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EG40CH07-Herrero ARI 14 October 2015 9:14
Livestock and the Environment:
What Have We Learned in the
Past Decade?
Mario Herrero,1Stefan Wirsenius,1,2
Benjamin Henderson,1Cyrille Rigolot,1,3
Philip Thornton,4Petr Havl´
ık,5Imke de Boer,6
and Pierre Gerber7,8
1Commonwealth Scientific and Industrial Research Organisation, Agriculture Flagship,
St Lucia 4067 QLD, Australia; email: Mario.Herrero@csiro.au, Ben.Henderson@csiro.au,
2Chalmers University of Technology, SE-412 96 Gothenburg, Sweden;
email: stefan.wirsenius@chalmers.se
3National Institute of Agricultural Research, F-63122 Saint-Gen`
es-Champanelle, France;
email: cyrille.rigolot@clermont.inra.fr
4CGIAR Program on Climate Change, Agriculture and Food Security, International Livestock
Research Institute, Nairobi 00100, Kenya; email: p.thornton@cgiar.org
5Ecosystems Services and Management, International Institute for Applied Systems Analysis,
Laxenburg, Austria; email: havlik.petr@gmail.com
6Animal Production Systems Group, Wageningen University, 6700 AH Wageningen,
The Netherlands; email: imke.deboer@wur.nl
7Food and Agriculture Organization of the United Nations, 00153 Rome, Italy
8The World Bank, Washington, DC 20433, United States; email: pgerber@worldbank.org
Annu. Rev. Environ. Resour. 2015. 40:177–202
The Annual Review of Environment and Resources is
online at environ.annualreviews.org
This article’s doi:
10.1146/annurev-environ-031113-093503
Copyright c
2015 by Annual Reviews.
All rights reserved
Keywords
livestock, nutritional security, environmental impacts, greenhouse gas
emissions, environmental indicators, integrated assessment, scenarios,
global change
Abstract
The livestock and environment nexus has been the subject of considerable
research in the past decade. With a more prosperous and urbanized
population projected to grow significantly in the coming decades comes a
gargantuan appetite for livestock products. There is growing concern about
how to accommodate this increase in demand with a low environmental
footprint and without eroding the economic, social, and cultural benefits
that livestock provide. Most of the effort has focused on sustainably
intensifying livestock systems. Two things have characterized the research
on livestock and the environment in the past decade: the development
of increasingly disaggregated and sophisticated methods for assessing
different types of environmental impacts (climate, water, nutrient cycles,
biodiversity, land degradation, deforestation, etc.) and a focus on examining
177
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ANNUAL
REVIEWS
Further
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EG40CH07-Herrero ARI 14 October 2015 9:14
the technical potential of many options for reducing the environmental footprint of livestock
systems. However, the economic or sociocultural feasibility of these options is seldom considered.
Now is the time to move this agenda from knowledge to action, toward realizable goals. This will
require a better understanding of incentives and constraints for farmers to adopt new practices and
the design of novel policies to support transformative changes in the livestock sector. It will also
require novel forms of engagement, interaction, and consensus building among stakeholders with
enormously diverse objectives. Additionally, we have come to realize that managing the demand
trajectories of livestock products must be part of the solution space, and this is an increasingly
important research area for simultaneously achieving positive health and environmental outcomes.
Contents
1.INTRODUCTION ............................................................ 178
2. A BRIEF OVERVIEW OF THE DEMAND AND SUPPLY DYNAMICS FOR
LIVESTOCKPRODUCTS.................................................... 179
3. RESOURCE USE AND EFFICIENCY ......................................... 179
3.1. Use of Land and Other Physical Resources in Livestock Systems:
AnOverview ................................................................ 179
3.2. Resource-Use Efficiency in Livestock Systems: A Key Dimension . . . . . . . . . . . . . 183
3.3. Water: Concepts and Usage in Livestock Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
4.LIVESTOCK ANDCLIMATECHANGE...................................... 187
4.1. Climate Impacts and Adaptation............................................. 187
4.2. Greenhouse Gas Emissions and Mitigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
5. FROM QUANTIFICATION TO ACTION: A RESEARCH AGENDA
ONLIVESTOCK ANDTHEENVIRONMENT.............................. 195
5.1. From Technical Potential to the Large-Scale Adoption of Key Practices . . . . . . . 195
1. INTRODUCTION
The past decade has produced a significant body of research on livestock and the environment,
mainly driven by two events. First, we recognize that the livestock sector is large, increasingly
competes for resources, and causes widespread environmental pressures in many parts of the
world (1, 2). This topic was comprehensively addressed by the Food and Agriculture Organization
(FAO) in their highly influential Livestock’s Long Shadow (3), which has set the stage and provided
impetus for a lot of subsequent work. Although it was light on the positive impacts of livestock,
it set the benchmark for improving the estimates of environmental impacts by livestock. Second,
given increased consumption of animal source food (ASF) caused by human population growth,
increasing incomes, and urbanization over the past 50 years at least, the sector has been growing
at an accelerated rate, and it is expected to continue growing. This phenomenon is often termed
the Livestock Revolution (4).
How to achieve this growth with a lower environmental footprint, without sacrificing the
livelihood and economic benefits that livestock bring, has dominated the agendas of those aiming
at designing more sustainable patterns of global food supply and demand. Traditionally, most
efforts were concentrated on increasing productivity per animal and/or per hectare. The goal
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then shifted toward sustainable intensification, that is, reducing impacts per unit of animal
product generated, which came to dominate the agenda (5). More recently, our perspectives
on the solution space for sustainably feeding the world have expanded (6). There is widespread
acknowledgment that waste reduction could play a significant role (7). Additionally, movement of
the food security agenda toward nutritional security has seen reductions in livestock consumption
by some age groups of the human population as an attractive option for the joint delivery of
health and environmental benefits (5).
This article reviews the major advances on livestock and the environment in the past five to
eight years. It provides a brief account of resource use by livestock (for land, biomass, nitrogen, and
water), climate change adaptation, and mitigation challenges for the livestock sector. We discuss
options for reducing the environmental footprint of livestock and provide guidance for building
a responsive research agenda on this topic for the coming years.
2. A BRIEF OVERVIEW OF THE DEMAND AND SUPPLY DYNAMICS
FOR LIVESTOCK PRODUCTS
Any synthesis of livestock and the environment needs to be elaborated in the context of the past
and future trends of global food consumption and its dynamics. Table 1 presents information on
patterns of food demand for different food groups to 2050 (8).
The key characteristics of these patterns are (a) higher overall consumption of food per capita in
the developed world; (b) large consumption gaps in meat and milk between the developed and the
developing world; (c) significant increases in meat and milk consumption, mostly in the developing
world, which although growing at a faster rate, will not reach even half of the consumption levels
of the developed world by 2050; and (d) a stagnation in consumption of cereals and tubers both
regionally and globally. These per capita consumption transitions toward higher ASF are rapidly
continuing due to increased incomes, urbanization, and changes in the retail structure serving
urban markets such as more supermarkets and more processed foods as indicated by increases in
sugar consumption and oils, for example.
If we consider these numbers together with projected increases in human population to 2050,
we can estimate gross increases in meat and milk demand in the order of 70 to 80% of current
levels. This is consistent across several forward-looking assessments (8, 9).
What is the structure of the supply of livestock products? The demand for livestock products is
met by very heterogeneous productions systems, with different levels of intensification, in varied
agroecological zones and in many cases with different production objectives. Recent global data
(10) suggest that most poultry products and pig meat are produced in industrial systems (more
than 75% of global production), but with smallholders still contributing large shares in places
such as Africa, South Asia, and parts of Southeast Asia, where the shares can be between 40% and
55%. Mixed crop-livestock systems produce the bulk of ruminant products globally (69% of milk
and 61% of meat, respectively), and grazing systems contribute significantly to the production of
cattle meat (Latin America, Oceania) and small ruminant meat (1, 10).
3. RESOURCE USE AND EFFICIENCY
3.1. Use of Land and Other Physical Resources in Livestock Systems:
An Overview
Table 2 presents aggregate numbers on some of the most important physical resources used in
livestock production; Figure 1 places the livestock sector in the broader context of the land use and
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Table 1 Per capita food demand: historical and projected values to 2050 (8)
Kg/person/year 1969/1971 1979/1981 1989/1991 2005/2007 2030 2050
World
Cereals, food 144 153 161 158 160 160
Cereals, all uses 304 325 321 314 329 330
Roots and tubers 84 74 66 68 73 77
Sugar and sugar crops (raw sugar eq.) 22 23 22 22 24 25
Pulses, dry 7.6 6.5 6.2 6.1 6.6 7.0
Vegetable oils, oilseeds and products (oil eq.) 7 8 10 12 14 16
Meat (carcass weight) 26 30 33 39 45 49
Milk and dairy, excl. butter (fresh milk eq.) 76 77 77 83 92 99
Other food (kcal/person/day) 194 206 239 294 313 325
Total food (kcal/person/day) 2,373 2,497 2,633 2,772 2,960 3,070
Developing Countries
Cereals, food 140 152 160 155 159 158
Cereals, all uses 193 219 229 242 254 262
Roots and tubers 79 70 62 66 73 78
(Developing minus China) 62 59 58 64 74 81
Sugar and sugar crops (raw sugar eq.) 15 17 18 19 22 24
Pulses, dry 9.3 7.8 7.3 7.0 7.4 7.7
Vegetable oils, oilseeds and products (oil eq.) 4.9 6.4 8.4 10.1 13.1 15.4
Meat (carcass weight) 11 14 18 28 36 42
(Developing minus China and Brazil) 11 12 13 17 23 30
Milk and dairy, excl. butter (fresh milk eq.) 29 34 38 52 66 76
Other food (kcal/person/day) 115 130 177 253 279 293
Total food (kcal/person/day) 2,056 2,236 2,429 2,619 2,860 3,000
Developed Countries
Cereals, food 155 156 162 167 166 166
Cereals, all uses 571 620 618 591 682 695
Roots and tubers 96 84 78 77 73 72
Sugar and sugar crops (raw sugar eq.) 41 40 36 34 33 33
Pulses, dry 3.6 2.9 2.9 2.9 3.0 3.1
Vegetable oils, oilseeds and products (oil eq.) 11 14 16 19 20 21
Meat (carcass weight) 63 74 80 80 87 91
Milk and dairy, excl. butter (fresh milk eq.) 189 195 201 202 215 222
Other food (kcal/person/day) 492 508 498 458 488 509
Total food (kcal/person/day) 3,138 3,222 3,288 3,360 3,430 3,490
biomass flows of the entire food system. Globally, livestock uses ∼3,900 million ha of land, which
is ∼80% of all agricultural land combined. The quality of this land and the intensity in which it is
used vary enormously, with most of it being used by extensive, grazing-based ruminant systems.
