In addition to housing the majority of the planet's biodiversity, forest ecosystems are the basis for trillions of dollars in global revenue. They are homes to indigenous groups, sources of food, medicines, and raw materials for industry, and they provide opportunities for recreation and tourism. They are also being logged, cleared, or otherwise altered by humans at alarming rates. Consequently, understanding the physical and biological consequences of deforestation has become one of the leading areas of research in forest ecology. This review aims to describe the physical and biological consequences of deforestation on four levels of ecosystem organization: individuals, populations, communities, and ecosystems. The most dramatic and immediately obvious consequence of deforestation is the loss of native habitat in newly cleared areas. However not all deforestation results in the denuded landscapes one typically associates with clear-cut logging or industrial cattle ranching. In many cases deforestation proceeds unevenly, leaving behind a patchwork of forest fragments that are isolated at varying degrees from one another.
[...] Changes in Ecosystem Dynamics Deforestation and fragmentation can also influence ecosystem processes at fragment, landscape, or continental scales. Within fragments, nutrient cycling can be substantially altered, since there is an increase in the amount of leaf litter on the forest floor and this litter often takes longer to decompose. At the regional scale, fragmentations can influence temperature and rainfall patterns. It is estimated that as much as 50% of rainfall in the parts of the Amazon is produced by the respiration of trees, and that by removing half the forest and replacing it with pastures total rainfall could be reduced by as much as 25%. [...]
[...] Many amphibians, insects, small mammals, and plants are habitat generalists tolerant of a broad range of habitat types. In some cases species diversity even increases despite the loss of forest-interior species, because their absence is compensated by an influx of generalists from the surrounding matrix. Perhaps one of the best examples of this phenomenon is tropical pool-breeding frogs, of which disturbed-habitat specialists (e.g., Scinax rubra, Adenomera hylaedactyla) can be found in recently isolated forest fragments and on the edges of continuous forest. [...]
[...] For instance, individuals of Pachira quinata, an important timber species found in the dry forests of Central and South America, were found to develop crowns with more reproductive branches when isolated by fragmentation than when in continuous forest. This increased reproductive effort can probably be attributed to a lack of competitors in disturbed areas. Perhaps less intuitive is the fact that forest fragmentation can also influence the behavior of individuals. An increasing number of studies have found that animals, even highly mobile ones such as migratory birds, are frequently averse to traversing roads, pastures, and the other types of clearings made by humans in forest landscapes. [...]
[...] As with individual physiology, however, the effects of fragmentation on population size are not uniformly negative. Populations of generalist invertebrates can increase dramatically in forest fragments, as can those of lianas, vines, rattans, and other pioneer plant species commonly found in natural forest gaps. The increased amount of edge habitat may also favor nest parasites such as cowbirds (Molothrus ater) or nest predators such as ravens (Corvus corax) and skunks (Mephitis mephitis), though the effects can vary considerably between species and locations. [...]
[...] Conclusion- Future directions The field of fragmentation biology remains a dynamic and exciting one, and there is still much to learn regarding the structure and functioning of fragmented forests. For instance the precise ecological mechanisms responsible for most local extinctions from fragments are still unknown, as are the details regarding the dispersal of plants and animals between the remaining patches of forest. Finally, while the populations of plants and animals surviving in fragments continue to be the subject of considerable research, one cannot understate the importance of the matrix habitat in which these fragments are embedded. [...]
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