Why are they replacing Taylor Lautner in Twilight?

Taylor Lautner is not being replaced in the Twilight Saga.

He played Jacob Black in all five films:

* Twilight (2008)

* New Moon (2009)

* Eclipse (2010)

* Breaking Dawn - Part 1 (2011)

* Breaking Dawn - Part 2 (2012)

He was a key character throughout the entire franchise, and his role was never recast.