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The Ecological Paw Print of Companion Dogs and Cats


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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.
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doi:10.1093/biosci/biz044 Advance Access publication 22 May 2019
The Ecological Paw Print of
Companion Dogs and Cats
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
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 etal. 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 etal. 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 etal. 2013, Vale and Vale
2009). Meat-based diets require more energy and water
468 BioScience June 2019 / Vol. 69 No. 6
and, therefore, have far greater environmental impacts than
plant-based diets (Pimentel and Pimentel 2003, Reijnders
and Soret 2003, Wirsenius etal. 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 etal. 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
etal. 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 etal.
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
Forum June 2019 / Vol. 69 No. 6 BioScience 469
meat. Nevertheless, the accuracy of his and Vale and Vales
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 etal. 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 etal. 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
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 etal. 1982, Mullis
etal. 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
470 BioScience June 2019 / Vol. 69 No. 6
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
etal. 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
etal. 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.
Forum June 2019 / Vol. 69 No. 6 BioScience 471
maintaining an animals 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 etal. 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
Netherlands China Japan
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
Netherlands China Japan
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.
472 BioScience June 2019 / Vol. 69 No. 6
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 etal.
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 pets 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
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 etal. 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.
Forum June 2019 / Vol. 69 No. 6 BioScience 473
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 etal. 2013).
Supplemental material
Supplementary data are available at BIOSCI online.
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at Shandong University, in Jinan, China.
... Trends in the pet food market often follow human dietary trends and is thought to be the driver of the increased interest in vegetarian and vegan dog foods. The same concerns about animal welfare, environmental sustainability, and perceptions of what a healthy diet contains exist in regard to pet foods (Deng and Swanson, 2015;Martens et al., 2019;Alexander et al., 2020;Xu et al., 2021;Knight et al., 2022). Although commercial pet foods typically incorporate animal and plant byproducts from the human food industry, which is a sustainable practice, an increasingly common trend among pet owners is to opt for diets that do not contain byproducts Deng and Swanson, 2015;Meeker and Meisinger, 2015). ...
Vegan, mildly-cooked, and human-grade dog foods are becoming more popular, as beliefs and views of pet owners change. To our knowledge, however, dog studies have not examined the digestibility of commercial vegan diets. Therefore, the objective of this study was to determine the apparent total tract digestibility (ATTD) of mildly-cooked human-grade vegan dog foods and their effects on blood metabolites and fecal microbiota, characteristics, and metabolites of adult dogs consuming them. Three commercial dog foods were tested. Two were mildly-cooked human-grade vegan dog diets, while the third was a chicken-based extruded dog diet. Twelve healthy adult female beagles (7.81±0.65 kg; 7.73±1.65 y) were used in a replicated 3x3 Latin Square design. The study consisted of three experimental periods, with each composed of a 7-day diet adaptation phase, 15 days of consuming 100% of the diet, a 5-day phase for fecal collection for ATTD measurement, and 1 day for blood collection for serum chemistry and hematology. During the fecal collection period, a fresh sample was collected for fecal scoring and dry matter, pH, metabolite, and microbiota measurements. All data were analyzed using the Mixed Models procedure of SAS (version 9.4). All three diets were shown to be highly digestible, with all macronutrients having digestibility values above 80%. The vegan diets had higher (P<0.001) ATTD of fat, but lower (P<0.05) ATTD of organic matter than the extruded diet. Dogs consuming the vegan diets had lower circulating cholesterol (P<0.001), triglyceride (P<0.001), and platelet (P<0.009) concentrations and lower (P<0.010) blood neutrophil percentages than dogs consuming the extruded diet. Dogs consuming vegan diets had lower (P<0.001) fecal dry matter percentages, lower (P<0.001) fecal phenol and indole concentrations, and higher (P=0.05) fecal short-chain fatty acid concentrations than those consuming the extruded diet. Fecal bacterial alpha and beta diversities were not different (P>0.05) among diets, but dogs consuming vegan diets had altered (P<0.05) relative abundances of nearly 20 bacterial genera when compared with those consuming the extruded diet. In conclusion, the mildly-cooked human-grade vegan dog foods tested in this study performed well, resulting in desirable fecal characteristics, ATTD, and serum chemistries. The vegan diets tested also led to positive changes to serum lipids and fecal metabolites, and interesting changes to the fecal microbial community.
