The real "missing middle" in Victoria is not mid-priced housing for an influx of more people, it is the green space between the houses these people are to live in. And it goes missing even faster, when multi-unit developments sprawl along city blocks that have to be paved.
The GREEN Middle is where people tend gardens, kids play, trees have space to grow large, bird habitat and crucially, insect habitat, is preserved. This is the "missing" space where crop-pollinating, soil-making, waste-consuming and bird-feeding insects are going 30% extinct.
See the dire data here: Oliver Milman says 'The Insect Crisis' is bad news for humans, too : Goats and Soda : NPR
"... three-quarters of the world's flowering plants and about a third of the world's food crops depend on pollinators at some stage. And so it's not just bees .... Flies are huge pollinators."
"There's been a ... 300% increase in the volume of agricultural production dependent on animal pollination in the last 50 years. So we're losing pollinators at a time when we're demanding more and more pollination. We have more mouths to feed. We need more farmland" -- plus we need space for urban agriculture and for private urban gardens.
It's not only the middle space between buildings that is crucial, but also the green corridors that link them up. Bees, squirrels and other small species need to move from one green area to another for mating and feeding. Birds move through tree canopy, frogs and insects in wet-space like ponds.
Cities need to create housing policy about more than just "more housing". Ultimately, what the planet needs is lower human population, so that Earth retains resources for the other life forms -- including those, paradoxically, that the human hordes depend on in order to eat.
So municipal "housing" is not only about housing, and municipal councilors need to do their part in making cities sane. They need to listen to more than the development industry. We can't build our way out of this quandary. Nor can the rest of the overpopulated world.