With the exception of land, these grazing-based systems appropriate relatively little of most
other crucial resources such as nitrogen and water. Grazing-based systems contribute very little to
the human food supply globally, accounting for less than 1% of its edible energy; however, these
systems do make critically important contributions to livelihoods and sociocultural interactions.
180 Herrero et al.
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Table 2 Use of key physical resources and production in global livestock sectors (circa 2000)a,b
Ruminant meat Dairy Pigs and poultry
Grazing MixedcAll Grazing MixedcAll All All
Total Total
Per
protein Total Total
Per
protein Total
Per
protein
Land (million ha, ha/Mg protein)d
Cropland (arable land) 8.0 80 92.0 130 6280 10
Permanent grassland 1 600 800 240 560 400 50 NA NA
Biomass (Tg DM year−1, kg DM/kg protein)d
All feed 610 2,200 280 180 1,200 60 880 30
Grains 24 130 NA 4.6 170 NA 880 NA
Grasses and legumes 500 1,200 NA 170 620 NA NA NA
Straw and stover 6.9 400 NA 1.6 230 NA NA NA
Other 81 410 NA 12 140 NA NA NA
Nitrogen (Tg N year−1, kg N/kg protein)e
Nitrogen in feed 12 38 53.6 21 126 1
Water (Pg year−1, Mg/kg protein)f
Blue water 5.1 33 42.3 51 365 2
Green water 220 620 80 45 460 20 590 20
Meat, dairy, and egg productiong
Energy (PJ ME year−1)90 440 NA 120 1 600 NA 1 600 NA
Edible protein (Tg year−1)1.7 8.4 NA 1.5 19 NA 28 NA
Abbreviations: ME, metabolizable energy; N, nitrogen; NA, not available; PJ, petajoule.
aUse per unit of edible-protein output is shown as an indicator of resource-use efficiency.
bThe numbers are rounded to two significant digits (one digit for most numbers on resource use per protein); resource use by predominantly draft-work
livestock (horses, mules, camels) is insignificant at the global scale and is, as such, ignored here.
cThese numbers include landless systems, as well.
dEstimates are provided by References 10, 15, and 16.
eThe data represent estimated levels of nitrogen in feed intake.
fThis is the water “footprint” estimated from Reference 101.
gThe data are provided by Reference 10.
Most of the global ruminant (beef, lamb, goat, and dairy) output comes from mixed systems
in which there is a significant use of cropland-produced feeds such as grains, hay, and silage.
Although these feed types amount to small fractions of average rations, the overall lower feed
conversion efficiencies of ruminant systems (see below) make them substantial when compared
to the systems’ output. On average globally, cropland use per unit of protein output in mixed
ruminant meat (beef, lamb, etc.) systems is similar to that of pork and poultry (Table 2). In
regions dominated by intensive systems such as Europe, beef systems’ cropland use per amount of
protein produced is several times higher than even that of pork and poultry (11). This contrasts
with the commonly held notion (12, 13) that beef does not subtract from global food supply because
it uses only inedible feed and/or land with no or little alternative value for food production. As
is evident from Table 2, ruminant meat supply relies on cropland, nitrogen, and water resources
to approximately the same extent as pork and poultry, per unit of output globally, and thus places
equivalent pressure on edible plant production resources.
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Processed
vegetable
food (our, etc.)
1,000 Tg DM/year
Pork and
poultry
82 Tg DM/year
Beef and lamb:
mixed systems
24 Tg DM/year
Dairy:
mixed systems
74 Tg DM/year
Beef, dairy, etc.:
grazing systems
10 Tg DM/year
Human food
supply
1,500 Tg DM/year
1,700 Tg
DM/year
Fish and seafood
20 Tg DM/year
Human food
intake
1,100 Tg DM/year
Unprocessed vegetable food (tubers, vegetables, fruits, etc.)
300 Tg DM/year
Food waste
400 Tg DM/year
Use as feed
50 Tg DM/year
Use as feed
250 Tg DM/year
Residues
650 Tg DM/year
Manure
Feces, urine
100 Tg DM/year
Manure
Manure
Manure
Residues
Products
3,700 Tg DM/year
650–700 Tg DM/year
900 Tg DM/year
250–300 Tg DM/year
250–300 Tg DM/year
450–550 Tg DM/year
1,000–1,100 Tg DM/year
250–350 Tg DM/year
500–600 Tg DM/year
Permanent
grassland
grazing
systems
2.2 Gha
Permanent
grassland
mixed
systems
1.2 Gha
Cropland
1.4 Gha
Figure 1
Land use and major flows of biomass and its derivatives in the global food and agriculture system (circa 2000). For simplicity, minor feed use flows and manure recycling
to fields are not shown; excluded also are all gaseous flows (CO2,CH
4, etc.). Figure adapted from Refs. 11, 16, and 17. Abbreviations: DM, dry matter; Gha, giga
hectares; Tg, teragrams.
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3.2. Resource-Use Efficiency in Livestock Systems: A Key Dimension
Assessing the efficiency with which livestock systems transform physical resources into food and
other products is essential, not only from a productivity measurement perspective but also be-
cause low resource-use efficiency is often linked to high environmental impacts. For example, low
efficiency in the utilization of nitrogen is closely correlated with high emissions of nitrous oxide,
ammonia, and nitrate (14).
Due to the nature of the resource use, several efficiency concepts are needed to realistically
portray the multifaceted nature of the physical efficiency of livestock systems. Feed conversion
efficiency is a key concept, given that it directly relates to the principal process of livestock pro-
duction: the conversion of plant mass into animal mass. Also, given feed is by far the dominating
physical flow (in energy terms) in livestock systems, feed conversion efficiencies correlate fairly
well to a system’s overall efficiency in the use of the often-scarce photosynthetic resources, land,
plant nutrients, and water. This is evident from the aggregated efficiencies given in Table 2 (ex-
pressed as use per kilograms of protein produced), where differences between the three sectors in
efficiency in the use of land, nitrogen, and water correlate relatively well with that of feed.
Because of variations in physical and economic conditions across regions and differences in
species-specific lifecycle properties, feed conversion efficiencies vary widely. Measured as the
amount of edible metabolizable energy in product per amount of total energy (gross energy) in
feed, regional averages amount to 0.3–2% for beef and lamb, 2–15% for dairy, and 5–15% for
pork and poultry (10, 15, 16). Current global averages are roughly 1% for ruminant meat, 7% for
dairy, and 10% for pork and poultry (10).
In addition to large differences in site-specific conditions, methodological challenges and lack
of detailed data add substantial noise to any estimates of feed efficiency at regional and global
levels. One example of this is given in Figure 2, which shows beef efficiency estimates from three
separate global analyses. From the relatively small differences in global averages, it is obvious
that part of the variance at regional levels is due to differences between the studies in regional
definitions and in the definition of production systems. Some variation is also due to differences
in model types, modeling design, and data sets. This is an area that requires better and more
disaggregated data to reduce the uncertainty of the estimates.
The inherent low feed efficiency of ruminant meat is mainly due to the comparatively low
reproductive rates of cattle, sheep, and goats. A healthy cow gives birth to one calf per year (a
female sheep/goat, two offspring), whereas a sow typically produces 20–25 piglets per year and a
hen 100+chicks per year. For ruminant meat, many more adult females are therefore needed per
meat output compared to pork and chicken, which means that the overhead of feed required for
adult, nongrowing animals is far higher for beef and lamb. In addition, potential animal growth
rates relative to liveweight are lower for cattle and sheep than for pork and poultry. In feed
efficiency terms, this is a disadvantage because the lower the growth rate, the larger the fraction
of feed energy that is expended on maintenance metabolism instead of growth (17).
Although feed efficiencies correlate with efficiencies in the use of photosynthetic resources,
large spatial heterogeneity (for example, in land use intensity and the opportunity cost of land for
ecosystem and human services) limits their relevance for more detailed analysis. More detailed
efficiency concepts are needed that specifically address the photosynthetic resources and, ideally,
their ecological and economic opportunity costs.
Van Zanten et al. (18), for example, developed a new land use ratio (LUR) concept, defined
as the maximum amount of human digestible protein (HDP) derived from food crops on all land
used to cultivate feed required to produce 1 kg ASF over the amount of HDP in that 1 kg ASF.
They illustrated this new concept for three case systems: laying hens, dairy farming on peat soils
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0
20
40
60
80
100
120
140
160
180
kg DM feed per kg beef carcass
Wirsenius 2000
Bouwman et al. 2005
Herrero et al. 2013
World
East Asia
Eastern Europe
Former Soviet Union
Latin America and Caribbean
Middle East and North Africa
North America and Oceania
South Asia
Sub-Saharan Africa
Western Europe
Figure 2
Comparison of feed efficiency estimates for beef [in kilograms of dry matter (DM) of feed per kilogram of
fresh carcass] in studies by Wirsenius (16), Bouwman et al. (15), and Herrero et al. (10). Numbers refer to
the efficiency of aggregate beef output from single-purpose beef cattle systems and dairy cattle bulls.
(i.e., low opportunity costs for food crops) and dairy farming on sandy soils. For dairy cows, the
LUR was 2.10 when kept on sandy soils, and 0.67 when kept on peat soils. A value of 2 implies
that all land required to produce 1 kg HDP from dairy cows on sand would yield approximately
twice as much HDP if used directly to cultivate human food crops. In terms of food security,
therefore, dairy cows on peat have a higher land efficiency than dairy cows on sand, whereas the
feed conversion ratio (i.e., kilogram of dry matter in feed per kilogram of product) appeared higher
for cows on peat (0.91) than for cows on sand (0.77).
Another example is new-fixed nitrogen and how its efficiency is linked to that of land (Figure 3).
New-fixed nitrogen represents the net input of reactive nitrogen to the system, mainly through
fertilizer application and biological fixation. New-fixed nitrogen per unit of output is a better
indicator of the nitrogen efficiency of livestock systems than most other concepts, given it factors
in the efficiency by which nitrogen in manure and soil organic matter is utilized in feed production
(19). Furthermore, any input of new-fixed nitrogen contributes to the downstream cascade of
emissions of reactive nitrogen species (20), which means that new-fixed nitrogen efficiency is also
an indicator of the potential environmental impact from nitrogen effluence.
