Invasive alien species (IAS) threaten livelihoods and biodiversity globally


Invasions from non-native plants, animals and pathogens threaten the economies of the world’s poorest nations, according to a new study.

The study, published in Nature Communications (‘Global threats from invasive alien species in the twenty-first century and national response capacities’) found that one-sixth of the world’s land is highly vulnerable to invasion, including substantial areas in developing countries and global biodiversity hotspots.

Once IAS arrive in a new region, many thrive and outcompete other species, which have adapted to the local ecosystem through evolution. There is a great possibility that IAS can become the dominant force in local environment and out-compete native organisms for resources and habitat, choking river systems and wells, and preventing cattle from grazing and out-competing or eating native species. Around the world, they can cost up to $1.4 trillion annually.

In light of this and how globalization and environmental change are exacerbating the negative impacts of IAS, an international team of researchers analyzed the threats and evaluated national capacities to prevent and manage species invasions.

Often seen as a problem in more developed countries, the new study showed that invasions are also threatening the few remaining biodiversity strongholds in the world’s most fragile economies. They found that many low-income countries stand to lose out as their natural resources are sapped. These negative impacts are only expected to get worse as more trade, cross boarder work and particularly air travel leads to increased biological invasions.

The report highlighted that developing countries also have limited resources or plans to act against invasions of non-native species and are ill-prepared. Their findings also suggest that livelihoods and food security in these fragile economies are likely to be affected.

Poorer economies are crucially reliant on international trade and have little power to regulate imports, so the introduction of highly dangerous species is continuing.

The report’s authors, therefore, call for more international cooperation between governments and NGOs to tackle IAS issues and are encouraging developed countries to share their expertise. By uniting global data, the authors believe we can improve early-warning and eradication schemes to help in the fight against invasive alien species.

CABI at EcoSummit 2016

EcoSummit 2a

CABI promoted its new invasive species initiative at this year’s EcoSummit event which took place in Montpellier, France, from 29 August – 1 September. CABI’s latest initiative aims to tackle the issue of invasive species to improve the lives of 50 million farmers in Africa and Asia.

Launched in Copenhagen in 1996, the event provides a platform for ecological scientists and researchers from around the world to share new knowledge and discuss sustainable solutions to global environmental and ecological challenges. This year’s EcoSummit conference focused on terrestrial ecosystems, especially fragile systems that are less resilient to climate change and the impact that human activities are having on the environment – especially agriculture. The increasing global demand for food was also discussed and how intensified agriculture to meet this demand can adversely affect ecosystems.

CABI’s work on invasive species was highly relevant here as many invasive species cause the loss of natural biodiversity and alter global ecosystems. CABI’s expertise in tackling invasive species in order to promote environmental sustainability, livelihoods and food security is a significant contribution to solving global environmental challenges.

Julien Lamontagne-Godwin was one of CABI’s representatives at the conference. He said: “This conference is vital to showcase the myriad avenues of research in ecology, and is a vital tool to describe and remind us of the importance of a healthy ecosystem for our way of life. Many discussions we had with top scientists here highlighted the value of CABI’s knowledge platforms, such as our Invasive Species Compendium. These conversations also helped us add depth and significance to our new livelihoods initiative on invasive species.”

CABI has been working on invasive species for over 100 years, exploring measures to prevent, mitigate and manage invasive species on a global level. Through a selection of different sustainable techniques such as biological control, CABI tackles some of the worst invasive species that negatively impact terrestrial ecosystems and impact the livelihoods of farmers who depend directly on the ecosystem for their sustenance.

New European Union IAS Regulation


Hydrocotyle ranunculoides

Floating pennywort (Hydrocotyle ranunculoides): on the EU species of Union concern list and a target for biocontrol (Credit: Kate Constantine, CABI)

Invasive alien species are a major threat worldwide, impacting upon millions of livelihoods and threatening biodiversity. The situation is worsening, due in no small part to increased global trade and transport. The economic costs of IAS can be vast: worldwide, invasive species are estimated to cost US$1.4 trillion per year – close to 5% of global GDP.

