  Many active systems display nematic order, while interacting with their
environment. In this work, we show theoretically how environment-stored memory
acts an effective external field that aligns active nematics. The coupling to
the environment leads to substantial modifications of the known phase diagram
and dynamics of active nematics, including nematic order at arbitrarily low
densities and arrested domain coarsening. We are motivated mainly by cells that
remodel fibers in their extra-cellular matrix (ECM), while being directed by
the fibers during migration. Our predictions indicate that remodeling promotes
cellular and ECM alignment, and possibly limits the range of ordered ECM
domains, in accordance with recent experiments.
