It's quite fitting that the genus is named after a 10th century Persian physician and naturalist, Ibn Sina or 'Avicenna'. For the Grey Mangrove grows as far west as the Levant, where stunted trees cast their roots through the saline dunes of the Sinai Desert in Egypt. A specimen from the Red Sea represented its species in the original botanical description of Avicennia marina. But this tenacious coloniser of fresh shores and fringe habitats ranges far from its type locality, holding fort in southern Japan and northern New Zealand and drifting with aplomb to reach Fiji and the southern tip of Victoria, Australia, where shrubby stands form bonsai swamps in a promontory of intemperate latitude.
In between, Avicennia marina shares the coasts of the Indo-Pacific with trees of other colours. Red Mangroves occupy the middle ground, extending their stilt roots to prop up tannin-rich trunks over mud or sand. Further inland, slower-growing Yellow and Orange Mangroves conspire to conquer the well-drained backwaters. In warmer climes, other pioneers, both congeneric and cousins from deep time, compete with marina for access to dwindling coasts and shrunken estuaries. But where the winters are too sharp for other mangals, the Grey Mangrove reigns, forming loose woods along riverbanks and inland tidal flats. On the banks of the Brisbane River, a floating boardwalk runs through an urban jungle of trees that litter the planks with a shower of split fruit. Closer to the heart of the city, rock and concrete dominate the flanks of the waterways. But patches of grayish green still dot the landscape between the river and the high rise blocks of a subtropical city.
The balmy shores of Singapore support a far richer array of mangals, yet Avicennia marina struggles to maintain a foothold in the island's tiny mangroves. It's unclear if this is due to the widespread clearing of its preferred foreshore habitats for seawalls and sanitised shores, or simply an artifact of ecological dynamics in a competitive community. But surviving trees are said to grow on Pulau Tekong, St John's Island and a sliver of a swamp at Ulu Pandan. Pulau Semakau and its adjoining landfill also shelter a handful of Grey Mangroves that have managed to overcome the luck of natural selection. The trees, including one barely taller than a man, flower and fruit profusely.
Despite their ability to tolerate the harshest of climes, the Grey Mangrove is largely displaced in more forgiving environments. More accustomed perhaps to a permanent state of stress and shortage, the saplings wither in conditions that favour rivals able to soak up nutrients and shoot up at higher rates. Up close, the tree is betrayed by its twigs that are squarish in cross section and inflorescence stalks that end in a tight clump of yellow flowers. The blooms emit a sickly sweet aroma and when pollinated, develop into fruit that resemble outsized lima beans with a beak-like tip. The bark is also distinctive, with flaky patches of green and yellow. While examining the trunk of a lone treelet on Semakau, another rarity was found lurking in the shade. Not quite as vulnerable as its chosen home, the Mangrove Big-jawed Spider shuns the sun and stays still in the daylight hours to elude diurnal hunters. At dusk, she will emerge to spin a sticky orb and take her toll of nocturnal visitors that fail to see a fatal gap in her treetop garden of fragrance.
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