One can easily understand the sentence posted by Stu if one changes the penultimate 'the' to 'to'.

I feel it's useless for individuals to wholeheartedly believe that climate change exists and should be addressed (as I do) when many industrial nations either choose not to believe in it or refuse utterly to limit their activities which are causing it.

I can faithfully recycle, live an Earth-friendly life as much as possible (which I do) but meanwhile gigantic chimneys and industrial plants all over the world are pouring out horrifyingly massive amounts. of toxins and pollutants.

I can limit as much as possible buying anything in plastic containers or wrappings (which I do) but at the same time, trillions of plastic bottles and polystyrene trays circle endlessly in a massive whirlpool of shame around the Pacific Ocean.

I suppose my point is a distressed wail of powerlessness in the face of worldwide indifference!