A new study suggests that, in the case of global catastrophe, urban agriculture alone could sustain only about one fifth of the population of a temperate, median-sized city, but the whole city could be fed by also farming land within a short distance of the urban area.
No qualms about medium sized, but I think you missed the mark on your temperate climate description. Temperate climates are characterized by four distinct seasons. Not much you can harvest in winter.
Tropical humid climates are stable year round. As long as it can produce there, it can produce all year. For instance, grapes normally yield once per year on temperate climates, but twice on tropical ones.
Four seasons yes, but not cold enough for snow - coldest normal temperture would be -3C. Different plants grow than summer but you can get something if you choose your winter plants. Or maybe you only lose out a month of growing season.
Not to “uhm, acktshually”, but technically New York is temperate (according to Koppen, temperate subtropical, which leads me to question his wisdom), and it snows quite a bit there.
But I see your point. There are plenty of people living in less favorable climates agriculture-wise.
The city in question is in new zealand. While new york may be temperate (though it doesn’t show up in the maps I see - might be looking at maps on my phone) that doesn’t mean it is really comparible.