When habitats are destroyed or made uninhabitable, the organisms living there are lost. But habitat loss affects even those remaining habitats that are not destroyed. As habitat fragments become smaller and more isolated, the fragments become more disturbed by "edge effects," in which an ecological community is changed by physical and biological factors coming from an adjacent community.
In 1979, researchers initiated a study on habitat patches in the rainforest north of the city of Manaus, Brazil, which highlighted the importance of edge effects. The rainforest in the study area was continuous at the time, but was scheduled to be logged. One of the key findings of the research was that the smaller fragments were disturbed to a greater extent by surrounding influences than were the larger fragments.
The Manaus, Brazil, research project is important because researchers were able to assess which species lived in the forested areas before the surrounding trees were logged. Soon after the surrounding forest was converted to pasture, the researchers could assess that some of the original species were beginning to disappear from isolated forest fragments.
On a positive note, some of the pastures that surrounded the experimental forest fragments in Brazil have been abandoned, and young forests are now growing in them. Within 7–9 years of abandonment, army ants and some of the birds that follow them recolonized forest fragments that were connected to larger forest fragments by young forests. Other species of birds that forage in the forest canopy also reestablished themselves. The young forest is not a suitable permanent habitat for most of these species, but they can disperse through it to find good habitat.
Textbook Reference: Concept 44.5 Community Ecology Suggests Strategies for Conserving Community Function