When the forest becomes fragmented into many small patches, most habitats are edge habitats. The cowbird has free access to the entire area and all songbird nests within. In Florida, for every native species that is lost, ten non-native species have become established. While this may be an increase in species richness, it is not an increase in ecological integrity, as non-natives tend not to contribute to the system as a whole. While Florida's native species are forced to compete with non-native species on small, isolated patches of habitat that are surrounded by roadways full of high speed traffic, they must also cope with the loss of actual acreage.
Habitat loss is the most common cause of the decline in wildlife populations.
For instance, if ten percent of a forest is cleared, you can expect a percentage of that area's wildlife to disappear. Species are usually adapted only for a particular type of habitat, and when that habitat is destroyed or altered, it may not provide the same quantity or quality of food, water, and shelter. If the alterations are severe, the area may cease to be a viable habitat for species that originally occurred there. Occasionally, alterations of habitat can occur without actually losing area. If we look at an area the size of Everglades National Park and Big Cypress National Preserve, you may wonder why those areas are unable to support their original array of species.