Sep 5

Europe’s towns and cities are particularly vulnerable to the threats posed by invasive alien species, and experts say that action needs to be taken to control them.

Close up photo of a northern raccoon

Native to North America, the northern raccoon is an invasive species in parts of Europe

Invasive alien species are plants or animals that are not native to an area and which therefore lack natural predators, meaning they are able to spread rapidly.

Urban areas are at high risk from invasive species because of their large number of transport links, with many non-native animals and plants arriving accidentally at ports and airports. Some species also arrive through the plant and pet trades.

Threats to native wildlife

Invasive alien species can pose a significant threat to native wildlife, often through competition or predation.

Photo of red-eared slider ssp. elegans on rock

Abandoned pet turtles such as the red-eared slider can threaten native turtle species

According to Chantal van Ham, European Programme Officer for IUCN, “These non-indigenous species represent one of the main threats to the world’s biodiversity. This threat is set to increase unless meaningful action is taken to control their introduction and establishment.”

Non-native species can also cause problems for humans living in urban areas. For example, common ragweed, which is native to North America, is spreading rapidly across Europe and can cause hay fever and asthma-like symptoms. Other plants, such as Japanese knotweed, can cause structural damage to buildings.

IUCN conference

IUCN has recently released a publication entitled Invasive Alien Species: The Urban Dimension, which lists case studies from more than 15 European countries which show action being taken on invasive species in urban areas.

Photo of harlequin ladybird

The harlequin ladybird is an invasive insect that threatens native species in Europe and elsewhere

To address the issues posed by invasive alien species in Europe, IUCN is also hosting a conference today in Gland, Switzerland. The aim of the conference is to bring together local authorities, scientists, NGOs and policymakers to analyse the problem of invasive species in urban areas, and to discuss potential solutions.

Chantal van Ham said that local authorities have a key role to play in taking action to reduce the risk of invasive species becoming established. However, she added that it will be important for local authorities to have the support they need to do this.

European action

Photo of American bullfrog sitting on grass at the water's edge

The American bullfrog has been named one of the top 100 most invasive alien species in the world by IUCN

Next week, the European Commission is expected to publish its plans on tackling invasive species across Europe and to announce a legal framework which will require action to be taken on the issue in all EU member states. It will also look at the control methods which are available and the ways in which established invasive species populations can be managed.


Read more on this story at BBC News – Invasive alien species threaten urban environments and IUCN – Invasive alien species: the urban dimension.

You can also find out more about invasive species at the GB Non-native Species Secretariat and the IUCN/SSC Invasive Species Specialist Group.

Do you teach 11-14 year olds? Take a look at the invasive species teaching resource on ARKive’s education pages!

Liz Shaw, ARKive Text Author

Apr 11

New Zealand’s Department of Conservation is facing criticism over its plans to use a controversial poison in the habitat of two unique and endangered frog species.

Photo of Archey's frog, dorsal view

Archey’s frog, an unusual and unique New Zealand frog

The poison, known as 1080, is used in New Zealand to eradicate invasive mammals such as possums, rats and stoats, which threaten the country’s native wildlife. Initially developed as an insecticide, 1080 naturally biodegrades in the environment over time and eventually becomes harmless. However, it is highly toxic and has no antidote, and many countries have banned its use.

New Zealand uses 80 to 90% of the world’s 1080, aerially dropping bait laced with the poison. Its use is highly controversial, with critics claiming that it can also kill native species such as birds and frogs.

Unique frogs

The Department of Conservation (DOC) plans to use 1080 on Moehau Mountain, on New Zealand’s North Island. However, one of the main concerns about the planned drop is the potential effects it could have on two unique and endangered frog species, Archey’s frog and Hochstetter’s frog.

Photo of Hochstetter's frog

Hochstetter’s frog is another primitive and unique frog found only in New Zealand

One of only a few surviving species from an ancient frog family, Archey’s frog is considered a ‘living fossil’, with primitive features such as a lack of eardrums or vocal sacs, and muscles to move a tail despite the frog having no tail to move. Unfortunately, this unusual frog is under threat from predation by non-native mammals and by the deadly amphibian disease chytridiomycosis, and is now considered to be Critically Endangered.

