (Carpenter and Turner 2000).
Therefore, the monitoring of long-term ecosystem performance should cover the productivity of the
ecosystem and the crucial variables that enable production. This is particularly evident when monitor
-
ing the productivity of croplands. Harvested yields are an important measure, but they may not tell the
full story. Long-term productivity likely depends on slower variables, such as the accumulation and
decomposition of soil organic matter.
box 6.11
Some basic principles for maintaining ecosystem resilience
IWMI Part 3 Ch4-7 final.indd 261 2/28/07 3:07:49 AM
262
planting trees in particular parts of the landscape can reduce vulnerability to waterlogging
and salinization in other parts of the landscape (Andreis 2005).
Other chapters in this volume propose multifunctional agriculture as a response to
the environmental degradation resulting from more narrowly based agricultural practices.
For example, chapter 14 on rice illustrates the different ecosystem services generated in rice
fields. Chapter 8 on rainfed agriculture illustrates how modifications to the water balance
and erosion control can increase crop production. And chapter 9 on irrigation emphasizes
multifunctionality in large-scale public irrigation systems that are dependent on surface
water. Chapter 15 on land also presents a comprehensive overview of multifunctional
agriculture and landscapes, including resource-conserving agriculture and emphasizes the
synergies that arise between multiple users of ecosystem services when agriculture is treated
as an integral part of the broader landscape. ese chapters also illustrate the close links
between environmental change and well-being and highlight the different roles and re-
sponsibilities of women and men in agriculture, the economy, and the household, and
their different effects on the environment, issues requiring further study.
Assessing tradeoffs and tools for dealing with them
Scientists are increasingly questioning the wisdom of seeking economic development, in-
cluding further development of agriculture and fisheries, at the expense of wider envi-
ronmental and social consequences (International Council for Science 2002; SIWI and
others 2005; Foley and others 2005; Kura and others 2004). Arrow and others (1995)
have shown convincingly that economic development without due consideration of the
ecological consequences may not provide the economic means to overcome environmental
concerns in the future, particularly if the ecological resilience of the wider environment
is undermined. e consequences of losing ecological resilience, especially when it re-
sults in irreversible change, have not been fully considered alongside the expected benefits
(MEA 2005c).
It is anticipated that the management of water for agroecosystems alone will be
subject to competition from wider environmental requirements (Lemly, Kingsford, and
ompson 2000; Molden and de Fraiture 2004) and may require further tradeoffs and
the adoption of wider and more inclusive mechanisms. For example, the public sector is
starting to buy back irrigation water from farmers to sustain or rehabilitate ecosystems
or ecosystem services, sometimes even paying farmers not to irrigate. Governments may
be able to buy the rights to water (whether the rights had previously been given away or
obtained through the market), or nongovernmental organizations may be able to lease the
water during dry years to support valued aquatic ecosystems. Water for the environment
can thus be seen as a new driving force to which agriculture needs to adapt.
Ecosystem management is increasingly undertaken through collaborative planning
and consultation processes, following past failures to transparently consider tradeoffs and
wider societal interests (Carbonell, Nathai-Gyan, and Finlayson 2001). e Millennium
Ecosystem Assessment (MEA 2005b,c) emphasizes the importance of overcoming sectoral
divides and encompassing wider stakeholder participation in planning and development.
Some of the people most vulnerable to ecosystem change depend directly on ecosystem
Given past
failures to
secure the wider
range of eco-
system services,
we highlight the
need for tools
that can be
used in striking
tradeoffs
between water
for different eco-
system services
IWMI Part 3 Ch4-7 final.indd 262 2/28/07 3:07:50 AM
263
6
Agriculture, water, and
ecosystems: avoiding the
costs of going too far
services for their livelihoods, and they have often lacked a voice in making decisions about
these services (Carbonell, Nathai-Gyan, and Finlayson 2001). Many local people who
depend on ecosystems have had to develop management practices to deal with distur
-
bances and change in a way that builds socioecological resilience (Berkes and Folke 1998).
ey can contribute their understanding of fundamental ecosystem processes (Olsson,
Folke, and Hahn 2004). For the social mechanisms of dealing with the conflicts that oc-
cur when making tradeoffs see chapter 5 on policies and institutions and chapter 16 on
river basins.
