Take the Red Palm Weevil (Rhynchophorus ferrugineus), for instance, a beetle native to Southeast Asia. It is thought to have been introduced to the archipelago in 2019 via the importation of date or coconut palms, since scientists first identified it in date palm (Phoenix dactylifera L.) plantations situated within 5 km of Hadiboh, the capital of the Socotra Governorate.
The authors of this initial survey, namely Arne Witt, Vladimir Hula, Kay Van Damme and local Socotran expert Ahmed Saeed Suleiman, consider that ‘more surveys are needed to determine the wider distribution of this palm pest on Socotra and what impact current invasions are having on date production’.
This survey is one of the few studies done on Socotra up to now to assess the impact of invasive species on the local economy and biodiversity. Yemeni scientists published just three articles in international journals between 2012 and 2019 on tackling invasive alien species, according to the UNESCO Science Report (2021).
Since date palms have traditionally been Socotrans’ primary source of food after milk and meat and their main agricultural output, the arrival of the red palm weevil poses a threat to local livelihoods. The larvae of these large snout beetles feed voraciously on the inside of palm trees, causing them to deteriorate rapidly, and the adult weevils can spread quickly to neighbouring trees.
Weevils can be controlled by the removal of infested palm trees, the widespread trapping of adult weevils and the targeted use of insecticides. The weevil’s natural enemies can also be used to manage its population. In 2014, a team led by Guiseppe Mazza identified more than 50 natural enemies of the weevil, the most effective of these being different species of fungi.
Invasive species have thronged to a less secluded island
Socotra remained relatively isolated until the latter half of the 20th century but development has surged in recent decades. This has made it easier for invasive species to reach the island via various means of transport.
Invasive plant species in Socotra include milkweed (Calotropis procera) and whiteweed (Ageratum), the mesquite tree (Prosopis juliflora) which has already wreaked havoc in Africa, a prickly pear cactus (Opuntia stricta), thorn apples (Datura) and the tobacco plant (Nicotiana). These invasive species are also damaging economies in other arid regions.
Some of these imported plants, like Opuntia cacti, Prosopis and Calotropis, are among the most infamous plant invasives outside their natural ranges. On the Yemen mainland, for instance, the large Opuntia cacti, which are native to the Americas, can occupy entire valleys, causing eye and snout infections in livestock when the small hair-like spines dislodge from the cactus and irritate the animals' eyes and nasal tissues. Other imported plants may bring disease or pests.
The UNESCO World Heritage Committee considers the Socotra Archipelago to be of ‘significant concern’. The latest state of conservation report by the International Union for Conservation of Nature, the World Heritage Outlook, 2020, lists invasive species as posing a ‘high threat’ to the archipelago.
However, invasive species are a growing threat worldwide, according to a report released on 4 September by the Intergovernmental Science–Policy Platform on Biodiversity and Ecosystem Services, of which UNESCO is an institutional partner. The study finds that invasive alien species have played a key role in 60% of the extinctions of plant and animal species around the world. The annual cost of invasive alien species has also quadrupled every decade since 1970 to the point where it now amounts to US$ 423 billion, according to the report.
Socotra’s numerous endemic species highly vulnerable to aliens
The Socotra Archipelago lies off the Horn of Africa, at the crossroads of the Arabian Sea and the western Indian Ocean. The archipelago comprises four islands and two rocky islets. Covering a land area of around 4 000 km2, the archipelago has a human population of about 100 000.
Isolated from the Afro-Arabian mainland millions of years ago and situated at the convergence point of multiple marine regions, the Socotra Archipelago harbours an extraordinarily large population of endemic species. More than one-third (37%) of Socotra’s terrestrial plant species are endemic, as are 42% of its insects. As much as 90% of its reptile species and 98% of its land snail species do not occur anywhere else in the world.
Socotra boasts at least 848 different plant species, 1 670 insect species and 250 bird species. Its marine biodiversity is also impressive, with 253 species of reef-building corals, 729 species of coastal fish and 300 species of decapod crustaceans.
Endemic species have adapted to the archipelago’s dry climate. For instance, Socotra’s emblematic trees are shaped like bottles or umbrellas to provide shade for their roots: the desert rose, the cucumber tree, the Socotra fig tree, Socotra’s Dragon Blood tree and several species of Frankincense tree.
The archipelago’s high ratio of endemic species makes it particularly vulnerable to invasive aliens. ‘Exotics are present in nearly all ecosystems of Socotra, in freshwater, terrestrial and even marine environments’, observes Dr Van Damme, chair of the charity Friends of Socotra.
Attempts to tackle some unwanted aliens
For Donia Abdelwahed from UNESCO’s office in Doha,‘direct monitoring, control and the eradication of exotics in Socotra is a priority. However, protecting the rich native biodiversity as a buffer against exotics can also be effective. Many invasive plant and animal species are opportunistic species that may benefit from weakened or disturbed ecosystems to establish themselves’, she says. ‘Over the past few years, the invasive Calotropis procera has proliferated along roads and in urban areas, for example’.
The local authorities have made attempts to tackle specific alien invasive species, in collaboration with community members, international donors and both local and international experts.
One example is the successful elimination of several hundred Opuntia cacti from Socotra in 2018, within an activity coordinated by Drs Van Damme and Witt and implemented by Ahmed Saeed Suleiman. This achievement was also possible, thanks to cooperation between the Socotra Branch of the Environmental Protection Authority, the Centre for Agriculture and Bioscience International and financial support from the United Nations’ Environment Programme’s Global Environment Facility.
‘There is an urgent need for monitoring, and quarantine facilities with trained people on Socotra to assess risks of exotics at entry sites such as airport and seaports’, observes Ahmed Saeed Suleiman. ‘We need support to manage the impact of exotics on local biodiversity and people’s livelihoods on the island and definitely more awareness about the potential risk is needed’.
Some invasive species arrived centuries ago, such as goats and smaller mammals such as rats (Rattus norvegicus) and mice (Mus musculus), cats and the Indian lesser civet cat (Viverricula indica). The civet is an active predator of reptiles, the majority of which are endemic to Socotra, but there has been little research into the civet’s impact on other animal species. The locals do know that civets may attack young goats, a state of affairs which has led them to place protective collars on their animals.
Socotra’s unique biodiversity has garnered global recognition, with the archipelago being designated a UNESCO biosphere reserve in 2003, a Ramsar site in 2007 for its Detwah Lagoon then as a natural World Heritage property in 2008. Last year, UNESCO’s Doha office published a book on Nature and People in the Socotra Archipelago which describes how the Socotra zoning plan was devised in 2000 to protect biodiversity while fostering sustainable development. Villagers often undertake spontaneous campaigns to replant emblematic plant species like the Frankincense tree in local nature sanctuaries and in the Socotra national park, which covers about 70% of the island.
Motivated young Socotrans are studying at universities abroad to complete MSc and PhD dissertations, in order to combine their traditional knowledge and love for the island with new skills, networks and techniques in various fields.
Salem Hamdiah, who chairs the Socotra Society for the Conservation of Endangered Flora, regrets that ‘mostly, local people are not aware of which are exotic plants on Socotra and they do not know the risks that they may bring to local species. However, the local communities in Socotra really do care strongly about the native plants they use traditionally’, he says, ‘such as the important frankincense and dragon’s blood trees. Through direct educational activities , people can become more aware of what exotics are and what they could do’.
Between October 2019 and February 2020, UNESCO organized an awareness-building campaign entitled Connect2Socotra with Friends of Socotra and international institutes, in order to promote the importance of Socotra and highlight the challenges it faces, through social media and targeted events.
Contact
UNESCO Office in Doha
