The environmental impacts of alien birds

Thousands of species have been moved by people to areas where they do not naturally occur. These alien species can have negative impacts on the environments into which they are introduced. Given the vast number of aliens, and the broad range of impacts they can have, how do we identify which are the worst in order to prioritise our remedial or preventative actions? One method that shows a lot of promise is the Environmental Impact Classification for Alien Taxa (EICAT). This is a new protocol that has been developed to enable invasion biologists to identify and categorise the magnitude and types of impacts associated with alien taxa, and in so doing, allow clear comparisons to be made regarding the impacts of alien species across different regions and taxonomic groups.

It is possible that EICAT will be formally adopted by the International Union for the Conservation of Nature (IUCN) as their formal mechanism for classifying the impacts of alien species. If this happens, EICAT assessments for all known alien species worldwide should be completed and peer reviewed by 2020, in-line with the requirements stipulated under Aichi Target 9 of the Convention on Biological Diversity (CBD) and Target 5 of the EU 2020 Biodiversity Strategy.

As EICAT is a new protocol, a key step in its development is to apply it to a set of species with alien populations, in order to test how readily it can be used, and to identify any aspects of the protocol that may need refinement. To do this, a team of invasion biologists based at University College London’s Centre for Biodiversity and Environment Research (CBER) and the Stellenbosch University DST-NRF Centre of Excellence for Invasion Biology recently carried out a global assessment of the environmental impacts of alien birds using EICAT.

Alien birds were categorised by the severity (Figure 1) and type (Figure 2) of their environmental impacts. Most impacts were categorised as either Minimal Concern (MC) or Minor (MN), although 37 bird species had moderate (MO) impacts or above, causing declines in the populations of native species. Alien birds were primarily found to impact upon the environment through competition, predation, hybridisation and frugivory (which caused the spread of alien plants). However, impact data were found for only around 30% of alien bird species worldwide, with the rest categorised as Data Deficient (DD).

Fig 1

Figure 1: The number of alien bird impacts assigned to each EICAT impact category. A further 296 species were Data Deficient (DD). MC = Minimal Concern; MN = Minor; MO = Moderate; MR = Major; MV = Massive (Evans et al., 2016).

Fig 2

Figure 2: The number of alien bird impacts assigned to each EICAT impact mechanism. Com = Competition; Pre = Predation; Int = Interaction with other alien species; Hyb = Hybridisation; Gra = Grazing/herbivory/browsing; Dis = Transmission of disease to native species; Che = Chemical impact on ecosystem; Par = Parasitism; Str = Structural impact on ecosystem (Evans et al., 2016).

The study demonstrates that EICAT can be used to categorise and quantify the impacts of alien species for a complete taxonomic class. However, it also indicates that there is much to learn about the impacts of aliens, as we have no information on the environmental impacts of most species, even in a well-studied group like birds. This is perhaps one of the key benefits of EICAT – by facilitating a global stocktake of the impacts of alien taxa, EICAT directs attention not only to the most damaging alien species, but also to those species, locations or impact mechanisms for which we do not have sufficient information from which to make informed management decisions to mitigate the impacts of alien taxa.

Click here to access the paper.

Posted in Alien birds, Alien species, Biodiversity conservation, Conservation Science, Environmental Impact Classification For Alien Taxa (EICAT), Environmental research, Invasive alien species, Invasive species, Wildlife management | Tagged , , , , , | Leave a comment

Invasive alien species, EICAT and the IUCN

In March 2016, I attended a workshop at the Institute of Botany in Průhonice in the Czech Republic, to discuss the implementation of a new methodology to quantify and categorise the impacts of alien species, known as the Environmental Impact Classification for Alien Taxa (EICAT). The workshop was planned and facilitated by Tim Blackburn, Professor of Invasion Biology at University College London’s Centre for Biodiversity and Environment Research (CBER). Attendees included invasion biologists and environmental scientists from 8 countries, along with the Chair of the IUCN SSC Invasive Species Specialist Group (ISSG), Dr Piero Genovesi.

