Before directly affecting the plants it will have to go into the soil. Because of this process the soil kind of cleans out the water. So for plants to be affected there has to be a high amount of desalination.
Desalination has a good impact on humans. It gives them fresh clean water out of the desalination factories.
Desalination is a good thing for human society but it can hurt nature. Low Precipitation causes less rain making it hard for glaciers to recieve water and for plants to get food.