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doi:10.1093/biosci/biz044 Advance Access publication 22 May 2019
The Ecological Paw Print of
Companion Dogs and Cats
PIM MARTENS, BINGTAO SU, AND SAMANTHA DEBLOMME
As an indicator of sustainable development, the ecological footprint has been successful in providing a basis for discussing the environmental
impacts of human consumption. Humans are at the origin of numerous pollutant activities on Earth and are the primary drivers of climate
change. However, very little research has been conducted on the environmental impacts of animals, especially companion animals. Often
regarded as friends or family members by their owners, companion animals need significant amounts of food in order to sustain their daily
energy requirement. The ecological paw print (EPP) could therefore serve as a useful indicator for assessing the impacts of companion animals
on the environment. In the present article, we explain the environmental impact of companion dogs and cats by quantifying their dietary EPP
and greenhouse gas (GHG) emissions according to primary data we collected in China, the Netherlands, and Japan and discuss how to reduce
companion dietary EPP and GHG emissions in order to understand the sustainability of the relationship between companion animals and the
environment.
Keywords: ecological paw print, greenhouse gas emissions, environment, dogs, cats
Companion animals are part of human societies
around the world (Amiot et al. 2016). Pets provide
a host of benefits to people including companionship,
improved mental and physical health, expanded social net-
works, and even benefitting child and teenage development
(Wood et al. 2005, Cutt et al. 2007, Beverland etal. 2008,
Okin 2017). Statistics describing companion animal num-
bers worldwide are scarce, and they fluctuate, but accord-
ing to the data from Vetnosis and the European Pet Food
Industry Federation, there were 223 million registered com-
panion dogs and 220 million registered companion cats in
the world in 2014. Dogs and cats are often regarded as fam-
ily members, and most owners show great concern for their
pet’s well-being, including the food and water requirements
of their pet, their living spaces, their health conditions, and
even their pet’s emotions and feelings (Flynn 2000, Martens
et al. 2016, Su et al. 2018a). Providing complete nutrition
during all stages of their lives is a common and effective way
for owners to have caring and loving relationships with their
animals (Fleeman and Owens 2007). Many owners feed their
animals more nutrients than minimum recommendations or
give them ingredients that are suitable for human consump-
tion (Fleeman and Owens 2007, Swanson etal. 2013). Given
the sheer numbers of companion dogs and cats globally and
their potentially nutrient-rich diets, we have ample reason to
suspect that resource consumption by companion animals is
more serious than has been heretofore imagined. However,
Okin (2017) indicated, “It could be argued that dogs and
cats eat meat that humans cannot consume and [that] is
simply a byproduct of production for human use and,
therefore, should not be counted as consumption beyond
that of humans.” But this is only partly true. For bone meal,
an ingredient in most food for cats and dogs, this is true;
humans generally do not eat this. For other ingredients, it
is more complex. Some byproducts could be made suitable,
after processing, for human consumption. Therefore, it is of
vital importance to identify companion animals’ resource
consumption and environmental impacts and to simultane-
ously investigate how current pet food production systems
can sustainably support their nutritional requirements.
The ecological footprint (EF) is a popular natural resource
accounting tool that is used to measure environmental
sustainability. Specifically, it is the total area of produc-
tive land and water required to continuously produce all
resources consumed and to assimilate all waste produced by
a defined population wherever on Earth that land is located
(Wackernagel and Rees 1998b, Csutora et al. 2009). The
dietary ecological paw print (EPP) is based on the EF and
measures how much biologically productive land is used
for companion animals’ food consumption. The diet of an
animal greatly affects its EPP, according to the animals’
particular metabolic needs or dietary preferences and the
availability of resources (Swanson etal. 2013, Vale and Vale
2009). Meat-based diets require more energy and water
AQ1
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and, therefore, have far greater environmental impacts than
plant-based diets (Pimentel and Pimentel 2003, Reijnders
and Soret 2003, Wirsenius etal. 2010, Okin 2017). For exam-
ple, in China, commercial pet dry food has higher percent-
ages of animal meat products than human foods. Therefore,
the dietary EPP and greenhouse gas (GHG) emissions of
companion dogs relying on commercial dry food was found
to be much higher than the dogs relying on human leftover
foods (Su et al. 2018b). If we look at differences between
countries—assuming all companion dogs and cats eat com-
mercial dry food—then the dietary EPP of all companion
dogs and cats in China equals the dietary EF of between 70
million and 245 million Chinese people, in terms of home-
made food (Su etal. 2018b). The carbon emissions resulting
from the food consumption of these animals are equivalent
to the emissions generated by the food consumption of
between 34 million and 107 million Chinese people (Su
etal. 2018b). Meanwhile, in Japan, companion dogs and cats
may consume between 3.6% and 15.6% of the food eaten by
Japanese people, and through their consumption, Japanese
companions release between 2.5 million and 10.7 million
tons of GHG per year (Su and Martens 2018). In the United
States, the energy consumption of companion dogs and cats
is approximately one-fifth of the US population’s energy
consumption, whereas animal meat product consumption
by dogs and cats alone is responsible for up to 80 million
tons of methane and nitrous oxide (Okin 2017). Therefore,
the individual and cumulative environmental impacts of the
commercial dry food consumption by companion animals
and the industries behind its manufacture are significant,
considering the sheer volumes of planetwide pet ownership
(Hammerly and DuMont 2012).