Over two days, we discussed processes required further to develop and implement EICAT, and reviewed the results of provisional EICAT assessments undertaken for a range of taxa, including all species of birds and amphibians with alien populations. A motion for the formal adoption of EICAT by the IUCN will be debated at the IUCN World Conservation Congress in September 2016, and the group also assessed the procedures and timetable for taking the motion forward. Assuming that the motion is passed, it is hoped that EICAT assessments will be completed and peer reviewed for all alien species worldwide by around 2020, and will be published online via the IUCN Global Invasive Species Database (GISD). In so doing, EICAT and the IUCN will provide the most comprehensive source of information on the environmental impacts of alien species globally.

Further details on EICAT can be found here.

The workshop was funded by the EU through COST (European Cooperation in Science and Technology), under Action TD1209: ALIEN Challenge. COST provides a framework for the support of trans-national research amongst research scientists. ALIEN Challenge aims to facilitate knowledge gathering and information sharing to improve decision-making regarding the identification and management of impacts associated with alien species. We would like to thank Dr Helen Roy, Chair of COST Action TD1209: ALIEN Challenge, for funding this workshop, which has been extremely useful in the development of EICAT.

Group photo

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Return of the reds

In a long and often disappointing story for UK conservation, finally some good news. In the north of England, the red is on the rise.

With the help of grassroots conservation, spearheaded by Red Squirrels Northern England, a species that some believe should be our national mascot is returning to areas where it hasn’t been seen for years.

Grey gardens

The red squirrel’s demise has been caused by the deliberate introduction of the grey (or eastern grey) squirrel. Native to north-east America, the grey was considered to be a fashionable addition to private estates in England, and widely introduced to the UK during the late nineteenth and early twentieth century.

Starting in 1876, with the release of a singe pair on an estate in Cheshire, by the 1930s the grey squirrel population had exploded. A bounty for culled squirrels was established in the 1950s, but by then it was too late to halt the invasion. It’s now estimated that there are at least 2.5 million grey squirrels living in our gardens, parks and woodlands.

Source: BBC News

Source: BBC News

Red peril

Red squirrels are fussy eaters – greys are not. Unlike reds, they tolerate tannins, munching on tannin rich unripened acorns, which are a high-energy food source. This means that although red squirrels can eat ripened acorns, by the time they get to the dinner table, there are no acorns left to eat.

Unfortunately, acorns are one of the main food sources used by reds to build up their winter fat reserves. As a consequence, over time, direct competition with greys results in the gradual starvation of reds, a loss of physical condition, and the reduced ability to reproduce. Through direct competition alone, greys can replace reds within approximately 15 years.

Grey squirrels are also larger, and able to store up to four times more fat that than reds, meaning they are more likely to survive a harsh UK winter. They also produce more young, and can live at higher densities than reds (up to 15 individuals per hectare, compared to 2-3 per hectare for reds).

On top of this, grey squirrels carry the squirrel pox virus, and although they aren’t particularly affected by it, reds have no immunity. When passed on, a red squirrel will die within weeks. Studies suggest that the squirrel pox virus results in red squirrel population decline that is up to 25 times more rapid than through competition with grey squirrels alone.

Effects of the squirrel pox virus. Source: Red Squirrels in South Scotland

Effects of the squirrel pox virus. Source: Red Squirrels in South Scotland

Unfortunately the virus is now widespread across England. In Cumbria it is believed that up to 75% of greys have the disease. It’s now also spreading into Scotland, which until recently has been pox free, and a key stronghold for red squirrels. This map shows the distribution of grey squirrels with the virus in southern Scotland.

As a consequence of all this, from a population estimated at 3.5 million prior to the introduction of grey squirrels, there are now only approximately 138,000 red squirrels left in the UK. The majority are found in Scotland, with only about 15,000 left in England and 3000 in Wales.

