Can Hydroponics Save Threatened Plants Species?

An annual report that examines the state of the world’s plants shows that there are approximately 390,000 plant species globally, with 2,000 new species of plants discovered each year. From a pure numbers perspective, that is good news.

Researchers at England’s Royal Botanic Gardens Kew, however, also note in their global assessment of flora that “one in five of the known plant species is threatened with extinction” due to a variety of factors like disease, urban encroachment, and climate change. Damian Carrington, environment editor at the Guardian, a British daily newspaper with a continent-spanning team of environmental journalists tracking the effects of man-made climate change, quoted the director of the report as saying, “Plants are absolutely fundamental to mankind—without them we would not be here. We’re facing some devastating realities if we don’t take stock and reexamine our priorities (because) the genetic diversity in our foods is becoming poorer and poorer.”

Though we stumble across a couple of thousand new plant species each year, we are annually losing more than that through habitat destruction for farming, deforestation for timber, infrastructure construction to accommodate urbanization, and the growing impact of climate change.

Maximum Yield wondered if any of these plants in danger of disappearing, especially those used for necessity items such as food or medicine, might be saved from extinction by bringing them indoors in a controlled, hydroponic environment where all their needs—a healthy grow medium, adequate sunlight, proper nutrients, temperature, disease control, and more—could be met.

It’s of possible benefit, perhaps, but it seems the notion doesn’t have a lot of strong proponents for a winner-take-all theory.

“Like every Irishman, there is no direct answer,” says Dr. Peter Wyse Jackson, who worked for 18 years in Kew heading up the International Network of Botanical Gardens and is now president of the Missouri Botanical Garden. As chairman of the Global Partnership for Plant Conservation and one who has played a lead role in the implementation of the Global Strategy for Plant Conservation, the well-known botanist and plant conservationist from Kilkenny, Ireland, stoically says, “Many plants could be saved through long-term conservation, and hydroponics is a method that could be useful for cultivation of plants. That being said, I don’t know of any examples where hydroponics has been used specifically for plant conservation.”

Referring to hydroponic growing as one possible path to travel for specific cases, Wyse Jackson notes, “It might be very helpful in cases where ground cultivation has failed. Sometimes species rely on having complex mycorrhizal associations in the soil surrounding their roots. They thrive because of that complex mixture of soil and fungi that help sustain them. But if you can’t get that mix correct, it may be that hydroponics could deliver the cocktail of needed nutrients in liquid form.”

Gary Paul Nabhan, an agricultural ecologist and ethnobotanist, is one of the original bring-them-back-from-the-dead researchers who co-founded Native Seed/SEARCH (NS/S), a non-profit conservation organization in Tucson, Arizona, that seeks to preserve indigenous southwestern plants as well as knowledge of their uses. Since its founding in 1982, NS/S has become a major regional seed bank and leader in the heirloom seedmovement. Housing more than 1,800 seed collections, many of them rare or endangered, the organization handles more than 90 crop varieties not being systematically preserved elsewhere.

Few know better than Nabhan, the former science director of the Arizona-Sonora Desert Museum, that once plants are gone, they’re gone—but he doesn’t see a controlled environment as a free ticket home.

“The hydroponic strategy is an extremely long shot, in my opinion,” he says. “I was involved in the first years of a Center for Plant Conservation consortium of nearly two dozen botanical gardens that legally grew threatened native plants, so there’s some experience of probability here—but that’s not the bottleneck. Habitat protection, where all their interacting species occur, is the key issue; the rest is merely a distraction.”

Fair enough. But one man’s ceiling can be another man’s floor.

Matt Johnson is program manager of Arizona’s world-renowned Boyce Thompson Arboretum, which has the mission to “create one of the largest living repositories of arid land germplasm in the world.” There are 3,200 desert plants to be found in this 320-acre living classroom. Species taken from the Earth’s many and varied deserts and arid lands are displayed alongside native Sonoran Desert vegetation.

“There are many kinds of plants that can be grown hydroponically, though most can be grown just as well using more conventional means,” says Johnson. “So, I don’t know that hydroponics offers any particular advantages for the purpose of conserving rare plants. For some species, it might be a practical methodology, but unless there are reasons the plants can’t be grown more conventionally, you can accomplish the same thing conventionally using proper horticultural techniques or in a greenhouse but without hydroponics. And growing in sterile soil in a container is also more cost effective.”

Johnson calls habitat preservation the “ultimate goal” in this situation and cites habitat loss as the single biggest threat, closely followed by climate change, slash-and-burn agriculture, and even plant collectors who have driven some species to the brink of extinction.

“The ultimate goal of an ex-situ conservation effort should be to eventually return a plant to its native habitat or, at least, to the wild in an area where reintroduction can be attempted. Even then, assuming an area for a reintroduction would become available, a major concern is that cultivated plants are unintentionally selected for traits that are adaptive to horticulture and these same traits may not necessarily be as adaptive to survival in the wild.”

Given the choice between optimism and pessimism, Johnson admits to being somewhat pessimistic. “We’re going to lose a lot of things, and even putting current political climate aside, altering the trajectory our society is on—changing our ways—can’t be done quickly enough to head off a lot more problems that will come back and bite us in the tail.”

One expert calls hydroponic cultivation “a long shot,” while another says it’s doable, but “seed-banking and cryo-preservation should be used to preserve as much genetic diversity as possible.”

Even Dr. Merle Jensen, a pioneer in soilless growing and a strong proponent of plant growth and reproduction in hydroponic liquid culture versus solid media growing, waffles a bit. “Hydroponics or soilless growing in water or perlite or vermiculite is one method that can be used in the saving of plant species, but it’s not a save-all solution,” he says. “Historically, plant species have come and gone and the technology we have today to control all aspects of growing crops or plants—in the ground or above it—under the watchful eye of horticulturists or scientists, could help save some of those species.”