However, a number of recent articles in influential scientific journals have questioned the urgency of addressing the threat to biodiversity from invasive species, amid concerns that conservationists may not be making the necessary distinction between invasive species and alien species in their desire to maintain pristine ecosystems.

The brown rat (Rattus norvegicus) has been the cause of many extinctions worldwide, particularly seabirds restricted to remote, predator-free islands.

Alien species are introduced outside their natural range by humans, and are in many cases harmless. Invasive species on the other hand, are not only introduced outside their range, but also cause substantial harm to biodiversity and human livelihoods. 

In certain cases, alien species may prove beneficial to human wellbeing. Examples include the honey bee, which has been introduced to North America, and various crops such as corn and potato which were introduced to Europe and have become staple dietary components for millions of people. 

Invasive species, not alien species, are however a major cause of biodiversity loss, and are implicated in the majority of extinctions recorded to date. 

To counter the concerns raised by some of the recent articles, a letter recently published in Science magazine aims to highlight the growing threat to biodiversity from invasive species, and addresses some of the dangerous misunderstandings of the issue.

The Cuban treefrog (Osteopilus septentrionalis) has been introduced to numerous Caribbean islands outside its native Cuba, and is preying on many rare amphibians.

The letter argues that the concerns raised over tackling the invasive species problem are unfounded, and that conservationists do recognise a clear distinction between alien species and invasive species. 

The letter is signed by several leaders of well-established and respected conservation organizations, including IUCN’s Director General, Julia Marton-Lefèvre; the Chair of the Species Survival Commission (SSC), Simon Stuart; and the Chair of SSC’s Invasive Species Specialist Group, Piero Genovesi. 

The authors highlight that threats from invasive species can be reduced, and that biodiversity can be protected through carefully targeted conservation interventions.

The honey bee has been beneficial to humans by providing food and pollinating crops.

“Tackling invasive species also addresses the economic damage they cause and the serious threats that they pose to human health and livelihoods,” says Julia Marton-Lefèvre. 

“Attempts to remove the most harmful invasive species are proving to be increasingly successful, with more than 1,000 eradications completed worldwide to date.” 

In speaking out and making clear the distinction between invasive and alien species, the authors of the letter have demonstrated their commitment to the fight against invasive species, and now call upon academics for support and, above all, action. 

Read the IUCN press release – Top scientists rally together in fight against invasive species.

Alex Royan, ARKive Species Text Author

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Ten years ago the Cayman Island blue iguana numbered just two dozen individuals, but thanks to concerted conservation efforts this rare lizard is on the road to a remarkable recovery.

Last ditch attempt to save the species 

Weighing in at over 11 kilograms and measuring over 1.5 metres in length, the Cayman Island blue iguana is by far the largest native animal on Grand Cayman, the only place in which it occurs. 

Predation was never a concern for this impressive lizard until cats and dogs were introduced to the island. Together with habitat destruction and collisions with cars, this has slowly pushed the species ever closer to extinction. 

In 2002, conservationists began a last ditch attempt to save the iguana. With help from local and international conservation partners, including the Wildlife Conservation Society and Durrell Wildlife Conservation Trust, the Blue Iguana Recovery Program has bred and released more than 500 blue iguanas back into the wild, increasing its population by twenty times.

Remarkable success 

Blue iguanas are raised in captivity until two years old, when they are big enough to keep feral cats at bay. Once they hit two, the blue iguanas are released and monitored in the Salina Reserve on Grand Cayman. 

The programme has been such a success that conservationists have also started releasing blue iguanas into a new protected area, the Colliers Wilderness Reserve. This month, the programme confirmed the first breeding blue iguanas in the reserve. The goal is now to hit a population of 1,000 blue iguanas and, given recent success, this may be achieved fairly quickly.

“For the past several years, we’ve succeeded in adding hundreds of animals to the wild population, all of which receive a health screening before release,” said Dr Paul Calle, Director of Zoological Health for WCS’s Bronx Zoo. 

Fred Burton, Director of the Blue Iguana Recovery Program, said: “We expect to reach our goal of 1,000 iguanas in managed protected areas in the wild in a few years. After that, we will monitor the iguanas to make sure they are reproducing in the numbers needed to maintain the wild population. If we get positive results, we will have succeeded.” 

View more images of the Cayman Island blue iguana on ARKive. 

Read the WCS press release – Grand Cayman blue iguana: Back from the brink of extinction.

Alex Royan, ARKive Species Text Author

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Scientists have confirmed that the world’s rarest albatross, the Amsterdam albatross (Diomedea amsterdamensis), is indeed a separate species, ending 20 years of debate on the status of this Critically Endangered bird.

This marine albatross spends the majority of its life out at sea, coming to land only to breed.

Genetic analysis 

The Amsterdam albatross is named after Amsterdam Island in the Indian Ocean, the only place in the world where this species breeds. It was first described in 1983, but the scientific community has since been divided over whether it is a separate species or a subspecies of the wandering albatross (Diomedea exulans), which also inhabits the Southern Ocean. 

A team of Canadian researchers aimed to resolve this debate by examining the Amsterdam albatross’ DNA. The study, which is published in the Journal of Avian Biology, revealed significant differences between this species’ DNA and that of the wandering albatross, proving that these close relatives are indeed separate species. 

The genetic analysis also showed that the Amsterdam albatross separated from the wandering albatross as long as 265,000 years ago.

Nesting occurs on a highland plateau, at 470 to 640 metres, in an area of peat bog that has an ample covering of moss.

Geographic isolation 

Dr Theresa Burg from the University of Lethbridge, Canada, one of the report’s authors, explained how the Amsterdam albatross differs in appearance from the wandering albatross.  