Commercial pet food has become one of the most popu-
lar feeds for companion animals in recent decades, replac-
ing human leftover food. Pet food industry is no longer a
niche market. As was demonstrated in previous studies, it
has become an economic sector of substantial importance
(Leenstra and Vellinga 2011), a commercial system of its
own in many Western countries, and a growing sector in
developing countries. Attention must therefore also be given
to commercial pet food production if we wish to reduce the
EPP of companion animals (of course, their impacts could
be reduced via, e.g., changing pet ownership laws—limits to
how many and types of pets people can own—and creating
better guidelines on pet feeding; see also the next section).
However, the pet food industry is unique with regard to
sustainability, because commercial pet food formulations are
based on consumer demand (e.g., sufficient energy, complete
nutrition, functional and balanced food) and often provide
an excess of nutrients (Hughes 1995). There is, further-
more, a growing obesity trend among companion animals
in Western societies, because they are overconsuming and
therefore potentially wasting resources. Both factors pose a
significant barrier to the sustainable optimization of the pet
food sector and to pet ownership in general (Swanson etal.
2013). Because the number of companion animal owners is
increasing, product sales are expected to grow in the near
future, creating an increasing demand for pet food. Leenstra
and Vellinga (2011) warned that this high demand is already
beginning to exceed the offal available from human meat
and fish consumption that is used to make pet food. Meat
used in pet foods and other plant-based ingredients are now
competing with food suitable for human consumption. The
sustainability of pet food industries, as both food produc-
ers and polluters, should therefore be seriously considered,
because they are now contributing significantly to global
climate change (Swanson et al. 2013). Given the growing
concern for environmental sustainable development, the pet
food industry should consider how to promote technological
progress in pet food production.
The goal of this research is to quantify the relation-
ship between companion food consumption and associated
environmental impacts. In the present study, we provide an
overview of the individual and total companion dogs and
cats’ dietary EPP and GHG emissions in China, Japan, and
the Netherlands, according to primary data we collected
from companion dog and cat owners in these countries. The
framework, findings, and recommendations in the pres-
ent study can serve as a motivational platform for further
research into the environmental impacts of companion ani-
mals from a global perspective.
Calculations of ecological paw prints
To measure the EPP of dogs, Vale and Vale (2009) analyzed
the ingredients of one common UK dog food brand and
assumed that the recommended portions indicated on the
packaging represented the actual quantities fed to compan-
ion animals. Using the square meters (m2) of land needed
to generate the previously converted dry grams into whole
chicken or grains present in the product (taking into account
specific water content), they obtained an EPP of 0.27 hect-
ares (ha) for an average medium-size dog (0.18 for small
dogs and 0.36 for large dogs). They compared this to a dog
having a completely omnivorous human diet and obtained
an EPP of 0.48 ha per year. For cats, they used the same
methodology to calculate the footprint of a 1-year supply of
dry cat food and obtained 0.3 ha per year. Vale and Vale also
assessed the footprint of the packaging but concluded that
it was too small an amount to be significant. For tinned cat
food, they assumed 80% moisture and converted the protein
content into its raw meat equivalent. Assuming a cat is fed
one 400-gram tin daily for a year, they calculated a paw print
of 0.84 ha per year for beef, 0.13 ha per year for all other
livestock meats, and 0.54 ha per year for fish meat.
Vale and Vale’s (2009) results were published in numerous
press articles (e.g., Alton 2009, Peeples 2009) and sparked an
uproar among the media and from pet owners. The results
of their study were later confirmed by John Barrett of the
Stockholm Environment Institute (United Kingdom) in New
Scientist magazine (Alton 2009). His calculations, based on
his own data, showed essentially the same (relatively high)
EPP results, mainly because of the high carbon footprint of
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meat. Nevertheless, the accuracy of his and Vale and Vale’s
calculations was criticized on different aspects: the over-
estimation of the number of calories a dog requires daily;
calculations being based on data for human-made meat
instead of meat by-products; and the omission of the foot-
prints produced by processing the ingredients, manufactur-
ing it into food, packaging it, and transporting it (Ravilious
2009, William-Derry 2009, Rastogi 2010, Rushforth and
Moreau 2013, Beynen 2015). Moreover, Vale and Vale (2009)
assumed that owners fed their companions exactly as recom-
mended by the pet food industry; however, many house-
holds choose noncommercial diets or supplement their pets’
diets with table leftovers.
