A citywide study should be launched to examine how global warming is affecting plants in Hong Kong and the knock-on effect on the rest of the ecosystem, botanists have urged after witnessing clear changes in leaf-shedding and flowering patterns.Some species, such as the red kapok tree and the flame tree, which should shed all leaves during winter, had shown signs of incomplete leaf drop by spring or early flowering in recent years, the experts said, stressing the importance of looking into...