The preliminary data of a tree census conducted by the Brihanmumbai Municipal Corporation is bound to give nature lovers in the city a cause for celebration. According to the data there are over 18 lakh trees in Mumbai. The civic body has said that the figure indicates an increase in the green cover over the last five years. However, the figures could also be attributed to the new parameter of measurement which categorizes a 4 feet high sapling with a diameter of 4 meter as a tree. The civic body will provide cash incentives to citizens to increase the green cover of the city.