Community conservation

In a good example of landscape scale, community conservation, Red Squirrels Northern England are culling grey squirrels, and monitoring approximately 300 woodlands, employing a team of rangers, an army of volunteers (over 1000 of them), and the buy-in of landowners with woodlands supporting red squirrels.

Culling involves catching and shooting greys using baited traps, whilst monitoring incorporates standardised techniques including observational surveys and camera trapping. This video provides a short summary of the work being undertaken by Red Squirrels Northern England.

Their efforts have been successful. A 2013 study indicates that in cull areas, red squirrel numbers rose by 7% from the previous year. This is the first recorded population increase of red squirrels in over 100 years. The study also indicates that grey squirrel numbers decreased by 18%.

Similar stories are being reported in other areas of the UK. Greys have been eradicated from Anglesey, viable populations of red squirrels have been established on offshore islands, and real progress has also been made in southern Scotland.

The future

Work is being undertaken to develop a vaccine, administered in food, to inoculate red squirrels against the squirrel pox virus. Perhaps this would be a more palatable outcome than widespread culling, which has received some criticism from animal welfare groups.

However, it will be several years before the vaccine is ready for testing. Until then, if we want to protect the few remaining red squirrels in the UK, it doesn’t look like we have many other options.

You can donate to Red Squirrels Northern England here. Should you wish volunteer your time, the Northern Red Squirrels website provides a database of local volunteer groups across the UK. Failing that, spread the word – because the red squirrel needs your help.

Posted in Biodiversity conservation, Conservation Science, Grey Squirrel, Invasive alien species, Red Squirrel | Tagged , , ,

Doctoral Training Partnerships (DTPs)

This year in the UK, we’ve seen a new approach to PhDs in environmental research, with the establishment of a national network of Doctoral Training Partnerships (DTPs) funded by the Natural Environment Research Council (NERC).

NERC is the principal funder of research and training in environmental science in the UK, investing public money to help sustain natural resources, predict and respond to natural hazards and understand environmental change.

Amongst others, DTPs established across the country include:

  • The Great Western Four+ (GW4+) DTP, which brings together four research-intensive universities located in the South West of the UK (Bath, Bristol, Cardiff and Exeter), with six research partners including three of the six major NERC research centres – the British Antarctic Survey, British Geological Survey and the Centre of Ecology and Hydrology, alongside the Plymouth Marine Laboratory, Meteorological Office and Natural History Museum.

The Great Western Four+ (GW4+) DTP. Source: The University of Bristol

  • The Central England NERC Training Alliance (CENTA) DTP, incorporating four universities from the Midlands region in the UK (Birmingham, Leicester, Loughborough and Warwick), alongside The Open University, and research institutes including the British Geological Survey and the Centre for Ecology and Hydrology.

Central England NERC Training Alliance (CENTA) DTP. Source: The University of Birmingham

  • The London NERC DTP, which consists of nine leading research institutions in the capital (University College London, Birkbeck University of London, Brunel University London, Royal Botanic Gardens Kew, King’s College London, The Natural History Museum, Queen Mary University London, Royal Holloway University of London and the Institute of Zoology at the Zoological Society of London).
The London NERC DTP. Source: University College London

The London NERC DTP. Source: The London NERC DTP

NERC has made funding available for five annual DTP cohort intakes (from 2014 to 2018), providing 240 studentships across the UK each year.

I am one of 36 students making up the first cohort of the London NERC DTP.

Over the first term of the DTP we have received training at each of the nine research institutions, which has been divided into different themes, drawing on the varied strengths of each institution.

At Royal Holloway’s Centre for Quaternary Research, we’ve learnt how the study of fossil records associated with past climates can provide valuable insights into the potential impacts of climate change on biodiversity across the globe.

Snowball Earth. Source: BBC

Snowball Earth. Source: BBC Science and Environment

At Brunel’s Institute for the Environment, we’ve learnt about environmental pollution, and the work being undertaken to assess the impacts of various widely used synthetic chemicals on the health of both humans and wildlife.

