Large-scale environmental changes are one of the most important factors in zoonotic disease transmission as well as the emergence of new diseases. They are often interrelated as you will see.
Here is just a mention of a couple of large-scale environmental changes that have affected the rate and emergence of zoonoses:
1. Deforestation
2-3% of global forests continue to be lost each year. Deforestation can lead both directly and indirectly to environmental changes that favor the transmission of zoonotic diseases. Indirectly, deforestation leads to less carbon sequestration which results in an increase in greenhouse gases which contributes to the warming of the earth. This is leading to increased incidence of animal and human diseases previously found mainly in more tropical regions.
Deforestation has direct effects as well, leading to fragmentation of environments (discussed below) and the creation of possible breeding grounds for vectors, as is the case with malaria. Also, increased activity in forests has led to increases in the disease of leishmaniasis, for instance.
2. Habitat Fragmentation
One of the key outcomes of peoples' various uses of the land, such as suburbanization, agriculture, and many others, is the fragmentation of wildlife habitats. Such fragmentation alters the composition of a host species in an environment and thus the fundamental ecology of microorganisms. An example in North America is the fragmentation of forests creating much smaller forested and fringe areas which have led to a decrease in small predator mammals and a resultant increase in white-footed mice populations. White-footed mice are reservoirs for the causative agent of Lyme Disease, Borrelia burgdorferi. In less fragmented habitats, predator species are more likely to survive; increasing diversity dilutes the risk of transmission as well.
Additionally, human encroachment on wildlife habitats, such as in suburban areas where houses have large amounts of land, has broadened the interface between humans and wildlife resulting in an increased likelihood of humans acquiring diseases from wildlife.