The study is a global approach that shows the impact that the loss or reduction of the regulatory service (carrion consumption) due to the decline of strict or obligate scavenger species can have.

The article reinforces the evidence available from previous studies, which already demonstrated with vultures that the absence of obligate scavenging vertebrates generally benefits the growth of facultative scavenger populations and/or opportunistic species. This can facilitate the spread of pathogens, with the consequent threat to human health. Hence, approaches under the One Health paradigm are increasingly necessary, because animal health, biodiversity and human health are interrelated.

The study is of high quality and is further endorsed by the very high quality of the journal in which it is published. In my opinion, in addition to its quality, the study has great potential. For years now, scavenging ecology has been a field that has been growing exponentially for two reasons: on the one hand, it had been neglected in the ‘classic’ overviews of ecology; on the other hand, these ecological functions are now threatened by the accelerated extinction of many species of scavengers, especially large vertebrates.

The study is actually a review, or re-examination, of previous studies and evidence that already pointed in the same direction as the one developed here. The value of this publication is that it provides a synthesis. Its significance lies in the fact that, as a top publication, it can give more visibility to the problem, especially if the conclusions are disseminated to the general public.

In my opinion, there are no major limitations to the study. Perhaps those inherent in any article that attempts to generalise. The strength and quality of the studies on which it is based vary, and this can undoubtedly lead to bias. However, I do not believe that this invalidates the main conclusions, which, as I said, were already part of the current discourse in the fields of ecology and conservation.

What is your overall opinion of the study?

‘The study does a tremendous job of reviewing both the conservation status of scavenger species worldwide and the scientific literature on the role these species may play in human health. This, together with the explicit acknowledgement of possible limitations or lack of evidence in some areas and the replicable methodology, illustrate the quality of the contribution.’

How does it fit in with existing evidence and what new insights does it provide?

"The results, as the authors themselves indicate, are consistent with previous scientific work. This is true both in terms of the threat level of the species studied (for example, larger species tend to be in a worse situation) and in terms of the potential effects that these declines could have on the maintenance of ecosystem functions and services. The study points to both direct effects from the disappearance of species that are highly efficient at consuming carrion and indirect effects from the increase in other species that are not as well adapted to such consumption. In this case, the focus is on ecosystem services related to the persistence of carrion in the environment and its possible relationship with various diseases and other risks to human health, in line with previous review work focusing on large vertebrate scavengers, but broadening the focus to include the role of other less specialised scavengers or those generally located at lower levels of food webs.

Are there any important limitations to bear in mind?

"As the authors of the study themselves acknowledge, despite this being a message that is repeated almost every time the ecology and conservation of scavenger species is discussed, the available evidence on the role these species play in disease control is still limited and sometimes even contradictory or highly context-dependent. Therefore, the main contribution of this study, apart from the exhaustive review already mentioned, is not so much to warn that the loss of apical scavenger species poses a threat to human health, but rather to highlight the importance of having more scientific evidence to understand when this effect occurs and its scope at the ecological level and how it may affect human health and well-being."