Three studies were carried out in response to these criti-
cisms. The first was conducted by Arizona State University,
investigating the EPP for dry dog food. Rushforth and
Moreau (2013) used a hybrid economic input–output life
cycle assessment to examine the supply chain and energy
production associated with pet food manufacturing, within
a particular factory. The goal of this study was to respond to
criticism of Vale and Vale’s methodology. Using the protein
content values for different livestock meats, they calculated
the meat needed in order to match the protein levels required
in a certain number of tons of pet food per year, then esti-
mated land-use requirements and the carbon and water foot-
prints for this quantity of meat. An interesting finding from
Rushforth and Moreau (2013) is that using lean meat in dog
food was better—in terms of environmental impacts—than
using offal, because its protein content more easily satisfies a
dog’s protein requirements. In addition, they found dog food
manufacturing processes to have significantly high carbon
footprints among all pet food manufacturers. Along with
careful selection of meat sources, they recommended alterna-
tive energy systems as possible methods to reduce the carbon
footprint of industrially manufactured pet foods (Rushforth
and Moreau 2013). In their results, they reported a value
of 1.06 ha of land required for a pet food manufacturer to
produce 1 ton of dog food, which is 11.72 m2 per kilogram.
The second study was published by Wageningen Livestock
Research (WUR) and was focused on competition for food
and space of cats, dogs, and horses in the Netherlands.
WUR’s calculations were based on human-edible products,
which might overestimate the EPP (Leenstra and Vellinga
2011). However, the researchers did not include spillage
or overfeeding, which usually compensates for these over-
estimations. Using data from relatively high crop yields of
North Western Europe, Leenstra and Vellinga (2011) esti-
mated a cat paw print of 0.1 ha and a dog paw print of 0.2
ha. They extrapolated these figures to pet ownership in the
Netherlands and found that approximately 40% of all Dutch
arable lands would be needed to produce the 82,000 ha
required for these pets’ diets (Leenstra and Vellinga 2011).
The third study was conducted by the authors of the pres-
ent article. We assessed the dietary EPP, as derived from the
EF, and greenhouse gas (GHG) emissions of cats and dogs
in China and Japan (Su and Martens 2018, Su etal. 2018b).
The key determining factors influencing these paw prints
included the average weight of cats and dogs in the sample,
their diets (based on chicken and cereal), and the daily quan-
tities they were fed. We assessed the environmental impacts
linked to pet ownership while improving further under-
standing of the nutritional requirements for cats and dogs,
pet food production, and its impacts on the environment.
The results of these studies showed that companion dogs (in
particular, large dogs) in China and Japan consumed more
food resources than their actual needs and, therefore, had a
relatively high dietary EPP and huge GHG emissions. These
findings indicate that overfeeding and food waste are a com-
mon phenomenon among companion animal (especially
dog) owners in China and Japan.
In the present study, the method used to calculate the
dietary EPP of average-size companion dogs and cats in
China, the Netherlands, and Japan (see the supplemental
material) was also derived from the EF, often used to mea-
sure humanity’s overall impact on nature, by analyzing six
main categories of ecologically productive land areas: arable,
grazing, forest, fishing, built-up, and energy (Wackernagel
and Rees 1998a, Fu etal. 2015). Each of these six land types
has its own annual productivity and equivalence factor. In
order to estimate and quantify the dietary EPP of compan-
ion animals regarding their commercial dry food, two mate-
rials of consumption (chicken and cereal) were identified
as relevant in this study, and as a result, only the arable and
grazing land categories are included (see the supplemental
material). In this research, we focus primarily on com-
mercial dry food consumption and on the environmental
impacts of average-size companion dogs and cats. Individual
and total companion dogs and cats’ dietary EPP and GHG
emissions in the Netherlands, together with the comparison
of findings from China and Japan, were included in the pres-
ent study (see box 1).
