Adhere to the road of sustainable development

It can be roughly translated into something like " hold on the pathway of sustainable development ". Depends on the contexts. The meaning of "坚持" could be slightly different.

I think it is unnecessary to translate it literally. It can be translated as 'put something on a sustainable footing' or 'continue to promote sustainable development'.

You can divide them into several parts to better understand it. 堅持/走/可持續發展之/路

坚持=Persist in doing; 走可持续发展之路=take the path/road of sustainable development; I think the most abstract part here is "可持续发展(sustainable development )”, which means we have to take our limited resource and planet into consideration in development so that our next generation won't get nothing left from us