If mangroves disappeared the ecosystem would take a heavy toll, as stupid as it sounds, even the smallest imbalance would change everything, it would even cause much of the fish that call Mangroves home to be stuck in an unfamiliar place and get eaten causing a disruption in the food chain, true they don't have much reason to say but scientists say that Mangroves can help with global-warming and floods...
sorry, i typed a lot i hope what i typed was helpful to you though~