Final answer:
The reservoir effect encompasses positive and negative ecological impacts due to dam creation, which can include water storage benefits for wildlife during droughts and the formation of wetlands with high biodiversity. Positive impacts are also seen with dam removal and habitat restoration, like reintroducing keystone species to improve ecosystem health.
Step-by-step explanation:
The reservoir effect refers to the range of ecological impacts as a result of creating reservoirs behind dams. While these impacts can be detrimental, such as blocking the migration of fish like salmon and altering aquatic habitats, there are also beneficial aspects. Reservoirs collect and store water during wet periods and provide it for use during dry spells, which can be critical for wildlife survival during drought conditions. Additionally, they can create new habitats for certain species, although these habitats might be very different from the river ecosystems they replace.
A positive impact on wildlife can also occur when reservoirs form wetlands, which provide unique habitats for plant communities and high biodiversity for animal species. These wetlands can slow down runoff, helping to prevent erosion, and they can remove excess nutrients before they enter rivers or lakes. Moreover, the introduction of features like fish ladders enables the continuation of the lifecycle of migratory species such as salmon, which is crucial for maintaining the balance of the ecosystems they inhabit.
Larger scale environmental projects, like dam removal and habitat restoration, aim to restore natural river flows and biodiversity. An example includes reintroducing keystone species like wolves in Yellowstone, which dramatically increased ecosystem biodiversity.
Reservoirs also provide flood control, recreation, and water supply for urban areas. However, it is important to balance the ecological benefits with the negative impacts on the environment, and where possible, mitigate adverse effects or pursue alternatives that can enhance biodiversity, such as the removal of aging dams that no longer serve their intended purpose.