Often caused by human activities, the depletion or degradation of an ecosystem has long-ranging effects. These effects can impact both the organisms living in an ecosystem as well as humans. There are programs in place to restore degraded ecosystems, but these programs try to simply rehabilitate -- not reproduce past conditions.
The depletion of ecosystems is often due to the over-exploitation of their resources. Although these activities may serve a short-term economic goal, this kind of exploitation can actually lead to direct adverse effects on social welfare in the medium and long terms. In the case of tropical forest degradation, population growth, poverty, environmentally damaging government subsidies, environmentally unsustainable export policies, failure to appreciate the ecology of natural systems and, as a consequence, failure to value the ecological services that the ecosystem provides can lead to degradation.
A 2012 study from American and Brazilian researchers published in the journal "Conservation Letters" revealed that freshwater habitats in the Amazon are highly susceptible to ecological degradation. River, lake and wetland ecosystems, covering approximately one-fifth of the Amazon basin area, are being progressively damaged by deforestation, contaminants, building of dams and waterways, and over-harvesting of plant and animal species. In the Chesapeake Bay area, extensive agriculture, urbanization and a rapidly growing population have significantly degraded the water quality of rivers, tributaries and the bay itself.
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Direct Impact on Human Health
Pressures on ecosystems might have unpredictable and possibly considerable future effects on health, according to a 2005 report from the World Health Organization. The report mentioned that many human diseases have originated in animals and that alterations in the habitats of animal populations that are disease vectors or reservoirs, may affect human health, either positively or negatively. For instance, the Nipah virus is thought to have come about after forest clearance fires in Indonesia forced carrier bats to neighboring Malaysia, where the virus attacked farmed pigs, and then humans. Forest clearance and climate-induced habitat changes also appear to have affected certain populations of disease-carrying mosquitoes, ticks and midges.
Degraded Ecosystem Restoration
A typical restoration effort, the Ecosystem Restoration Program in California, is guided by six main principles: recover endangered, at-risk and indigenous biotic populations; rehabilitate environmental cycles; preserve or boost harvested populations; restore and protect habitats; prevent the establishment of and mitigate effects from non-native invasive species; and improve or maintain sediment and water quality. According to the Society for Ecological Restoration, a typical misconception about ecological restoration is that it aims to revive past conditions. Instead, the goal of restoration should be to reestablish the evolutionary trajectories of ecosystems that were disrupted.