Surtsey loses vulnerable plant species as species count falls

Surtsey is continuing to change, with fewer vascular plant species recorded on the island and some previously established plants appearing to be in decline or gone, mbl.is reports. The findings came from the Natural History Institute’s annual monitoring expedition.

The expedition was unusual because difficult weather prevented all members of the team from reaching the island. Only five of the 10 participants made it to Surtsey, forcing them to prioritise the most important tasks, including the annual survey of vascular plants.

The survey has been conducted continuously since the first vascular plant was found on Surtsey. Expedition leader Olga Kolbrún Vilmundardóttir said the resulting dataset was unique globally and had been used in a wide range of research. Some projects, including further research into the distribution of crowberry, had to be postponed.

The team found 57 living vascular plant species on Surtsey this summer, two fewer than the previous year. The most vulnerable populations are those that have not become firmly established. Vilmundardóttir said the number of vascular plant species had risen quickly in the island’s early years, then slowed before increasing again as gull colonies developed. The increase slowed once more after 2007, and the island now appeared to be losing species.

Angelica appeared to have withered and disappeared, meaning the team could no longer confirm that it was still present. Coastal erosion was also clearly visible. One permanent monitoring plot was about one metre from the cliff edge and was deemed unsuitable for further measurements.

“You can really feel how quickly the erosion is happening because you have these reference points and visit the same places year after year,” Vilmundardóttir said.

The island is mapped by drone every other year, providing detailed information about how its land is eroding and changing. The force of the sea was particularly evident at the southern cliff, where sea spray reached over the 20 to 30-metre-high cliff and spread inland.

Vilmundardóttir said the sea could be directly affecting vegetation on the island, while waves were also continually changing bird habitats. Other plant species were thriving, however. Rush was unusually lush, eyebright was found in many places, and meadow foxtail had spread since it was first recorded last year.

Gulls have played a key role in shaping the vegetation by carrying seeds and nutrients inland. This is believed to be the main reason why southern Surtsey has become so green and fertile. Greylag geese, which feed on grass, can make use of the grassland that has formed there, and the team saw adult geese with well-grown young on the island this summer.

The group also saw several thistle butterflies, which are carried by winds from Europe. Vilmundardóttir said it was uncommon to see such large and noticeable butterflies on Surtsey. Some were seen feeding on bladder campion.