Mangrove seeds sprout on the tree, then sail off for a year
Most seeds wait for soil. Many mangroves germinate while still hanging from the parent tree, then drop a ready-made seedling into the sea. A red mangrove's floating offspring can stay alive for up to a year, drifting until it finds calm, less salty mud where it tips upright and takes root.
Mangroves are trees and shrubs that live where most plants die: in salty or brackish tidal water along tropical and subtropical coasts, mostly between 30 degrees north and south, with the largest areas within 5 degrees of the equator. They are not one family but several that evolved similar tricks independently, a textbook case of convergent evolution. About 70 true mangrove species, spread across 16 families, grow almost only in these habitats. Some tolerate water more than twice as salty as the ocean.
Getting rid of salt is their first problem. Red mangrove roots are heavily waterproofed with suberin and act as an ultrafilter; one study found an Indian mangrove's roots block 90 to 95 percent of the salt in the water they absorb. A popular idea holds that leftover salt is dumped into old leaves that are then shed, but research on the red mangrove found yellowing leaves carry no more salt than green ones.
Breathing is the second. Waterlogged mud holds little oxygen, and bacteria there release sulfides and methane. Red mangroves raise themselves on stilt roots and take in air through pores in their bark, while black mangroves send up pneumatophores, snorkel-like roots typically up to 30 centimetres tall and in some species over 3 metres. Leaves save fresh water by limiting how far their pores open and angling away from the midday sun.
A 2025 estimate puts the global mangrove area at 15.9 million hectares, with Indonesia holding the most, at 3.4 million, and Europe none. Losses continue at roughly 0.16 percent a year worldwide, which matters because mangroves buffer coasts against tsunamis and storms and lock away carbon. Mangrove plant families date to the Late Cretaceous, and the oldest mangrove palm fossils are 75 million years old.
Source: Mangrove
