Viral emergence is often a consequence of both nature and human activity. In particular, ecological changes can greatly facilitate the emergence and re-emergence of zoonotic viruses. Factors such as deforestation, reforestation, habitat fragmentation and irrigation can all impact the ways in which humans come into contact with wild animal species, and consequently promote virus emergence. Additionally, climate change can affect ecosystems and vector distribution, which in turn can affect the emergence of vector-borne viruses. Other ecological changes - for example, species introduction and predator loss - can also affect virus emergence and prevalence. Some agricultural practices, for example livestock intensification and inappropriate management/disposal of farm animal faeces, are also associated with an increased risk of zoonosis.