Reducing companion animals’ dietary ecological paw
print
The majority of studies in the literature that were intended
to analyze animal energy consumption and make policy rec-
ommendations often regard animal health as a key indicator
(Nutrition 1971, Fleeman and Owens 2007, Bermingham
et al. 2010, Linder and Freeman 2010, Fowler et al. 2013,
Bermingham et al. 2014, Okin 2017). They generally con-
firm a positive correlation between energy consumption and
an animal’s health condition. These studies imply that ani-
mals consume a lot of energy (i.e., through meat consump-
tion), and therefore, more attention should be paid to reduce
their energy intake and to simultaneously safeguard their
health and nutritional well-being (Collier etal. 1982, Mullis
etal. 2015). The present study establishes a clear relationship
between companion animal food consumption and environ-
mental impacts by reviewing the data from three countries.
In it, we highlight a neglected predictor of environmental
damage and develop novel approaches not only to the rela-
tionship between a companion’s energy intake and health
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condition but also to the relationship between their food
consumption and environmentally sustainable development.
However, in contrast to human diets, pet food products
present a limited set of options, especially if companion
animal owners’ choices are limited to the predetermined
blends of ingredients used by manufacturers (Rushforth
and Moreau 2013). Reducing the dietary EPP of com-
panion animals becomes highly dependent on selecting
which recipes and ingredients require less land, produce
the least emissions, and provide sufficient nutrients
(Rushforth and Moreau 2013). This requires pet food
industries to take responsibility for producing more
sustainable pet food through product design and manu-
facturing processes (e.g., production facilities running
on renewable energy or green supply chains; Rushforth
and Moreau 2013, Swanson et al. 2013, Beynen 2015).
Moreover, increasing the bioavailability and digestibility
of pet foods may also help to reduce food waste (Swanson
etal. 2013).
Previous research has demonstrated that the protein
content in animal-based products is around 11 times higher
than that of plant-based products, meaning that pet food
manufacturers can reach required protein content lev-
els more efficiently if they use more animal products in
pet food production (Swanson et al. 2013). However, the
proteins found in meat also have a higher environmental
impact than those found in plants and cereals (Swanson
etal. 2013), so consuming fewer animal proteins or replac-
ing them with plant-based proteins would lower GHG
emissions (Westhoek et al. 2011). Therefore, the first and
most evident solution for dramatically reducing companion
animals’ dietary EPP is to adopt vegetarian or vegan diets.
This alternative diet has generated an ongoing and divisive
debate, because it may not be the best possible path for
Box 1. Three cases: China, Japan, and the Netherlands.
Basic information about the nutrients and calorie content of companion animals’ commercial dry food in China, Japan, and the
Netherlands is presented in table 1.
According to the data we collected from these three countries, we quantified individual and total companion dog and cat food con-
sumption (table 2).
The environmental impacts of companion dogs and cats in the Netherlands, Japan, and China
We quantified companion dogs and cats’ dietary EPP, GHG emissions and energy consumption according to their food consumption
of commercial dry food in these three countries (i.e., the Netherlands, Japan, and China). The dietary EPP of an average-size dog in
China was between 0.82 and 4.19 ha per year, whereas for a cat, it was between 0.36 and 0.63 ha per year. Given that China has a large
companion dog and cat population; their total environmental impacts are undoubtedly significant. Specifically, if we assume that all
companion dogs and cats eat commercial dry food in China, their dietary EPP is calculated to be between 43.4 million and 151.4
million ha per year, which is equivalent to the dietary EF of between 72.3 million and 252.3 million Chinese people in a year. GHG
emissions from this dry-food consumption are between 16.7 million and 57.4 million tons per year. The dietary EPP of an average-size
dog in Japan was between 0.33 and 2.19 ha per year, whereas for a cat, it was between 0.32 and 0.56 ha per year. The dietary EPP of all
companion dogs and cats in Japan lies between 6.6 million and 28.3 million ha per year, equivalent to the dietary EF of between 4.62
million and 19.79 million Japanese people. The GHG emissions from Japanese dog and cat food consumption were between 2.52 mil-
lion and 10.70 million tons, which is equivalent to the GHG emissions resulting from the food consumption of between 1.17 million
and 4.95 million Japanese people. With regard to companion dogs and cats in the Netherlands, our results showed that the dietary EPP
of an average-size dog was between 0.90 and 3.66 ha per year, whereas for a cat, it was between 0.40 and 0.67 ha per year. The dietary
EPP of all companion dogs and cats in the Netherlands was between 2.9 million and 8.7 million ha per year, which was equivalent to
the whole EF of between 0.50 million and 1.51 million Dutch people. The GHG emissions from Dutch dog and cat food consumption
was in the range of between 1.09 million and 3.28 million tons, which is equivalent to between 94,000 and 284,000 Dutch peoples’
GHG emissions regarding their total resource consumption (table 3, table 4).
