Parsley fern

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Mid-Atlantic

Even when Charles Darwin visited what would become known as Ascension Island, he noted there was little to see. But despite the fact this scrap of British territory marooned in the tropical Atlantic was not well regarded, it has spawned a host of new species over its geologically young life. At least ten plants were known to be found only on this precipitous black rock.

That was until sailors introduced goats, rabbits, sheep, rats and donkeys, along with hundreds of invasive plants in a bid to boost the volcanic soils productivity and create a much-needed pit stop for passing ships. Yet this had disastrous consequences.

When botanists finally got around to studying the flora of the island some 350 years after its discovery, the island had radically altered. By the mid-20th century, it was found that four of the unique species of plants once common had been eaten and competed out of existence. Or so it was thought.

 

Finding the fern

While conducting a routine plant survey across the island in 2009, Ascension Island’s Conservation Department decided to see what was growing along a precarious knife-edge ridge that ran down on side of Green Mountain, the dominant volcano on Ascension. Clambering along steep slopes of volcanic rock slick with water and vegetation, their team knew exactly what they had found the moment they set eyes upon it.

They discovered a small green-yellow plant, with frilled leaves not unlike those on parsley, poking out among some of the boulders on the rocky slope. Easily overlooked by many, scientists had been searching for this plant since it was last seen almost 60 years previously. Now, clinging on precariously to the side of an unstable cliff, botanists could confirm the rediscovery of the Ascension Island parsley fern, Angogramma ascensionis.

Once commonly found in a restricted range on the island, it had even caught the attention of the acclaimed explorer and botanist Joseph Hooker when he visited Ascension in 1876. At that time Hooker was on a mission from Kew Gardens, a botanical garden in southwest London, to plant non-native trees on the island. But following the introduction of hungry herbivores, and competition from the invasive maidenhair fern, the population of the native fern crashed. It was last seen when a single specimen was found during a survey in 1958.

The four individuals that had been rediscovered were found growing in a treacherous place. The unsteady cliff on which they grew was dry, and largely unsuitable for the ferns. And so, the botanists set out on a daring mission to save them.

The scientists needed to keep the plants alive, and so scaling down the cliff on ropes they constructed a drip feed, climbing the mountain twice weekly to top up the water supply. Next, they needed to get a sample of the spore forming parts of the fern, in order to try and grow them in a more controlled environment. After collection, two of these remaining plants died.

 

Kew knowledge

The island did not have the facilities needed to propagate the fern, and so the samples had to be placed in a sterile box and rushed to the nearest airstrip, where they were then flown to a military airport in the UK before being hurtled on to Kew Gardens. There, the scientists were tasked with getting the spores to grow.

First, the samples had to be placed in bleach to kill off any microbes that might have been transported with the fern leaves. This in itself is a risky process, as too long in the bleach kills the spores, but too short a time in the bleach allows the bacteria to survive. Finally, the team had a tiny piece of sterile fern to work with and try to propagate.

From these humble beginnings, the scientists at Kew managed to successfully grow 60 Ascension Island parsley ferns. Since then the botanists on Ascension have even managed to grow some back on the island itself in their own shade house.

The goal is now to eventually restore the endangered plant back to its native habitat and protect them from the threats that lead to their close brush with extinction. Since the original four plants were found and propagated, researchers have even discovered another small patch of the ferns just a stone throw away.

The perilous story of the Ascension Island parsley fern is, unfortunately, not a unique one. Island ecosystems are well known for their tendency to evolve endemic species found nowhere else on Earth in naturally restricted areas. But this is a double-edged sword.

Living in isolation, these plants are also incredibly susceptible to extinction due to their naivety to introduced species, naturally low numbers, and limited distribution. There are a countless number of species from islands now balancing on the brink of extinction. But if the parsley fern tells us anything, then it is that all may not be lost. Even if just a handful of individuals remain then the species can be spared, and with it, a unique piece of the puzzle that is the planet’s rich and varied ecosystem.

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