What are four things people have done to threaghten wetlands

Pollution- from factories, fertilisers, pesticides or from major spills, all pose serious threats to wetlands. Humans have not helped, and have sadly contributed to this.
Unsustainable development- hundreds of thousands of hectares of wetlands have been drained to provide land for housing, industry and agriculture.
Dumping- numerous people dump unwanted items into wetlands, lakes and rivers as an ‘easy’ way to be rid of them, but this destroys the landscape.
Hydrologic alterations- can significantly alter the soil chemistry and plant and animal communities. These alterations can be the results of: draining, damming, addition of harmful substances in the water, which increases water and pollutant runoff into wetlands.

Hope this helps!