Hawaii’s En­dan­gered Ohia

Newsweek - - Con­tents - BY LESLIE NEMO @leslie_nemo

mythol­ogy holds that the god­dess Pele, in a fit of jeal­ous rage, trans­formed the man she loved into a gnarly ev­er­green called the ohia. That’s the tragic tale be­hind the beau­ti­ful tree that, in its many forms, makes up most of Hawaii’s for­est canopy. (It also grows as a shrub or an epi­phyte—a tree that grows on other trees.) It would be hard to imag­ine the ar­chi­pel­ago with­out the ohia, but some worry that day could come.

Few were con­cerned when ohia trees started dy­ing from blight in 2010. In re­cent years, how­ever, “rapid ohia death,” as the dis­ease is called, has spread across more than 135,000 acres on the Big Is­land and jumped to the nearby is­land of Kauai. Sci­en­tists and pub­lic of­fi­cials are now in a des­per­ate ef­fort to stop the dis­ease and save the canopy, along with the mul­ti­tude of flora and fauna that de­pend on it.

It’s not go­ing to be easy. The cul­prit is for­mi­da­ble: two pre­vi­ously un­known species of fungi, which ap­par­ently ar­rived on the is­land via spores from a mys­te­ri­ous source. Lisa Keith, a plant pathol­o­gist with the U.S. Depart­ment of Agri­cul­ture, iden­ti­fied the fungi in 2014. “They were mys­te­ri­ous then,” she says, “and they’re still mys­te­ri­ous.”

A treat­ment is not forth­com­ing. Of­fi­cials are fo­cused in­stead on con­tain­ment. The fungi kill the trees from the in­side by clog­ging their wa­ter path­ways,

turn­ing the leaves brown and re­leas­ing new spores. By the time the trees ap­pear to be sick, it’s too late. In Au­gust, in what might be con­sid­ered an act of des­per­a­tion, the Hawaii Vol­canic Na­tional Park teamed up with pri­vate groups and fed­eral re­search labs to of­fer a $70,000 prize to who­ever can come up with tools for early de­tec­tion.

Greg As­ner could be a front-run­ner for the prize. An ecol­o­gist with the Carnegie In­sti­tu­tion for Science, he built a de­vice that can de­tect in­fected trees be­fore symp­toms ap­pear. From an air­plane, he uses a laser beam to out­line the trees that pass be­low and a spec­tro­graph to mea­sure the pre­cise color of light re­flected off the leaves. Turns out the pres­ence of fungi slightly al­ters the color of the leaves in a way As­ner’s de­vice can see.

In re­cent months, his team and for­est man­agers have been iso­lat­ing in­di­vid­ual trees from As­ner’s data, de­ter­min­ing which have the chem­i­cal sig­na­ture in­di­cat­ing the spores’ im­mi­nent re­lease. These are then com­mis­sioned for log­ging, be­fore they taint neigh­bor­ing trees. The method is ex­pen­sive—as­ner gets fund­ing for only one fly­over per year—and more fre­quent up­dates would be help­ful.

Should con­tain­ment fail, sci­en­tists are con­sid­er­ing prop­a­gat­ing va­ri­eties of ohia that are in­her­ently re­sis­tant to the in­fec­tions. Also, a con­sor­tium of gov­ern­ment and non­profit groups is build­ing a seed bank, in case they’re needed for restora­tion.

This is just the be­gin­ning of a bat­tle that will likely last for many years, says As­ner. But he’s de­ter­mined to keep fight­ing. “You get mo­ti­vated,” he says, “when you see your na­tive for­est go belly up.”

THROW­ING SHADE “Rapid Ohia death” has spread over 135,000 acres on the Big Is­land and jumped to Kauai.

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