MUMBAI: More than half of the city’s 29.75 lakh tree population is of exotic or foreign origin, shows the latest BMC census. The census data was provided by the BMC after a woman was killed near Diamond Gardens after an exotic tree fell on her.In the past six months, four people have lost their lives in different parts of the city in tree fall incidents—all involving exotic varieties.The data is therefore a cause for worry considering that exotic trees are more likely to get uprooted than their sturdier local counterparts. Keeping this fact in mind, three years ago, the BMC began to promote plantation of only native trees. Experts have suggested gradual phasing out of exotic trees and replacing them with native varieties to avoid fatal incidents. Exotic varieties were preferred because they grow faster than native trees.The BMC recently completed its GPS mapping census of trees across the city and found that the city has 450 varieties of trees that total 29.75 lakh. Of these, 52% are exotic trees. That apart, there are 4.85 lakh trees in Aarey Colony. Data on Sanjay Gandhi National Park is not available with the civic body.Environmentalist D Stalin said, “Roots of exotic trees cannot penetrate deep inside the earth. Poor maintenance of such trees by the BMC has led to tree fall incidents. The BMC-appointed contractors never follow guidelines to ensure safety of roots while conducting digging and concretization work around these trees. Exotic trees were planted earlier because they grew fast. But native trees, which take longer to grow, are any time a more preferable option than exotic trees. The BMC must phase out exotic trees after replacing them with native ones with a long-term plan, and not all at one go.”The BMC had started a tree census program four years ago by appointing an agency to map each and every tree in the city, according to the latitude and longitude. The census was completed recently and the BMC could finally create a tree database along with identities of individual trees.The BMC has uploaded its census data online with information on the kinds of trees. It is now compiling a report to find out the families to which these 450 varieties of trees belong. Banyan and peepal, for instance, are different varieties but belong to the same family of trees.Civic officials admitted that during monsoon, chances of exotic trees falling due to strong winds are higher than native ones. The BMC only supports planting of native trees. Jitendra Pardeshi , the BMC superintendent of gardens, said, “Since three to four years, we have been promoting planting of native trees. Most of the exotic trees were planted long ago and were unable to adapt to the local climate. We regularly trim such trees and spray pesticides.”