Hochstetter’s frog is also a primitive and unique species, and is found in just ten fragmented and isolated populations. Listed as Vulnerable by the IUCN, it is under threat from chytridiomycosis as well as the destruction of its habitat.

Unclear impacts

It is not known for certain whether 1080 has any impact on frogs. The DOC says that the poison has been used previously in areas of frog habitat and that rather than harming the frogs, it has benefitted them by removing predatory mammals.

Last year DOC started a controlled experiment in the Whareorino forest and dropped 1080 in an area where the frogs (Archey’s and Hochstetter’s) had been well monitored and excluded it from another well-monitored area,” said Phil Bishop, a scientist at the University of Otago. “The data has yet to be fully analysed as its still early days and still being collected, but the results are looking good and the frogs seem to be doing as well if not better in the area that received the 1080 drop.”

Photo of common brushtail possum on tree trunk

The common brushtail possum has been introduced to New Zealand, where it is threatening native wildlife

However, others believe that insects may feed on the poisoned bait, and the frogs may therefore ingest the poison when they eat the insects. There are also fears that 1080 could have less direct impacts, with chronic exposure to the poison potentially making the amphibians more vulnerable to disease or affecting their circulatory or nervous systems. This adds to a growing body of research worldwide showing that the non-lethal effects of pesticides can cause considerable harm to wildlife and humans.

Further fears

There is also concern that native birds could be affected by 1080, although others point out that this threat is outweighed by the benefits to the birds of removing non-native predators. Local people are also concerned for the safety of livestock and pets, with dogs being particularly vulnerable to the lethal effects of the chemical.

Some opponents argue that safer, less controversial pest control measures could be used, and accuse the government of self-interest as they own the factory which produces the 1080 pellets.

Photo of Archey's frog, anterior view

Archey’s frog is listed as Critically Endangered on the IUCN Red List

Invasive pest mammals comprise an obvious threat to New Zealand biodiversity. But to dismiss out of hand suggestions that 1080 might harm native species through sublethal physiological effects and thereby contribute to long-term population declines is just foolish,” said Bruce Waldman, an expert on New Zealand’s frogs. “Until we know why Archey’s frogs are dying… we cannot just proceed on the assumption that dangers that they incur by exposure to 1080 drops have been sufficiently mitigated. To do proper studies on 1080’s effects on frogs would not be difficult, so why have they not been done?

Despite the controversy, the DOC has stated that the poison bait drop is still to go ahead, with the aim of saving native frogs and birds from invasive predators.


Read more on this story at Mongabay – Saviors or villains: controversy erupts as New Zealand plans to drop poison over Critically Endangered frog habitat.

View photos and videos of amphibian species on ARKive and find out more about endangered amphibians at EDGE of Existence – Amphibians.

Find out more about amphibian conservation on ARKive.

Liz Shaw, ARKive Text Author

Jan 10

Invasive reindeer are to be eradicated from South Georgia in an attempt to save the unique environment of this sub-Antarctic island.

Reindeer are normally found in the Arctic

As well as being home to 3,000 reindeer, the island of South Georgia has many endemic species of fauna and flora that evolved in the absence of grazing pressures. These species are now struggling to survive in the reindeer’s overbearing presence, and the Government of South Georgia and the South Sandwich Islands has announced plans to eradicate the population in an effort to save the island’s unique species.

Habitat destruction

Reindeer were first introduced to South Georgia by the Norwegians in the 1900s to provide fresh meat on whaling missions in Antarctica. The population was originally managed by regular hunting, but when whaling stations were shut down in the 1960s, all hunting ceased.

Since then, the reindeer population has increased dramatically to a point where the island’s flora and fauna can no longer cope. Reindeer trample the indigenous plants, threaten king penguins and other local birds by destroying their nests and habitat, and cause substantial soil erosion.