In the European Union alone, invasive alien species (IAS) are estimated to cost €12-20 billion a year.

In response to this threat, the European Union adopted Regulation (EU) No 1143/2014 which makes compulsory the management of key IAS that are of concern to the region. Methods include limitation of spread, eradication of early invasions and active management of established IAS. A list of 37 species to be included under the regulation was approved by EU Member States in December 2015 and has recently come into force (Regulation (EU) 2016/1141). It includes 23 animals and 14 plants whose current and potential impacts across the region will mean that collaborative and concerted action is required across the EU.

This is part of the EU’s biodiversity strategy which aims to halt the loss of biodiversity and ecosystem services in the EU by 2020 and is in line with the Convention on Biological Diversity’s (CBD) Aichi Targets, particularly Target 9:

“By 2020, invasive alien species and pathways are identified and prioritized, priority species are controlled or eradicated, and measures are in place to manage pathways to prevent their introduction and establishment.”

At CABI, we have been working on invasive species at a global scale for decades and are experts in their management using both traditional methods and through biological control. This new legislation is welcome; recognising the serious threats that invasive species pose and imposing compulsory measures to lessen the spread and impacts of IAS in the EU.

The three Cs of the Invasives’ programme development: concepts, compromise and coffee

Since March 2016, I have been working as the programme support manager for the multi-sectorial development initiative called the Invasives programme. Our new Invasives initiative will be undertaking regional, national and local technical and partnership activities to deal with some of the worst biological invasions that are threatening livelihoods in poor rural areas. As we look to leverage the successful Plantwise initiative (, the Invasives programme team is looking to build additional partnerships in the private, public and civil society sectors. Needless to say, from a personal point of view, it has been a steep learning curve!

But it has been productive! In 3 months, we have managed to finalise the strategy (the first version of it anyway), develop a logical framework, partnership and budget documents, a theory of change, and link our activities to CABI’s global gender strategy and monitoring and evaluation process.

How did we achieve this, all in time for the CABI review conference in July? Through the excellent combination of concepts, compromise and coffee

Let me explain.


You cannot develop a multi sectorial global programme without a strong conceptual basis.

The Invasives programme definitely has strong roots: as an organisation, CABI has over 100 years of experience dealing with problems species in agriculture around the world, notwithstanding staff’s academic and practitioner knowledge is immense working on projects throughout the globe. This experience is underpinned by a world leading invasive species information database: the Invasive Species Compendium ( What is more, the programme’s goals are complementary with CABI’s largest programme to date, the prize winning Plantwise initiative. Indeed, our partnerships with local partners as well as the analysis of plant clinic information will be crucial for the development of timely invasive species integrated pest management interventions in local areas. The approach at a regional level means we can deal with cross border issues, whilst our locally focused activities means helping vulnerable groups out of poverty through job creation and/or better agricultural yields. The core team developing the programme, the technical management teams, composed of 8 senior staff, headed by Dr Sean Murphy, have been given the responsibility of developing the programme’s work packages. Their intimate knowledge of invasive species and international development will be invaluable for the smooth running of the programme in its infancy.


Whilst our experience and knowledge on the Invasive species theme is definitely an advantage, it also means CABI contains some opposing views on how to achieve the programme’s goals. Hence the second “c”: compromise

As a programme manager, the role is principally to keep the programme moving forward. This inevitably means you will have to manage conflict between ideologies. For example, the programme from a marketing or commercial sense might stray far from what a research professional might see as a successful programme. A donor-focused professional will want to see different aims than a development profession working in the field. Indeed, it is the programme manager’s role to listen, analyse and suggest compromises. A degree in psychology would be helpful, let alone one in ecological economics, social dynamics or conservation agriculture (luckily I have one of those!). A programme manager’s role, while content driven, will most likely earn his/her corn by his ability to diplomatically find a solution and move forwards.


