Global Register of Introduced and Invasive Species - Chad

This annotated checklist is focused on introduced (alien) and invasive species that are known to occur in Chad. The International Union for Conservation of Nature, (IUCN) describes an Introduced/ Alien and Invasive alien species as follows: An Introduced or Alien species means a species, subspecies, or lower taxon occurring outside of its natural range (past or present) and dispersal potential (i.e. outside the range it occupies naturally or could not occupy without direct or indirect introduction or care by humans) and includes any part, gametes or propagule of such species that might survive and subsequently reproduce. An Invasive Alien Species is an alien species which becomes established in natural or semi-natural ecosystems or habitat, is an agent of change, and threatens native biological diversity. In GRIIS, species are recorded as having an impact (as 'yes' under 'isInvasive') if there is evidence of the species negatively impacting biodiversity, and including species that are widespread, spreading rapidly or present in high abundance (Pagad et al. 2018). This usage is relevant to the purpose of GRIIS, and consistent with the concept of impact as formulated by Parker et al. (1999) and now widely used (e.g. Didham et al. 2005, Strayer et al. 2006, McGeoch et al. 2010, 2012, Vila et al. 2011), where impact is a function not only of the per capita effect of an individual organism, but is a combined function of the effect, abundance and range size of a species. Impact can of course be defined in different ways, driven by different objectives, such as its usage in EICAT where it is defined as a measurable change to the properties of an ecosystem caused by an alien taxon (Hawkins et al. 2015).