Chemical structure of phthalates. Source: Wikipedia

Chemical structure of phthalates. Source: Wikipedia

At UCL’s Centre for Environment and Biodiversity Research (CEBR) we’ve discussed a variety of issues facing scientists when addressing current rates of global biodiversity decline, including the impacts of invasive alien species and the use of indicators, such as the Living Planet Index (LPI), to monitor biodiversity.

Every Friday has been spent at the Natural History Museum for specialist training in the skills required to become effective research scientists. Amongst other topics, we’ve learnt about possible funding mechanisms available to early career scientists, approaches to writing academic publications and the Vitae Researcher Development Framework (RDF).

The Vitae Researcher Development Framework. Source: Careers Research and Advisory Centre (CRAC) Limited

The Vitae Researcher Development Framework. Source: Careers Research and Advisory Centre (CRAC) Limited

At each institution, we’ve also received presentations from research scientists with potential PhD projects. Next term we chose our research projects, either taking on a project offered by one of the institutions, or developing a proposal of our own. Following that, we put together a detailed project plan for approval by the London NERC DTP Board, before proceeding with our chosen field of research.

It’s been an interesting experience thus far. The cohort now has a better understanding of each others interests, and the breadth of environmental research being undertaken in London. Hopefully this will foster future collaborations and cross-disciplinary research in a city widely recognised as a global centre for science and innovation.

Posted in Doctoral Training Partnership (DTP), Environmental research, Natural Environment Research Council (NERC), The London NERC DTP | Tagged , , , , , , , , , , , , ,

Alien invasion

The aliens have landed. They’ve taken up residence in our waterways, our cities, our farmland and forests. They threaten the very existence of our wildlife, cost a fortune to control, and they aren’t going home any time soon. So what are ‘alien species’?

In short, they are animals, plants or other organisms that we have introduced to areas outside of their natural range. They are considered to be ‘invasive’ when they become established, spread, and have negative impacts on people and/or nature.

Free oyster cards

Pretty much every habitat across the globe has been invaded by alien species – and the inalienable fact is, we put them there. The world is getting smaller – with improvements to transport by air, land and sea, international travel and trade have increased dramatically.

As a result, species that wouldn’t otherwise have the opportunity to travel (mussels don’t have feet – well actually they have a foot, but it’s not made for walking long distances) are hitching a ride across the globe.

Alien species have been introduced to new surroundings both intentionally and unwittingly. The unrelenting frogmarch of the cane toad along the eastern seaboard of Australia, much to the detriment of large predator populations (think quolls, snakes, lizards and goannas) is an example of a deliberate introduction with significant environmental consequences.

The Shine Lab at Sydney University has been working to contain the toad invasion for many years.

A death adder killed by a cane toad. Source:

A death adder killed by a cane toad. Source:

The zebra mussel’s grip on the Great Lakes, where it clogs water supply infrastructure and outcompetes native species, reducing the food supply for important commercial fish species, is an example of an accidental introduction with disastrous environmental, recreational and economic impacts.

In this case, the tenacious mollusc was transported to North America in the ballast water of ships embarking from ports in Western Europe. The Centre for Invasive Species Research (CISR) at the University of California, Riverside (UCR), recently estimated that costs to control zebra and quagga mussels in the Great Lakes amount to $500 million/year.

Ponto-Caspian catastrophe?

The UK has not escaped the impacts of invasive alien species. Earlier this month, the quagga mussel was found in the UK for the first time. Prior to this unwelcome discovery, the quagga mussel was identified by scientists at the Centre for Ecology and Hydrology (CEH) as the single greatest threat to British wildlife of all alien species.

Equally alarming is this month’s revelation that the threat of invasion by the quagga mussel, along with several other species from the Ponto-Caspian region (that’s Southeast Europe to you and me) is now so real that parts of Great Britain face the grim prospect of invasional meltdown1.

