Invasive species: A global threat to trade and livelihoods


Copyright: CABI. Credit: Sven Torfinn, Panos Pictures


A new report supports the fact that invasive species have the potential to undermine global food security and sustainable development, a vital statement supported by Goal 15 of the Sustainable Development Goals which states that we need to: introduce measures to prevent the introduction and significantly reduce the impact of invasive alien species on land and water ecosystems and control or eradicate the priority species.

Invasive species are a plants, fungi or animals that are not native to a specific location (an introduced species) which spread and can cause damage to the environment, human economy or human health. If not managed sustainably, these invasive species often negatively impact natural biodiversity and ecosystems, and consequently, farmers’ livelihoods.

Rapid globalization and increased trade is compounding this problem. As agricultural and non-agricultural products move from one country to another, the risk of introducing invasive species to non-native regions is also increased.

Research carried out by Dean Paini (senior research scientist – CSIRO) on the Global threat to agriculture from invasive species was carried out across 124 countries. He found that 40 of the countries in the study had the possibility of being invaded by at least one of the 1,297 invasive pests reviewed. The research identified a correlation between the type of crops grown in a country, the level of trade with other countries and invasive pests present in trading countries. He reported that China and USA were the greatest potential sources of invasives species due to the scale of their agricultural production and high levels of trade with other countries.

The report found that countries in sub-Saharan Africa were more vulnerable to the impacts of invasive species. This is because of their less resilient farming systems and increased reliance on the natural ecosystem. Impacts of invasive species are mostly experienced by rural farmers but it’s also felt at the national economic level as agriculture contributes significantly to their Gross Domestic Product (GDP). It is therefore pertinent to understand the source, nature and method of spread of invasive species so that they can be prevented, mitigated or managed – if they’re already established.

We at CABI have launched a global initiative to raise awareness of the global threat of invasive species on food security, trade, sustainable development and rural livelihoods – see our dedicated website. CABI has over 100 years of scientific expertise and knowledge on invasive species and we are using this knowledge to help tackle the worst invasive species across Africa, Asia and Latin America. For instance, Opuntia stricta – an invasive cactus – has colonized vast grazing areas in Kenya, resulting in minimized grazing land and the death of livestock. We have therefore used our scientific expertise to help address this invasive by introducing a sap-sucking bug (Dactylopius opuntiae) which is known to feed only on Opuntia stricta without causing harm to any other native plant species. This bug has previously been successful in controlling Opuntia stricta in South Africa and has already started being effective in addressing the same issues in Kenya.

As sustainable agriculture and rural development is at the core of our work, we aim to tackle invasive species by improving the knowledge of local people on the different methods of preventing the arrival and spread of invasive species. We also want to support agencies responsible for early detection and eradication of invasive species as well as mitigate invasive species through sustainable measures. This will ensure that invasive species are addressed without causing further harm to the environment and livelihoods.

Tackling invasive species to protect farmer incomes and livelihoods

Elias Kamuga“I have suffered [crop] losses amounting to 90%. I have no other source of income apart from tomato farming. I was relying on this crop to feed my family. I have nothing to do now other than try to think of what to do next.”

Elias Kamuga, Farmer, Kenya

Elias is a smallholder farmer from Kenya. Every year he sells his tomato crop at the local market, which gives him enough money to feed his family. But the arrival of a tomato pest to his region in Kenya has stopped that. The pest – a moth called a tomato leaf miner or Tuta absoluta – was recently introduced to Africa. This pest is an invasive species, and is destroying people’s livelihoods.

In 2015, Elias started to notice his tomatoes were being damaged by this pest. He tried taking them to market, but customers said they had too many holes and spots and were no good. He could not sell his produce. He believes he lost 90% of his tomato crop to the pest, and had no other source of income. Elias tried fighting this tomato pest with chemicals but they did not work. Elias now has to find another way to earn money. Thousands of farmers are in his position.

Invasive species, like Tuta absoluta, are devastating livelihoods. Tomatoes are one of the most widely cultivated crops in sub-Saharan Africa, grown in the backyards of almost every home. This important cash crop and source of nutrition is now being threatened by the recent arrival of the pest.

Tuta absoluta is rapidly moving across the African continent, decimating crops in Egypt, Ethiopia, Kenya and Tanzania. It has recently reached Nigeria, where a state of emergency has been declared – the pest has destroyed an estimated US$5.1 million of tomatoes and forced at least one major tomato processing plant to close. Growers do not know how to control it and many have abandoned tomato farming altogether. The race is on to prevent its spread with management schemes planned to limit its devastation.

