Saving snails: an invasive species becomes an unlikely hero

A land snail (Photo/ Petr Kratochvil)

Now, I know snails don’t come with the same poster-child charisma factor of more fuzzy, wide-eyed creatures  like pandas or baby tigers. But I hope you’ll imagine a tiny, high-pitched, “Help me!” issuing from the leaf litter at your feet, and stick with these little guys for a minute.

With that said, I’d like to tell you a story of a rat, a snail and a tree. They all live on the tiny island of Anijima, one of several in a chain of islands off the southeastern coast of Japan. The snail is critically endangered. The rat and tree are invasive species. You know those bullies of the natural world, the unwelcome visitors, the home wreckers of entire ecosystems. But before you go, “Oh here comes another invasive species story,” here’s the kicker – one of these encroachers, the tree, is actually in a sense the hero of this story, buying time for the snail and those trying to save it. The study, published online in the journal Conservation Biology, offers conservationists a new framework for restoring native ecosystems.

Anijima is part of the Ogasawara Island chain, a remote group of islands off Japan nominated for World Heritage listing. It’s also snail central. These islands are home to more than 100 species of land snail, 94 percent of which are endemic to those islands. Many of the snails have disappeared over the years, thanks in part to habitat loss and introduced predators.

Anijima was the exception. No one has lived there since the 1830s, and until recently, the environment looked much like it did 100 years ago. But a plant, the Casuarina tree has taken over the mid-western part of the island, converting natural forestland into a monoculture of dry coniferous forest. This delivered a significant blow to the land snails, as the snail’s home was turned into less ideal living quarters. Another blow came with the introduction of black rats in the 1930s. These voracious predators, gobble up the slow-movers, and since about 2006, have enjoyed an unprecedented population boom on the island, likely due to the eradication of goats – a competitor for food – and of feral cats – the rat’s main predator. In short, things weren’t looking good for the snails.

One might think, “Well, if you want to save the snails, just go in there and clear out the invasives.” But not all invasive species are created equal, and one scientist, Satoshi Chiba, with Tohuku University in Japan, has figured out that the Casuarina tree is actually helping the snail weather the rat boom.

Chiba looked specifically at the Ogasawarana genus of snails, a critically endangered group of snails considered a “natural monument” by the Japanese government. They are the only group of snails on the island still living on native vegetation on the island. Chiba surveyed plots in both Casuarina-laden habitat and native habitat, clearing sites of leaf litter, counting and identifying snail species and then returning everything to its place. Chiba also checked for rat carnage, and found that while initially, the tree causes a decline in snail populations, once the rat population went crazy, the Casuarina tree actually provided the snail with a better refuge from the predator than the snail’s native habitat.

The ground litter in the Casuarina habitat is deeper and denser than the snails’ natural environment. Black rats like to forage at the surface, and thus, the snails stand a better chance of avoiding a rat’s tooth and claw in the debris of a Casuarina forest.

The lesson here is not that an invasive species is necessarily good, but that there is an order to things when it comes to restoring an environment impacted by multiple non-native species. For Anijima Island, and the Ogasawarana snails, if they are to be saved, it’s likely that the black rats need to go before the invasive trees.

So, do you care a little more about a tiny mollusk? I don’t know, but at the very least, the story has a rich history, and just think how many other species suffering from a similar tale this study could help.

Reclamation, restoration and mountaintop removal

My first taste of reclamation came as a grad student while on a fieldtrip along Colorado’s “Uranium Highway.” We stopped in the ghost town of Uravan, a former Uranium/Vanadium boomtown. And except for a couple buildings, everything had been torn down, the tailings ponds evaporated, land reclaimed or in the process of being so. It was then that I learned that reclamation and restoration were not the same thing. Above the once upon town sat tailings sites. Instead of a rust-colored desert environment,  meticulous patterns of white and black rock zig-zagged across the hilltop, laid out like some sort of interpretive landscape project.

Reclamation, I thought, was supposed to help clean up after we’d finished using the land. It was supposed to help return the land to itself. I’ve seen many reclaimed sites since that fieldtrip, and have yet to come across one that resembled nature’s design.

That’s not to say that reclamation is a lost cause or a sham, just that it can be better. Now scientists are trying to help make that happen with arguably one of the most destructive and controversial mining practices at work today, mountaintop removal. Sarah Hall, of Kentucky State University,  and her colleagues Christopher Barton and Carol Baskin, of the University of Kentucky, have discovered a new method of replanting mined Appalachian sites, one that gives native landscapes a leg up at renewal. (You can find their study in the online early edition of Restoration Ecology)

Mountaintop removal reclamation projects often involve planting blasted and terraced mountainsides with non-native grasses. (Early surface mine reclamation would sometimes simply abandoned the site.) Perhaps one of the more unexpected outcomes of reclamation comes from Mingo County, W. Va., where reclamation turned a blast site into what’s now known as the Twisted Gun Golf Course.

Rather than seeding mined areas with grasses, which tend to stunt recovery of native species, Hall sought to test the possibility of replanting mountaintop removal sites with the trees and forbs kin to the forests that had existed before the mines. Hall’s idea seems in hindsight to be quite obvious. Put back the original topsoil scraped away when creating the mine. This soil she found was rich with the seeds and microbial recipe that could help re-establish forest. Where Hall and her team tried the method, the plants started to grow, including arrow-leaved asters, Virginia pines and blueberry.

The method is not enough to completely recover the forest, but it’s a start, and a step up from the grassy slopes that have come to replace so many of Appalachia’s mined mountainsides. Hall’s research highlights a two-fold lesson  – we need to recognize that reclamation is not restoration, and there are practical ways to make reclamation better. Then maybe these environments that have given us so much of their riches at least have a chance to return to themselves, even if it’s just a little.