King penguins are just one of the species threatened by the presence of reindeer

The reindeer herd is currently restricted by glaciers to the only suitable grazing habitat, which is also the most biologically productive. However, the impending threat of climate change and glacial recession will serve to increase the damage caused by opening up access to the rest of the island.

The government has decided to eradicate the reindeer population on South Georgia on the grounds of responsible environmental management practices.

Reindeer are grazing on the most biologically productive parts of the island

Island restoration

The reindeer cull will be led by the Norwegian Sami herdsmen whose expertise will ensure the programme goes smoothly, and it is estimated that it will take place over two summers. Meat from the cull will not go to waste and will be sold on the Falkland Islands, since South Georgia has no permanent resident population.

The Sami herdsmen are experienced in handling reindeer

Scientists hope that this, alongside a rat eradication programme currently in progress, will restore the island of South Georgia by allowing native plant species and bird populations to recover. Two native bird species which scientists hope will benefit from the removal of rats and reindeer are the South Georgia pipit and the South Georgia pintail, a subspecies of the yellow-billed pintail.

The endemic South Georgia pintail will benefit from the eradication of rats and reindeer


Read more on this story at BBC News – South Georgia prepares to cull its invasive reindeer.

Find out more about the invasive reindeer population from the IUCN Species Survival Commission Invasive Species Specialist Group newsletter.

View photos and videos of reindeer on ARKive.

Kaz Armour, ARKive Text Author

Feb 7

Native ladybird species in the UK and Europe are declining rapidly due to the spread of the invasive harlequin ladybird, according to scientists.

Photo of harlequin ladybird

Harlequin ladybird

Invasive alien

Native to Asia, the harlequin ladybird (Harmonia axyridis) has been introduced to many countries as a pest control agent, but is now spreading rapidly and has itself become a pest species.

Introduced to North America in 1988, the harlequin is now the most widespread ladybird on the continent, and the species has also invaded much of northwest Europe. It was first spotted in Belgium in 2001, and arrived in the UK and Switzerland in 2004.

Since the harlequin’s arrival, scientists have warned about its potentially harmful impacts on native ladybird species. However, new research published in the journal Diversity and Distributions has now measured the scale of these impacts and demonstrated a strong link between the spread of the harlequin and rapid declines in native ladybirds.

Photo of harlequin ladybirds, showing variation in the species

Harlequin ladybirds showing some of the colour variation in this species

Rapid declines

Led by the Centre for Ecology and Hydrology in the UK, the study was made possible by thousands of records submitted as part of “citizen science” projects that record ladybird observations across Britain, Belgium and Switzerland.

Using this data, the researchers found that in the five years following the harlequin ladybird’s arrival in the UK, seven out of eight native ladybird species declined. Similar declines were also found in Belgium and Switzerland.

Particularly badly affected was the two-spot ladybird (Adalia bipunctata), which is estimated to have declined by 44% in the UK and 30% in Belgium. It is now difficult to spot in some areas where it was once common.


Like many other native ladybirds, the two-spot ladybird is smaller than the harlequin and likely to be outcompeted for food and habitat. The harlequin is also likely to prey on the eggs and larvae of native ladybird species. In addition, the harlequin ladybird may potentially be more toxic than native species, giving it better protection against predators.

Photo of harlequin ladybird in flight

Harlequin ladybird in flight

Speaking about the results, Helen Roy of the Centre for Ecology and Hydrology said, “It’s a very real decline, which should be put amongst a whole other set of factors putting ladybirds in a more fragile situation.”

Such factors may include the intensification of agriculture and climate change.

The only UK species apparently unaffected by the harlequin’s arrival was the seven-spot ladybird (Coccinella septempunctata), which is similar in size to the harlequin and not in such direct competition for habitat as other native species.

Photo of seven-spot ladybird eating aphids

Seven-spot ladybird feeding on aphids

Ecosystem impacts

The researchers have warned of potentially serious consequences if the harlequin ladybird continues to spread. Ladybirds play an essential role in ecosystems, keeping pests such as aphids in check. Although the harlequin ladybird also feeds on aphids, having just one species playing this role could make the overall ecosystem weaker.