New tools are emerging for dealing with tradeoffs, including some that provide
economic incentives and support the formulation of policies and regulations. Given past
failures to secure the wider range of ecosystem services, we highlight the need for develop
-
ing and adopting tools that can be used in striking tradeoffs between water for different
ecosystem services. Such tools include economic valuation and cost-benefit analysis of
ecosystem services, assessment of environmental flows, risk and vulnerability assessments,
strategic and environmental impact assessments, and probability-based modeling.
Successful employment of such tools requires an adequate information base and im-
proved predictive capacity about how ecosystems respond to change, and articulation of
what is unknown or uncertain (Carpenter and others 2001). While the use of such tools
has been increasingly promoted through international forums, conventions, and treaties,
lack of awareness and capacity still seems to impede their use. We focus here on two tools
that have considerable potential to assist in making tradeoffs: economic valuation of eco-
system services and allocation of environmental flows.
Ecosystem valuation. Economic valuation is a powerful tool for addressing the tradeoffs
between food production and other ecosystem services when making decisions about water
management in agriculture. Its broad aim is to quantify the benefits (both market and
nonmarket) that people obtain from ecosystem services to enable decisionmakers and the
Total economic value involves assessing the value of four categories of ecosystem services:
Direct use values are derived from ecosystem services that are used directly by people and in-
clude the value of consumptive uses, such as the harvesting of food products, timber, medicinal
products, and the hunting of animals, as well as the value of nonconsumptive uses, such as the
enjoyment of recreational and cultural amenities, water sports, and spiritual and social services.
Indirect use values are derived from ecosystem services that provide benets outside the eco-
system itself, for example, the water ltration function of wetlands, the storm protection function
of mangrove forests and delta islands, and carbon sequestration by forests.
Option values are derived from preserving the option to use services in the future rather than now,
either by oneself (option value) or by heirs or others (bequest value).
Nonuse (or existence) values refer to the value people may place on knowing that a resource exists
even if they never use that resource directly.
Source: MEA 2005b.
box 6.12
The total economic value of ecosystems
A wide range
of methods
are available
for valuing eco-
systems beyond
the use of direct
market prices
IWMI Part 3 Ch4-7 final.indd 263 2/28/07 3:07:51 AM
264
public to evaluate the economic costs and benefits of any proposed change in an ecosystem
and to facilitate comparison with other aspects of the economy. Economic valuation is just
one way of assessing tradeoffs. It is especially useful in the context of economic arguments
favoring actions leading to ecosystem degradation that fail to take full account of the eco
-
nomic costs. Ecosystem valuation assists in the efficient allocation of resources, enhances
the scope for market creation, and can reduce the magnitude of market failures.
Total economic value (box 6.12) has become a widely used framework for identifying
and quantifying ecosystem services (Balmford and others 2002; MEA 2005c). It consid
-
ers the full range of ecosystem characteristics together—resource stocks or assets, flows of
environmental services, and attributes of the ecosystem as a whole. It covers direct and
indirect values and option and nonuse values.
A wide array of methods can be used for economic valuation of ecosystems. Some of the most com-
mon are:
Replacement costs. Even where ecosystem services have no market value themselves, they often
have alternatives or substitutes that can be bought and sold. These replacement costs can be
used as a proxy for ecosystem resources, although they usually represent only partial estimates
or are underestimates.
Effects on production. Other economic processes often rely on ecosystem resources as inputs or
on the essential life support provided by these services. Where they have a market, it is possible
to look at the contribution of the services to the output or income of these wider production and
consumption opportunities in order to assess their value.
Damage costs avoided. The reduction or loss of ecosystem services frequently incurs costs in
terms of damage to or reduction of other economic activities. The damage costs that are avoided
can be taken to represent the economic losses forgone by conserving ecosystems.