It is somewhat ironic that a programme manager’s staple drink is one of the key crops in conservation agriculture and commodities. Indeed, coffee is one of the sole (soul?) constants in a complex management role. Do you think I am overstating it? Try the 3 day workshops to hash out logical frameworks with technical teams, tight deadlines to learn about, and draft, a programme theory of change, organising milestones, integrating gender and monitoring and evaluation strategies, fixing and predicting budgets and partnerships… Oh yes, add a new-born child and the business end of a PhD in the mix, and you can understand why coffee has become a pretty important part of my life!

The programme is in good shape, with strong endorsements from all sides. The programme strategy will be out very soon. That is enough of a reward for now.

That is, until we roll out the initiative and help 50 million farmers improve their livelihoods.

A fifth of the world’s plants under threat, as report says 391,000 species now known to science

Dave Simpson – 11 May 2016

A ground-breaking report from the Royal Botanic Gardens, Kew, has produced an estimate of the number of plants known to science. By searching through existing databases, the researchers have estimated that there are now 390,900 known plant species, of which around 369,400 are flowering plants. But this figure is only those species currently documented: new species are being discovered all the time, including over 2000 in 2015 alone. But more worryingly, it is suggested that 21% of plant species are under threat, from a range of pressures including climate change, habitat loss and invasive species. The invasive species component of the report, which draws heavily on CABI’s Invasive Species Compendium, says that nearly 5,000 plant species are documented as invasive, from over 13,000 vascular plant species naturalised outside their native range.

Prof Kathy Willis, director of science at RBG Kew, said: “It’s really important to know how many plant species there are, where they are and the relationship between the groups, because plants are absolutely fundamental to our well-being”

And on invasive species, the head of conservation science at Kew, Dr Colin Clubbe, said that invasive species are one of the biggest challenges for biodiversity. Quantifying the number of species regarded as invasive is a key step towards addressing the problem. “Now that we’ve got this list and this number, it’s certainly a bit like know your enemy,” said Dr Clubbe.


Japanese knotweed, a major invasive
“We know what we are dealing with, we can then look at them, and see what’s similar, what makes a good invasive, and then see how we can use that information to have better management practices in place or recommendations for how you deal with them.”

Trade, plant collecting, and movement of people, has led to at least 13,168 species of vascular plants becoming naturalised outside their native range. The report says that they become classed as invasives once they start to compete with native vegetation and spread to a degree that causes damage to the environment, the human economy or human health. The effects on livelihoods, and on ecosystem services such as agriculture, forestry, water and pollinators, can be staggering: the Kew report cites one study as estimating the total costs from all invasive species as nearly 5% of the world economy, and it also quotes CABI research which estimated the impact on the British economy alone as around £1.7 billion every year. Japanese knotweed, one of the most invasive plants in the UK, costs Great Britain over £165 million annually to control.

The Kew report synthesizes invasive species data from the open-access CABI Invasive Species Compendium, the Global Invasive Species Database (GISD), global reviews of invasive trees and shrubs by Rejmánek and Richardson, and Weber’s Invasive Plant Species of the World: a Reference Guide to Environmental Weeds published by CABI in 2003. CABI’s ISC – flagged in the report as “the most comprehensive web-based resource” – has datasheets for 4,841 of the total of 4979 invasive vascular plants in Kew’s consolidated list.

Identifying other threats to plant biodiversity, the report says that farming is the biggest extinction threat, representing 31% of total risk to plants. Logging and the gathering of plants from the wild is responsible for 21.3% of the risk, followed by construction work with 12.8%. The report said that some 1,771 areas of the world have been identified as “important plant areas” but very few have conservation protection measures in place.

Highlighting just how many plant species are already important to humans, the report says that some 17,810 plant species have a medical use, 5,538 are eaten, 3,649 become animal feed and 1,621 are used for fuels. Over 11,000 plant species are used for materials, for example fibres and timber.

“[Plants] provide us with our food, our fuel, our medicines – even controlling our climate” says Professor Willis.

