Peste des petits ruminants (PPR) är en epizootisjukdom som drabbar små idisslare. Sjukdomen är obotlig, ger allvarliga symptom och har i regel hög morbiditet och mortalitet. Orsakande agens är peste des petits ruminants virus (PPRV) som tillhör familjen Paramyxoviridae och genus Morbillivirus. PPR breder ut sig i flera utvecklingsländer i framför allt Afrika, Mellanöstern och Asien. Sjukdomen orsakar stora ekonomiska förluster för lantbrukare och bidrar därmed till fattigdom.

Biodiversity is under threat in Sweden and many species are on the brink of extinction. This is mainly due to the large-scale drainage projects during the 19th and 20th century and the increasingly intensive land use in agriculture and forestry. The intensive land use with sharply defined boundaries between the production units has in many cases led to either overgrazing or overgrowing. As a result many species have been pushed back to "leftover" habitats like shooting ranges, power line corridors, roadsides, dumps, embankments and other similar areas. Therefore the question has been raised, wether or not it is needed to re-introduce large herbivores into the wild in order to maintain the biodiversity that is related to the extensive land use.This study has been conducted as a literature review and will focus on the European bison?s (Bison bonasus) impact on other species and biodiversity; conditions for reintroducing large herbivores in Sweden are also discussed.Free roaming populations of large herbivores have a positive impact on plants, insects and many other groups of organisms.