Changing Beaches

HIDING: Some animals like crabs go underground to avoid the extremes of unfriendly beach ecosystems

By Mary Margaret

SUN, sand and sea — what do these words mean to us? Do we think of holidays by the sea, seaside resorts, diving, snorkelling or walking into the sunset along a never-ending white sand beach?

Beaches, however, arehostile environments for plants, animals and other living creatures.

They change constantly with the tides rushing in and running; blowing sand; strong winds; and the creatures, which inhabit the transitional zones between land and water, have to adjust to the unvarying variation.

CHANGING: The succession of a beach habitat can be seen in this picture. Near the water there are no plants; a few metres in pioneer creepers and Rhu Laut seedlings colonise; and slighter farther inland pure stands of the graceful Rhu laut trees sway in the wind. caption

GET A GRIP: Primary succession occurs when plants colonise new habitats such as beaches. Flotsam, biodegradable and non-biodegradable materials, which land on beaches, pioneer plant species create niches. One of the first colonisers is the vine Ipomoea pes-caprae and it covers sandy beaches with long vines and fibrous spreading roots that hold the sand in place.

NEW RESIDENT: Beach pioneer species have special adaptations which enable it to survive potentially being buried by sand, salt water and dehydration. Sand is a course porous material that is prone to drying out. Rhu Laut (Causuarian equisetifolia) is a pioneer tree of tropical beaches. Its shallow spreading roots anchor it in the sand. The narrow needle-like twigs as well as tiny and modified scale-like leaves means it is not prone to drying out. The flowers are not easily seen, but the dark brown cones can be picked up under the pure stands of this tree.