Base your answer(s) to the following question(s) on the information below and on your knowledge of biology.

A pond in the Adirondack Mountains of New York State was once a fishing spot visited by many people. It was several acres in size, and fishermen in boats were a common sight. Over time, the pond has become smaller in area and depth. Places where there was once open water are now covered by grasses and shrubs. Around the edges of the pond, there are cattails and other wetland plants.

Identify the ecological process responsible for the changes to this pond.