Mitigative or avertive expenditures. It is almost always necessary to take action to mitigate or avert
the negative effects of the loss of ecosystem services so as to avoid economic damage. These
costs can be used as indicators of the value of conserving ecosystems in terms of expenditures
avoided.
Hedonic pricing. Hedonic methods look at the differentials in property prices and wages between
locations and isolate the proportion of this difference that can be ascribed to the existence or
quality of ecosystem services.
Travel costs. Many ecosystems typically hold a high value as a recreational resource or destina-
tion. Although in many cases no charge is made to view or enjoy less human-dominated eco-
systems, people must still spend time and money to reach them. This expenditure—on transport,
food, equipment, accommodations, time, and so on—can be calculated, and a demand function
can be constructed relating visitation rates to expenditures made. These travel costs reect the
value that people place on the leisure, recreational, or tourism aspects of specied ecosystems.
Contingent valuation. Even where ecosystem services have no market price and no close replace-
ments or substitutes, they frequently have a high value to people. Contingent valuation techniques
infer the value that people place on these services by asking about willingness to pay for them (or
willingness to accept compensation for their loss) under the hypothetical scenario that they would
be available for purchase.
box 6.13
Commonly used valuation tools
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Agriculture, water, and
ecosystems: avoiding the
costs of going too far
A wide range of methods are available for valuing ecosystems beyond the use of direct
market prices. ese include approaches that elicit preferences directly (such as contingent
valuation methods) and those that use indirect methods to infer preferences from actions
to purchase related services (for example, through production functions, dose-response
relationships, travel costs, replacement costs, and mitigative expenditures). ese methods
are summarized in box 6.13.
While economic tools may prove useful in striking tradeoffs, they are unlikely to be
useful in all circumstances. e more sophisticated the method, the less useful it is likely to
be in situations where data are not available or where political issues hold sway. Economic
tools can assist in understanding only the economic tradeoffs, not the political tradeoffs or
the role of complex social relationships such as the role of gender and culture.
In the last two decades the notion of paying for ecosystem services has begun to
emerge (WWF 2006). Such projects typically involve local land and water managers (in-
cluding farmers) and use financial initiatives to encourage management changes that in-
crease ecosystem services. e idea behind the initiatives is that beneficiaries of the service
should compensate those who “provide” the environmental services by conserving natural
ecosystems. Some of the better known projects concern watershed restoration (decreased
erosion, decreased nutrient runoff).
Environmental water flows. Environmental flows refer to the quantity, seasonality, and
quality of water considered to be sufficient for protecting the structure and function of an
ecosystem and its dependent species and services, taking into account temporal differences in
water requirements and spatial variability. e allocation of an environmental flow is defined
by the long-term availability of water, including the extent of natural and anthropogenic
temporal and spatial variability and identified ecosystem responses (Dyson, Bergkamp, and
Scanlon 2003). Environmental flows are often established through environmental, social,
and economic assessments (King, arme, and Sabet 2000; Dyson, Bergkamp, and Scanlon
2003). Determining how much water can be allocated to consumptive human uses without
the loss of ecosystem services is becoming a more common component of efforts to maintain
and rehabilitate rivers and wetlands, including estuaries and other coastal ecosystems.
To date, most developing countries with significant irrigation have paid relatively lit-
tle attention to safeguarding flows for the environment (arme 2003), but this situation
is expected to change rapidly in the coming decades. Water legislation in South Africa and
the Mekong Agreement are examples of the recognition of environmental water require-
ments in developing countries. More explicit bulk allocation of water to the environment
may provide a major challenge to irrigators to manage with smaller and less dependable
allocations for cropping. While the assessment of water availability, water use, and water
stress at the global scale has been the subject of ongoing research, the water requirements
of aquatic ecosystems have not been considered explicitly or estimated globally (Smakhtin,
Revenga, and Döll 2004). It could be possible to establish an environmental allocation
beyond which substantial degradation of ecosystem services and human well-being results
(King, arme, and Sabet 2000). Defining this allocation entails also defining what con-
stitutes a degraded ecosystem.