Since 2014, CABI helped governments in Africa halt the Tuta absoluta threat and continues to do so. We are currently helping countries like Burundi, Kenya, Nigeria and Tanzania understand how they can best prepare prior to a pest invasion and are delivering practical knowledge on how to manage the pest once it has arrived. To address the recent severe outbreak in Kaduna State, Nigeria, we have provided the government with a technical brief on the tomato leaf miner together with available management experiences to help them develop a control strategy.

In 2015, we launched an important initiative to raise awareness of the threat of invasive species to the livelihoods of the rural poor. Our aim is to draw partners together from around the world to bring pest management solutions that exist already to the people who need them. We included Tuta absoluta as one of the priority targets for coordinated management. Our goal is to protect rural communities in developing countries from the devastating impacts of specific invasive species.

See Elias’ story.

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.

100 invasive weed factsheets project and my development bursary

Development bursary group pic

Workshop attendees: Invasive weed factsheet development. Nairobi, Kenya. February 2016.


Keen to meet colleagues and external partners in Kenya, and to learn new skills, I applied to CABI’s annual staff Development Bursary in 2015. Successful, I journeyed to Nairobi in February 2016 where I assisted with a workshop focussed on developing factsheets on invasive weed identification, management and control. These factsheets will ultimately help improve the livelihoods of farmers by reducing crop losses.

Who am I?

I am Kate Dey, a Content Editor for CABI’s Invasive Species Compendium (ISC) (kneeling front, right of image above). Sitting in the small compendia office on the second floor at Wallingford HQ, UK, I spend the majority of my time commissioning and editing datasheets. I also update distribution and pest records for the Crop Protection Compendium (CPC) and help manage the @CABI_Invasives Twitter account.

Leading up to my bursary application

In October 2015, I was asked to assist with a project which is part of an initiative known internally as the Invasives Big Push. The aim of this initiative is to stop the world’s worst invasive species undermining the livelihoods of 50 million farming families. To help achieve this aim, the project’s focus was to produce 100 factsheets on invasive weeds for East Africa (Kenya, Tanzania, Ethiopia, Malawi, Rwanda and Uganda) and Southeast Asia (Myanmar, Thailand and Vietnam) with the overarching theme of empowering farmers by providing them with clear and practical information on weed management and control. This exciting project is a collaborative one which involves CABI’s Invasives and Plantwise teams, and external partners, working together.

So I got stuck in, assisting with the prioritisation of species to be covered. They were largely prioritised by taking into account: impact on major crops (mainly maize and rice); number of countries affected by weed; and amount of information CABI already has (largely looking at the ISC and CPC) which could be repurposed and shared more widely.

I proceeded to create the first drafts, editing information from the Compendia so that it was compatible with the factsheet format required by CABI’s Plantwise Knowledge Bank (PWKB) – an online pest information resource on which the factsheets were to be hosted. Making this information available via the PWKB means it will be more readily available to extension workers who can use it to give effective advice to farmers struggling with weed infestations.

More specifically, I helped draft the first few species-specific Pest Management Decision Guides (PMDGs) which hold clear, practical, country-specific advice on pest management and control, and support Integrated Pest Management principles (IPM). These are usually produced by Plantwise but on this occasion their creation was the responsibility of the Invasives Big Push Team because of the focus on invasive weeds. Hence, Plantwise were instrumental in the creation of these factsheets, providing us with useful training and ongoing support.

The second type of factsheets produced was species-specific descriptive factsheets. The creation of these would fulfil the objective to repurpose and disseminate information from weed ID guides, produced by CABI employee Arne Witt. Along with the PMDGs, these were to be developed at two workshops in Kenya and one in Bangkok, making them country-specific in the process. Keen to be part of the development phase and to see what would become of our drafts, I applied for the development bursary in December 2015.

The workshop

I was lucky enough to attend the first four day workshop in Nairobi, Kenya, where the drafted factsheets would be developed. Attendees included specialists in weed ecology and control from a variety of research organisations and universities, and had travelled from Tanzania (2 people), Ethiopia (6 people) and within Kenya itself (6 people).

Day 1


Arne Witt, talking about impacts invasive alien species on crops

Participants were welcomed and introduced, and opening presentations were given, covering: background to the Invasives Big Push and Plantwise initiatives (by Marion Seier); introduction to factsheets and PWKB (by me); impacts of invasive alien species on crop production, and introduction to integrated pest management (IPM) principles (by Arne Witt).

