The Conversation Spain
Biodiversity and emerging diseases: beyond the ‘clickbait’
The relationship between the rate of extinction of species and the increase in emerging infectious diseases has returned to the scientific and social agenda. The idea dates back at least a century, but made a comeback in 2000 when Richard Ostfeld and Felicia Keesing defined the formal framework for this inverse relationship. They called it the “dilution effect hypothesis.” This idea suggests that biodiversity can protect humans from these types of diseases, which are mostly zoonotic and transmitted by wild animals. The hypothesis was reinforced by a series of evidences, mostly correlational, obtained in various natural systems, such as that of the West Nile virus or that of Lyme disease, a source of inspiration for Ostfeld and Keesing. In the latter case, the causative agent of the disease is the bacterium Borrelia burgdorferi, transmitted to humans by ticks that have previously been infected by feeding on a carrier animal, especially the white-footed mouse. This is where biodiversity comes into play. In the extensive deciduous forests of the United States, this rodent is more abundant where biodiversity is lower and therefore the chances of finding an infected tick are increased. In other words, the risk of disease is diluted by biodiversity, as in more diverse areas ticks feed on hosts that are less likely to infect them. With examples of this type, the dilution effect seemed to give a solvent and universally applicable response to the relationship between biodiversity and emerging diseases. However, at the beginning of the current decade, some scientists contested the validity of certain studies that supported the dilution effect; they even singled out authors and editors of alleged malpractice. In sum, despite the ecological and social convenience of the hypothesis, its causal nature and, even more so, its generality, remain controversial. Currently, there is evidence that supports that the relationship between biodiversity and emerging infectious diseases can be negative (the aforementioned dilution effect), positive (the “amplification effect”) and even neutral. There is some consensus. A recent review in Nature indicates that the dilution effect is related to at least two parameters: 1. The type of parasite. Vector-borne and specialist pathogens are the most likely to be affected by alterations in biodiversity. 2. The scale of the study. A negative correlation between biodiversity and infectious diseases would be more detectable on a smaller scale. However, beyond these specific variables, it is not clear under what conditions species diversity dilutes or amplifies exposure to these pathogens. And then the covid-19 arrived The scientific debate is today more alive than ever, stimulated by the covid-19 pandemic. The health, social and economic effects of this crisis have shown that the violation (and vulnerability) of the environment affects human beings. In this sense, a scientific hypothesis that combines human health and protection of the environment is ethically and aesthetically irresistible, especially when it takes the following form: «If we take care of nature, it – as if it were a subject with its own will – will take care of us. we”. Now, this quasi-romantic preconception, which has been branded anthropocentric, and even Panglosian, may relax the standards of scientific rigor. If we add to this that the hypothesis of the dilution effect slips from time to time and without nuances in the fast and effective media, the scientific question (empirical analysis, validity, conclusions) quickly turns into ideology. It is a proven fact. that attacks on the environment expose human beings to new diseases. The examples are many: deforestation exposes us to previously unknown pathogens; markets and macro-farms are the perfect breeding ground for the recombination and selection of virulent strains; globalization accelerates its expansion. However tempting, for the moment it is illegitimate to assume that protectionist measures will always have positive effects on human health. You have to be scientifically cautious. This does not mean denying the major premise – protecting the environment – but rather avoiding a hasty syllogism that has consequences not only for basic research, but also for applied research. Rushed biodiversity management, based on erroneous conclusions, can affect public health: the management of certain areas of the Amazon would be a good example. A 2013 study found evidence that both forest cover and deforestation were related to the incidence of malaria. However, surprising as it may seem, the results suggest that forest cover is associated with a higher incidence of malaria than deforestation itself. Thus, this would contribute to curbing malaria by eliminating forest cover, while conservation efforts would pose a risk to human health, at least as far as malaria is concerned. Responsibility for how to address the dilution effect, in its theoretical dimensions and practices, it is inescapable: both in its research –which requires caution and nuances– and in the progressive dissemination of the message –which calls for social and political action and, therefore, blurs the nuances. Now, where and how to draw the line between the two tasks? Should it be done? Who is it responsible for? We do not have the answers to these questions, but we believe that they lead to a reflection on production in science. In this regard, it is worth considering whether, in the current publishing context –competitive, accelerated, affected by extra-scientific interests–, some analyzes are moving towards a more attractive spectrum of trends. And if the reason for this attraction is its rigor or, rather, the media impact and the consequent academic benefits that it can generate. The risk of researchers becoming victims of fads, of scientific clickbait, is present. With this, it can complicate the possibility of introducing more refined analyzes and, sometimes, also more complex messages to disseminate by the scientific community. Max Weber said: “Who is not capable of putting on, so to speak, blinders and persuade themselves himself that the salvation of his soul depends on his being able to prove this conjecture and not some other […] it is little made for science. ”That science is not neutral is not a new idea. However, sometimes the topic prevents us from seeing the trees: in this case, that of the responsibility of specialists in the media debate of the dilution effect. Will scientists be able to put on blinders, according to Weber, and analyze this hypothesis without being influenced by its ideological and social repercussions? This article was originally published in The Conversation. Read the original. The signatories are not salaried, or consultants, nor do they own shares, nor do they receive funding from any company or organization that can benefit from this article, and they have declared that they lack relevant links beyond the academic position cited above.