  We show that the Korevaar-Schoen limit of the sequence of equivariant
harmonic maps corresponding to a sequence of irreducible $SL_2({\mathbb C})$
representations of the fundamental group of a compact Riemannian manifold is an
equivariant harmonic map to an ${\mathbb R}$-tree which is minimal and whose
length function is projectively equivalent to the Morgan-Shalen limit of the
sequence of representations. We then examine the implications of the existence
of a harmonic map when the action on the tree fixes an end.
