Sometimes the best things you can do are invisible.
Such as fighting cholera by ensuring drinking water wasn’t contaminated by sewage, as happened in London in the 1840s.
Or setting up an emissions trading scheme, which drove emissions down, despite former prime minister Tony Abbott attacking it as a “so-called market in the non-delivery of an invisible substance to no one”.
Air free from contamination is as invisible as uncontaminated water, but the case for air isn’t yet as widely accepted as it is for water.