The report can be downloaded in full, or data from individual sections accessed, at the website A symposium on the report is being held at Kew on 11-12 May. Moving forward, the global assessment will now be carried out annually, allowing scientists to monitor how plants are changing over time.

Malaria incidence and invasive plants – is there a link?


3.2 billion people are still at risk of getting malaria. Although progress has been made, if we are to achieve a 90% reduction in global malaria incidence and mortality by 2030 we must do more. Controlling invasive species may be part of the solution.

The path will not be easy. Mosquitoes are becoming increasingly resistant to pesticides – the front line of defence from malaria today. But there are other aspects we can consider, like the potential link between the incidence of malaria and invasive, non-native weeds.

It is widely known that mosquitoes need plant sugars, among other things, to survive and proliferate. Studies in Israel show that mosquitoes are much more likely (250 times more likely) to transmit malaria in areas rich in plant sugars. Could the improved management of invasive plants abundant on the African continent lead to a reduction in the incidence of malaria?

It is this question that brought together experts on malaria and plant invasions to a workshop in Kenya in December 2015, funded by the Bill & Melinda Gates Foundation. The broad objective of the workshop was to explore whether mosquitoes benefit from invasive plants and whether these plants have a positive influence on the rate of malaria transmission. The workshop also looked at whether invasive plants could be managed on a large scale.

Experts agreed that access to particular plant sugars increases the ability of Anopheles mosquitoes to transmit malaria. Although it is not known if invasive plants produce more sugars, they are more widespread and abundant than native plant species. In fact, many have the ability to invade semi-arid and arid areas, possibly increasing the prevalence of malaria in regions where mosquitoes could not survive in the past. Invasive plants also actively grow and produce flowers and fruit for longer periods than native plants, thereby extending the availability of plant sugars over longer periods than in the past. This may allow mosquitoes to retain high population numbers for much longer periods in invaded areas than in areas where there are no suitable invasive plants.

If there is an obvious link between invasive or weedy plants and Anopheles mosquitoes, can we significantly reduce the incidence of malaria by managing invasive plants?

There is no doubt that problematic plants can be controlled. Landowners, especially farmers, do it all time. The Government of South Africa allocates approximately US$120 million a year to control invasive plants, especially in water catchments, biodiversity hotspots and protected areas. It also invests in biological or natural control of invasive species. This is considered one of the most cost-effective management options, ideal for use in developing countries that do not necessarily have the resources for chemical or conventional control.

So, we can control weeds but would it reduce the incidence of malaria?

Lowering the abundance and density of any plant species favoured by Anopheles mosquitoes should lower malaria incidence. Managing many of these non-native weeds will also result in a multitude of other benefits for poor rural communities – like protecting farmland, for example.

This possible malaria-invasives linkage must be explored further. We need to do more research to fill in knowledge gaps. This includes looking at what plant species the Anopheles mosquitoes use within a given environment. Methodologies are being developed to see if rapid assessments of mosquito gut contents can provide information on what plant species they have been feeding on. We also need to look at the impact of removing certain species of invasive plants on mosquitoes. If we can compare mosquito abundance, longevity and ability to transmit malaria in areas where the invasive plant is dominant and where it is less dominant, we can build a fuller picture of the potential problem and solution.

Malaria is a terrible disease that still affects too many people. We must do all we can to understand the possible link between the incidence of malaria and invasive, non-native weeds. If a link can be found, management of invasive weeds could offer hope to many living under the threat of malaria.

By Dr Arne Witt, Coordinator, Invasive Species, CABI

For more information about CABI’s work managing invasive species, click here.

New in January and February 2016 from the ISC

In January and February 2016 the following datasheets were published on CABI’s Invasive Species Compendium (ISC). You can explore the open-access ISC here:

By Franz Xaver (Own work) [CC BY-SA 3.0 ( or GFDL (], via Wikimedia Commons

1. Agropyron cristatum

Agropyron cristatum (crested wheatgrass)

A. cristatum is a resilient and long-lived perennial grass with stems that are 20-70 cm long and with finely-branched deep roots that extend to a depth of 1 m. It is able to grow in a wide range of habitats making it a very effective invader. Its native range is the Russian and Siberian steppes but it is now present in the North American prairies where it was planted in the 20th century to reseed abandoned cropland. It has since invaded vast areas of rangeland across the upper USA and southern Canada where it outcompetes native vegetation, altering soil chemical properties as a result.