Tools have been
developed to
assist in making
decisions for
allocating
water for both
economic and
environmental
purposes
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266
Poff and others (1997) emphasize that analysis of environmental flows should con-
sider both the quantity and the timing of flows to maintain “naturally variable flow
regimes” with the aim of retaining the benefits provided by seasonally low and high
flows. Several methods have been used to establish environmental flow allocations and
to reduce or remediate problems caused by previous water regulation. King, Brown,
and Sabet (2003) emphasize that monitoring and management adjustments are a neces-
sary component of such methods. ere are many methods for estimating the amount
of water that is critical for preserving aquatic ecosystems and resources (Annear and
others 2002).
In addition to determining the suitable quantity and timing of an environmental
flow, it may be necessary to consider how to deliver ows. e engineering structures
along rivers can constrain flow releases and may need adjustment. e rate and volume
of releases and the temperature and oxygen content of the water are all important com-
ponents of a flow release. Tools have been developed to assist in making decisions for
allocating water for both economic and environmental purposes. e Downstream Re-
sponse to Imposed Flow Transformation framework (box 6.14) differs from others such as
the Instream Flow Incremental Methodology and Catchment Abstraction Management
Strategies in its explicit consideration of the socioeconomic implications of different re-
lease scenarios.
Conceptualizing uncertainty
Most of the tools that have been developed for dealing with tradeoffs involving ecosystem
services work best in environments where ecosystem behavior and response to change
are well understood and the problems and benefits are already known. But ecosystem
The Downstream Response to Imposed Flow Transformation (DRIFT) framework is an interactive
and holistic approach for providing advice on environmental ows in rivers. It incorporates knowl-
edge from experienced scientists from a range of biophysical disciplines as well as socioeconomic
information to establish ow-related scenarios that describe a modied ow regime, the resulting
condition of the river or species, the effect on water resource availability for off-stream users, and the
social and economic costs and benets. DRIFT highlights the importance of maintaining groundwater
ecosystems along with surface water ecosystems in securing streamows for ecosystem purposes.
The process is developed through interactive and multidisciplinary stakeholder workshops to develop
agreed biophysical and socioeconomic scenarios.
The development of scenarios requires an assessment of biophysical, social, and economic data
and draws on results from other predictive models that assess the responses of specic biota to ow
conditions (such as the Physical Habitat Simulation model). To be effective DRIFT should be run in
parallel with a macroeconomic assessment of the wider implications of each scenario and in conjunc-
tion with a public participation process that enables people other than direct users to contribute to
nding the best solution for the river.
Source: Acreman and King 2003; MEA 2005b.
box 6.14
Guiding environmental flows: the Downstream Response
to Imposed Flow Transformation framework
Most of the
tools for dealing
with tradeoffs
involving eco-
system services
work best in
environments
where eco-
system
behavior is well
understood, but
mechanisms
are needed for
dealing with
uncertainty
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6
Agriculture, water, and
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complexity and variability are common, so uncertainty is high, resulting in outcomes that
are unpredictable and difficult to control. Mechanisms are needed for dealing with uncer-
tainty that enable proactive rather than reactive responses to change.
Two interrelated approaches, adaptive management and scenario planning (see chap-
ter 3 on scenarios), have been suggested for dealing with unpredictability (figure 6.5).
Adaptive management and scenario planning both examine alternative models of how the
world might work and seek to develop policies that are robust to this uncertainty. What
distinguishes them is that the models used in adaptive management build in management
experiments. e approaches are complementary to the integrated approaches described
above and can be used together.
Adaptive management. Adaptive management emphasizes learning and flexibility in man-
agement institutions to cope with situations that involve unknown and uncertain ecologi-
cal management tradeoffs (Walters 1986; Holling 1973; figure 6.6). Treating management
policies as hypotheses rather than solutions, adaptive management has been a highly visible
High
Low
Controllable
Controllability
Uncontrollable
Adaptive management
Maximum sustainable yield
Hedging
Uncertainty
Source: Adapted from Peterson, Cumming, and Carpenter 2003.