... Another diet trend gaining popularity is that of plant-based foods. Interest in vegetarian or vegan dog foods may be attributed to concerns about animal welfare, environmental sustainability, or perceptions of what a healthy diet contains (Deng and Swanson, 2015;Martens et al., 2019;Alexander et al., 2020;Xu et al., 2021;Knight et al., 2022). ...
Full-text available
The pet food market is constantly changing and adapting to meet the needs and desires of pets and their owners. One trend that has been growing in popularity lately is the feeding of fresh, human-grade foods. Human-grade pet foods contain ingredients that have all been stored, handled, processed, and transported in a manner that complies with regulations set for human food production. While most human-grade pet foods are based on animal-derived ingredients, vegan options also exist. To our knowledge, no in vivo studies have been conducted to analyze the performance of human-grade vegan diets. Therefore, the objective of this study was to investigate the amino acid (AA) digestibility and nitrogen-corrected true metabolizable energy (TMEn) of mildly-cooked human-grade vegan dog foods using precision-fed cecectomized rooster and conventional rooster assays. Three commercial dog foods were tested. Two were mildly-cooked human-grade vegan dog diets (BC; BR), while the third was a chicken-based extruded dog diet (CT). Prior to the rooster assays, both mildly-cooked diets were lyophilized, and then all three diets were ground. Diets were fed to cecectomized roosters to determine AA digestibility, while conventional roosters were used to determine TMEn. All data were analyzed using the Mixed Models procedure of SAS (version 9.4). The majority of indispensable and dispensable AA across all diets had digestibilities higher than 80%, with a few exceptions (BC: histidine, lysine, threonine, and valine; BR: histidine). The only difference in indispensable AA digestibility among diets was observed with tryptophan, with its digestibility being higher (P=0.0163) in CT than BC. TMEn values were higher (P=0.006) in BC and BR (4.55 and 4.66 kcal/g dry matter, respectively) than that of CT (3.99 kcal/g dry matter). The TMEn/GE was also higher (P=0.0193) in BR than CT. Metabolizable energy (ME) estimates using Atwater factors accurately estimated the energy content of CT, but modified Atwater factors and the predictive equations for ME recommended by the National Research Council underestimated energy content. All calculations underestimated the measured TMEn values of BC and BR, with Atwater factors being the closest. Although testing in dogs is required, these data suggest that mildly-cooked human-grade vegan dog diets are well digested. Moreover, TMEn data suggest that existing methods and equations underestimate the ME of the mildly-cooked human-grade vegan foods tested.
... First, the present study used only feline eye, and therefore, more animal eyes with direct gaze would be helpful to generalize the current results. Second, our data were taken from a sample of Chinese college students without controlling their experience of pets (Martens et al., 2019). Research shows that people with pets are generally healthier than those without pets as pets provide people with companionship and expanded social networks (Okin, 2017). ...
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This study investigated the eye gaze cost in cognitive control and whether it is human-specific and body-related. In Experiment 1, we explored whether there was a cost of human eye gaze in cognitive control and extended it by focusing on the role of emotion in the cost. Stroop effect was found to be larger in eye-gaze condition than vertical grating condition, and to be comparable across positive, negative, and neutral trials. In Experiment 2, we explored whether the eye gaze cost in cognitive control was limited to human eyes. No larger Stroop effect was found in feline eye-gaze condition, neither the modulating role of emotion. In Experiment 3, we explored whether the mouth could elicit a cost in Stroop effect. Stroop effect was not significantly larger in mouth condition compared to vertical grating condition, nor across positive, negative, and neutral conditions. The results suggest that: (1) There is a robust cost of eye gaze in cognitive control; (2) Such eye-gaze cost was specific to human eyes but not to animal eyes; (3) Only human eyes could have such eye-gaze costs but not human mouth. This study supported the notion that presentation of social cues, such as human eyes, could influence attentional processing, and provided preliminary evidence that the human eye plays an important role in cognitive processing.