Our results show that the dietary EPP of one companion dog relying on commercial dry food in the Netherlands or in China was
around two times that of a dog relying on commercial dry food in Japan. Consequently, their GHG emissions and energy consump-
tion were higher than their Japanese equivalents. China has the largest number of companion dogs among the three countries, and the
Netherlands has the least. Therefore, the dietary EPP, carbon emissions, and energy consumption of all companion dogs in China were
the largest, whereas these values in the Netherlands were the smallest (table 3). With regard to cats, our results show that dietary EPP,
GHG emissions, and energy consumption per capita for companion cats are similar across the three countries. However, although the
per capita environmental impacts were similar, their total environmental impacts were quite different. The total number of companion
cats in China, because of their greater numbers, consumed more resources and, to a large extent, contributed to greater environmental
impact than companion cats in the Netherlands and Japan (table 4).
In addition, we also found that many companion dogs in the Netherlands and China consumed more energy than their actual needs,
whereas in all three countries, the calorie intake of companion cats was sufficient to offset their energy requirements.
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maintaining an animal’s health (or may be impossible, given
certain dietary needs—e.g., cats, which are obligate carni-
vores) while significantly reducing its dietary EPP. However,
alternative diets do not have to mean a complete abstention
from meat. The choice of the sources of protein offers a
large potential for reductions depending on the selection of
high- or low-impact meat (Nijdam et al. 2012). By prefer-
ring poultry or fish sources over beef, for instance, desirable
protein quality and content can be achieved while lowering
both the EPP and GHG emissions (Schwartz 2014, Vale and
Vale 2009).
It has been shown that the prevalence of companion ani-
mal obesity increases in line with human obesity (German
2006, Morrison etal. 2014). Most large companion dogs in
China, Japan, and the Netherlands consume more energy
than their actual needs to maintain normal activity, suggest-
ing that overfeeding and food waste is commonplace among
their owners. Maintaining ideal body weight and avoiding
overfeeding nutrients in excess could diminish food waste
and reduce dietary EPP and GHG emissions (Swanson
et al. 2013, Schwartz 2014). Besides veterinarians, the pet
food industry and relevant retailers could try to promote
awareness of this salient fact by providing informative label-
ing. Improving the uniformity of food labels and providing
insight to customers as to the meaning of indications on
labels are strongly emphasized and could improve owners’
Table 1. The percentage of nutrients and calorie contents in commercial dry dog and cat food.
Dog Cat
China Japan
The
Netherlands China Japan
The
Netherlands
Protein (in percent) 25.21 25.67 24.70 29.15 26.00 33.18
Fat (in percent) 13.80 14.67 8.33 13.17 7.50 12.76
Ash (in percent) 9.23 8.00 6.25 8.39 8.00 7.70
Fiber (in percent) 3.72 3.83 2.33 4.66 6.25 3.58
Moisture (in percent) 10.44 10.00 13.44 8.75 10.00 10.12
Carbohydrates (in percent) 37.60 37.83 44.95 35.88 42.25 32.66
Calories (in kilocalories per kilogram) 3371.35 3533.3 3145.80 3395.50 3445.0 3389.00
Table 2. Companion animal numbers and their commercial dry food consumptions in three countries.
Dog Cat
China Japan
The
Netherlands China Japan
The
Netherlands
Per capita food consumption
(in kilograms per year)
48–243 19–123 61–247 20–34 18–31 20–33
Total numbers (in millions) 27.4 10.35 1.8 58.1 9.96 3.2
Total food consumption (in millions of
kilograms per year)
1308–6656 194–1271 109–445 1168–1954 178–311 64–106
Table 3. The dietary ecological paw print (EPP) and greenhouse gas (GHG) emissions of companion dogs in the
Netherlands, Japan, and China.
Cat size Country EPP (in hectares) GHG emission (in tons)
Per capita average-size dog The Netherlands 0.90–3.66 0.349–1.424
Japan 0.33–2.19 0.127–0.831
China 0.82–4.19 0.313–1.592
Lifetime of one dog The Netherlands 10.77–43.93 4.188–17.087
Japan 4.01–26.28 1.522–9.972
China 9.89–50.32 3.756–19.104
Total dogs The Netherlands 1.62 million–6.59 million 0.608 million–2.480 million
Japan 3.40 million–22.70 million 1.312 million–8.596 million
China 22.5 million–114.8 million 8.576 million–43.621 million
Note: An average-size dog weights 10–20 kilograms.
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knowledge on how to feed their animals (PBL 2013). Owners
could be encouraged to check labeling claims of nutritional
adequacy and to ask manufacturers what evidence they can
provide in order to ensure nutritional soundness and consis-
tency of their animals’ diets (Knight and Leitsberger 2016).
