GAM models could integrate a formal change point analysis

[AdamCSmithCWS]

It would be relatively easy to add an integrated change-point parameter by estimating the second derivative of the smooth component on the log-scale.
e.g., the probability of the a negative second derivative in a given year, could flag portions of the trajectory with some minimum probability of indicating a down-turn in a species' status. yet another example of the utility of decomposing the smooth and year-effect components of the trajectory.