They're census officials too, with the same relentless door-knocking and number crunching to do. Only, they count trees, not heads. Also, they're only one census old. In 1999, the civic Tree Authority actually conducted the city's first ever tree census, with volunteers combing the city-12km at the widest and 40 km north-south. They peered into compounds and backyards, gardens and highways, in each of 24 wards in the Mumbai city.