pollution is indeed an issue, although more prevalent in the open waters of the bay, littered by the outflow from sewers and industrial sites.

the draining of the mangrove, though, is another issue altogether - inland, the marshes which characterized guaratiba in the colonial era were drained with the passing of time, to make way for transport lanes and habitation areas.

more recently the works to build the army installations forced the drainage of wide areas of mangrove - the creation of the portinho canal, which ends right besides suruquai, in the southern edge of the island, did little to prevent the accumulation of sediments in the shallower wetlands.