... Around the world, companion animals are part of human societies (1,2), and provide people with companionship, improved mental and physical health (including reduced depression, increased levels of oxytocin and decreased blood pressure and cholesterol levels), and expanded social networks. Many of these roles depend on physical activity, Palestrini et al. . ...
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Climate change is a threat to global health and can affect both veterinary and human health. Intense weather events, including sudden and violent thunderstorms or periods of extreme heat, are predicted to rise in frequency and severity and this could lead owners to significantly change their habits and schedules based on the weather, could modify human management and could aggravate pre-existing behavioral problems in pets. The aims of the present study were to identify and quantify possible weather events impact on management, behavior, and behavioral problems of Italian dogs and cats, based on previous owners' experiences with their animals. Two questionnaires were prepared, one for dogs and one for cats, investigating owners' perceptions of the impact of weather events on their pets' behavior. A number of 392 dogs and 426 cats' owners answered the questionnaire. Our study showed that many behaviors in both species were equally modified by environmental temperature. Play and activity increased with cold weather and decreased with heat, and sleep increased with drops in temperature and with hot weather. In particular, the increase in activity in correspondence with the thermic drop was more significant in males, while the increase in playing behavior was statistically greater in the Sheepdogs and Cattle dogs –group1. Weather events did not affect aggressive and house soiling behaviors in both dogs and cats, but weather events, including wild thunderstorms, torrential rains influenced the pets' behavior. Understanding how pets modify their behaviors based on a different owners' schedule and to weather events can help to refine prevention strategies through societal changes and owner education.
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... With increasing urbanisation and economic growth, the number of companion animals is also increasing and must be considered when assessing food security requirements (70). Companion animals such as cats (obligate carnivores) and dogs (omnivores) require meat-based diets and therefore have greater environmental impacts than herbivores (71). For example, in the United States of America, the energy consumption of companion dogs and cats is approximately 20% of the human population' s energy consumption, and animal-source food consumption by dogs and cats alone is responsible for up to 58 ± 14.5 million tonnes of carbon dioxide-equivalent of methane and nitrous oxide, two powerful GHGs (47). ...
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National Veterinary Services (NVS) play a crucial role in animal health, production and welfare. They are also intimately involved with safeguarding global health security and the health of the planet. Climate change is just one of the nine planetary boundaries (PBs), i.e. Earth system processes, that can be used to monitor the vital signs of our living planet. In this paper, the authors identify the positive and negative impacts of humaninduced management of aquatic and terrestrial animals in relation to these PBs. In the context of NVS, the authors provide an overview of the real and potential impacts of NVS policies on Earth systems and offer suggestions as to how new sustainability paradigms may assist with reviewing and revising NVS mandates and facilitating stakeholder engagement. Opportunities are proposed for the World Organisation for Animal Health to contribute to the global debate on the role of aquatic and terrestrial animal agriculture and wildlife in sustainable development. In addition, the paper suggests that a wider debate is required in relation to recent significant increases in domestic animal populations and PBs. Intersectoral and interdisciplinary collaboration are required to achieve the transformation of the framework in which NVS operate. While such transformations cannot be driven by the veterinary profession alone, veterinarians have proven very effective operators in the One Health arena. By building on these intersectoral linkages, it will be possible for our profession and NVS to actively contribute to the crucial discussions and transformations required to pull Earth system metrics back within safe boundaries.