The large differences between beef and other systems in Figure 3 are mainly related to the
patterns of feed conversion efficiencies described above. However, given beef systems rely largely
on perennial grass crops, which in general have much lower nitrogen losses than most annual
crops (see below), the inferiority of beef in terms of new-fixed-nitrogen efficiency is slightly less
compared with that of feed conversion efficiency. Also, beef production tends to occur on land
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Beef extensive
Beef semi-intensive
Beef intensive
Dairy semi-intensive
Dairy intensive
Pork intensive
0
10
20
30
40
50
60
70
80
90
100
012345
Land use per unit of output (ha/Mg protein)
New-xed-nitrogen use per unit of output (Mg N/Mg protein)
100 kg
N/ha/year
50 kg
N/ha/year
30 kg
N/ha/year
Figure 3
Efficiency of land and new-fixed-nitrogen (N) use in different livestock systems of varying intensity. These
data refer to specific regions/farms, and under different conditions, numbers can deviate significantly from
those presented here. Dashed lines represent the equivalent new-fixed-N flux on land at 30, 50, and
100 kg N/ha/year and correlate to the intensity in the plant subsystems (i.e., feed production). Author
calculations based on data in Refs. 102–105.
with lower opportunity costs, which means that often the economic and ecological cost of land
use for beef is typically not as high as its physical land area.
Differences between intensive dairy and pork systems are generally small in absolute terms
and are likely to be within the range of influence of site-specific conditions and technology and
management choices. However, under similar conditions, pork systems tend to be more land
and nitrogen efficient because of the relatively high feed cost in dairy systems of producing the
replacement heifer (i.e., the female calf that is reared for replacing the dairy cow).
In Figure 3, we plot land use efficiency against that of new-fixed nitrogen as a means
of illustrating to what extent these two resources substitute for each other when moving be-
tween different levels of intensity. Although such substitution generally is characteristic of the
feed-producing plant subsystem (because lower intensities and yields in plant production typically
are associated with lower relative nitrogen losses), it is not necessarily so for the entire livestock
system. Figure 3 illustrates this with its examples for beef and dairy, where despite the lower land
use efficiencies of the less intensive systems—owing largely to their lower intensity in plant pro-
duction (compare the iso-nitrogen-flux lines)—the nitrogen efficiencies do not rise consistently.
This is because in less intensive beef and dairy systems, some factors, in particular lower feed con-
version efficiency in the animal subsystem, counteract the higher new-fixed-nitrogen efficiency
related to low intensity in the plant subsystem.
An even more important feature, however, than low feed production intensity that contributes
to high new-fixed-nitrogen efficiency of extensive ruminant systems is their greater reliance of
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perennial grass crops. Such crops have densely developed root systems, whereas the uptake effi-
ciency of plant-available nitrogen is very high and, under normal conditions, little nitrogen is lost
through leaching below the root zone (21). Furthermore, being permanent or semipermanent,
these crop systems are more efficient than annual crops in the reuse of soil organic nitrogen that
originates from the previous growing seasons (21).
However, perennial grass systems are not entirely closed with respect to nitrogen, and there
are significant, inevitable gaseous losses, such as ammonia. Although these combined losses are
small as a fraction of total nitrogen turnover in the soil-plant system (∼5–10%), they are scaled
up to a larger proportion relative to the systems’ output because of their inferior performance
relative to intensive systems in other respects. First, feed conversion efficiencies are generally
lower in extensive systems because of poorer herd performance in terms of reproduction rates,
milk yield, and weight gain rates. Second, utilization efficiency of produced plant mass as feed
is lower in extensive systems because of their reliance on grazing, which under good conditions
utilizes 50–60% of above-ground production, compared to ∼80% in the case of (mechanized)
cutting.
3.3. Water: Concepts and Usage in Livestock Systems
Fresh water is essential for livestock production; it is used for meeting the drinking and cooling
needs of animals, for cleaning services (e.g., washing animals, cleaning housing facilities), for
processing of livestock products and for the cultivation of feed (23).
To understand freshwater use along global livestock supply chains and their associated envi-
ronmental impacts, we have to distinguish between so-called green and blue water. Green water
refers to precipitation on land that does not run off or recharge an aquifer and is stored in the
upper part of the rooted soil or temporarily stays on top of vegetation. This part of precipitation
can eventually evaporate or transpire through soils and crops or can be embodied in crop material
(23, 24). Blue water use is also referred to as consumptive water use. Water is considered consump-
tive if it is withdrawn from a watershed and not discharged into that same watershed, because it
evaporates, is embodied in plant or animal product, or is discharged into another watershed (25).
These definitions of green and blue water clearly demonstrate that green and blue water flows are
not independent but interact spatially and geographically (22).
Fresh water used for drinking, cooling, cleaning, and processing is blue water, whereas fresh
water used for cultivation of feed crops can include both green water (rainfall) and blue water
(irrigation). At a global scale, livestock uses ∼10% of the global annual rainfall (including green
and blue water), which is ∼25–32% of the total agricultural water use (3, 23, 26). Blue water used
by livestock for drinking, servicing, and processing contributes only 0.2% to the total water use of
livestock production. Almost all fresh water used in livestock production, therefore, is related to
cultivation of feed. The majority of the fresh water currently used during the cultivation of feed
crops, however, is green water (3, 22). Although exact estimates of the share of green and blue
water used during the cultivation of feed crops are missing, irrigation of feed crops is currently
assumed to be of minor importance at a global scale (3, 22).
The environmental impacts associated with the current production of ASF, therefore, are
associated mainly with blue water use. Although it is relevant to quantify the green water use
during cultivation of feed crops as it yields insight into the efficiency of using rainwater, it is
not clear if there is an environmental impact associated with green water use. In cases in which
green water would not have evaporated or transpired by grassland or cultivated maize land, the
natural ecosystem might evapotranspire the same amount of green water (27). Green water use,
therefore, does not generally have an impact on the environment. Only changes in land use or
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management (deforestation, ploughing grassland) or land degradation (such as from overgrazing)
might affect the environment, because these processes affect the partitioning between green and
blue water. At present, however, insights into changes in water partitioning from changes in land
use or management and land degradation are missing. Insight into green water evapotranspired
during feed cultivation, furthermore, might be valuable from the perspective of food security. In
situations in which grassland is also suitable for cultivation of food crops production, the available
green water may be used more efficiently for cultivation of food crops for humans (18).
Finally, the amount of blue water use in livestock production, especially irrigation water for
cultivation of feed crops, is expected to rise, because of the increasing demand for ASF. Blue water
use can have an impact on human health and ecosystem quality and can result in depletion of water
resources. The environmental impact of blue water use, however, is very site specific and varies
across seasons (28).
Studies that assess and compare water use in livestock production systems, therefore, should
report both green and blue water use, distinguish between green water used on land suitable and
unsuitable for cultivation of feed crops, and assess the site- and seasonal-specific impact of blue
water use. At present, such assessments are lacking, which hinders a sound comparison of different
livestock production systems and potential improvement options. In theory, however, ruminant
systems have the potential to be highly water efficient in situations where they use efficiently
land that is less suitable for crop production that is not irrigated, and where sustainable grazing
management is applied. The use of irrigation water to increase grass or forage productivity is
only sustainable in regions with low water scarcity. Water use efficiency in monogastric systems
can be improved by increasing the proportion of by-products from human food production that
are nonedible for humans, especially if these feed ingredients are cultivated with efficient use of
rainwater or with additional irrigation in regions with low water scarcity.
4. LIVESTOCK AND CLIMATE CHANGE
4.1. Climate Impacts and Adaptation
The impacts of climate change on livestock systems have not received as much attention as those
of crops. Thornton et al. (29) reviewed the major relevant biological impacts. Their documented
impacts included (a) effects on the quantity and quality of feeds; (b) heat stress on animals; (c) water
stress on animals and crops; (d) likely changes in distributions and increased prevalence and
intensity of livestock diseases, e.g., the spread of bluetongue virus (sheep) across Europe (through
increased seasonal activity of the Culicoides vector), the amplification of gastrointestinal parasites,
and the spreading of ticks (responsible for Lyme disease and tickborne encephalitis) towards higher
altitudes and latitudes (30; see http://www.ipcc.ch/report/ar5/wg2/); and (e) biodiversity losses.
Table 3 summarizes some of these impacts.
Adaptation options have been classified in several ways, such as the level at which each
option operates and the pathway taken (31), and the time horizon that is being considered
(32). Particularly, a classification has been proposed distinguishing between incremental,
systemic, and transformational adaptations (Table 3). Incremental adaptations correspond to
progressive technical improvements (feeding, grazing management, etc.). Systemic adaptations
correspond to reconfigurations of farming systems. At the household level, four basic strategies
in relation to incremental and systemic adaptation and mitigation options can be considered (33):
(a) intensification of existing patterns of production; (b) diversification of production and
processing; (c) extensification of existing or modified patterns of production; and (d) better risk
management, that is, options designed expressly to address production and/or financial risk,
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Table 3 Climate change impacts, adaptation options, and knowledge gaps in livestock systems
Climate change impacts Adaptation options Knowledge gaps
Specific impacts on
crop, livestock
and feed
Quantity/quality of feed
(34):
Reduced grass or stover
availability:
Lower digestibility and N
content of pastures and
fodder crops
Lower grain consumption
Incremental adaptation:
Improved feeding:
Diet supplementation, improved
grassland fodder species
Grazing management:
Adjust stocking densities to feed
availability
Rotational grazing
Rangelands:
Primary productivity impacts, species
distribution, and change due to CO2
and other competitive factors
Estimation of carrying capacities
Mixed systems: Localized impacts
on primary productivity, harvest
indexes, and stover production, and
the extent of the problem, in a
development context
Heat stress on animals Change livestock breed:
Use of improved and/or
stress-tolerant breeds
Change livestock species:
Stress-tolerant species
Water stress on animals
and crops
Change crop varieties:
Higher-yielding, stress-tolerant,
dual-purpose varieties
Change crops:
Increased use of dryland crops
from cereals to tubers
(i.e., cassava)
Use of perennial crops
Crop management:
Modify planting dates, using
multi-crop varieties with different
times to maturity
Water-use efficiency and
management:
Irrigation to maximize water use
Modify cropping calendar
Surface and groundwater supply,
and impacts on livestock,
particularly rangeland systems:
Effective ways to increase livestock
water productivity
Farm level Loss of income/household
food security (34, 52):
Reductions in cash flows
Incremental and Systemic:
Weather-index insurance:
For crops and livestock
Use of weather information:
To modify crops and for livestock
management
Localized impacts on livelihoods
and how systems will evolve in
future:
Magnitude and effects of systems
changes on ecosystem goods and
services
(Continued )
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Table 3 (Continued )
Climate change impacts Adaptation options Knowledge gaps
Less food available or for sale
Compromised children
nutritional status
Alter integration within the
system:
With the addition/deletion of
enterprises within the farming
system, changing the ratio of
crops to livestock and/or the ratio
of crops to pasture, or the
addition of trees/shrubs
Issues at regional
level
Four dimensions of
regional food security:
food availability, access,
utilization, and their
stability at the regional
level
Loss of biodiversity
through habitat and
landscape change (44):
Changes in distributions of
livestock diseases
Increased prevalence and
intensity
Systemic and transformational:
Livestock farming system
transition:
Place transformation and locations
shift
Dietary shifts:
Substituting a proportion of maize
meal in the diet for sorghum
and/or millet meal
Food processing and storage:
More efficient to reduce
postharvest losses and waste and
added value at the farm gate
Change livestock breed and/or
species:
Resistant breed and/or species
Change in farming systems:
From grazing systems to mixed
systems
Increases in industrial systems
More diversified production
systems
Interactions between climate
change, well-informed
socioeconomic scenarios, and the
evolution of farming systems at
several scales:
Reconciling growing demand for food
in the South and stagnating demand
in the North from a nutritional
security perspective
Ecological biodiversity:
The potential effects of a change in
systems on the numbers of species
Animal breed biodiversity:
Specifying the genetic resources of an
animal that could be useful in the
future
How the prevalence and intensity of
key epizootic livestock diseases can
change in the future
How climate change can affect
diseases as systems intensify
Table adapted from Reference 29, with updates from Reference 34.
