Essentially, for nonnative species:

Risk = probability of invasion x probability of impact

Invasion science has much greater capacity to address the 1st half of this equation (though timing of invasion still eludes prediction) than the 2nd half. We can explain many impacts, but struggle to predict them. Theories of impact are mostly explanatory, but provide a foundation on which we can build (see a review my colleagues & I wrote several yrs ago: https://redpath-staff.mcgill.ca/ricciardi/Ricciardi_etal_EcolMonog.pdf )
#invasivespecies