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Consumer suspicion of conventional pet foods, along with perceived health benefits of alternative diets, are fuelling development of the latter. These include raw meat diets, in vitro meat products, and diets based on novel protein sources such as terrestrial and marine plants, insects, yeast and fungi. However, some claim vegan diets may be less palatable, or may compromise animal welfare. We surveyed 4,060 dog or cat guardians to determine the importance to them of pet food palatability, and the degree to which their animals displayed specific behavioural indicators of palatability at meal times. Guardians were asked to choose one dog or cat that had been within their household for at least one year, and not on a prescription or therapeutic diet. Of 3,976 respondents who played some role in pet diet decision-making, palatability was the third most important among 12 factors cited as important when choosing pet diets. For 1,585 respondents feeding conventional or raw meat diets, who stated they would realistically consider alternative diets, palatability was the fourth most important among 14 desired attributes. For the 2,308 dogs included, reported observations of 10 behavioural indicators of palatability at meal times reliably indicated significant effects of increased reports of appetitive behaviour by dogs on a raw meat diet, as opposed to a conventional diet. There was no consistent evidence of a difference between vegan diets and either the conventional or raw meat diets. For the 1,135 cats included, reported observations of 15 behavioural indicators indicated that diet made little difference to food-oriented behaviour. Based on these owner-reported behaviours, our results indicate that vegan pet foods are generally at least as palatable to dogs and cats as conventional meat or raw meat diets, and do not compromise their welfare, when other welfare determinants, such as nutritional requirements, are adequately provided.
Synopsis The interactions of dogs and wildlife are receiving increasing attention across the globe. Evidence suggests that dogs can negatively affect wildlife in a variety of ways, including through the risk of predation, by hybridizing with other Canis species, by acting as a reservoir or vector of pathogens, and by competing with wildlife for resources. A multitude of observations and case studies for each of these interactions has led to calls to prioritize increased management of dogs, for instance, through population reduction, vaccination, movement restrictions, and enhanced care of the dogs themselves. Here, I argue that while the risks that dogs present to wildlife are real, they vary in their importance across the globe. Furthermore, often the approaches used to address these risks are championed without a full understanding of the likelihood of success given the necessary spatial scale of management, the availability of alternative management approaches, and the role dogs play in societies. For instance, culling, vaccination, and animal husbandry approaches in reducing the impacts of dogs on wildlife sometimes fail to recognize that local human populations actively recruit replacement dogs, that vaccination often fails to reach levels necessary for herd immunity, and that enhanced dog husbandry may have indirect impacts on wildlife by requiring environmentally impactful activities. I suggest there is a need for attention not only to identify the impacts of dogs but also to determine where and when such interactions with wildlife are problematic and the likelihood of success for any proposed management approach. The impacts of dogs should be mediated in a context-specific manner that accounts for factors such as the local density of dogs, the susceptibility of local wildlife populations to the risks that dog populations may represent, and the local societal norms that underpin how dogs might be managed.
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Recently, studies in the United States and European countries have shown that the degree of attachment is associated with the attribution of emotions to companion animals. These studies imply that investigating the degree of attachment to companion animals is a good way for researchers to explore animal emotions and then improve animal welfare. Although a promising area of study, in Japan, no empirical studies have examined the correlation between the degree of attachment and the attribution of emotions to companion animals. In this research, we aimed to assess companion animal owners’ attribution of six primary (anger, joy, sadness, disgust, fear and surprise) and four secondary (shame, jealousy, disappointment and compassion) emotions to their dogs and cats, as well as how the degree of attachment related to such attribution of emotions from a Japanese cultural perspective. The “Pet Bonding Scale” (PBS), which is used to determine the level of bonding between humans and animals, was introduced to measure respondents’ degree of attachment to their companion animals. The results of a questionnaire (N = 546) distributed throughout Japan showed that respondents attributed a wide range of emotions to their animals. Companion animals’ primary emotions, compared to secondary emotions, were more commonly attributed by their owners. The attribution of compassion and jealousy was reported at a high level (73.1% and 56.2%, respectively), which was surprising as compassion and jealousy are generally defined as secondary emotions. All participants were highly attached to their companion animals, and this attachment was positively associated with the attribution of emotions (9/10) to companion animals (all p < 0.05). This study is one of the first to investigate animal emotions by analyzing the bonding between companion animals and owners in Japan, and it can therefore provide knowledge to increase Japanese people’s awareness of animal welfare.
