A recent letter from a group of Spanish scientists calls a popular phrase into question: they argue that domestic and feral cats pose a major threat to biodiversity. The letter critiques a government bill that aims to protect animal welfare and rights, noting that its provisions clash with European laws and established biodiversity strategies. The scientists suggest that environmental goals should eventually move toward reducing reliance on broad animal protection policies and focus on situations where wild cats and cat colonies threaten native ecosystems.
The letter, published in the journal Conservation Science and Practice, highlights a growing body of work over the past several years about cats and their ecological impact. Among the key points are:
– Domestic cats contribute to more than a quarter of the current extinctions of birds, mammals, and reptiles worldwide and are described as a highly harmful invasive predator.
– Predation by cats ranks among the most important causes of death for small mammals and birds, often outweighing other risks such as poisoning or direct human hunting.
– Even well-managed cat colonies are found to hunt wildlife, and due to high population density, feral cats can have several times greater influence on prey populations than domestic predators.
– The effects of cats are especially severe on island ecosystems, and current Spanish laws are unlikely to adequately protect the endemic fauna of the Canary and Balearic Islands.
– In addition to predation, cats act as vectors and reservoirs for various diseases, potentially endangering wildlife and public health.
– Cat colonies can play a crucial role in disease dynamics because of the large number of individuals and the intense interactions within colonies and with owned or feral cats.
Criticism of animal welfare law
The letter opens by noting that moral considerations have historically expanded beyond humans to include nonhuman beings. As a result, legal instruments around the world have begun to confer some rights to animals.
In addition, the authors point out that the draft bill focuses on a subset of native species and may conflict with European and Spanish laws and broad strategies for conserving biodiversity. They argue that the approach could undermine conservation goals if it fails to address the broader ecological context.
The draft places particular emphasis on stray cat colonies—dense groups that rely on artificial food sources. The scientists say the proposal would grant nutritional and veterinary protections to these colonies and to their volunteer caretakers, with local administrations overseeing support and formal recognition for caretakers.
Moreover, the bill proposes banning extermination of felines and shifting away from culling, a method that has helped reduce cat populations on islands through fertility control. This approach is described as more ethical, yet it is not without challenges.
According to the researchers, fertility control can drive population decline only with high, sustained application over wide areas. This requires significant resources and careful management to avoid unintended consequences.
Harmful effects on public health
The researchers argue that current management strategies are often too complex and expensive to scale, which can leave feral cat numbers high in both urban and rural settings. This persistence may shield biodiversity threats in the short term while allowing harm to accumulate in the long term.
Images of people feeding stray cats illustrate the social dimension of the issue.
While the letter acknowledges the appeal of reducing harm, it asserts that the medium-term objective should be the elimination of feral cats, including dense colonies, through effective public education about the ecological and health risks involved.
Scientists also note that some proposals appear contradictory, as they aim to improve biodiversity while being led by the same ministry responsible for the 2030 Agenda. They warn that wildlife management can raise ethical questions when it prioritizes the well-being of a few species over the entire ecosystem. This could lead to biotas dominated by a small set of favored animals, undermining broader biodiversity goals.
The authors urge legal instruments to pursue clear action: reduce the negative effects of free-roaming cats by decreasing their numbers promptly and limiting outdoor access for owned cats as much as possible.
Barcelona alone is cited as having more than 9,000 stray cats, underscoring the scale of the problem. The letter bears the signatures of researchers from Pablo de Olavide University, Doñana Biological Station, Miguel Hernández University, the Mediterranean Institute for Advanced Studies, and several CSIC institutes.
A schematic representation accompanying the discussion illustrates the known impacts of feral cat colonies on biodiversity and humans.
For further reading, the letter from the Spanish researchers appears in Conservation Science and Practice. A preliminary animal protection bill and related documents are provided by the relevant government portals for context, and readers are encouraged to review them for a complete understanding of the policy landscape.
Environment department inquiries and general information are typically routed through formal channels established for public consultation and science-based decision-making.