Arborists in the UK are definitely in the top three. We have far more accidents than industrial roped access, for example. They have a secondary rope system and rarely use chainsaws. They also don't shock load ropes with unknown weights either! The statistics would be much worse if all the accidents were reported. This is why we are the current focus of the Health & Safety Executive - They don't like the fact that our work and safety rope are one and the same, that our anchor points are sometimes questionable, that we are exposed to uncontrolled swings, and we use chainsaws that are easy to use one handed!
Anyone who thinks tree work isn't a hazardous business hasn't accurately assessed the risks. We work closely with the HSE to prove our professionalism, and have developed training programmes and guides for a basic national standard. Accident stats are then measured against this.
As far as basic standards in tree work certification are concerned, I feel the UK has a lot to offer the rest of the world. Even so - its still rated a risky business.