If you have a close look at the environment, you would find that it is not only about the flora and fauna, but also about the people that live far away. For example, think about the people living in Africa. They do not have ready access to unlimited drinking water. Unlike you, most of them would actually have to travel miles from their house before they can even come face to face with the drinking water source. So, for them, securing a source to water is a near impossibility in the confines of their own house.
So, how do disposable plastic plates play a part in the preservation of water? Well, most of the plastic plates are disposable by nature, therefore ensuring that you need not have to worry about spending water in cleaning them. All you need to do is to be them after you finish eating. At the end of the day, discounts towards the amount of water that you save that can actually be used towards replenishing the people in Africa. It is a very noble thought, and actually serves the purpose if everybody takes an initiative to do so. This is definitely going to bring about a noticeable change in the ecosystem.