Aside from consumer choice, the selection of more sustain-
able suppliers for ingredient composition and selection may
also increase pet food sustainability—for example, by opting
for foods from crops using fewer fertilizers (Swanson etal.
2013, Beynen 2015).
Another option, raised by Rastogi (2010), is to recycle
companion animal owners’ (human) food that would oth-
erwise be wasted, by processing it into pet food (providing
it would entail the correct balance of nutrients). Broader
efforts for reducing daily emissions—for instance, by
cycling to work—may also constitute a personal trade-
off for pet owners, to balance their EF against the EPP of
their companion animals (Rastogi 2010), although this
may seem rather artificial. Schwartz (2014) cited other
simple solutions for reducing the environmental impacts
of companion animals besides their diets. For example,
disposing of a dog’s excrement responsibly could prevent
animal waste from polluting water sources. Vale and Vale
(2009) noted that pet food packaging is not such a signifi-
cant issue for a pet’s EPP as their main recommendations:
sharing a communal pet instead of owing an individual
pet, adopting edible pets such as egg-laying hens, or sim-
ply owning smaller dogs and cats in general. All the solu-
tions and strategies proposed by others and in this present
study, some of them being more realistic than others, reaf-
firm the importance of the environmental impacts of pet
food and any other resource consumption by companion
animals.
Conclusions
The research shows that people with a pet are, in general,
healthier than non–pet owners. Pets also increase the capac-
ity for empathy and social contact among children (which
are useful characteristics for a healthy and happy life).
Furthermore, people who are heavily involved in animal
welfare appear to have more compassion for the problems
of people (Amiot etal. 2016). However, on the other side,
the negative environmental impacts of food consumption
by companion animals are expected to grow worldwide
in the near future (Okin 2017). Besides food, companion
animals also need water, entertainment, healthcare, living
space, and many other resources and services, all of which
dramatically affect their environmental impact. Therefore,
a broader quantification of all companion animal resource
consumptions (e.g., water footprint, health footprint) and
waste production (e.g., feces) should be considered in future
studies. Furthermore, the environmental impact of other
animal groups, such as farm animals, wild animals, zoo
animals, working animals, and laboratory animals are also
interesting areas for further research. The present study was
conducted according to data from the Netherlands, China,
and Japan; further studies into the environmental impacts of
other animal groups from global or cross-cultural perspec-
tives also deserve more attention.
Animal products have greater environmental impact than
plant-based products, and some researchers have quantified
the different carbon or GHG emissions of meat and cereal.
Therefore, quantifying the different impacts of animal and
plant-based products consumed by companion animals in
different countries should also be considered. Besides com-
mercial dry food, companion animal owners feed their
animals with canned food, homemade food, and pure meat.
Therefore, another interesting avenue for further research
would be to quantify companion animals’ dietary EPP regard-
ing their exact daily food consumption. As Rushforth and
Moreau (2013) suggested, further research might also include
comparisons of the contributions of pet ownership to various
activities associated with society (e.g., dogs versus cats).
Although animal companionship can benefit physiologi-
cal, psychological, and social aspects of the quality of human
life, further knowledge and awareness are needed to enable
Table 4. The dietary ecological paw print (EPP) and greenhouse gas (GHG) emissions of companion cats in the
Netherlands, Japan, and China.
Cat size Country EPP (in hectares) GHG emission (in tons)
Per capita average-size cat The Netherlands 0.40–0.67 0.150–0.251
Japan 0.32–0.56 0.121–0.211
China 0.36–0.63 0.141–0.237
Lifetime of one cat The Netherlands 5.62–9.39 2.102–3.511
Japan 4.46–7.80 1.693–2.959
China 5.04–8.82 1.974–3.318
Total cats The Netherlands 1.28 million–2.14 million 0.480 million–0.803 million
Japan 3.20 million–5.60 million 1.204 million–2.105 million
China 20.90 million–36.60 million 8.192 million–13.770 million
Note: An average-size cat weights 2–6 kilograms.
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cat and dog owners to acknowledge the environmental costs
of owning pets. Providing a broader perspective, Swanson
and colleagues (2013) argued that ensuring sustainable pet
ownership includes meeting the current and future needs of
pets in providing their appropriate nutrition. Consequently,
assessing whether and how the pet food system as a whole
can sustainably support the health and nutrition of the grow-
ing population of companion animals is of also significant
importance in the near future (Swanson etal. 2013).
Supplemental material
Supplementary data are available at BIOSCI online.
References cited
Alton R. 2009. Polluting pets: The devastating impact of man’s best friend.
Independent (25 December 2009).
Amiot C, Bastian B, Martens P. 2016. People and companion animals: It
takes two to tango. BioScience 66: 552–560.