through, e.g., using climatic or market-related information to help make crop and livestock
management decisions. A great variety of possible adaptive responses related to one or more of
these main farm strategies is available for different production systems globally (see Ref. 34 for
options for mixed crop-livestock systems in developing countries). The list of available options is
also continuously evolving and expanding (Table 3). Examples of emerging or growing research
areas are the genetic selection of robust animals (35), and adaptive management of resource re-
dundancies and diversity at farm level (36). To identify appropriate adaptation options, trade-offs
with mitigation potential and food security need to be considered (34), together with institutional
constraints and the three dimensions of sustainability (economic, environmental, and social).
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An emerging challenge in recent years has been to move toward integrated frameworks
considering timeframes and uncertainties associated with climate change, with the aim of bet-
ter informing adaptation planning. Given that livestock systems are highly dynamic, the most
appropriate options will change throughout time. In this area, a focus has progressively grown
around transformational change as an adaptive response to climate change (37–39). In contrast
with incremental and systemic adaptations, which have been described as extensions of “what is
already being done,” Kates et al. (36) identify at least three classes of adaptations as transforma-
tional: “(a) those that are adopted at a much larger scale or intensity, (b) those that are truly new
to a particular region or resource system, (c) those that transform places and shift locations.” As
incremental adaptations, transformational changes can be autonomous or planned, responsive, or
proactive (35). With the aim of supporting decision making, one major challenge is to study trans-
formational changes in terms of the interaction with the dynamic evolution of farming systems
and their socioeconomic context (40, 41), as indicated in knowledge gaps in Table 3. Scenario
processes are being used as parts of frameworks to understand better transformational responses
in the livestock sector (41). According to certain intensification theories (42), most transitions of
livestock farming systems (LFS) can be described as dynamic evolutions from pastoral to mixed
crop-livestock systems, and then from mixed crop-livestock to industrial systems. The main driver
of this trend is human population growth, among other factors such as changes in consumption
patterns and urbanization. Some empirical validation exists (43), confirming a particularly high
dynamism of LFS transitions in countries with high population growth, where there are huge
food security issues at stake. However, in general, there are many other factors that may radically
modify these kinds of processes of intensification. Many challenges remain in assessing the impacts
of climate change on such systems’ transitions, as well as the impacts of ongoing transitions on
mitigation potential and other dimensions of sustainable development. As an illustration of the
complexity of these linkages, Searchinger et al. (44) found that converting Africa’s wet savannahs
to cropland would have high carbon and biodiversity costs, contrasting with previous influential
studies that asserted that these lands provide a large, low-environmental-cost cropland reserve.
Major methodological advances have been achieved in integrated approaches (see, e.g., 45,
46), but to date these developments mainly have been focused on the environmental impacts of
livestock systems (47), and more work on adaptation is needed. Building on previous studies,
however, Lecl`
ere et al. (48) and Weindl (49) have developed integrated assessment frameworks
linking combined general circulation models, global gridded crop models, and global economic
models of the agricultural sector with a detailed and wide LFS database. On the basis of such
a modeling chain, Weindl has been able to explore the effectiveness of two alternative livestock
system transitions (shift to mixed crop-livestock systems or to rangeland systems) as an adaptation
strategy with five different climate projections. The results of this study suggest that shifts toward
mixed crop-livestock systems could reduce global agricultural adaptation costs from 3% to 0.5%
of total production costs, because of higher feeding efficiencies in the mixed systems. Lecl`
ere et al.
(48) found that transformational changes of agricultural systems would be required in most regions
by the 2050s to cope with climate change, and that the nature and extent of the changes required
vary across climate change scenarios. They also found that flexibility is the key to achieving cost
effective solutions, as maladaptation can be very costly.
Finally, whereas climate change impact studies have tended to focus on progressive changes
in climate, it is essential to include a focus on climate variability and climate extremes (47, 50,
51). Without this, the full impacts of climate change on livestock systems are probably being
seriously underestimated (50). In a recent review, Thornton et al. (50) identified key knowledge
and data gaps in this area. These include the timing and interactions of different climatic stresses
on plant growth and development, particularly at higher temperatures, and the impacts of changes
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in climate variability and extreme events on pest-weed-disease complexes (50). At the farm scale,
Van Wijk et al. (52) reviewed diverse modeling tools able to analyze the combined effects of
climate variability and change on food production and economic performance. In addition to
improving the sensitivity and robustness of crop and animal components of these farm models,
three modeling research areas to better tackle the combined effects of climate variability and
change are (a) decision making and adaptive management (53), (b) integration within integrated
multiscale frameworks (34), and (c) participatory codesign of systemic adaptations (54, 55).
4.2. Greenhouse Gas Emissions and Mitigation
Livestock are a significant source of greenhouse gases globally. Accepted global greenhouse gas
(GHG) emissions estimates from 17 billion domestic food-producing animals vary from 8 to 18%
of global anthropogenic emissions (1, 56–59), with this range reflecting methodological differences
(inventories versus life cycle analysis) and attribution of CO2from land use changes (livestock
rearing, feed production). These numbers have been the subject of significant debate as regional
differences and emissions sources have been contested (60–62). The main sources and types of
GHGs from livestock systems include methane production from enteric fermentation and animal
manure, CO2from land use and its changes, and N2O from manure and slurry management (1).
Figure 4 shows the spatial distribution of GHG emissions and the associated emissions intensities.
The most important sources of emissions were enteric methane (1.6–2.7 Gt CO2eq); N2O
emissions associated with feed production (1.3–2.0 Gt CO2eq); and land use for animal feed and
pastures, including change in land use (∼1.6 Gt CO2eq). Cattle production dominates emissions
(65–78%). The developing world contributes 70% of emissions from ruminants and 53% of
emissions from monogastrics. Mixed crop-livestock systems dominate livestock emissions (58%
of global livestock emissions), while grazing systems contribute 19% (10). Of all processes, feed
production is the most important, accounting for 45% of global emissions (1).
In this section we review a range of field-tested and modeled management options for the
mitigation of GHG emissions associated with livestock products. These mitigation options include
animal-based measures, which target enteric methane as well as methane and nitrous oxide from
manure; land-based mitigation measures, which are based on increasing carbon stocks through
soil carbon sequestration in grazing lands and from intensification practices that avoid emissions
from land use changes (e.g., conversion of forestland to pastureland); and reductions in the human
consumption of livestock products.
4.2.1. Animal-based mitigation options. A description of the various animal-based mitigation
options can be found in Gerber et al.’s (63) comprehensive review. In aggregate, these options have
the potential to mitigate 0.01–0.5 Gt CO2eq/year−1. Owing to its dominant share of animal-based
GHG emission sources, most of the mitigation research for livestock has focused on options for
reducing enteric methane produced by ruminants (64–66).
4.2.1.1. Feed additives and feed improvements. A range of feed additives have been assessed in
experiments to reduce methane through the manipulation of rumen microbial processes. These ad-
ditives include chemical compounds such as alternative electron receptors, ionophoric antibiotics,
enzymes, and probiotic cultures (63). Although often effective in the short term, these compounds
are generally less effective in the long term due to adaptation by the rumen microbial ecosystem.
For some of these additives (e.g., ionophoric antibiotics), public acceptance and prohibitive reg-
ulations in some countries present additional obstacles for their application. Dietary lipids and
nitrates (an electron receptor) appear to be the most promising feed additive options (63).
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a
b
7.5 15 30 45 60 75 90 105 120
10 25 50 75 100 250 500
Mt CO2 eq/km2/year
Kg CO2 eq/kg protein
Figure 4
Greenhouse gas emissions (a) and emissions intensities (b) in global ruminant systems. Figure adapted from Reference 10.
Perhaps the most well-researched approach for mitigating enteric methane per unit of product
emission intensity is the provision of higher quality, more digestible livestock feeds. This can
lower emissions by improving animal productivity and, by lowering energy lost as methane, will
be most effective in the developing countries where feed quality is a pervasive production constraint
and productivity gains are needed to improve food security and economic growth in rural areas
(67). The digestibility of feed rations can be improved by providing higher quality forages, the
inclusion of energy-dense concentrates (e.g., cereal grains), and the processing and treatment of
available low-quality feeds (e.g., urea treatment of straws) to improve their nutritional value (68).
Because improved feed quality can significantly boost animal productivity, this approach may
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result in a net increase of emissions, despite substantial reduction in emission intensity. Although
it is obviously possible for the sector to deliver the same level of output with fewer but more
productive animals, feed improvement options can create incentives for farms to increase their
herd sizes to extract higher investment returns (67). These incentives are, for instance, known
to occur when farmers invest in pasture improvement (69). We estimate the technical mitigation
potential of this option to be 0.68 Gt CO2eq year−1, under the assumption of a 10% improvement
in the digestibility of animal feed rations and widespread application among developing countries.
