  We present an index for the local sensitivity of spatiotemporal structures in
coupled oscillatory systems based on the asymptotic scaling of local-in-space,
finite-time Lyapunov Exponents. For a system of nonlocally-coupled R\"{o}ssler
oscillators, we show that deviations of this index reflect the sensitivity to
noise and the onset of spatial chaos for the patterns where coherence and
incoherence regions coexist.