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In the US, there are more than 163 million dogs and cats that consume, as a significant portion of their diet, animal products and therefore potentially constitute a considerable dietary footprint. Here, the energy and animal-derived product consumption of these pets in the US is evaluated for the first time, as are the environmental impacts from the animal products fed to them, including feces production. In the US, dogs and cats consume about 19% ± 2% of the amount of dietary energy that humans do (203 ± 15 PJ yr⁻¹ vs. 1051 ± 9 PJ yr⁻¹) and 33% ± 9% of the animal-derived energy (67 ± 17 PJ yr⁻¹ vs. 206 ± 2 PJ yr⁻¹). They produce about 30% ± 13%, by mass, as much feces as Americans (5.1 ± Tg yr⁻¹ vs. 17.2 Tg yr⁻¹), and through their diet, constitute about 25–30% of the environmental impacts from animal production in terms of the use of land, water, fossil fuel, phosphate, and biocides. Dog and cat animal product consumption is responsible for release of up to 64 ± 16 million tons CO2-equivalent methane and nitrous oxide, two powerful greenhouse gasses (GHGs). Americans are the largest pet owners in the world, but the tradition of pet ownership in the US has considerable costs. As pet ownership increases in some developing countries, especially China, and trends continue in pet food toward higher content and quality of meat, globally, pet ownership will compound the environmental impacts of human dietary choices. Reducing the rate of dog and cat ownership, perhaps in favor of other pets that offer similar health and emotional benefits would considerably reduce these impacts. Simultaneous industry-wide efforts to reduce overfeeding, reduce waste, and find alternative sources of protein will also reduce these impacts.
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Companion animal owners are increasingly concerned about the links between degenerative health conditions, farm animal welfare problems, environmental degradation, fertilizers and herbicides, climate change, and causative factors; such as animal farming and the consumption of animal products. Accordingly, many owners are increasingly interested in vegetarian diets for themselves and their companion animals. However, are vegetarian canine and feline diets nutritious and safe? Four studies assessing the nutritional soundness of these diets were reviewed, and manufacturer responses to the most recent studies are provided. Additional reviewed studies examined the nutritional soundness of commercial meat-based diets and the health status of cats and dogs maintained on vegetarian and meat-based diets. Problems with all of these dietary choices have been documented, including nutritional inadequacies and health problems. However, a significant and growing body of population studies and case reports have indicated that cats and dogs maintained on vegetarian diets may be healthy-including those exercising at the highest levels-and, indeed, may experience a range of health benefits. Such diets must be nutritionally complete and reasonably balanced, however, and owners should regularly monitor urinary acidity and should correct urinary alkalinisation through appropriate dietary additives, if necessary.
In Japan, there are more than 20 million companion dogs and cats that consume resources. Yet, little is known about their environmental impacts and the related energy policies aiming to reduce such impacts. In this study, we quantified Japanese companion dogs and cats’ environmental impacts regarding their food consumptions. More specifically, we analyzed their dietary “ecological paw print” (EPP), greenhouse gas (GHG) emissions and energy consumption. Our results showed that the dietary EPP of an average-sized dog was 0.33–2.19 ha per year, which was equivalent to one Japanese people’s dietary “ecological footprint” (EF) in a year. The dietary EPP of an average-sized cat was lower with 0.32–0.56 ha per year. All companion dogs and cats in Japan could consume about 3.6–15.6% of the amount of food that Japanese people do and release 2.5–10.7 million tons of GHG through their diet in a year. Many companion animals (particularly medium-sized and large dogs) consumed more energy than they actually needed to sustain their normal activity. By providing direct data on food consumption, this study gained an insight into the future of possible energy policies to reduce Japanese companion animals’ environmental impacts.