“They are slightly smaller in size” she said. “They lay their eggs at a different time and have slightly browner plumage than the other wandering albatrosses.” 

The report’s authors suggest that this species’ isolation from other albatrosses on the remote, volcanic Amsterdam Island, where it is the only breeding albatross, possibly led to its separation and development as a unique species.

Although the population is currently stable, its small size and existence on just a single island means the Amsterdam albatross has a precarious status.

A Critically Endangered species 

With only around 170 individuals remaining, and just 18 to 26 pairs breeding annually, it is hoped that efforts to conserve the Amsterdam albatross will be increased. 

Grazing by livestock on Amsterdam Island, predation by introduced mammals and accidental entanglement in long-line fishing gear have all imperilled this species, which is listed as Critically Endangered on the IUCN Red List. 

“This is one additional, but important, piece of evidence that hopefully can help protect the remaining Amsterdam albatrosses” said Dr Burg. 

View 20 photos of the Amsterdam albatross on ARKive.

Read the study at the Journal of Avian Biology.

Alex Royan, ARKive Species Text Author

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The largest rat eradication programme in history is to begin on a remote UK island, in a bid to save millions of seabirds from these invasive predators.

The South Georgia pipit is the only songbird in the Antarctic region, but is under threat from predation by brown rats.

Brown rats reached the island of South Georgia, in the South Atlantic Ocean, around 200 years ago, transported on sealing and whaling ships. Since then, the rodents have wreaked havoc on the island’s bird life, eating the eggs and chicks of ground-nesting seabirds and driving the endemic South Georgia pipit towards extinction.

Largest ever rat eradication

The eradication programme will involve dropping poison bait from helicopters in an attempt to rid the island of rats. The first poison drops are about to begin, but will initially take place over a limited area to assess whether the techniques are working. If successful, the programme will then be extended to the whole island.

The brown rat has been introduced to many islands around the world, often causing great damage to native wildlife.

With 800 square kilometres to cover, this is the largest eradication programme ever attempted. However, scientists hope that it will clear South Georgia of rats within the next five years.

South Georgia’s birds to benefit

Once the rats are gone, tens of millions of seabirds could return to South Georgia each year to breed. According to Professor Tony Martin, the South Georgia Habitat Restoration Project Director, “The vast majority of birds that should be breeding on South Georgia have been displaced by the presence of rats. Rats have gone virtually everywhere except the very cold southern coast. We are looking to restore millions, possibly tens of millions of sea birds to the island.”

Found only on South Georgia, the South Georgia pintail is the most southerly recorded waterfowl species.

Species which will benefit from the rat eradication include the South Georgia pintail, a subspecies of yellow-billed pintail endemic to South Georgia, as well as seabirds such as Wilson’s storm-petrel and the white-chinned petrel.

Scientists are also confident that the programme will help save the South Georgia pipit from extinction. The world’s most southerly songbird, this endemic species has been lost from most of the main island and is now restricted largely to offshore islets. 

Wilson’s storm-petrel is just one of many seabirds that will benefit from rat removal on South Georgia.

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Another Valentine’s day has passed us by and it seems as though invertebrates have been overlooked. If our spineless friends had the capability to feel emotion, this would surely be a blow to their fragile self esteem.

One of my personal favourite invert groups are the crayfish. At a time of year when couples are demonstrating love for one another by dancing in the manner of a bird of paradise, or showing commitment by fusing with their other half in the in the style of a deep sea anglerfish, these enigmatic Arthropods are simply left out.

In the spirit of ARKive’s Love Species Campaign, I want more people to appreciate crayfish for what they are, so here is why I love them.

Freshwater lobsters

You might have noticed that crayfish strongly resemble lobsters in appearance, and that’s because they are, in fact, very closely related. Both groups belong to the infra-order Astacidea.

Unlike lobsters however, which are marine crustaceans, crayfish only inhabit freshwater systems such as streams and rivers. Generally speaking, crayfish are also a fair bit smaller than your average lobster, but some have been shown to reach truly massive sizes.

Owing to their riverine existence, crayfish are often referred to as freshwater lobsters, neatly leading on to my next point.

Funny names

As a group, crayfish are rather cosmopolitan. They exist on a variety of continents and so people have labelled them with a host of interesting names. Focusing on the English speaking world, ‘craw’ seems to be a preferred prefix in the USA. Names there range from crawfish, crawdad and crawdaddy, all the way over to mudbug and my personal favourite; spoondog.

As always, Australia takes the cake for far-flung nomenclature, referring to a variety of crayfish species as yabbies.

The yabbie - crayfish are amphibious, able to traverse stretches of land between freshwater systems such as rivers and streams.

Crayfish plague my heart

Crayfish around the world are susceptible to a nasty fungal disease known as crayfish plague. Europe is currently seeing the worst effects, with the plague being highly lethal to native species such as the now Endangered white-clawed crayfish.

What’s worse, European species are being outcompeted by an invasive called the American signal crayfish. Not only is it larger and more efficient at catching food, but the American signal is resistant to plague. It acts as a carrier for the disease as it spreads across the continent, obliterating native European crayfish when entering new freshwater systems.

American signal crayfish feasting on a common carp. This species acts as a carrier for crayfish plague.

There you have it. I love crayfish because they look like lobsters, have a variety of strange names (bonus name; grave digger) and are threatened by a lethal fungal disease.

It’s all too easy to overlook less aesthetic species in favour of fluffier ones, but I hope this will inspire you to spare a thought for invertebrate life at this lonely time of year.

Robert Morgan, ARKive Media Researcher

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