Say Hello to the Tree That Eats Metal

A plant just discovered in the jungles of the Philippines could help clean up contaminated industrial sites.

Though nearly all plants have evolved to exclude from their roots any metal in the surrounding soil, Rinorea niccolifera, endemic to the island of Luzon, accumulates it. (Photo: Aff Ei/Flickr)

May 27, 2014· 1 MIN READ
Katharine Gammon has written for Nature, Wired, Discover, and Popular Science. A new mom, she lives in Santa Monica.

Researchers have made an astonishing discovery in the jungles of the Philippines: a scrubby tree that sucks metals out of the ground and stores them in its leaves. It’s not the first hyperaccumulating plant, as scientists reported in the journal PhotoKeys earlier this month, but it is the newest addition to a family that could give a boost to green tech.

The plant, called Rinorea niccolifera, can accumulate up to 18,000 ppm of metal in its leaves and roots without being poisoned. These plants could be used to clean up old mines or metal-filled soils, and the roots and leaves can be burned, leaving behind valuable metals that can be sold and repurposed.

Only about 450 species around the world have the ability to suck up nickel from the soil. “Most plants—99.99 percent of plant species—are very good at excluding the metal from entering their roots and shoots,” said Augustine Doronila, a research fellow at the University of Melbourne in Australia and co-author of the paper on the new species. Instead, hyperaccumulators like R. niccolifera have evolved the ability to load their tissues with the excess nickel, a clever adaptation that enables them to live in tough soils where other plants can’t.

The find occurred in metal-rich soils on the island of Luzon, the Philippines’ largest. The researchers had to carefully measure the characteristics of the new species and gather its fruits and flowers over the course of years. Because the species was in a mining region, Doronila said, "it was even more imperative to try to learn more about it in order to gain knowledge, which can help us propagate [the plant] and return it to the mined-out areas."

The idea of deploying plants in the fight for cleaner ecosystems is not new; using them for the purpose of extracting metals from contaminated soil started to get popular in the 1990s. Environmental remediation with plants may be more attractive in developing countries because of the low cost—there’s even the potential to pay for the effort by selling the extracted metals. Countries that have taken the lead in harnessing this green technology are China, Thailand, Brazil, and India.

Doronila points out that the new species may have another benefit: “What is significant about this newly described species is it is a tree as most of the other species previously discovered are shrubs,” he said.

The plant’s possibilities could go beyond mining and remediating contaminated soils. “If we can understand the chemistry of how these plants can load themselves with so much nickel without being poisoned, it may help us make novel compounds to combat some degenerative disease,” said Doronila.

That makes it all the more important to save the new species, and others like it, in their native habitats, Doronila said—the chief threat being the type of industrial activity they could be used to clean up after. “If we are to allow mining or logging in these areas, we have to oblige the miners and the loggers to restore these habitats.”