This is primarily because it is usually not necessary to manage the complex fluctuations of species over time and space in ecosystems which are large and intact. Many ecologists now subscribe to the concept that some regions of a wildlife population may be the source of most of the offspring, while other areas produce few offspring and may have higher mortality. Because these shifts are not necessarily predictable from direct habitat observation, wildlife biologists have begun to develop models which predict when a population reaches a point where chance events may cause extinctions. Wildlife needs and habitat quality can shift over periods of years, seasons, days, or even hours. Fragmentation of habitat can remove transitional parts of the landscape, creating gaps in the number of suitable habitats available.
Interspersed urbanization can create barriers to species attempting to follow habitat changes.
The social structures and demographics of wildlife populations adds another layer of complexity to habitat fragmentation. In many species, individuals migrate to locate mates or sites for reproduction. Fragmenting habitats can interfere with these movements, disrupting the ratio of males to females or patterns of mate selection. This interference can lead to inbreeding and the concomitant loss of genetic material. It has been suggested that this loss of genetic variability may leave species with less ability to adapt to future changes, thereby hastening extinction.