Scenario planning
gure 6.5
Different management approaches for dealing with uncertainty
in information and the controllability of outcomes
Assessment
of knowledge
and
uncertainities
Focal
issues
Management
models
Policy
synthesis
and
screening
Experimental
management
gure 6.6
Adaptive management treats policy as hypothesis
and management as experiments, emphasizing
learning and evaluation of interventions
IWMI Part 3 Ch4-7 final.indd 267 2/28/07 3:07:55 AM
268
policy instrument in the management of major river systems, including the Columbia
(Lee 1993), Colorado (Walters and others 2000), San Pedro and the Apalachicola-
Chattahoochee-Flint River (Richter and others 2003), and rivers in Kruger National Park
(Rogers and Biggs 1999) and the Everglades (Walters, Gunderson, and Holling 1992).
e key is identifying management-relevant uncertainties that underlie policies and then
evaluating the management alternatives through scientific assessment, modeling, and if
necessary, experimental management.
Successful adaptive management requires time, resources for learning, and social sup-
port (Richter and others 2003; Walters 1986). Consequently, it often focuses on building
ecological resilience, establishing knowledge for ecological management by working to
integrate knowledge from many different scientific and local sources, and developing con-
nections between the system being managed and its larger context (Berkes, Colding, and
Folke 2003).
In an example of adaptive management Carpenter (2002) describes how a partner-
ship of university researchers and state ecological managers collaborated to design and
operate a management experiment to improve water quality in Lake Mendota, Wisconsin,
by altering the fish community dynamics in the lake to increase predation of algae. e
experiment was made possible by a history of collaboration between lake managers and
academics and supported by the availability of decades of lake monitoring.
Scenario planning. Many problems related to management of water for agriculture and
other ecosystem services are too complex and involve too many interest groups to be
solved through narrowly focused experiments or computer model projections. Scenario
planning offers a structured way of coping with complex systems and outcomes through
learning and preparing for change (Peterson, Cumming, and Carpenter 2003; MEA
2005c). Decisions about how, when, and where to act are typically based on expectations
for the future. When the world is highly unpredictable and when we are working from a
limited range of experiences, our expectations may be proved wrong. Scenario planning
provides a means to examine these expectations through a set of contrasting plausible
futures described though a set of narratives. It has been applied in recent assessments
such as the Intergovernmental Panel on Climate Change, the Millennium Ecosystem
Assessment, and the International Assessment on Agricultural Science and Technology
for Development.
Ideally, scenarios should build understanding of the potential costs and benefits of al-
ternative futures. Scenario planning integrates diverse qualitative and quantitative informa-
tion into a set of plausible narratives to explore policy-relevant futures. A scenario planning
process functions similarly to an adaptive management process, but uses scenarios rather
than computer models or management experiments to develop and test policy alternatives.
One of the biggest shortcomings of scenario planning is the inability of participants to
perceive their own assumptions (Keepin and Wynne 1984) and the potential consequences
of being wrong. is problem cannot be completely avoided, but more robust scenarios
can be created if a wide diversity of stakeholders and perspectives are included and if the
exercise is repeated several times.
Scenario
planning offers
a structured
way of coping
with complex
systems and
outcomes
through learning
and preparing
for change
IWMI Part 3 Ch4-7 final.indd 268 2/28/07 3:07:55 AM
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6
Agriculture, water, and
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costs of going too far
Conclusions
Human society depends on an array of services provided by ecosystems, including agro-
ecosystems. However, agriculture has resulted in the serious degradation of the compo-
nents and processes of many other ecosystems, including processes that are essential for
food production. ese include:
River depletion and consequent degradation of downstream aquatic ecosystems, in
-
cluding effects on groundwater and fisheries.
