12 May 2023

Why Koa Haole is Trouble

…and what we can do about it for Hawaiʻi

Why Koa Haole is Trouble

by Shannon Takahashi

Koa Haole, or “foreign Koa,” is an invasive shrub that is overrunning Hawaiʻi’s vulnerable native ecosystems. Deemed one of the top 100 worst invasive species in the world, Koa Haole poses a major threat to Hawaiʻi’s indigenous plants and environment. According to Dan Rubinoff of the Dept. of Plant and Environmental Protection Sciences, Koa Haole is especially problematic for Hawaiʻi because it can grow anywhere – even in rocky soil. Its seeds spread far and fast, and they are extremely difficult to get rid of.

“A fire can sweep through native dry forest and clear the land, and when you get those open clearings, the Haole Koa comes in and grows... it will re-sprout from its root,” said Dan in an interview with KHON2 about Hawaiʻi’s Koa Haole problem.  

Koa Haole were originally brought to Hawaiʻi to feed livestock, but like many invasive species in the state, the plant did a poor job of fulfilling its intended purpose and instead went on to wreak havoc on our environment. The invasive Koa Haole displaces native plants by taking away resources like space, light, water, and soil nutrients, and advances quickly into forests after native flora is wiped out by invasive grazers or brush fires. The spread of invasive plants like Koa Haole threaten Hawaiʻi’s indigenous plant populations and biodiversity– a problem that will only continue to grow.

However, Dan says locals can fight back by “removing Haole Koa from their properties and more broadly supporting control of invasive grazers, especially goats and deer, which make restoration of areas where Haole Koa has taken over impossible.” He also adds that people “can volunteer on any island to help restore native Hawaiian plants with groups that protect and preserve Hawaiʻi.” 

To learn more about Koa Haole, check out Dan’s interview with KHON2 here

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