The wording is odd because of how it can be read:
A strong economy means a healthy environment
The way I read the words is that if we have a strong economy we will have a healthy environment. To me this is the most logical reading of the sentence.
Replace healthy environment with more income or early retirement and read the statement again. As soon as you do that, it becomes clear the second phrase is intended to derived form or caused by the first.
I am certain this is not what the NDP intended because I asked some of them. The NDP was trying to saying a strong economy comes from a healthy environment, which ultimately does not have to be true.
The NDP already has a problem with ambiguity because they are refusing to give the public any sense of how they would govern and what their priorities are for the province. Releasing this ambiguous photo does not help people come to clarity on the NDP
I think what they wanted to say is a strong economy requires a healthy environment, but then again maybe they like the wording not being clear so there is nothing to hold them to?