This is a pretty well done study as far as the investigators using the tools available and accurately reporting the results. We are not qualified to review the
mathemetics involved, however, the methodolgy seems reasonable.
While it is dangerous to take a statement out of context, the conclusions do state:
“Our results suggest that off-leash dogs have no effect on the
diversity or abundance of birds and small mammals in urban parks, but it is also possible
that other factors, such as leash law compliance, reduced or obscured the effects of off-leash
dogs in this study”.
Its worth reading this report which is linked below.