Bermingham EN, Thomas DG, Cave NJ, Morris PJ, Butterwick RF, German
AJ. 2014. Energy requirements of adult dogs: A meta-analysis. PLOS
ONE 9 (art.e109681).
Bermingham EN, Thomas DG, Morris PJ, Hawthorne AJ. 2010. Energy
requirements of adult cats. British Journal of Nutrition 103: 1083–1093.
Beverland MB, Farrelly F, Lim EAC. 2008. Exploring the dark side of pet
ownership: Status-and control-based pet consumption. Journal of
Business Research 61: 490–496.
Beynen AC. 2015. Green Pet Foods. Creature Companion (March): 54–55.
Collier R, Beede D, Thatcher W, Israel L, Wilcox C. 1982. Influences of envi-
ronment and its modification on dairy animal health and production.
Journal of Dairy Science 65: 2213–2227.
Csutora M, Mózner Z, Tabi A. 2009. Sustainable consumption: From
escape strategies towards real alternatives. Sustainable Consumption
Conference. Sustainable Consumption, Production, and
Communication.
Cutt H, Giles-Corti B, Knuiman M, Burke V. 2007. Dog ownership, health
and physical activity: A critical review of the literature. Health and Place
13: 261–272.
Du B, Zhang K, Song G, Wen Z. 2006. Methodology for an urban ecological
footprint to evaluate sustainable development in China. International
Journal of Sustainable Development and World Ecology 13:
245–254.
Fleeman LM, Owens E. 2007. Applied animal nutrition. Pages 14–31
in McGowan C, Gott L, eds. Animal Physiotherapy: Assessment,
Treatment and Rehabilitation of Animals.
Flynn CP. 2000. Battered women and their animal companions: Symbolic
interaction between human and nonhuman animals. Society and
Animals 8: 99–127.
Fowler V, Fuller M, Close W, Whittemore C. 2013. Energy requirements for
the growing pig. Pages 151–156 in Mount LE, ed. Energy Metabolism:
Proceedings of the Eighth Symposium of the European Association of
Animal Production. Butterworths.
Francke I, Castro J. 2013. Carbon and water footprint analysis of a soap bar
produced in Brazil by Natura Cosmetics. Water Resources and Industry
1: 37–48.
Fu W, Turner JC, Zhao J, Du G. 2015. Ecological footprint (EF): An
expanded role in calculating resource productivity (RP) using China
and the G20 member countries as examples. Ecological Indicators 48:
464–471.
Gerber PJ, Steinfeld H, Henderson B, Mottet A, Opio C, Dijkman J, Falcucci
A, Tempio G. 2013. Tackling Climate Change Through Livestock: A
Global Assessment of Emissions and Mitigation Opportunities. Food
and Agriculture Organization of the United Nations.
German AJ. 2006. The growing problem of obesity in dogs and cats. Journal
of Nutrition 136: 1940S–1946S.
Hammerly T, DuMont B. 2012. The environmental impact of pets. Green
Teacher 25.
Hughes D. 1995. Animal welfare: The consumer and the food industry.
British Food Journal 97: 3–7.
Knight A, Leitsberger M. 2016. Vegetarian versus meat-based diets for com-
panion animals. Animals 6: 57.
Leenstra F, Vellinga T. 2011. Indication of the ecological foot print of com-
panion animals: First survey, focussed on cats, dogs and horses in the
Netherlands. Wageningen UR Livestock Research. Report no 410650.
Linder DE, Freeman LM. 2010. Evaluation of calorie density and feeding
directions for commercially available diets designed for weight loss in
dogs and cats. Journal of the American Veterinary Medical Association
236: 74–77.
Liu H, Wang X, Yang J, Zhou X, Liu Y. 2017. The ecological footprint evalu-
ation of low carbon campuses based on life cycle assessment: A case
study of Tianjin, China. Journal of Cleaner Production 144: 266–278.
Martens P, Enders-Slegers M-J, Walker JK. 2016. The emotional lives of
companion animals: Attachment and subjective claims by owners of cats
and dogs. Anthrozoös 29: 73–88.
Morrison R, Reilly J, Penpraze V, Pendlebury E, Yam P. 2014. A 6‐month
observational study of changes in objectively measured physical activ-
ity during weight loss in dogs. Journal of Small Animal Practice 55:
566–570.
Mullis RA, Witzel AL, Price J. 2015. Maintenance energy requirements of
odor detection, explosive detection and human detection working dogs.
PeerJ 3: e767.
Nemecek T, Weiler K, Plassmann K, Schnetzer J, Gaillard G, Jefferies D,
García–Suárez T, King H, i Canals LM. 2012. Estimation of the vari-
ability in global warming potential of worldwide crop production using
a modular extrapolation approach. Journal of Cleaner Production 31:
106–117.
