- from Conservation
To sustain something means to keep it in existence.
When we talk about resources, sustainability means living today in a way that will let people meet their needs in the future. For example, look at paper. It’s usually made from trees. Sure, new trees can be grown. But if people use too much paper, we might cut down trees faster than new ones can grow. Then our use of this resource would not be sustainable. Also, it takes a lot of water and fuel to turn trees into paper. It takes even more fuel to get that paper to you.
We still have plenty of trees, but other resources are running low. We’re nowhere near sustainability, but change is taking place.