All Hail The Halophytes


With climate changing leading to a rise in sea levels and an increase in droughts and floods, Mark Anderson worries that “the acreage available for conventional, freshwater agriculture is shrinking rapidly.” Which leads him to this thought:

More than 97 per cent of the water on Earth is saline. Wouldn’t it be cruel if nature had locked up the vast bulk of the planet’s vital fluids in a form that no plant could drink? Well, as it happens nature is not quite that cruel. Of the 400,000 flowering plant species around the world, 2,600 do drink seawater. They are halophytes, meaning ‘salt-plant’, and they might just be the answer to a question surprisingly few governments have yet asked: namely, how can we put our planet’s practically infinite volumes of saltwater to good use?

Among the halophytes he believes holds promise is a perennial species called “seashore mallow,” a plant that “can grow in salty soil, using saltwater irrigation” and has been championed by the University of Delaware researchers John Gallagher and Denise Seliskar:

Last year they published a paper in the journal Renewable Energy, co-written with a group from the US Department of Agriculture, that analysed the plant’s potential as a biodiesel and ethanol source. By their calculations, it comes out roughly on par with soybeans, one of the commonest sources of biofuel now in use. A second paper, in Biomass and Bioenergy, examined the perennial’s stems’ absorbency, revealing commercial potential as mulch, erosion control and even kitty litter and animal bedding.

That variety of applications is important. ‘The thing that became apparent to us is it wasn’t going to run economically just on the oil you squeezed out of it,’ Gallagher says. ‘It’s taken 8,000 years to evolve corn from the teosinte [wild grass] found in the Mexican highlands to the Iowa cornfields. I just don’t have that long. So we thought we’d try to come up with an array of things we can get from the plant.’ Gallagher and Seliskar estimate that the entire crop can be harvested for products that could compete with existing markets of conventionally farmed commodities. The absorbency of its inner stem makes it attractive for animal bedding, while the outer bark has been developed into a thread for cloth. The seed, as noted, is a promising stock for ethanol and biodiesel. And the seedmeal offers a spread of amino acids that make it attractive as animal feed. Roots, spent flowers and the biopolymers in the plant are also being investigated for everything from gums to industrial chemicals.

(Photo of Salicornia, a genus of halophyte plants, by Rusty Clark)