Environmentalists at a discussion yesterday urged the government to declare February 14 as Sundarbans Day. They said the Sundarbans with its rich bio-diversity is protecting the southwestern region of the country from natural calamities, but the forest resources are being plundered, threatening ecological disaster. The largest mangrove forest in the world must be preserved in its natural form as it is essential not only for our survival but also for the existence of the mankind, they added.