Friday 22nd May: International Day for Biological Diversity
The United Nations has proclaimed May 22 as the International Day for Biological Diversity to increase understanding and awareness of biodiversity issues. This year, the theme is invasive alien species - one of the greatest threats to biodiversity, and to the economic and ecological well-being of society and the planet.
We have highlighted some examples of species that are facing extinction due to the threats posed by invasive alien species, and also some where this threat has been reduced or where species have been brought back from the brink of extinction. These species highlight the incredible success that can be gained by eradicating invasive alien species, and are a testament to the real and valuable impact conservation work can have and the importance of continuing such work in the ongoing battle against biodiversity loss around the world.
Threatened by invasive alien species
Zono (Bedotia geayi) |
The detrimental influence of human development and invasive species in the lower reaches of the Mananjary River has restricted Bedotia geayi to safer higher altitudes. Although this species is reasonably abundant within its limited range, a major problem in the future is likely to be competition from invasive species, such as Gambusia holbrooki, which have completely replaced this species in the lower parts of the Mananjary River. As deforestation spreads to higher regions, these invasive species may eventually replace Bedotia geayi entirely. | Lepinia (Lepinia taitensis)
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The single greatest threat to the native flora of the Polynesian Islands, such as Lepinia taitensis, is invasive alien plants. In Tahiti in particular, the invasive South American tree Miconia calvescens has displaced as much as 70 percent of the island's native vegetation. The dense stands formed by this vigorous species severely limit the regenerative ability of the smaller native understorey plants, by preventing their seedlings from receiving sufficient sunlight. It is reported that in forest dominated by Miconia calvescens on Tahiti, seedlings comprise only 7 percent of the Lepinia taitensis population, compared with 60 percent in intact, native forest on Moorea. | Bekko tombo (Libellula angelina) |
Once relatively abundant, bekko tombo populations have undergone drastic declines in recent decades as a result of introduced predators, as well as habitat destruction and degradation. Introduced alien species, such as Procambarus clarkii (a crustacean), Micropterus salmoides (a carnivorous fish), and Myocastor coypus (a large, semi-aquatic rodent), have all contributed to the dragonfly's demise either through direct predation, or through feeding on the water plants that sustain this native species. Sadly, the pattern of decline is only expected to continue. | Tristan albatross (Diomedea dabbenena) |
Astonishing research has shown that introduced house mice, three times the size of those in Europe, are devastating seabird populations on Gough Island by preying upon chicks. Approximately 1,000 Tristan albatross chicks are thought to be killed each year in this way and in 2008, the number of chicks that went on to fledge was five times lower than expected. A study of the mice has shown that their eradication from the island is feasible. However, until the initiative receives adequate funding, the Tristan albatross will continue to be driven towards extinction. |
Saved from invasive alien species
Antiguan racer (Alsophis antiguae) |
The Antiguan racer was once common in Antigua, but by the twentieth century it had completely disappeared from the island and was thought to be extinct, mainly as a result of the introduction of black and brown rats and the Asian mongoose. In 1989, the Antiguan racer was rediscovered on Great Bird Island and the Antiguan Racer Conservation Project was formed to try to save the species. This award-winning project led to the eradication of rats and mongooses from Great Bird Island and 11 other offshore islands. The results were highly successful, however, there are still fewer than 150 Antiguan racers in existence. | Harlequin sprite (Pseudagrion newtoni) |
Invasive alien plants such as black wattle are by far the most important threat facing endemic South African dragonflies such as the harlequin sprite. An additional impact is habitat disturbance by domestic livestock, which use trees for shade and trample the natural vegetation, as well as damaging stream banks. However, thanks to a national scheme, threatened species have begun to recover in restored areas. The initiative has proved a major conservation success story, with the highlight being the re-discovery of the harlequin sprite and two other presumed extinct dragonflies along river stretches where alien trees had been removed and the natural vegetation re-established. | Pisonia (Pisonia sechellarum) |
The small area in which Pisonia sechellarum occurs lies within forest protected by the Nature Protection Trust of Seychelles (NPTS). The NPTS has been protecting the island's environments and endeavouring to restore them to a near-natural state since 1997. Through the valuable work of the NPTS, which includes conducting research into the animals and plants of the island and efforts to control invasive species, hopefully the exceptional biodiversity of this island, including Pisonia sechellarum, will be preserved. | Tahiti monarch (Pomarea nigra) |
The Tahiti monarch used to be common throughout the island, but during the last century populations dramatically decreased due to introduced species. The black rat and Indian mynah both prey on their eggs and chicks. Introduced plants such as the dense shrub Miconia calvescens are altering areas where the Tahiti monarch likes to nest and feed. In 1997, when the population was only 27 individuals, a new conservation programme focused on the control of the black rat. The population had increased to around 45 birds in 2004. Future measures include removing invasive plants and trees, and encouraging the growth of native plant species. |
In order to bring you the most accurate and up to date information, we are always looking for relevant scientific experts to authenticate our species texts. Whether you are the world authority on an entire family group, or a graduate student with an intricate knowledge of one particular species, the ARKive text team would love to hear from you.
The role of the authenticator is simply to verify the accuracy of the species information researched and written by our in-house team of biologists. We are extremely grateful to all our authenticators for their time and enthusiasm, and acknowledge them personally at the foot of each species text.
If you would like to share your knowledge, please contact arkive@wildscreen.org.uk.
Recent ARKive authenticators include the evolutionary biologist Peter Grant, renowned for his groundbreaking work on Darwin’s finches in the Galapagos. To read the finch texts authenticated by Professor Grant, click on the images below:
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