Tim Adriaens of the Research Institute for Nature and Forest (INBO) in Belgium, said, “At the continental scale, the arrival of the harlequin could impact on the resilience of ecosystems and severely diminish the vital services that ladybirds deliver.”

Read more on this story at BBC News – Ladybird decline driven by ‘invading’ harlequin and at The Telegraph – Harlequin ladybirds threaten British species.

Find out more about how to record UK ladybird sightings at The Harlequin Ladybird Survey and UK Ladybird Survey.

View photos and videos of ladybirds on ARKive.

Liz Shaw, ARKive Species Text Author

Jan 31

Non-native Burmese pythons are believed to be the cause of severe mammal declines in the Florida Everglades, according to new research.

Photo of Asiatic rock python (Python molurus bivittatus) resting in shallow water

Asiatic rock python (Burmese python) resting in water

Escaped pets

Also known as the Asiatic rock python, the Burmese python (Python molurus bivittatus) is a large constricting snake native to Asia. The exact origins of the pythons in the Everglades are unknown, but many have been imported into the United States through the pet trade, and some are likely to have escaped or been released into the wild.

In the absence of natural predators, the Burmese python population has exploded. Since 2000 the species has been recognised as being established across large parts of southern Florida, where it is known to eat a wide variety of mammals and birds.

Close up photo of Asiatic rock python showing heat receptors

Close up of Asiatic rock python showing heat receptors, used to detect the body heat of prey

Worrying mammal declines

In new research published in the journal PNAS, a team of scientists studied the number of live and dead mammals spotted along roads in the Everglades National Park. The team compared mammal surveys performed before and after the pythons became common, and found a strong link between the spread of the snakes and a decrease in many mammal species.

In particular, observations of racoons and opossums dropped by about 99%, while white-tailed deer fell by 94% and bobcats by 87.5%. No rabbits or foxes were seen during more recent surveys, despite rabbits being one of the most common mammals in earlier studies.

Most of these mammal species have been recorded in the diet of Burmese pythons in the Everglades National Park, with raccoons and opossums being particularly vulnerable to ambush as they often forage at the water’s edge.

Photo of Asiatic rock python with hog deer prey in water

Asiatic rock python killing hog deer

The decline in mammals was found to coincide with the spread of the pythons, with mammals being more common in areas were the pythons have only recently arrived, and most common outside of the python’s current range. The pythons are also likely to be eating other types of prey, including alligators.

We have documented pythons eating alligators, we have also documented alligators eating pythons. It depends on who is biggest during the encounter,” said Professor Michael Dorcas, one of the authors of the study.

Ecosystem impacts

The exact number of Burmese pythons in the Everglades is unknown, but their numbers are increasing year by year.

Any snake population – you are only seeing a small fraction of the numbers that are actually out there,” said Professor Dorcas. “They are a new top predator in Everglades National Park – one that shouldn’t be there.”

Photo of Asiatic rock python (Python molurus bivittatus) resting on foliage

Although a problem where it has been introduced in the US, the Asiatic rock python is classified as Near Threatened in its native Asia

Professor Dorcas has also stated that more research is needed to assess the potential impacts of the large mammal declines. “It’s not unreasonable to assume that any time we have major declines in mammals like this it’s going to have overall impacts on the ecosystem. Exactly what those are going to be, we don’t know. But it’s possible they could be fairly profound.”

Import ban

Earlier this month, it was announced that the US was poised to approve a ban on the import of Burmese pythons and on the sale of the snake across state lines. Another species that has been found in the Everglades, the African rock python, is also likely to be added to this list of “injurous” species.

Although reptile breeders and collectors have challenged the ban, and it would come too late to reverse the situation in Florida, Professor Dorcas has pointed out that it could help prevent the species from invading other suitable habitats in the United States, such as in southern Louisiana and south Texas.

Read more on this story at BBC – Pythons linked to Florida Everglades mammal decline.

View photos and videos of the Asiatic rock python on ARKive.

Liz Shaw, ARKive Species Text Author


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