Quarks Daily Special Episode 57 – Pets – How big is their ecological footprint?

With bags of cocoa in the nature reserve

With the excessive fertilization of water bodies and the toxic effect on the environment, animal excreta were responsible for most of the environmental pollution. The researchers analyzed the components of the dog’s feces. It contains phosphorus, nitrogen and heavy metals, which the dog absorbs through food, water and air. Phosphorus and nitrogen are nutrients, but in many ecosystems, especially sensitive ones, they lead to over-fertilization and fuel species extinction. “In our part of the world, eutrophication is the environmental aspect that causes the greatest damage to biodiversity,” says Matthias Finkbeiner. Germany is home to many species that rely on nutrient-poor habitats that only come into play when their more demanding, faster-growing competition can’t find food. If fertilizer is introduced into such a habitat – for example by dogs – their chances disappear. An experiment in Ghent, Belgium showed that there are indeed significant inflows around metropolitan areas. The consequences of over-fertilization are still underestimated: niches are emptying, species essential to the survival of ecosystems in our soil and water are disappearing. One thing is clear: dog excrement is not the biggest driver or eutrophicator here. But with the quantities now piling up in Germany, they should not be neglected either. In fact, according to Berlin’s calculations, the additional environmental impact caused by the production of the plastic bag for faeces is significantly less if it is disposed of correctly than if the faeces end up in the environment.

What does “natural” actually mean here?

With alternatives to conventional dog and cat food, it quickly becomes very emotional. The dog is descended from the wolf and above all must eat meat, is an argument often heard at dog parks. In reality, however, the dog has developed differently over many thousands of years, evolving away from the wolf and adapting to life with humans. This has not only happened externally through breeding, but the digestive system of the dog is very different from that of the wolf. Several studies have now shown that dogs process plant starch many times better than wolves. A recent study shows that vegan-fed dogs not only seem possible, but could be healthier, but much more research is needed here. Many veterinarians are still cautious about recommending a vegan diet because there are still very few reliable long-term studies. But others are already offering advice on a balanced meat-reduced or vegan diet. One thing is certain: the dog cannot simply eat what the vegan owners eat, otherwise there is a risk of malnutrition and disease.

The cat as a problem predator

For cats, the study situation is a bit more nuanced, but here too there is evidence that with the right supplements, cats could also be fed less meat or even vegan. Unlike dogs, cats have another ecological problem: hunting small mammals and birds. The population of rare bird species in Germany has been declining for years – but formerly common species are also raising fewer and fewer young birds. The role domestic cats play in this is controversial. The German Association for the Protection of Nature does not consider the cats to be decisive, after all the decline of the birds occurred at a time when the cat population had almost increased. Certainly, however, hunting pressure from domestic tigers is now hitting some populations harder, because they are already threatened by insect mortality and habitat loss due to industrial agriculture.

Solutions for the smallest footprint

Cats are still the biggest carnivores compared to dogs. Obviously, it has a positive effect, at least in the bird world, when the meat content of cat food is relatively high. If the feed contains mostly meat, 36% fewer dead birds end up in the cat’s claws. On the other hand, colorful slip-on collars and cat activity also play a major role in slowing down hunting success – a University of Exeter study of 355 cats shows. Play and colorful collars together show much more success than the meat content of the feed. More and more pet owners are reducing their pets’ carbon footprint by relying on wild or insect meat. In fact, these products can be significantly more climate friendly. From an ethical point of view, the problems of hunting remain natural, and individual studies have already shown that insects are capable of suffering. Other tips for a smaller footprint are large food packaging units, toys that are actually used and last a long time, the size of a dog matters too! The smaller the dog, the less food it needs and the less excrement enters the nature reserve!


Katharina Adick is a freelance journalist. She especially enjoys reporting on sustainability, agriculture, health and all things living.

Sebastian Sonntag is a passionate radio presenter and host of Quarks Daily.

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