Zebra mussels smothering a current meter (Lake Michigan). Source: National Oceanic and Atmospheric Administration (NOAA)

Zebra mussels smothering a current meter (Lake Michigan). Source: National Oceanic and Atmospheric Administration (NOAA)

Evicting toad from Toad Hall

Last month, in recognition of the growing threat posed by potential invasions, along with the lack of a coherent EU wide strategy to address invasive alien species, and the mounting costs associated with their control (recently estimated to be €12 billion/year in Europe), the EU adopted a new regulation.

This legislation requires Member States to develop a list of species of Union concern, informed by risk assessments for individual species. It therefore encourages a cross-border approach to a cross-border problem – something that has been lacking to date.

The regulation will be published in the Official Journal of the European Union in the coming weeks.

Instructions to boaters at Lake Mead, Nevada to prevent quagga mussel transportation. Source: JN Stuart. (CC BY-NC-ND 2.0).

Instructions to boaters at Lake Mead, Nevada. Source: JN Stuart (CC BY-NC-ND 2.0)

A number of recent research initiatives within the field of invasion biology aim to compliment and inform the above process.

A protocol for scoring the impacts of invasive species has recently been developed2 and refined3, enabling the severity of a suite of environmental, economic and social impacts associated with a species to be calculated, informing risk assessments for potential invasions.

Studies have shown that this methodology can be effectively applied to different taxonomic groups4 (see also Kumschick et al. In press5), and can also be used to inform studies that aim to predict the impacts of a species prior to invasion6.

This scoring methodology is also integral to a proposal to develop a global list of alien species classified by their environmental impacts7 that aligns with the existing IUCN Red List of Threatened Species (which is celebrating its 50th birthday in 2014, having become a global reference tool for biodiversity).

The development of a standardised approach to quantify and compare the impacts of alien species will help us to predict whether potential invaders are likely to have negative impacts. This is important, as it allows for early intervention, and the swift allocation of resources to prevent the establishment of invasive alien species.


  1. Gallardo B, Aldridge DC (2014) Is Great Britain heading for a Ponto–Caspian invasional meltdown? Journal of Applied Ecology. doi: 10.1111/1365-2664.12348.
  2. Nentwig W, Kühnel E, Bacher S (2010) A generic impact-scoring system applied to alien mammals in Europe. Conservation Biology 24: 302–311. doi: 10.1111/j.1523-1739.2009.01289.x
  3. Kumschick S, Nentwig W (2010) Some alien birds have as severe an impact as the most effectual alien mammals in Europe. Biological Conservation 143 (2010) 2757–2762.
  4. Kumschick S, Bacher S, Blackburn TM (2013) What determines the impact of alien birds and mammals in Europe? Biological Invasions 15: 785–797.
  5. Kumschick S et al. (In press) Comparing impacts of invasive plants and animals using a standard scoring system.
  6. Evans T et al. (2014) Comparing determinants of alien bird impacts across two continents: implications for risk assessment and management. Ecology and Evolution 2014; 4(14): 2957–2967.
  7. Blackburn T et al. (2014). A unified classification of alien species based on the magnitude of their environmental impacts. PLoS Biology 12(5): e1001850. doi:10.1371/journal.pbio.1001850.
Posted in Biodiversity conservation, Conservation Science, Invasive alien species, Wildlife management | Tagged , , ,

Feral cats – they’re so un-Australian

Australia has the worst rate of mammal extinctions on the planet, with 29 since European settlement. That’s about 10% of Australia’s original mammal wildlife, including mice, bandicoots, potoroos, bettongs, rats, a wallaby and one of Australia’s only two bilby species – and marauding moggies are the principal culprits.


A feral cat and prey. Source: The State of Victoria

The Action Plan for Australian Mammals, published earlier this year, represents the first assessment of the conservation status of mammals across Australia – it identifies feral cats as the most significant threat to their survival.


