Conservation biology aims at understanding and maintaining the biological diversity
that is critical for the sustainability of entire ecosystems while benefiting human societies. Plastic materials have brought many improvements in human daily life but also have many positive or negative
impacts on conservation efforts. They include obvious detrimental effects on the environment (plastic
pollution of lands and seas) as well as positive or even irreplaceable roles in animal care and biological research. Specifically, plastic enables us to save species from extinction by providing tools (including medical and laboratory supplies) and allowing technologies (assisted reproduction or genomic
studies) that would be impossible to implement otherwise. Conversely, the presence of plastic waste
in the environment threatens wildlife species that eat or become entangled by debris. In addition,
plastic polymers are leaching out chemicals (mostly plasticizers) that can be transferred to wildlife
and humans through simple contact or by ingestion. With controversial and sometimes contradictory
reports on issues related to plastic, the difference between good plastic and bad plastic in conservation
biology still needs to be thoroughly explored. The objective of this paper is twofold: first, to review
the current interactions of plastic with natural habitats and animal populations either in the wild or
in captive conditions and, second, to propose the design of systematic studies and wildlife monitoring
to better identify and then mitigate the most significant, detrimental effects of plastic.