### Instruction: From this text, find out the pros and cons of dredging
### Input: Dredging is the excavation of material from a water environment. Possible reasons for dredging include improving existing water features; reshaping land and water features to alter drainage, navigability, and commercial use; constructing dams, dikes, and other controls for streams and shorelines; and recovering valuable mineral deposits or marine life having commercial value. In all but a few situations the excavation is undertaken by a specialist floating plant, known as a dredger.

Dredging is carried out in many different locations and for many different purposes, but the main objectives are usually to recover material of value or use, or to create a greater depth of water. Dredges have been classified as suction or mechanical. Dredging systems can either be shore-based, brought to a location based on barges, or built into purpose built vessels.

Dredging has significant environmental impacts: it can disturb marine sediments, leading to both short- and long-term water pollution, destroy important seabed ecosystems, and can release legacy human-sourced toxins captured in the sediment. These environmental impacts can significantly hurt marine wildlife populations, contaminate sources of drinking water and interrupt economic activities such as fishing.
### Response: The benefits of dredging are:
1. improves existing water features for better drainage, navigability, and commercial use
2. important for constructing dams, dikes, and other controls for streams and shorelines
3. helps in recovering valuable mineral deposits or marine life having commercial value

The demerits of dredging are related to its severe environmental impact, for example:
1. it can disturb marine sediments, leading to both short- and long-term water pollution
2. it can destroy important seabed ecosystems
3. it can release legacy human-sourced toxins captured in the sediment
All the above impacts can significantly hurt marine wildlife populations, contaminate sources of drinking water and interrupt economic activities such as fishing.