There's very good evidence, again, we don't necessarily have a peer-reviewed methodology that's bulletproof yet, but there's very good evidence that the average cat in Europe has a larger environmental footprint in its lifetime than the average African.
Hay bastantes pruebas-- quizá no tengamos la mejor metodología, contrastada y a prueba de balas-- pero hay suficientes pruebas que indican que el gato medio europeo tiene un mayor impacto ecológico durante su vida que el africano medio.