However, considering economic constraints and the historically low adoption rates of improved
feeding practices in developing countries (67, 70), we estimate this potential to fall to 0.12–0.15 Gt
CO2eq year−1.
4.2.1.2. Animal management. In addition to improved feed quality, there are several animal
management options that can also improve animal and herd productivity. These include a com-
bination of genetics, animal health, nutrition, and modern reproductive management to raise
reproductive efficiency, reduce the burden of “unproductive” animals in herds, raise the produc-
tive lifespan of animals, and reduce mortality rates of calves and adult animals. These measures
can reduce the breeding herd overhead and raise the production efficiency at the herd and animal
levels, thereby reducing GHG emissions of per unit of product (63). We estimate that improved
animal management could mitigate 0.2 Gt CO2eq year−1by 2050. As with the feed improve-
ment options, the productivity benefits associated with better animal management could, where
profitable, create incentives for an expansion in animal numbers and thereby reduce their overall
mitigation effectiveness.
4.2.1.3. Manure management. There are several manure management options available to mit-
igate emissions of CH4and N2O associated with the handling, storage, and spreading of manures.
In situations where manure can be collected and stored, N2O emissions can be prevented by re-
ducing nitrogen losses to the environment, by using manure storage practices that minimize losses
from volatilization and leaching (71). These include simple approaches such as the covering and
compacting of manure (72, 73), as well as more sophisticated approaches such as the anaerobic
digestion of manure slurries prior to this application to soils. However, the evidence for the anaer-
obic digestion of manure reducing field-scale emissions is mixed (74, 75). In contrast, this measure
has proven to be very effective for reducing manure CH4emissions. Nevertheless, this technol-
ogy is only suitable for relatively confined production systems where wet manure is collected and
stored. This is not typical for most of the world’s livestock production, where excretion occurs
in the field. The highest mitigation potential for manure (0.01–0.07 Gt CO2eq year−1)comes
from options to lower nitrogen losses to environment when manure applied to soils as a fertility
amendment. These losses can be managed through method of application and timing, to better
match plant requirements and to avoid heavy rains (76, 77). Nitrification inhibitors also have the
potential to lower N2O emissions in crop and grazing lands (78, 79).
4.2.2. Land-based mitigation options. Carbon sequestration in grazing lands. Improving graz-
ing management, by adjusting grazing pressure to optimize forage production, can help to reverse
historical soil carbon losses and build soil carbon stocks. This practice could sequester up to 148 Mt
CO2eq year−1in the world’s grazing lands, with a significant share of this potential (81%) located
in developing countries (80). The oversowing of grasses with legumes can also build grazing land
carbon stocks. This practice has the potential to sequester up to 203 Mt CO2eq year−1globally;
however, associated increases in soil N2O emissions of 57 Mt CO2eq year−1are estimated to
wipe out 28% of these sequestration benefits (80). The implementation of these practices could
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be economically attractive in many sites, given that these practices can substantially raise forage
productivity (71). However, for many areas within the world’s grazing lands, these offsets from ni-
trous oxide emissions can lead to a negative carbon balance. Therefore, their effectiveness depends
fundamentally on being able to identify, a priori, areas that will be amenable to these practices,
which would clearly be a great challenge for their large-scale application (80). Furthermore, be-
cause these practices generally result in increased forage consumption by ruminants, the implied
additional animals and the offsetting impact of their associated emissions would also need to be
accounted for.
4.2.2.1. Avoided land use changes due to sustainable intensification. Therearearangeofsus-
tainable intensification options that can address widespread unsustainable practices within the
global food system (81), including both the adoption of new technologies and improving the
efficiency of current food production. High-tech options include cloning, genetic modification,
and nanotechnology (7, 9, 82), although controversy surrounding some of these practices may
continue to rouse resistance from regulators and consumers for some time. A growing number of
studies (83, 84) have estimated yield gaps in crop production and the potential food supply benefits
from closing these gaps. Such yield improvements could also help to reduce land requirements
for both crop and livestock production (63).
Hertel et al. (85) showed that the substantial crop yield increase between 1961 and 2006,
associated with the Green Revolution, led to more than a 200% increase in crop production, with
only an 11% expansion in the global cropland area. The authors estimated that ∼1.3 Gt CO2of
emissions were avoided from land cover changes that would have otherwise occurred without the
crop yield improvements of the Green Revolution. Looking at future land use changes, Havl´
ık
et al. (45) computed that maintaining past trends in crop yield growth would prevent the expansion
of ∼290 Mha of cropland and 120 Mha of grassland by 2030, compared to a baseline of stagnant
yield growth. The authors estimate that these avoided land use changes would save more than
2GtCO
2eq year−1, with most of these savings coming from land use changes that would have
been at least partly associated with livestock.
4.2.3. Mitigation packages. Introducing single mitigation practices is likely to generate relatively
limited mitigation effect. There is growing recognition that significant and cost effective mitigation
will require the development of mitigation packages that are adapted to local conditions, and that
are adoptable and economically viable. Such packages have been estimated to generate emission
intensity reduction ranging between 15 and 40% (1).
4.2.4. Mitigation through managing livestock consumption. Given that the resource-use ef-
ficiency of livestock production is low compared to crop production, and that livestock consume
approximately one-third of global crop production (3), a shift away from livestock consumption
to more crop-oriented human diets could substantially reduce global food resource requirements.
For instance, although ∼80% of the world’s agricultural land is used for grazing or feed and
fodder production for livestock (3), meat supplies only 15% of the total energy and 30% protein
in the average global human diet. However, many extensively grazed areas would be unsuited to
crop production. A handful of studies have explored the emissions and resource implications of
lowering the human consumption of meat and other livestock products. Under the extreme case
of eliminating the consumption of animal products entirely, Stehfest et al. (86) estimate that re-
quired food production in 2050 could be achieved with less agricultural land than is presently used,
permitting a substantial increase in forest land and reducing emissions by 7.8 Gt CO2eq year−1.
More moderate scenarios, such as the removal of ruminant meat from diets and the adoption of a
healthy diet (87), resulted in slightly lower mitigation benefits of 5.8 and 4.3 Gt CO2eq year−1.
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Smith et al. (81) also explored a range of scenarios demonstrating that a shift to more crop-oriented
human diets could deliver large benefits, by sparing land for either bioenergy or carbon seques-
tration through afforestation, resulting in emission reductions of a similar magnitude. Although
certainly promising, demand-side mitigation options need to be further investigated. Current
studies capture only very imperfectly the indirect effects that massive consumption shifts would
have, for example on elements such as land use, household expenditures, agricultural productivity,
employment, and others.
5. FROM QUANTIFICATION TO ACTION: A RESEARCH AGENDA
ON LIVESTOCK AND THE ENVIRONMENT
Undoubtedly, research on the issues surrounding livestock and the environment in the past decade
has been prolific. It has produced vast amounts of information that was not available previously. We
know a lot more about livestock now than ten years ago. The research has spanned not only multiple
environmental dimensions but has also helped organize the livestock research community around
critical issues. However, at the same time, it has in many cases polarized the views surrounding
the roles of livestock in the food system.
Two features have dominated this research agenda: the focus on quantifying the impacts of live-
stock on the environment, and the evaluation of the technical potential of the improved strategies
proposed. These have been important and foundational, as many of these impacts had not been
robustly quantified before, nor did we have adequate baseline information globally for making de-
cisions on the most appropriate strategies for increasing the sustainability of livestock production
in different parts of the world.
Although it is important to refine some of these basic numbers, the agenda now needs to move
forward. More effort needs to be focused on developing mechanisms that will create tangible
changes and transformations in the livestock sector in a reasonably short timescale (the next
10 years). Most of these are heavily interconnected and are described below.
5.1. From Technical Potential to the Large-Scale Adoption of Key Practices
Many of the practices that could improve environmental performance look good on paper as in
many cases they not only reduce environmental footprint, but also increase incomes and food
security. The reality is, however, that farmers are not adopting these options at significant rates,
and figures of 10–20% of farmers adopting new options over periods of a decade are not uncommon
(67). Farmers may not adopt technologies for a host of reasons, which may be related to downside
risk, unknown benefits, labor and cash constraints, costs of implementation, increased management
needs, lack of fit with farmer objectives and sociocultural norms, and lack of incentives and markets,
for example. More importantly, long-term environmental impacts may not be high on farmers’
agendas in many cases, but are a cobenefit and not necessarily the key entry point for improving
their systems. Studies on farmer behavior, decision-making and environmental and sociocultural
perceptions (88) are desperately needed to address this challenge.
5.1.1. Getting the policy framework right. Policies at different levels have a massive role to
play in making sure that the incentives and regulations exist for promoting growth of the livestock
sector at a lower environmental cost. Most of the work done so far on supply-side policies has
been on taxes and subsidies and their potential role in reducing land use changes and emissions
(46, 89). It is essential that studies of this kind are taken a step forward toward pilot studies with
real cases implementing these strategies to understand better how they work, and for identifying
perverse incentives and unexpected impacts on different types of producers, for example.
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Policy interventions are also needed on the demand side, in particular in affluent economies,
for promoting the sustainable consumption of livestock products. Dietary changes hold a large
theoretical potential for mitigating environmental impacts, which has been shown in numerous
studies (86, 90–95). However, most of these analyses have been based on purely hypothetical
changes in diets, with little consideration to existing constraints, such as consumer preferences,
which tend to be conservative. Relatively little is known about the effectiveness of different policy
options for guiding diets toward low-impact food, although knowledge may be drawn from health-
oriented analyses (96, 97). Price-based policy instruments such as consumption taxes differentiated
by impact levels are likely to be essential policy components, as they may be more effective and
economically efficient than other options. However, hitherto, very few, and rather limited, studies
have been carried out on such options (98, 99), and more comprehensive analyses of the potentials,
administrative and social costs, and implementation hurdles of such interventions are needed.
5.1.2. Value chain/stakeholder harmonization. As the livestock sector increases in complex-
ity and sophistication in terms of consumer demands, production methods, sectoral integration,
and regulations, improved value chains and communication between stakeholders also become
more critical. Understanding the perceptions, incentives, and the political economies of different
actors involved in a particular location of the sector could determine whether desired sustain-
ability outcomes are achieved. Public and private sector stakeholders, pressure groups, farm-
ers associations, supermarkets and other retailers, support services, and consumers help shape
the way in which we act (or not) with regard to livestock. Consensus and harmonization will
be required to develop a viable, credible strategy and to implement an appropriate agenda of
action, and multi-stakeholder platforms, such as the Global Agenda for Sustainable Livestock
(http://www.livestockdialogue.org), have a significant role to play in this.
