Now listen to part of a lecture in an environmental science class.

OK. So for example, let's say a construction company is planning to build a shopping center on a large piece of land. Before starting the project, the construction company does some researches and makes a study of the area. They learned that the area where they plan to build the shopping center is a wetland, you know, a soft marshy area where there is lots of water in the soil. They plan to bring in additional soil to fill in the area to make the ground more solid and firm, so they can build on it.

But what effect might this filling in of the wetland have on the area. Well, the construction company finds out that the wetland is actually very important to the region. The wetland is helpful in prevent flooding in the surrounding area. You see wetland holds a lot of water the soil is very absorbed and so by absorbing and holding extra rain water, the wetland functions in a beneficial way it actually reduces the chance of flooding in the area.

So, the construction company if it filled in the wetland and then built the shopping center on it, the wetland would be destroyed. Well, they can't do that, right? So the construction company decides to cancel their original plan. Instead, they move the entire shopping center project to a different location.