John Gould print image of the pig-footed bandicoot – a species extinction largely attributed to feral cat predation. Source: Museum of Victoria

Predation by feral cats is now listed as a key threatening process under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act), which specifically identifies 35 bird species, 36 mammals, seven reptiles and three amphibians to which feral cats represent a specific threat.

Evidence also suggests that feral cats are on the verge of causing a second wave of extinctions in Australia’s north – the nation’s sole remaining landscape reflecting Australian wildlife prior to the arrival of Europeans.

You get the picture – one of only two continents in the world with no native cat species is now the world’s largest cattery.

Time is running out, but for whom?

It seems shameful that feral cats are still able to run riot in a relatively stable and wealthy country, which without doubt has the capacity to deal with the issue. So what’s being done about it?

Last Wednesday, the Federal Environment Minster, Greg Hunt, set out a plan to halt the loss of mammals in Australia by 2020. At the centre of this plan is a pledge to eradicate feral cats.

Presumably this is because the Australian Government recognises that if it is going to make any progress towards meeting its 2020 biodiversity targets, signed up to under the Convention on Biological Diversity (CBD), then feral cats have to go. All hail the power of the multilateral agreement.

This pledge has been met with a mixed response. Some describe Hunt as a hero, others question the Australian Government’s motivations, the likelihood of achieving the task, and in particular, the current proposals to use a poison bait called Curiosity.

Hunt believes this approach “has the potential to make a real difference to the protection and recovery of our native species”. The bait contains a toxin that restricts the flow of oxygen in the bloodstream. Placed within a small piece of food, it is ‘less likely’ to be eaten by wild animals because unlike cats, they tend to nibble their food, resulting in rejection of the bait.

However, tests have yet to demonstrate that this approach won’t harm other animals. It is curious then, that the success of the Australian Government’s strategy to eradicate feral cats relies quite heavily on the use of an unapproved poison bait.

Landscape management

In truth, there may be sites where a program of targeted baiting could be successful in reducing feral cat populations. However, it is unlikely to work in isolation. Australia is an enormous continent – baiting simply isn’t feasible.

What’s needed is a range of techniques to deal with feral cats, including the broader management of Australia’s landscapes. The Victorian Government is currently progressing with plans to introduce the Tasmanian devil into Wilsons Promontory National Park.

Tasmanian Devil. Source: Wikimedia Commons

Tasmanian devil. Source: Wikimedia Commons

The proposition here is that this top carnivore will compete with feral cats for food and nesting space, and may also take their young, reducing feral cat numbers.

Interestingly, Hunt recently acknowledged that he had not heard about the Victorian Government’s proposals, which perhaps suggests that Australia has yet to develop a coordinated national approach to deal with feral cats.

The cat-proof fence

Another approach that has proved successful in recent years is the establishment of a network of cat-proof enclosures. The AWC manages 23 properties, covering three million hectares of cat free land, with successful results for native species. One out of every five wild greater bilbys, and one of every three numbats now live within these enclosures.

The AWC is currently constructing a 43 km fence to create the largest cat free area on mainland Australia, with the aim being to reintroduce nine of Australia’s most endangered mammal species.


Cat-proof fence at Kakadu National Park. Source: National Environmental Research Program

The message here is that when feral cats are removed, wildlife bounces back. I leave you with a final quote from the Chief Executive of the AWC, Atticus Flemming:

“…if we remove feral cats from the landscape, we will see massive increases in the numbers of native animals… You wander at night through those areas where we’ve eradicated feral cats, and it’s like stepping back 200 years. The bush is alive. There are bilbys everywhere, bettongs everywhere, bridled nailtail wallabies. The ground is moving with little animals. That is what the bush must have been like before there were foxes and cats.”

Sounds purrfect to me.

Posted in Biodiversity conservation, Conservation Science, Feral cats, Invasive alien species, Wildlife management | Tagged , , , , , , , ,