Destroying habitats, poaching wildlife and changing the climate will cause mammals and birds to experience “substantial ecological downsizing” over the next 100 years.
Source:
https://www.newscientist.com/article/2204256-the-average-animal-will-be-10-per-cent-smaller-in-the-next-century/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home