Biodiversity
Tropical Rainforest
Biodiversity is the variety of life from the number of species (species diversity) to genetic variability (genetic diversity) to environmental processes vital to life (functional diversity) to variety of ecosystems (ecological diversity). Biodiversity improves the productivity of ecosystems. Species diversity allows life to sustain; ecosystems can recover from natural and human disasters. Genetic diversity allows evolution to occur in populations. The loss of biodiversity has become significant because of the increase in species extinction. Species are becoming extinct at a faster rate than seen in history and most extinctions are a result of human activity. The loss of biodiversity results from habitat loss and destruction, removal of a species from an ecosystem (such as keystone species), introduction of invasive species, and climate change. Biodiversity is declining worldwide.
http://www.esa.org/education_diversity/pdfDocs/biodiversity.pdf
http://www.esa.org/education_diversity/pdfDocs/biodiversity.pdf
Top-down regulation
Top-down regulation is means that species from the highest trophic levels influence species on the lower levels of the trophic ladder. Top-down regulation is very common and important to both marine and terrestrial ecosystems. Removing top predators can cause simplification of ecosystems due to extinctions of smaller species. Competitive exclusion and trophic cascades are consequences of a loss in top-down regulation. Competitive exclusion is the process of regulating competition of similar species with carnivores. Competitive exclusion creates diverse habitats. The loss of competitive exclusion allows species to out compete and eliminate other species. Trophic cascades is the effects down the trophic ladder when a species is eliminated. Each trophic level is limited by the next. The relationship between wolves, moose, and balsam fir on Isle Royale National Park explains trophic cascade. When the wolf population is low, the abundance of firs decrease because of the increase of moose grazing. Top predators are important because predators control populations of other species. Eliminating predators can cause an explosion in prey species which would degrade the habitat and effect other populations. Removing predators can cause species to change behavior. It has been observed that deer are more willing to venture apart when wolves are removed from environment. The deer population causes more harm dispersed than grouped. Loss of top predators also increases the number of smaller predators. This increases the predation of prey species because the smaller predators prey on more vulnerable species. The loss of predators may cause other species to act more boldly.
Conserving Nature at Regional and Continental Scales: A Scientific Program for North America by Michael E. Soulé and John Terborgh. BioScience, Vol. 49, No. 10. (Oct., 1999), pp. 809-817.
Fragmentation
Fragmentation is a state and a process. A fragmented area is a landscape resulting from a patchwork of small habitats within an area with a linkage from one site to the other. The process of fragmentation is disrupting ecological connections between the separated habitats of a landscape. Fragmentation has occurred due to the expansion of the human population however natural barriers due exist, like rivers. Many habitats have become broken by fences, roads, agriculture, and development. Obstacles that cause fragmentation effect species differently. For instance, a road has detrimental effects on larger animals with migratory behaviors while the migration patterns of birds may not be effected due to birds way of travel. Reducing the area of an habitat does lower the number of species it can sustain. Decreasing the number of species within an area reduces the genetic variability, leading to inbreeding. Furthermore, continual fragmentation of an area increases difficulty of connectivity between patches. However, fragmenting a population may prevent extinction of an entire species by creating subpopulations but the fragmented areas must not be totally isolated from each other (See metapopulation). Fragmentation has two components: habitat loss and insularization which decrease biodiversity. Insularization is the degree of isolation between the patches. A high degree of insularization decreases genetic variability due to the lack of migration between patches and the small number of species sustained by each patch. Applying Ecology by Alan Beeby
Top-down regulation is means that species from the highest trophic levels influence species on the lower levels of the trophic ladder. Top-down regulation is very common and important to both marine and terrestrial ecosystems. Removing top predators can cause simplification of ecosystems due to extinctions of smaller species. Competitive exclusion and trophic cascades are consequences of a loss in top-down regulation. Competitive exclusion is the process of regulating competition of similar species with carnivores. Competitive exclusion creates diverse habitats. The loss of competitive exclusion allows species to out compete and eliminate other species. Trophic cascades is the effects down the trophic ladder when a species is eliminated. Each trophic level is limited by the next. The relationship between wolves, moose, and balsam fir on Isle Royale National Park explains trophic cascade. When the wolf population is low, the abundance of firs decrease because of the increase of moose grazing. Top predators are important because predators control populations of other species. Eliminating predators can cause an explosion in prey species which would degrade the habitat and effect other populations. Removing predators can cause species to change behavior. It has been observed that deer are more willing to venture apart when wolves are removed from environment. The deer population causes more harm dispersed than grouped. Loss of top predators also increases the number of smaller predators. This increases the predation of prey species because the smaller predators prey on more vulnerable species. The loss of predators may cause other species to act more boldly.
Conserving Nature at Regional and Continental Scales: A Scientific Program for North America by Michael E. Soulé and John Terborgh. BioScience, Vol. 49, No. 10. (Oct., 1999), pp. 809-817.
Fragmentation
Fragmentation is a state and a process. A fragmented area is a landscape resulting from a patchwork of small habitats within an area with a linkage from one site to the other. The process of fragmentation is disrupting ecological connections between the separated habitats of a landscape. Fragmentation has occurred due to the expansion of the human population however natural barriers due exist, like rivers. Many habitats have become broken by fences, roads, agriculture, and development. Obstacles that cause fragmentation effect species differently. For instance, a road has detrimental effects on larger animals with migratory behaviors while the migration patterns of birds may not be effected due to birds way of travel. Reducing the area of an habitat does lower the number of species it can sustain. Decreasing the number of species within an area reduces the genetic variability, leading to inbreeding. Furthermore, continual fragmentation of an area increases difficulty of connectivity between patches. However, fragmenting a population may prevent extinction of an entire species by creating subpopulations but the fragmented areas must not be totally isolated from each other (See metapopulation). Fragmentation has two components: habitat loss and insularization which decrease biodiversity. Insularization is the degree of isolation between the patches. A high degree of insularization decreases genetic variability due to the lack of migration between patches and the small number of species sustained by each patch. Applying Ecology by Alan Beeby
Natural Disturbances
Forest Fire
Natural disturbances are environmental events that create temporary changes for an ecosystem for populations and resources. Natural disturbances invoke a large response from populations; natural disturbances include floods, fire, disease,and landscapes/avalanches and drought. Even though natural disturbances are deemed catastrophic they play a vital role in ecosystem organization. Suppressing natural disturbances can cause habitat degradation and consequences for populations over a long time span. Disturbances make resources more available to life in the ecosystem, and depending on the disturbance can create open space for growth and renewal. For example, fire provides the opportunity for the process of succession by removing the current vegetation and opens up the space to more sunlight. Shade intolerant species now have an opportunity to grow in the area. Disturbances usually do not effect an entire landscape. Small parts of the landscapes will be effected at different times creating a patchwork of different habitats for species to thrive.
Relative importance of natural disturbances and habitat degradation on snail kite population dynamics
by Julien Martin, Wiley M. Kitchens, Christopher E. Cattau, and Madan K. Oli Endangered Species Research Vol. 6: 25–39, 2008
Relative importance of natural disturbances and habitat degradation on snail kite population dynamics
by Julien Martin, Wiley M. Kitchens, Christopher E. Cattau, and Madan K. Oli Endangered Species Research Vol. 6: 25–39, 2008