Mumbai/navi MUMBAI, July 20 -- Are Mumbai's trees stronger than those in Navi Mumbai? If that seems like an absurd question, let the experts weigh in. In Mumbai, the BMC has consistently cited a stormy monsoon as the primary reason for the city's trees toppling with alarming regularity. It has firmly refused to admit that pouring concrete around their bases during the city-wide road concretisation drive, now in its third year, has built concrete coffins around their roots, depriving them of nourishment and weakening even the sturdiest species. Then, on Friday, chief engineer (roads and traffic) Mantayya Swami said something that took tree experts and citizens by surprise. He told HT, "Experts have told us that even if the base of a fully grown tree is concretised completely, it does not pose a risk to the tree falling. Mature trees continue to grow despite concrete around them. It is therefore incorrect to attribute tree falls to concretisation." In Navi Mumbai, an expert panel has a diametrically opposite view. Advising the NMMC on tree collapses, it has categorically cited concretisation as the primary reason for the excessive number of tree collapses in July. Despite torrential rain and strong monsoon winds, experts pointed out that more than 90% of tree collapses occur along roads and within housing societies, where excessive concretisation leaves little room for root growth. In contrast, tree collapses are negligible in gaothan and slum areas, where concretisation is relatively limited, the panel said. Similar weather conditions, neighbouring coastal cities, similar vegetation - diametrically opposite reasons. The number of trees collapsing is in focus for the excessive number that fell in just one week in early July, and the death of an 11-year-old when a tree toppled in Chembur. The inquiry by senior civic officials that followed exonerated the BMC's roads and garden departments, triggering a backlash from experts and the public. Even the civic house has rejected the inquiry report. In Navi Mumbai, experts have also told NMMC - a special meeting was convened by civic chief on Friday to discuss the findings - that frequent excavation for utilities further weakens tree root systems, reducing ability to withstand adverse weather. Experts say adverse weather is only the trigger for a disaster long in the making. Both Swami and experts advising the NMMC have also said that phototropism-the tendency of trees to lean towards sunlight-is a contributing factor to tree collapses. In densely built areas, trees grow asymmetrically as they seek sunlight around buildings....