'Crazy' tree planter greening Sao Paulo concrete jungle

In just over two decades, Helio da Silva has single-handedly planted about 40,000 trees in the urban jungle that is Sao Paulo.

The former food industry executive says he was called "crazy" when he started his quest to transform what used to be a hangout for drug users.

Today, there stands the Tiquatira Park with thousands of trees.