Answer: the correct answers are water stopped nourishing the ecosystem of the river's delta and native species inhabiting the river’s delta lost their habitats.
Explanation: the cost and consequences of damming a river are:
- 40-80 million people displaced by dam projects in past 50 years
- Sediment settles behind dams, filling reservoir and not nourishing downstream floodplains
- Small risk of catastrophic failure
- Habitat alteration (upstream and downstream)
- Lost recreational opportunities on river
- Fisheries declines from thermal pollution and blockage of migration
- Disruption of flooding that builds topsoil
