whitewave, that's the key point, that the image is of a real child, who was being abused so yes, the individual looking at that image is contributing to that abuse. As for your question about the extent of abuse of children, it's always been significant in all societies. I suspect that the easy access to images of that kind of abuse on line, along with ease of access to various types of pornography will lead to an increase in the sexual abuse of children and of adult sexual partners.
Men (and women) who access images of children being abused do so because they find it sexually arousing. Once images have been viewed, it's more than possible that the excitement gained needs to increase so more depraved images are viewed and the perpetrator my find his/her people out their on the dark web or they may find children in their family or friendship circle are easy to draw into sexual behaviour which escalates along with the child's fear of telling anyone.
The police officer was, if I understood him properly, suggesting that a risk assessment would determine whether someone looking at images posed an immediate risk to children, what the level of that risk developing was etc. I have friends who work with perpetrators, I worked with victims/survivors. I am not enthusiastic about current perpetrator programmes because I believe that one's sexual interest tends to be fixed.