Beach Heliotrope is an introduced tree widely distributed throughout the Pacific and has been documented in the Northwestern Hawaiian Islands since the 1960s. As observed over the years on Kure Atoll, heliotrope demonstrates strong colonizing qualities, especially after a significant storm and tsunami event. Once they mature into trees, they shade out all plants inhibiting other plants from growing underneath it. Also, heliotrope erodes the dunes because they lack hair-like roots that capture sand.
A massive spread of heliotrope trees occurred after the Japan tsunami of 2011 that inundated parts of Kure Atoll increasing the tree’s range tenfold along the coast, inland and across other atolls throughout the Northwestern Hawaiian Islands. Simultaneous to that massive increase in range has been a significant loss of dunes since the 60’s where hundreds of heliotrope trees were allowed to establish themselves.
A dense stand of heliotrope roots crawling right up to the beach strand is a common sight on Midway Atoll, Lisianski and Laysan Islands. The density of heliotropes at the shoreline creates a wind block for the interior of the island where high concentrations of seabirds nest. It can greatly affect the bird’s ability to take flight and the increased temperature in the lee of the trees causes heat stress and mortality in albatross.
As a result, the root structure also obstructs the pathways for monk seals, turtles, and birds to access to their resting or nesting habitat inland where they are safer from storm and tsunami events. Some birds are able to perch and nest on them, like the ʻiwa (frigate bird) and red-footed boobies. However, when the heliotrope tree dies, they become a stiff strike hazard for albatross. When an albatross flies into the branches they can injure themselves and fall into the tree where they become entangled and die from injuries or starvation.
The management plan for this tree is of significant importance to the vitality of the dune structures on Kure. It directly competes with naupaka (Scaevola taccada), a dune-building plant, for scarce water resources, sunlight and nutrients. The eradication of heliotrope involves a multi-prong approach to eliminate all growth stages, exhaustion of the seed bank and removal of the dead trees. Currently, it is targeted for control through the year 2020 and will be considered for an eradication program after that. The final phase is to replace it with native plants.