5.1.3. Multi-currency approaches, beyond single metrics. We know enough about impacts
of livestock on individual environmental metrics such as GHG emissions, nitrogen balances, wa-
ter productivity, etc. However, there is no single best indicator that describes the environmental
performance of livestock systems, and there are always trade-offs between them (100); choice of in-
dicator may compromise another key environmental dimension. With our current knowledge, the
agenda is mature enough to move to multi-currency frameworks with indicators covering liveli-
hoods, economics, human nutrition, sociocultural function, and a range of environmental metrics.
5.1.4. From single interventions to testing packages of options. Similarly to the above, there
are many instances that require the study of packages of interventions, rather than studying them
in isolation. It is essential that we quantify the constraints in implementing these potentially more
complex practices and weigh them against the additive impacts they might have. Some notion of a
household-level or systems-level framework for studying these seems essential, as well as methods
for upscaling the potential impacts.
5.1.5. Data consolidation. There is a wealth of information on the environmental impacts of
livestock systems. This information needs to be collated, consolidated, and expanded for the
benefit of the research community. The study of environmental impacts in livestock systems can
be expensive and time consuming, and any effort to share and compare data for subsequent studies
would reduce significantly the costs in estimating these metrics and would advance the agendas of
those interested in improving the environmental performance of livestock systems.
196 Herrero et al.
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SUMMARY POINTS
1. The livestock sector is large and growing at an accelerated rate due to the increased
demand of a fast-growing and affluent human population for animal products.
2. The contribution of different livestock systems to the supply of livestock products varies
widely. Most meat and milk come from mixed crop-livestock production systems and
industrial systems. Grazing systems contribute relatively little to food supply globally,
but they occupy most of the land and play key social roles, especially in very extensive
conditions.
3. Livestock systems emit 8–18% of GHGs and use 25–32% of global fresh water.
4. Livestock systems have vastly different resource-use efficiencies, which in large part drive
their environmental performance per unit of product.
5. Mixed crop-livestock systems are the major source of GHGs, but their emissions intensi-
ties are usually lower than those of grazing systems. Monogastric systems have the lowest
GHG intensities.
6. Large-scale adoption of many intensification technologies that could lead to improved
environmental performance remain relatively slow, especially in large parts of the devel-
oping world.
7. The livestock and environment agenda of the past 10 years has been dominated by the
assessment and quantification of the environmental impacts of livestock. A large body of
novel information has been produced, but the design and adoption of practical sustainable
solutions remain a considerable challenge.
FUTURE ISSUES
1. Research on the most efficient, equitable, and gender-sensitive pathways for transitioning
to more sustainable livestock systems is urgently needed. We understand the current
status reasonably well and have an idea of what might constitute a more sustainable
system, but we do not know well how to get there.
2. Incentives and other policies for effecting consumption changes of livestock products
are urgently needed to ensure that livestock contributes to the sustainable and nutritious
diets of different age groups of the human population, and that they are regionally and
culturally sensitive.
3. The costs and benefits associated with adopting more environmentally friendly practices,
including land use changes, need considerable research. These need to be studied with
multidimensional environmental, economic, and social indicators.
4. From a technical standpoint, the study of the impacts of livestock on biodiversity remains
a large missing link. This needs to be rectified.
5. We must explore what the impacts are of climate variability and change on the environ-
mental performance of livestock systems.
www.annualreviews.org •What Have We Learned in the Past Decade? 197
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EG40CH07-Herrero ARI 14 October 2015 9:14
DISCLOSURE STATEMENT
The authors are not aware of any affiliations, memberships, funding, or financial holdings that
might be perceived as affecting the objectivity of this review.
LITERATURE CITED
1. Gerber PJ, Steinfeld H, Henderson B, Mottet A, Opio C, et al. 2013. Tackling Climate Change Through
Livestock—A Global Assessment of Emissions and Mitigation Opportunities. Rome, Italy: FAO
2. De Haan C, Steinfeld H, Blackburn H. 1997. Livestock and the Environment: Finding a Balance.Rome,
Italy: FAO
3. Steinfeld H, Gerber P, Wassenaar T, Castel V, Rosales M, De Haan C. 2006. Livestock’s Long Shadow:
Environmental Issues and Options. Rome,Italy:FAO
4. Delgado C, Rosegrant M, Steinfeld H, Ehui S, Cour C. 1999. Livestock to 2020: The Next Food Revolution.
Food Agric. Environ. Discuss. Pap. 28, Intl. Food Policy Res. Inst.
5. Garnett T, Appleby MC, Balmford A, Bateman IJ, Benton TG, et al. 2013. Sustainable intensification
in agriculture: premises and policies. Science 341:33–34
6. Keating B, Herrero M, Carberry PS, Gardner J, Cole MB. 2014. Food wedges: framing the global food
demand and supply challenge towards 2050. Glob. Food Sec. 3(3–4):125–32
7. Godfray HCJ, Beddington JR, Crute IR, Haddad L, Lawrence D, et al. 2010. Food security: the challenge
of feeding 9 billion people. Science 327(5967):812–18
8. Alexandratos N, Bruinsma J. 2012. World Agriculture Towards 2030/2050: The 2012 Revision. Rome, Italy:
FAO
9. Intl. Asess. Agric. Sci. Technol. Dev. 2010. Agriculture at a Crossroads: Global Report. Washington, DC:
Island Press
10. Herrero M, Havl´
ık P, Valin H, Notenbaert A, Rufino MC, et al. 2013. Biomass use, production, feed
efficiencies, and greenhouse gas emissions from global livestock systems. Proc. Natl. Acad. Sci. USA
110(52):20888–93
11. Wirsenius S. 2003. The biomass metabolism of the food system: a model-based survey of the global and
regional turnover of food biomass. J. Ind. Ecol. 7(1):47–80
12. Bradford G. 1999. Contributions of animal agriculture to meeting global human food demand. Livest.
Prod. Sci. 59(2–3):95–112
13. Peralta JM, Reynolds J, Kerr CV. 2013. Sustainability and animal agriculture. Encycl. Food Agric. Ethics
2013:1–8
14. Bouwman AF, Goldewijk KK, Van Der Hoek KW, Beusen HW, Van Vuuren DP, et al. 2013. Exploring
global changes in nitrogen and phosphorus cycles in agriculture induced by livestock production over
the 1900–2050 period. Proc. Natl. Acad. Sci. USA 110(52):20882–87
15. Bouwman AF, Van der Hoek KW, Eickhout B, Soenario I. 2005. Exploring changes in world ruminant
production systems. Agric. Syst. 84(2):121–53
16. Wirsenius S. 2000. Human Use of Land and Organic Materials: Modeling the Turnover of Biomass in the
Global Food System. Gothenburg, Swed.: Chalmers Univ. Technol.
17. De Vries M, de Boer IJM. 2010. Comparing environmental impacts for livestock products: a review of
life cycle assessments. Livest. Sci. 128(1–3):1–11
18. Van Zanten HHE, Mollenhorst H, Klootwijk CW, van Middelaar CE, de Boer IJM. 2015. Global food
security: land the efficiency of livestock systems. Int. J. Life Cycle Assess. In press. doi: 10.1007/s11367-
015-0944-1
19. Gerber PJ, Uwizeye A, Schulte RPO, Opio CI, de Boer IJM. 2014. Nutrient use efficiency: a valuable
approach to benchmark the sustainability of nutrient use in global livestock production? Curr. Opin.
Environ. Sustain. 9–10:122–30
20. Galloway JN, Aber JD, Erisman JANW, Sybil P, Howarth RW, et al. 2003. The nitrogen cascade.
Bioscience 53(4):341–56
198 Herrero et al.
Annu. Rev. Environ. Resourc. 2015.40:177-202. Downloaded from www.annualreviews.org
Access provided by CSIRO on 11/05/15. For personal use only.
EG40CH07-Herrero ARI 14 October 2015 9:14
21. Velthof GL, Oudendag D, Witzke HP, Asman WAH, Klimont Z, Oenema O. 2009. Integrated as-
sessment of nitrogen losses from agriculture in EU-27 using MITERRA-EUROPE. J. Environ. Qual.
38:402–17
22. Steinfeld H, Mooney HA, Schneider F, Neville LE. 2010. Livestock in a Changing Landscape,Vol.1:
Drivers, Consequences, and Responses. Washington, DC: FAO
23. Hoekstra AY. 2009. Human appropriation of natural capital: a comparison of ecological footprint and
water footprint analysis. Ecol. Econ. 68(7):1963–74
24. Falkenmark M. 1995. Land-water linkages: a synopsis. Land and water integration and river basin man-
agement. FAO L. Water Bull. 1:15–16
25. Bayart J-B, Bulle C, Deschˆ
enes L, Margni M, Pfister S, et al. 2010. A framework for assessing off-stream
freshwater use in LCA. Int. J. Life Cycle Assess. 15(5):439–53
26. De Fraiture C, Wichelns D, Benedict Kemp E, Rockstrom J. 2007. Scenarios on water for food and
environment. In Water for Food, Water for Life: A Comprehensive Assessment of Water Management in
Agriculture, ed. D Molden, pp. 91–145. London: Earthscan
27. De Boer IJM, Hoving IE, Vellinga TV, Van de Ven GWJ, Leffelaar PA, Gerber PJ. 2012. Assessing
environmental impacts associated with freshwater consumption along the life cycle of animal products:
the case of Dutch milk production in Noord-Brabant. Int. J. Life Cycle Assess. 18(1):193–203
28. Pfister S, Koehler A, Hellweg S. 2009. Assessing the environmental impacts of freshwater consumption
in LCA. Environ. Sci. Technol. 43(11):4098–104
29. Thornton PK, van de Steeg J, Notenbaert A, Herrero M. 2009. The impacts of climate change on
livestock and livestock systems in developing countries: a review of what we know and what we need to
know. Agric. Syst. 101(3):113–27
30. IPCC. 2014. Summary for policymakers. In Climate Change 2014: Impacts, Adaptation, and Vulnerability.
Part A: Global and Sectoral Aspects. Contribution of Working Group II to the Fifth Assessment Report of
the Intergovernmental Panel on Climate Change, ed. CB Field, VR Barros, DJ Dokken, KJ Mach, MD
Mastrandrea, et al., pp. 1–32. Cambridge, UK: Cambridge Univ.