By Homer Edward Price (Bushy-Bluestem Uploaded by Amada44) [CC BY 2.0 (], via Wikimedia Commons

2. Andropogon glomeratus

Andropogon glomeratus (bushy bluestem)

A. glomeratus is another invasive perennial grass, but is taller than A. cristatum, with stems that can be 1.5 m in height. It is a popular ornamental because of its bushy/tufted appearance and is consequently found outside of its native range of southeastern USA, Mexico and parts of Central Mexico and the Caribbean. Introduced to Hawaii, USA, where it is considered a noxious weed, it is outcompeting the small, native and endemic shrub Vaccinium reticulatum. A. glomeratus can also change fire regimes as it is highly flammable. This can promote invasion by other non-native species.

By scott.zona (Flickr: Atriplex semibaccata) [CC BY 2.0 (], via Wikimedia Commons

3. Atriplex semibaccata

Atriplex semibaccat (Australian saltbush)

A. semibaccata is a perennial shrub which can grow up to 80 cm tall and is drought and salt-tolerant. It is a valued fodder crop but it can form dense and fire retardant groundcover that displaces native species. In Hawaii, USA, it is impacting on a number of endangered plants such as Panicum niihauense, along with other invasive species. In California, USA, it is competing with Verbesina dissita which is endangered and restricted to the Laguna Beach area of Orange County.

I, Hugo.arg [GFDL (, CC-BY-SA-3.0 ( or CC BY-SA 2.5-2.0-1.0 (], via Wikimedia Commons

4. Phleum pratense

Phleum pratens (Timothy grass)

P. pratense is a (yet another!) invasive perennial grass which can grow up to 1.5 m tall and spreads vigorously. It is an important forage grass, native to Europe and Asia, which can alter native plant communities by forming monocultures (vegetation consisting of the same species). Its seed is considered a contaminant of grass and other seed lots in the eastern US states of Delaware, Maryland, New Hampshire, New Jersey, Pennsylvania, Virginia and West Virginia, thus reducing seed lot quality and price. P. pratense is also a host to diseases, such as ergot (Claviceps purpurea), that are serious pathogens of cereal crops.

By Walter Siegmund (Own work) [GFDL ( or CC BY-SA 3.0 (], via Wikimedia Commons

5. Rubus parviflorus

Rubus parviflorus (thimbleberry)

R. parviflorus is a deciduous, perennial raspberry species which produces edible fruits and can act as a soil stabiliser. Its fruits are eaten by the indigenous peoples of North America who also use parts of the plant to treat a wide variety of ailments such as stomach ache and diarrhoea. It is native to North America and Canada, however it has been recorded as invasive in British Columbia, Canada, due to the fact it can outcompete seedlings of economically important conifer species. It has also been recorded as invasive in parts of Europe.

  1. Agropyron cristatum by Franz Xaver (Own work) [CC BY-SA 3.0 ( or GFDL (, via Wikimedia Commons
  2. Andropogon glomeratus by Homer Edward Price (Bushy-Bluestem  Uploaded by Amada44) [CC BY 2.0 (, via Wikimedia Commons
  3. Atriplex semibaccata by scott.zona (Flickr: Atriplex semibaccata) [CC BY 2.0 (, via Wikimedia Commons
  4. Phleum pratense by I, Hugo.arg [GFDL (, CC-BY-SA-3.0 ( or CC BY-SA 2.5-2.0-1.0 (, via Wikimedia Commons
  5. Rubus parviflorus by Walter Siegmund (Own work) [GFDL ( or CC BY-SA 3.0 (, via Wikimedia Commons