Freshwater Lakes and Rare Forests

Surprisingly, 40 freshwater lakes are captured in the hollows of sand dunes across the island. Some of these bodies of water are known as perched lakes because they sit in large depressions on top of towering sand dunes. What prevents the water from seeping away? An organic liner, or peat caulking, in the form of partially decomposed leaves, bark, and branches.

The island also has window lakes, which form when depressions in the sand dip below the level of the groundwater table. Fresh water seeps into the hollows, creating crystal-clear, sand-filtered pools that are, in effect, windows in the water table.

The island’s lakes are replenished by 60 inches [150 cm] of rain a year. Water not trapped by lakes or soaked up by sand forms creeks that run into the sea. One stream is estimated to empty well over a million gallons [5 million L] of water an hour into the Pacific Ocean.

The abundance of water makes Fraser Island verdant. Normally, rain forests will not form in nutrient-deficient sand. But Fraser Island is one of the few places on earth where rain forests flourish on a sand base. Indeed, at one time the forest was so dense that for more than 100 years, it echoed to the chop of the lumberjack’s ax. Blackbutt, kauri, and tallowwood trees appealed to woodsmen. Said one in 1929: “The traveller strikes a living wall of giant timber trees up to 150 [feet] [45 m] high . . . These great monarchs of the forest are from six to ten feet [2 to 3 m] in diameter.” Some trees, such as the satinay tree and the turpentine tree, ended up in the pile walls of the Suez Canal. Today, however, the trees of Fraser Island grow old in peace.

A rare phenomenon​—rain forests that grow in sand