31. Kurukulasuriya P, Rosenthal S. 2003. Climate change and agriculture: a review of impacts and adaptations.
Work. Pap. 78739, Environ. Dep., World Bank
32. Washington R, Harrison M, Conway D, Black E, Challinor A, et al. 2006. African climate change: taking
the shorter route. Bull. Am. Meteorol. Soc. 87(May):1355–66
33. Mendelsohn R, Dinar A, ed. 2012. Handbook on Climate Change and Agriculture. Cheltenham, UK: Edward
Elgar Publ.
34. Thornton PK, Herrero M. 2014. Climate change adaptation in mixed crop-livestock systems in devel-
oping countries. Glob. Food Sec. 3(2):99–107
35. Dumont B, Gonz´
alez-Garc´
ıa E, Thomas M, Fortun-Lamothe L, Ducrot C, et al. 2014. Forty research
issues for the redesign of animal production systems in the 21st century. Animal 29:1–12
36. Darnhofer I, Bellon S, Dedieu B, Milestad R. 2010. Adaptiveness to enhance the sustainability of farming
systems. A review. Agron. Sustain. Dev. 30:545–55
37. Rickards L, Howden SM. 2012. Transformational adaptation: agriculture and climate change. Crop
Pasture Sci. 63(March):240–50
38. Kates RW, Travis WR, Wilbanks TJ. 2012. Transformational adaptation when incremental adaptations
to climate change are insufficient. Proc. Natl. Acad. Sci. USA 109(19):7156–61
39. Vermeulen SJ, Challinor AJ, Thornton PK, Campbell BM, Eriyagama N, et al. 2013. Addressing un-
certainty in adaptation planning for agriculture. Proc. Natl. Acad. Sci. USA 110(21):8357–62
40. Claessens L, Antle JM, Stoorvogel JJ, Valdivia RO, Thornton PK, Herrero M. 2012. A method for
evaluating climate change adaptation strategies for small-scale farmers using survey, experimental and
modeled data. Agric. Syst. 111:85–95
41. Herrero M, Thornton PK, Bernu´
es A, Baltenweck I, Vervoort J, et al. 2014. Exploring future changes in
smallholder farming systems by linking socio-economic scenarios with regional and household models.
Glob. Environ. Change 24(1):165–82
42. McIntire J, Bourzat D, Pingalii P. 1992. Crop-Livestock Interaction in Sub-Saharan Africa. Washington,
DC: The World Bank
www.annualreviews.org •What Have We Learned in the Past Decade? 199
Annu. Rev. Environ. Resourc. 2015.40:177-202. Downloaded from www.annualreviews.org
Access provided by CSIRO on 11/05/15. For personal use only.
EG40CH07-Herrero ARI 14 October 2015 9:14
43. Baltenweck I, Staal S, Ibrahim MNM, Herrero M, Holmann F, Jabbar M. 2003. Crop-livestock intensifi-
cation and interaction across three continents. Proj. Rep. ILRI, CIAT, IITA, BAIF
44. Searchinger TD, Estes L, Thornton PK, Beringer T, Notenbaert A, et al. 2015. High carbon and
biodiversity costs from converting Africa’s wet savannahs to cropland. Nat. Clim. Change 5:481–86
45. Havl´
ık P, Valin H, Mosnier A, Obersteiner M, Baker JS, et al. 2013. Crop productivity and the global
livestock sector: implications for land use change and greenhouse gas emissions. Am.J.Agric.Econ.
95(2):442–48
46. Havl´
ık P, Valin H, Herrero M, Obersteiner M, Schmid E, et al. 2014. Climate change mitigation through
livestock system transitions. Proc. Natl. Acad. Sci. USA 111(10):3709–14
47. Herrero M, Thornton PK. 2013. Livestock and global change: emerging issues for sustainable food
systems. Proc. Natl. Acad. Sci. USA 110:20878–81
48. Lecl`
ere D, Havl´
ık P, Fuss S, Schmid E, Mosnier A, et al. 2014. Climate change induced transformations
of agricultural systems: insights from a global model. Environ. Res. Lett. 9(12):124018
49. Weindl I, Lotze-Campen H, Popp A, Muller C, Havlik P, et al. 2015. Livestock in a changing climate:
production system transitions as an adaptation strategy for agriculture. Environ. Res. Lett. 10:094021
50. Thornton PK, Ericksen PJ, Herrero M, Challinor AJ. 2014. Climate variability and vulnerability to
climate change: a review. Glob. Chang. Biol. 20:3313–28
51. Wood S, Ericksen P, Stewart B, Thornton P, Anderson M. 2010. Lessons learned from international
assessments. In Food Security and Global Environmental Change, ed. J Ingram, P Ericksen, D Liverman,
pp. 46–62. London: Earthscan
52. Van Wijk MT, Rufino MC, Enahoro D, Parsons D, Silvestri S, et al. 2014. Farm household models to
analyse food security in a changing climate: a review. Glob. Food Sec. 3:77–84
53. Martin G, Magne MA. 2015. Agricultural diversity to increase adaptive capacity and reduce vulnerability
of livestock systems against weather variability—a farm-scale simulation study. Agric. Ecosyst. Environ.
199:301–11
54. Carberry PS, Hochman Z, McCown RL, Dalgliesh NP, Foale MA, et al. 2002. The FARMSCAPE
approach to decision support: farmers’, advisers’, researchers’ monitoring, simulation, communication
and performance evaluation. Agric. Syst. 7 4:141–77
55. Fenner K, Canonica S, Wackett LP, Elsner M. 2013. Evaluating pesticide degradation in the environ-
ment: blind spots and emerging opportunities. Science 341(6147):752–58
56. Olivier JGJ, Van Aardenne JA, Dentener FJ, Pagliari V, Ganzeveld LN, Peters JAHW. 2005. Recent
trends in global greenhouse gas emissions: regional trends 1970–2000 and spatial distribution of key
sources in 2000. Environ. Sci. 2:81–99
57. Baumert KA, Herzog T, Pershing J. 2005. Navigating the Numbers: Greenhouse Gas Data and International
Climate Policy. Washington, DC: World Res. Inst.
58. US Environ. Protect. Agency (EPA). 2006. Global Anthropogenic Non-CO2Greenhouse Gas Emissions:
1990–2020. Washington, DC: EPA
59. O’Mara FP. 2011. The significance of livestock as a contributor to global greenhouse gas emissions today
and in the near future. Anim. Feed Sci. Technol. 166–167:7–15
60. Pitesky ME, Stackhouse KR, Mitloehner F. 2009. Chapter 1. Clearing the air. Livestock’s contribution
to climate change. Adv. Agronomy 103:1–40
61. Goodland R, Anhang J. 2009. Livestock and climate change. World Watch 22:10–19
62. Herrero M, Gerber P, Vellinga T, Garnett T, Leip A, et al. 2011. Livestock and greenhouse gas emissions:
the importance of getting the numbers right. Anim. Feed Sci. Technol. 166–167:779–82
63. Gerber P, Henderson B, Makkar H. 2013. Mitigation of Greenhouse Gas Emissions in Livestock Production—
A Review of Technical Options for Non-CO2Emissions. Washington, DC: FAO
64. Martin C, Morgavi DP, Doreau M. 2010. Methane mitigation in ruminants: from microbe to the farm
scale. Animal 4(3):351–65
65. Cottle DJ, Nolan JV, Wiedemann SG. 2011. Ruminant enteric methane mitigation: a review. Anim.
Prod. Sci. 51:491–514
66. Boadi D, Benchaar C, Chiquette J, Mass´
e D. 2004. Mitigation strategies to reduce enteric methane
emissions from dairy cows: update review. Can. J. Anim. Sci. 84:319–35
200 Herrero et al.
Annu. Rev. Environ. Resourc. 2015.40:177-202. Downloaded from www.annualreviews.org
Access provided by CSIRO on 11/05/15. For personal use only.
EG40CH07-Herrero ARI 14 October 2015 9:14
67. Thornton PK, Herrero M. 2010. Potential for reduced methane and carbon dioxide emissions from
livestock and pasture management in the tropics. Proc. Natl. Acad. Sci. USA 107(46):19667–72
68. Bl ¨
ummel M, Anandan S, Prasad CS. 2009. Potential and limitations of by-product based feeding systems to
mitigate green house gases for improved livestock productivity. Presented at Bienn. Anim. Nutr. Conf. Anim.
Nutr. Soc. Ind. Divers. Anim. Nutr. Res. Chang. Scen., 13th, Bangalore, Ind.
69. Alcock DJ, Hegarty RS. 2011. Potential effects of animal management and genetic improvement on
enteric methane emissions, emissions intensity and productivity of sheep enterprises at Cowra, Australia.
Anim. Feed Sci. Technol. 166–67:749–60
70. Ripple WJ, Smith P, Haberl H, Montzka SA, McAlpine C, Boucher DH. 2013. Ruminants, climate
change and climate policy. Nat. Clim. Change 4(1):2–5
71. Smith P, Martino D, Cai Z, Gwary D, Janzen H, et al. 2008. Greenhouse gas mitigation in agriculture.
Philos.Trans.R.Soc.Lond.B.363(1492):789–813
72. Chadwick DR. 2005. Emissions of ammonia, nitrous oxide and methane from cattle manure heaps: effect
of compaction and covering. Atmos. Environ. 392005:787–99
73. Chadwick D, Sommer S, Thorman R, Fangueiro D, Cardenas L, et al. 2011. Manure management:
implications for greenhouse gas emissions. Anim. Feed Sci. Technol. 166–67:514–31
74. Thomsen IK, Pedersen AR, Nyord T, Petersen SO. 2010. Effects of slurry pre-treatment and application
technique on short-term N2O emissions as determined by a new non-linear approach. Agric. Ecosyst.
Environ. 136:227–35
75. Clemens J, Trimborn M, Weiland P, Amon B. 2006. Mitigation of greenhouse gas emissions by anaerobic
digestion of cattle slurry. Agric. Ecosyst. Environ. 112:171–77
76. Van Groenigen JW, Velthof GL, Oenema O, Van Groenigen KJ, Van Kessel C. 2010. Towards an
agronomic assessment of N2O emissions: a case study for arable crops. Eur. J. Soil Sci. 61(6):903–13
77. Smith KA, Conen F. 2004. Impacts of land management on fluxes of trace greenhouse gases. Soil Use
Manag. 20:255–63
78. Snyder CS, Bruulsema TW, Jensen TL, Fixen PE. 2009. Review of greenhouse gas emissions from crop
production systems and fertilizer management effects. Agric. Ecosyst. Environ. 133(3–4):247–66
79. Clough TJ, Ray JL, Buckthought LE, Calder J, Baird D, et al. 2009. The mitigation potential of hippuric
acid on N2O emissions from urine patches: an in situ determination of its effect. Soil Biol. Biochem.