Drainage of wetlands and runoff or discharge of wastewater to surface water– and
groundwater-dependent ecosystems.
Groundwater depletion by overexploitation for irrigation, causing damage to ground-
water-dependent ecosystems.
Land degradation and alterations of local to regional climate from land-use changes.
Pollution from overuse of nutrients and agrochemicals, with consequences for terres-
trial and aquatic ecosystems and for human health because of water pollution.
A worsening of water pollution problems by river depletion, decreasing possible river
dilution, as illustrated in the tributaries to the Aral Sea and in the severe health prob-
lems caused to downstream populations.
ere are four ways to respond to these adverse impacts:
By rehabilitating lost or degraded ecosystems and ecological processes.
By improving agricultural practices using existing and improved technology.
By ensuring more careful forward planning that includes conscious striking of trade-
offs between water for food production and for other ecosystem services and dealing
with uncertainty.
By addressing the underlying social issues and divisions that affect how decisions are
made in many communities, especially within poor rural communities that often
disproportionately suffer the effects of environmental degradation.
It is also essential that unknown, poorly understood, or uncertain phenomena be
brought into these tradeoffs. e social context for addressing these issues can be important,
especially when such issues as culture, gender, health, and education come to the fore.
Where ecosystem degradation has not progressed too far, it may be possible to re
-
habilitate ecosystems, for instance, to reduce severe eutrophication of lakes and coastal
waters or important wetlands and to secure, by reallocation, enough residual stream flow
to restore environmental flows that support downstream ecosystems and ecosystem ser
-
vices. More essential are actions that focus on preventing further degradation and loss of
important ecosystems.
Because food production will have to increase to alleviate undernutrition and to feed
a projected 50% increase in the world population (before it stabilizes by the middle of
the present century), many challenges remain for land and water managers. e type of
responses available will differ depending on whether the effects of particular instances of
ecosystem degradation are avoidable or unavoidable. Avoidable effects can be minimized
largely through concerted responses, while unavoidable effects have to be considered when
striking tradeoffs.
A more cautious
approach
toward water
management
and food
production will
be essential to
ensure social
and ecological
sustainability
IWMI Part 3 Ch4-7 final.indd 269 2/28/07 3:07:56 AM
270
A catchment-based and integrated approach to land use, water, and ecosystems will
be essential for a knowledge-based balancing of water among different ecological processes
and the provision of ecosystem services. It will be necessary to develop the scientific and
administrative capability and capacity to analyze the conditions necessary for securing
social and ecological resilience to change in ecosystems, including in those that are par
-
ticularly vulnerable to large or episodic events, such as drought, storms, and floods, and
those that are subject to multiple and cumulative impacts. Climate change raises questions
about how the future use of water and land for agriculture will constrain the ability of eco-
systems to respond. at is, will water and land uses adversely affect ecosystem resilience
and responses to climate change?
We are dependent on the ecological components and processes and ecosystem servic
-
es that provide or support much of our food. us a more cautious approach toward water
management and food production will be essential to ensure social and ecological sustain-
ability. While food production will continue to be at the forefront of our endeavors to
support human well-being, sustainability can be achieved only through a more conscious
striking of tradeoffs between different interests. Underlying all must be a clear understand-
ing of the vital role that ecosystems and ecosystem services play in supporting human well-
being and the recognition that much past ecological change has undermined the provision
of many vital ecosystem services, often with complex social and economic inequities.
Reviewers
Chapter review editor: Rebecca D’Cruz.
Chapter reviewers: Maria Angelica Algeria, Andrew I. Ayeni, Donald Baird, orsten Blenckner, Stuart Bunn, Zhu Defeng,
Rafiqul M. Islam, Ramaswamy R. Iyer, Mostafa Jafari, Joan Jaganyi, Hillary Masundhire, Randy Milton, A.D. Mohile, Jorge
Mora Portuguez, V.J. Paranjpye, Bernt Rydgren, Marcel Silvius, Elizabeth Soderstrom, Douglas Taylor, and Yunpeng Xue.
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