We formulate a strengthening of the Zariski dense orbit conjecture for birational maps of dynamical degree one. So, given a quasiprojective variety X defined over an algebraically closed field K of characteristic 0, endowed with a birational self-map φ of dynamical degree 1, we expect that either there exists a non-constant rational function f : X P 1 such that f • φ = f , or there exists a proper subvariety Y ⊂ X with the property that for any invariant proper subvariety Z ⊂ X, we have that Z ⊆ Y . We prove our conjecture for automorphisms φ of dynamical degree 1 of semiabelian varieties X. Also, we prove a related result for regular dominant self-maps φ of semiabelian varieties X: assuming φ does not preserve a non-constant rational function, we have that the dynamical degree of φ is larger than 1 if and only if the union of all φ-invariant proper subvarieties of X is Zariski dense. We give applications of our results to representation theoretic questions about twisted homogeneous coordinate rings associated to abelian varieties.