Cats (and dogs): the decadency in land use

The world is getting a bit crowded, and most people have no idea of the real impact of their activities, especially when it comes to land degradation, as the ultimate foudnation for our existence. They might be somewhat aware of their travel behavior (such as flight shame) or their eating habits (’flexitarian’) , but certainly not of many daily activities, which often seem harmless. For example, ordering packages or renovating their homes (applying materials such as aluminum), but especially not of activities that at first glance seem to have no material impact, no real physical relationship with land/resource use. For instance, as I previously wrote about golf: hitting a ball on a grass field, what’s wrong with that? But, yes, since all impacts can be traced back to land use, golf is no exception; its land use is immense. [1] Land that can not be used for basic needs like food or materials. And the same for many other things, like horse riding, recently discussed.[2] More data about the impact of sports and social activities will be available soon.

But now, let’s dive into another hobby: pets, specifically dogs and cats. The human population is already crowded, and it’s even more so when it comes to meat and milk livestock, but pets also contribute a fair amount in land impact. [3]

In total, in 2019 there were 2.9 million cats and 1.7 million dogs in the Netherlands, according to the statistics(with 18 million people) . And their impact is significant, as shown by a study in the U.S., and even more; “If dogs and cats in the U.S. formed a country, they would rank fifth in the list of the most carnivorous nations in the world,” and: “With such meat consumption, dogs and cats are responsible for 30 percent of the environmental impact of meat production in the U.S.” [4][5][6]

That’s no small matter… But that’s far from everything. In the U.S., cats and dogs are responsible for 20% of the population’s energy usage, and “whereas animal meat product consumption by dogs and cats alone is responsible for up to 80 million tons of methane and nitrous oxide.” [7] And it’s not only disastrous in the U.S., but everywhere, take Brazil: there are more dogs than children there[6], and with CO2 emissions of 828 kg CO2/year for dry food to 6500 kg CO2/year for wet food, this is 12 to 98% of what an average Brazilian emits… [8]

Such numbers roughly apply to the Netherlands as well, of course. But for me, it’s not primarily about CO2, that’s just a side effect [9], but mainly about the real capital, the land need: land as the ultimate intermediary between the sun, which is the only source contributing positively to the Earth system via energy, and its capture and storage by us. And land need by, for example, cats (food), cannot be used for anything else. Regarding land use by cats, there are several studies, and each one is a revelation and sparks much debate. Especially regarding food and land:

In ‘Time to Eat the Dog’, Vale and Vale calculate the eco-footprint of animals**. I’ll quote what the Guardian at the time wrote about it: “According to the authors… it takes 0.84 hectares [2.07 acres] of land to keep a medium-sized dog fed. In contrast, running a 4.6-litre Toyota Land Cruiser, including the energy required to construct it and drive it 10,000km a year, requires 0.41 hectares. Dogs are not the only environmental sinners. The eco-footprint of a cat equates to that of a Volkswagen Golf. If that’s troubling, there is an even more shocking comparison. In 2004, the average citizen of Vietnam had an ecological footprint of 0.76 hectares. For an Ethiopian, it was just 0.67 hectares.” [10]

That’s immense, of course. So, for example, having a dog as a pet in Europe has a larger footprint than someone from Vietnam or Ethiopia… Can you still justify that? Or that a dog or cat has at least as much impact as the car you own?* That 0.84 hectares is for a dog that exclusively eats beef all year round. But on average, we calculate with 0.27 hectares of land for an average dog (ranging from 0.18 for small dogs to 0.36 for large dogs). For a cat with dry food, they calculated 0.3 hectares.

Others arrive at somewhat lower values, such as Leenstra and Vellinga, who calculate 0.1 hectares per year for a cat and 0.2 hectares per year for a dog. [11] But note that this might seem not so much, but realize that in the Netherlands, only 0.2 hectares are available per person on average! Half of someone’s ‘share’ of land in the Netherlands would already go to their cat…! If its translated for the Netherlands, then 40% of all food agricultural land is needed for dog and cat food, (82,000 hectares) ([11] Leenstra and Vellinga 2011). However, we import a lot, shifting the burden to others, but still…

Martens et al. have compared several such studies and added their own, which looks at the total impact expressed in the ecological footprint (or ‘paw print’ – EPP, Ecological PAW print). Their results are even higher, reaching 0.90-3.6 hectares for dogs and 0.4 to 0.67 hectares for cats. This is comparable to Vale and Vale’s results. And this is huge! For dogs, it’s even more than what’s available per person in the Netherlands…! [12]