Nutrition NRCCoA. 1971. Nutrient Requirements of Poultry. National
Academies Press.
Okin GS. 2017. Environmental impacts of food consumption by dogs and
cats. PLOS ONE 12 (art.e0181301).
PBL. 2013. Netherlands Environmental Assessment Agency (PBL), in
Agency NEA, ed.
Peeples L. 2009. How big is a dog’s eco-pawprint? Audobon (25 November
2009). www.audubon.org/news/how-big-dogs-eco-pawprint
Pimentel D, Pimentel M. 2003. Sustainability of meat-based and plant-based
diets and the environment. American Journal of Clinical Nutrition 78:
660S–663S.
Rastogi NS. 2010. The trouble with kibbles: The environmental impact of pet
food. Slate (23 February 2010). https://slate.com/technology/2010/02/
the-environmental-impact-of-pet-food.html
Ravilious K. 2009. How green is your pet? New Scientist 204: 46–47.
Reijnders L, Soret S. 2003. Quantification of the environmental impact
of different dietary protein choices. American Journal of Clinical
Nutrition 78: 664S–668S.
Rushforth R, Moreau M. 2013. Finding Your Dog’s Ecological “Pawprint”: A
Hybrid EIO-LCA of Dog Food Manufacturing. Arizona State University.
Schwartz L. 2014. The surprisingly large carbon paw print of your beloved
pet. Salon (20 November 2014) www.salon.com/2014/11/20/the_sur-
prisingly_large_carbon_paw_print_of_your_beloved_pet_partner
Shanahan H, Carlsson Kanyama A. 2005. Interdependence between con-
sumption in the North and sustainable communities in the South.
International Journal of Consumer Studies 29: 298–307.
Su B, Koda N, Martens P. 2018a. How Japanese companion dog and cat
owners’ degree of attachment relates to the attribution of emotions to
their animals. PLOS ONE 13 (art.e0190781).
Su B, Martens P. 2018. Environmental impacts of food consumption
by companion dogs and cats in Japan. Ecological Indicators 93:
1043–1049.
Su B, Martens P, Enders-Slegers M-J. 2018b. A neglected predictor of envi-
ronmental damage: The ecological paw print and carbon emissions of
food consumption by companion dogs and cats in China. Journal of
Cleaner Production 194: 1–11.
Forum
474 BioScience •June 2019 / Vol. 69 No. 6 https://academic.oup.com/bioscience
Swanson KS, Carter RA, Yount TP, Aretz J, Buff PR. 2013. Nutritional sus-
tainability of pet foods. Advances in Nutrition: An International Review
Journal 4: 141–150.
Vale, Vale. 2009. Time to Eat the Dog? The Real Guide to Sustainable
Living. Thames and Hudson.
Wackernagel M, Onisto L, Bello P, Linares AC, Falfán ISL, Garcıa JM,
Guerrero AIS, Guerrero MGS. 1999. National natural capital account-
ing with the ecological footprint concept. Ecological Economics 29:
375–390.
Wackernagel M, Rees W. 1998a. Our Ecological Footprint: Reducing
Human Impact on the Earth. New Society Publishers.
Wackernagel M, Rees W. 1998b. Our Ecological Footprint: Reducing
Human Impact on the Earth. New Society Publishers.
Westhoek H, Rood T, van den Berg M, Janse J, Nijdam D, Reudink M,
Stehfest E, Lesschen J, Oenema O, Woltjer G. 2011. The Protein Puzzle:
The Consumption and Production of Meat, Dairy and Fish in the
European Union. Netherlands Environmental Assessment Agency.
William-Derry C. 2009. Dogs vs. SUVs. Sightline Institute (2 November
2009). www.sightline.org/2009/11/02/dogs-vs-cars
Wirsenius S, Azar C, Berndes G. 2010. How much land is needed for global
food production under scenarios of dietary changes and livestock pro-
ductivity increases in 2030? Agricultural Systems 103: 621–638.
Wood L, Giles-Corti B, Bulsara M. 2005. The pet connection: Pets
as a conduit for social capital? Social Science and Medicine 61:
1159–1173.
Xu X, Lan Y. 2017. Spatial and temporal patterns of carbon foot-
prints of grain crops in China. Journal of Cleaner Production 146:
218–227.
Pim Martens (p.martens@maastrichtuniversity.nl) and Samantha Deblomme
are affiliated with Maastricht University, in Maastricht, the Netherlands.
Bingtao Su is affiliated with the School of Philosophy and Social Development
at Shandong University, in Jinan, China.
