Emerald Ash Borer (EAB) and Dutch Elm Disease, now common in south-central Ontario are on the move northward. See these recent articles:
Bruce Grey Woodlands Association
Promoting healthy forests and ecosystems in Bruce and Grey Counties through education, recreation and sustainable management practices.
Bruce Grey Woodlands Association 
Just the EAB target and those who question good science.
The baseline for an unaddressed risk is that the Ash population will be ravaged…..in fact is being ravaged by the current set-up,
Ignorance by many who haven’t thought that they might be part of the problem (shipping dead ash firewood elsewhere) contributes to the outcome.
We need to support good, expert science wherever we can.