41(10):2222–29
80. Henderson B, Gerber P, Hilinski T, Falcucci A, Ojima D, et al. 2015. Greenhouse gas mitigation
potential of the world’s grazing lands: modelling soil carbon and nitrogen fluxes of mitigation practices.
Agric. Ecosyst. Environ. 207:91–100
81. Smith P, Haberl H, Popp A, Erb K, Lauk C, et al. 2013. How much land-based greenhouse gas mitigation
can be achieved without compromising food security and environmental goals? Global Change Biol.
19:2285–302
82. Foresight. 2011. The future of food and farming: challenges and choices for global sustainability. Proj. Rep.,
Gov. Off. Sci.
83. Foley JA, Ramankutty N, Brauman KA, Cassidy ES, Gerber JS, et al. 2011. Solutions for a cultivated
planet. Nature 478(7369):337–42
84. Mueller ND, Gerber JS, Johnston M, Ray DK, Ramankutty N, Foley JA. 2012. Closing yield gaps
through nutrient and water management. Nature 490(7419):254–57
85. Hertel TW, Ramankutty N, Baldos ULC. 2014. Global market integration increases likelihood that a
future African Green Revolution could increase crop land use and CO2emissions. Proc. Natl. Acad. Sci.
USA 111(38):13799–804
86. Stehfest E, Bouwman L, Vuuren DP, Elzen MGJ, Eickhout B, Kabat P. 2009. Climate benefits of
changing diet. Clim. Change 95(1–2):83–102
87. Willett WC. 2001. Eat, Drink, and Be Healthy: The Harvard Medical School Guide to Healthy Eating.New
York: Free Press
88. Solano C, Bernu´
es A, Rojas F, Joaqu´
ın N, Fernandez W, Herrero M. 2000. Relationships between
management intensity and structural and social variables in dairy and dual-purpose systems in Santa
Cruz, Bolivia. Agric. Syst. 65(3):159–77
www.annualreviews.org •What Have We Learned in the Past Decade? 201
Annu. Rev. Environ. Resourc. 2015.40:177-202. Downloaded from www.annualreviews.org
Access provided by CSIRO on 11/05/15. For personal use only.
EG40CH07-Herrero ARI 14 October 2015 9:14
89. Cohn AS, Mosnier A, Havl´
ık P, Valin H, Herrero M, et al. 2014. Cattle ranching intensification in
Brazil can reduce global greenhouse gas emissions by sparing land from deforestation. Proc. Natl. Acad.
Sci. USA 111:7236–41
90. Tukker A, Bausch-Goldbohm S, Verheijden M, Koning A de, Kleijn R, et al. 2009. Environmental impacts
of diet changes in the EU. Rep. 23783 EN, Inst. Prospect. Technol. Stud. Eur. Comm.
91. Westhoek H, Lesschen JP, Rood T, Wagner S, De Marco A, et al. 2014. Food choices, health and
environment: effects of cutting Europe’s meat and dairy intake. Glob. Environ. Change 26(1):196–205
92. Berners-Lee M, Hoolohan C, Cammack H, Hewitt CN. 2012. The relative greenhouse gas impacts of
realistic dietary choices. Energy Policy 43:184–90
93. Popp A, Lotze-Campen H, Bodirsky B. 2010. Food consumption, diet shifts and associated non-CO2
greenhouse gases from agricultural production. Glob. Environ. Change 20(3):451–62
94. Hedenus F, Wirsenius S, Johansson DJA. 2014. The importance of reduced meat and dairy consumption
for meeting stringent climate change targets. Clim. Change 124:79–91
95. Green R, Milner J, Dangour AD, Haines A, Chalabi Z, et al. 2015. The potential to reduce greenhouse
gas emissions in the UK through healthy and realistic dietary change. Clim. Change 129:253–65
96. Thow AM, Downs S, Jan S. 2014. A systematic review of the effectiveness of food taxes and subsidies to
improve diets: understanding the recent evidence. Nutr. Rev. 72(9):551–65
97. World Health Organization (WHO). 2015. Using Price Policies to Promote Healthier Diets. Copenhagen,
Den.: WHO
98. Wirsenius S, Hedenus F, Mohlin K. 2011. Greenhouse gas taxes on animal food products: rationale, tax
scheme and climate mitigation effects. Clim. Change 108:159–84
99. Edjabou LD, Smed S. 2013. The effect of using consumption taxes on foods to promote climate friendly
diets—the case of Denmark. Food Policy 39:84–96
100. Herrero M, Thornton PK, Gerber P, Reid RS. 2009. Livestock, livelihoods and the environment: un-
derstanding the trade-offs. Curr. Opin. Environ. Sustain 1:111–20
101. Mekonnen MM, Hoekstra AY. 2012. A global assessment of the water footprint of farm animal products.
Ecosystems 15:401–15
102. Cederberg C, Sonesson U, Henriksson M, Sund V, Davis J. 2009. Greenhouse Gas Emissions from Swedish
Production of Meat, Milk and Eggs 1990 and 2005. Gothenburg: SIK
103. Flysj ¨
o A, Henriksson M, Cederberg C, Ledgard S, Englund J-E. 2011. The impact of various parameters
on the carbon footprint of milk production in New Zealand and Sweden. Agric. Syst. 104(6):459–69
104. Bryngelsson D, Wirsenius S, Hedenus F, Sonesson U. 2015. How small can the climate impact of food
be made through changes in diets and technology? Food Policy. In press
105. Sasu-Boakye Y, Cederberg C, Wirsenius S. 2014. Localising livestock protein feed production and the
impact on land use and greenhouse gas emissions. Animal 8:1339–48
202 Herrero et al.
Annu. Rev. Environ. Resourc. 2015.40:177-202. Downloaded from www.annualreviews.org
Access provided by CSIRO on 11/05/15. For personal use only.
EG40-FrontMatter ARI 23 October 2015 13:7
Annual Review of
Environment
and Resources
Volume 40, 2015
Contents
II. Earth’s Life Support Systems
Environmental Change in the Deep Ocean
Alex David Rogers pppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp1
Rewilding: Science, Practice, and Politics
Jamie Lorimer, Chris Sandom, Paul Jepson, Chris Doughty,
Maan Barua, and Keith J. Kirby pppppppppppppppppppppppppppppppppppppppppppppppppppppppppp39
Soil Biodiversity and the Environment
Uffe N. Nielsen, Diana H. Wall, and Johan Six pppppppppppppppppppppppppppppppppppppppppppp63
State of the World’s Amphibians
Alessandro Catenazzi pppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp91
III. Human Use of the Environment and Resources
Environmental Burden of Traditional Bioenergy Use
Omar R. Masera, Rob Bailis, Rudi Drigo, Adrian Ghilardi,
and Ilse Ruiz-Mercado ppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp121
From Waste to Resource: The Trade in Wastes and Global Recycling
Economies
Nicky Gregson and Mike Crang pppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp151
Livestock and the Environment: What Have We Learned in the Past
Decade?
Mario Herrero, Stefan Wirsenius, Benjamin Henderson, Cyrille Rigolot,
Philip Thornton, Petr Havl´ık, Imke de Boer, and Pierre Gerber pppppppppppppppppppppp177
Safe Drinking Water for Low-Income Regions
Susan Amrose, Zachary Burt, and Isha Ray ppppppppppppppppppppppppppppppppppppppppppppppp203
Transforming Consumption: From Decoupling, to Behavior Change,
to System Changes for Sustainable Consumption
Dara O’Rourke and Niklas Lollo ppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp233
Universal Access to Electricity: Closing the Affordability Gap
Subarna Mitra and Shashi Buluswar pppppppppppppppppppppppppppppppppppppppppppppppppppppp261
Urban Heat Island: Mechanisms, Implications, and Possible Remedies
Patrick E. Phelan, Kamil Kaloush, Mark Miner, Jay Golden, Bernadette Phelan,
Humberto Silva III, and Robert A. Taylor pppppppppppppppppppppppppppppppppppppppppppppp285
vi
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EG40-FrontMatter ARI 23 October 2015 13:7
IV. Management and Governance of Resources and Environment
Broader, Deeper and Greener: European Union Environmental
Politics, Policies, and Outcomes
Henrik Selin and Stacy D. VanDeveer pppppppppppppppppppppppppppppppppppppppppppppppppppp309
Environmental Movements in Advanced Industrial Democracies:
Heterogeneity, Transformation, and Institutionalization
Marco Giugni and Maria T. Grasso ppppppppppppppppppppppppppppppppppppppppppppppppppppppp337
Integrating Global Climate Change Mitigation Goals with Other
Sustainability Objectives: A Synthesis
Christoph von Stechow, David McCollum, Keywan Riahi, Jan C. Minx,
Elmar Kriegler, Detlef P. van Vuuren, Jessica Jewell, Carmenza Robledo-Abad,
Edgar Hertwich, Massimo Tavoni, Sevastianos Mirasgedis, Oliver Lah,
Joyashree Roy, Yacob Mulugetta, Navroz K. Dubash, Johannes Bollen,
Diana ¨
Urge-Vorsatz, and Ottmar Edenhofer pppppppppppppppppppppppppppppppppppppppppp363
Opportunities for and Alternatives to Global Climate Regimes
Post-Kyoto
Axel Michaelowa pppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp395
V. Methods and Indicators
Designer Ecosystems: Incorporating Design Approaches into Applied
Ecology
Matthew R.V. Ross, Emily S. Bernhardt, Martin W. Doyle,
and James B. Heffernan ppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppppp419
Inclusive Wealth as a Metric of Sustainable Development
Stephen Polasky, Benjamin Bryant, Peter Hawthorne, Justin Johnson,
Bonnie Keeler, and Derric Pennington pppppppppppppppppppppppppppppppppppppppppppppppppp445
Regional Dynamical Downscaling and the CORDEX Initiative
Filippo Giorgi and William J. Gutowski Jr. ppppppppppppppppppppppppppppppppppppppppppppppp467
Indexes
Cumulative Index of Contributing Authors, Volumes 31–40 ppppppppppppppppppppppppppp491
Cumulative Index of Article Titles, Volumes 31–40 ppppppppppppppppppppppppppppppppppppp496
Errata
An online log of corrections to Annual Review of Environment and Resources articles may
be found at http://www.annualreviews.org/errata/environ
Contents vii
Annu. Rev. Environ. Resourc. 2015.40:177-202. Downloaded from www.annualreviews.org
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