  Quantum systems prepared in pure states evolve into mixtures under
environmental action. Physically realizable ensembles are the pure state
decompositions of those mixtures that can be generated in time through
continuous measurements of the environment. Here, we define physically
realizable entanglement as the average entanglement over realizable ensembles.
We optimize the measurement strategy to maximize and minimize this quantity
through local observations on the independent environments that cause two
qubits to disentangle in time. We then compare it with the entanglement bounds
for the unmonitored system. For some relevant noise sources the maximum
realizable entanglement coincides with the upper bound, establishing the scheme
as an alternative to locally protect entanglement. However, for local
strategies, the lower bound of the unmonitored system is not reached.