On a global scale, studies are also known about the impact of cat food, in embodied energy and land use. And what are those numbers? [14] Annually, around 49 million hectares of agricultural land are needed to feed all the household dogs and cats in the world. (That’s 12 times the Netherlands…! Or as large as Spain…) [13][14]. (for dry food, wet food is even more…)

These last figures only represent the first-line impact: from the food itself. Not everything around it is included, such as packaging or factory construction. And that can be significant if you calculate honestly (with resource recovery)*. However , there is more when it comes to the impact of especially cats. Because for what is the food and land use being deployed? You could say, after reading research: cats are used to decimate bird populations…

Prey and Hunting

A large research has been conducted on this issue at Tilburg University, by researchers like Trouwborst: “We focus on bird mortality caused by wind turbines, power lines, and illegal hunting,” says Trouwborst. “However, the mortality caused by cats is greater than all these other causes combined.” says Trouwborst [15].

If that’s 10 prey per cat per month (as some observations suggest), that would be 350 million birds per year… That’s perhaps somewhat pessimistic; the Tilburg University study found 140 million. Let’s go with that. But of course, that’s incredibly high. According to scientific research, especially over the past fifteen years, the domestic cat in Europe, and globally, is even one of the most harmful invasive species. [16][17]

“Moreover, member states should ban letting the many cats that are kept as pets roam freely and should effectively enforce this ban. This follows fairly inevitably from a standard legal analysis of obligations that have existed for decades.” (regarding EU nature management-RR) says Arie Trouwhorst in this video.[18] In short, a cat lays a large claim on land that is already very scarce. In the Netherlands, there isn’t enough to meet the needs of both humans and animals, so we claim land outside our borders, import it, to meet our standard of living, but due to our cats, land becomes even scarcer globally for many people who live in much lower prosperity elsewhere in the world.

But cats don’t just claim land; they also actively help destroy biodiversity, which in turn makes that same land less productive! At my home, three cats wander through my garden uninvited every day, keeping the birds away and even eating them. This all certainly calls for strict regulation, of which keeping cats on a leash is the least to expect… And consider that there’s not even a cat tax… While these cats burden the world to the same extent as a car or a person from a developing country. A ban on cats would help a lot.

*Land is our capital, and everything can be expressed in the space-time needed for an activity, in hectares-year yield to capture and store (solar) energy. The sun is, after all, the only source that adds something to the Earth; the rest is limited within the Earth’s surface and can only be depleted, nothing else is added. Except through the sun and land, food, raw materials, or stored energy can be captured, from which all other activities arise (including iron mining and processing, for example). (And without fossil fuels, of course). So, it’s important to map out how much land is needed for a particular activity.

**Eco-footprint: The eco-footprint is a useful method, but not absolute, and not complete. There are two major differences with space-time, or the land-sun approach. The eco-footprint is a CO2-based approach: how much land is needed to compensate for the CO2? Space-time, (also called Maxergy), is an energy/exergy-based approach, not a CO2 approach. For example, fossil fuels are not calculated in terms of CO2 (-compensation) but as the required amount of solar energy (and land), needed for the production of those fuels over time (biomass). So, you can use them, at the speed they are generated or compensated (which is very low) [19].

Secondly, Maxergy is based on a combined energy and mass approach, including regeneration of the source (not just the side effect of use, CO2, but also the actual energy and land needed to compensate for exergy loss, to restore stock). As a result, the eco-footprint provides an overly optimistic view of the matter, and the land use throughout the chain is much greater. Incidentally, Maxergy can benefit from a large number of data collected in the footprint.

(partly in Dutch)

[1] golf: https://www.ronaldrovers.com/?s=golf

[2] paarden: https://www.ronaldrovers.com/horses-decadency-in-our-land-use/

[3] https://edepot.wur.nl/542974

[4] https://www.mo.be/nieuws/honden-en-katten-hebben-enorme-milieu-impact

[5] https://newsroom.ucla.edu/releases/the-truth-about-cats-and-dogs-environmental-impact

[6] https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0181301

[7] Okin 2017: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0181301 .

[8] brazilie: https://www.nature.com/articles/s41598-022-22631-0

[9] co2 neven effect blog: https://ronaldrovers.nl/het-co2-wespennest/

[10] https://www.theguardian.com/environment/2009/nov/13/ethical-living-carbon-emissions

[11] https://www.amazon.co.uk/Time-Eat-Dog-Sustainable-Living/dp/0500287902