Food consumption has considerable impacts on the environment. Recently, increasing numbers of companion animal owners feed their animals with high nutritional food, which requires much land space and has great impacts on carbon emissions. Therefore, the environmental impacts of food consumption by companion animals can be significant, especially in a country with a large companion animal population, like China. In the present study, the ecological indicators of the ecological paw print (EPP), carbon emission and energy consumption have been introduced for the first time to quantify the environmental impacts of food consumption by companion dogs and cats in China. Our results showed that the dietary EPP and carbon emissions of an average-sized dog relying on commercial dry food (0.82–4.20 ha year⁻¹ and 0.037–0.190 ton. year⁻¹) were ca. eight and three times higher than those of the dog relying on human leftover food (0.11–0.53 ha year⁻¹ and 0.014–0.064 ton. year⁻¹). There were more than 27.4 million companion dogs and 58.1 million companion cats in China in 2015. Assuming all these dogs and cats eat commercial dry food, the dietary EPP of the total dogs and cats was 43.6–151.9 million ha. year⁻¹, which was equivalent to the dietary ecological footprint (EF) of 5.1%–17.8% (70.3–245.0 million) of Chinese people in 2015. The annual food consumption of all these dogs and cats was responsible for up to 2.4–7.5 million tons carbon emissions, which was equivalent to the entire carbon emissions of 2.5%–7.8% (34.3–107.1 million) of Chinese people in terms of food consumption in 2015. Our results also demonstrated that some companion animals (especially large dogs) consumed more food energy than their actual needs to keep normal activity, which resulted in food waste and exacerbated the environmental burden. This research develops an accurate method for companion animals’ dietary EPP calculation and quantifies the significant environmental impacts by investigating their dietary carbon emissions and energy consumptions. Findings from this study will motivate companion animal owners to reconsider the feeding regimens and husbandry activities, improve owners and even the whole Chinese people's awareness of sustainability, and ultimately promote the whole country's sustainable development.
Global warming is a very serious environmental problem. Universities, the most active organizations and locations for scientific research and social activities, have a responsibility to construct low carbon campuses and to play an important role in reducing CO2 emissions. The concept and definition of a low carbon campus were proposed in this paper along with a comprehensive model. Tianjin Polytechnical University (TJPU) was used as a case study because of its innovative efforts in this aspect. The ecological footprint evaluation (EFE) and life cycle assessment (LCA) were integrated to evaluate a low carbon campus qualitatively; The ecological footprint index (EFI) was proposed for a quantitative evaluation. The EFI of TJPU was 0.61, which indicated that the low carbon campus of TJPU is classified as having strong sustainability. Last, effective recommendations were proposed based on data analysis to improve the low carbon campus; qualitative and quantitative evaluations were also discussed to enhance the progress of constructing low carbon campuses worldwide.
Quantifying the carbon footprints of grain crops is of great importance to the mitigation of agricultural greenhouse gases. Previous studies revealed that the agricultural greenhouse gas emissions of China kept increasing in the past few years. In this study, the life cycle assessment method was used to calculate the product and farm carbon footprints of rice, wheat and maize based on the governmental statistical datasets and published results. The spatial and temporal patterns of carbon footprint was analyzed, and the impacts of environmental and socioeconomic factors on carbon footprints were evaluated using canonical correspondence analysis. The results showed that the product carbon footprints of rice, wheat and maize corresponded to 1.06 ± 0.03, 0.50 ± 0.04 and 0.40 ± 0.03 kg CO2 eq/kg, while the farm carbon footprints were 7285 ± 78, 2800 ± 222 and 2707 ± 151 kg CO2 eq/ha. The total greenhouse gas emissions from three crops increased by 1.94%/y from 2004 to 2013. The farm carbon footprints of grain crops in the southern provinces were higher than those in the northern provinces. Topsoil clay fraction, latitude, arable land per capita in the rural areas, and longitude significantly affected the spatial distribution of carbon footprints. This study provides a novel insight into the spatial and temporal patterns of carbon footprint from grain crops in China. The results can serve as references for the development of mitigation measures of greenhouse gas in China.
Animals have accompanied humans for thousands of years, with a strong bond forged between humans and other species. Our relationships with animals can take different forms. On one hand, animals can serve instrumental purposes: We currently use animals for clothing, for testing a range of human products, for gaining basic insights into human biology and behavior, and as food. On the other hand, human–animal relations are social. The clearest example is the practice of pet keeping, with people attributing a special status to their companion animals. We review the current state of research on human–animal relations by focusing particularly on companion animals and on the psychological mechanisms involved in this special relationship. Our aim is to highlight key findings from human–animal relations research that also have implications for different scientific disciplines.