Before beginning factsheet development, we needed to ask each country group what weeds they thought we should focus on. Participants were asked to complete a prioritisation table which would enable them to rank the importance of weeds in their country. It contained criteria such as area affected, crops affected, health impacts and ease of control. Species selected were those ranked 1-10 by at least two countries, luckily resulting in a large cross-over with the countries we had previously prioritised. We then started reviewing the country-specific descriptive factsheets together, asking participants to look over the drafts (some created beforehand and some created during the workshop itself) and confirm the most important common local names for each species.

Day 2

The descriptive factsheets were completed in the morning, before further presentations were given on PMDG writing (by René Eschen) and international pesticide agreements (by Sarah Thomas). We then started discussing how to write the PMDGs. Importantly, the information needed to: promote the use of preventative methods as the first line of defence; provide monitoring guidance so an infestation could be identified early on; and promote the use of the least harmful control methods if an infestation is present (i.e. non-chemical control). If these methods proved ineffective, it was essential to provide information on how to correctly use potentially harmful control methods (i.e. pesticides) safely and effectively.

The first step was to talk through the content of an existing PMDG together, in order to gain an understanding of what should go in the Prevention, Monitoring and Direct Control columns, and what restriction and limitation information was essential to include along with pesticide recommendations. We then reformed into country groups and had a go at creating a PMDG from scratch (for Parthenium hysterophorus, a weed that can not only reduce crop yields by over 90% but also poses a serious health risk to people and livestock).

After completing this task, we joined together again and listened to a representative from each country group present the PMDG they had produced. Content was debated and discussed, helping everyone further their understanding of the information required and providing inspiration by comparing differences and similarities. We then started on PMDGs for the rest of the prioritised species.

Days 3 & 4


Sarah Thomas, assisting with PMDG development

During the final days, PMDG drafts were reviewed, refined and added to. Along with Marion, René, Arne, and Sarah, I sat with the participants, answering their questions on what information was required, where it should be placed and how to make it clear. We assisted with entering the text into the forms and helped look up pesticide information; checking whether they were on Plantwise’s Red List (containing internationally restricted/not to be used pesticides) and on the nationally approved lists.

Some PMDGs were placed on the walls so groups could gain ideas from each other’s factsheets, particularly since many management and control methods would be the same for each country. For this reason also, PMDGs were rotated around the groups, so that as the factsheets were circulated participants added to and edited what a country group before them had written, thereby maximising efficiency. By the final day 18 weed species had been covered, and 33 PMDGs and 30 descriptive factsheets had been produced – a fantastic outcome which was thanks to an engaging, friendly and hard-working group.

What will happen next?

The factsheets will now need to pass through a review process, whereby content will be edited by Plantwise and a weed specialist will validate the information. The final versions will be uploaded the PWKB, a key resource for extension workers, called Plant Doctors, who advise farmers on what action to take when a pest is impacting on their crop. Farmers bring their affected crop along to a local Plant Clinic where the Plant Doctor makes a diagnosis (find out more at The factsheets will provide Plant Doctors with the tools they need to help farmers loose less of what they grow to crop weeds, increasing the amount of food they can sell and eat and ultimately improving their livelihoods.

What did I get out of it?

Firstly, I really enjoyed working with such dedicated and passionate participants, listening to them talk about their research and experience and how much they care about helping farmers. Many of them had farming backgrounds, and/or had close friends and family who were farmers, so they had a good understanding of the challenges they face.

Two particular subjects that we discussed with participants stuck with me; firstly, the presence and growing dominance of women in farming businesses. More and more men are leaving farms to go to the cities and towns to find jobs, which is not surprising when you consider the back-breaking work, high running costs, unpredictable outputs and slim profit margins. 60% of pre-harvest labour in Africa is hand weeding, mostly by women and children (who often have to leave school during peak weeding periods). 100 million women in Africa spend 20 billion hours weeding every year. Secondly, the extent to which pesticides are used unsafely and ineffectively is huge, with many farmers developing health problems from incorrect use, such as not wearing protective clothing or using too high a concentration. More than one participant mentioned that many farmers who use pesticides in Africa don’t eat the crops they spray because even they aren’t sure that they’re safe. Furthermore, there was a story of one farmer not being able to get their beans to market, consequently feeding those beans to their livestock, and their livestock dying from poisoning as a result.

It was also great to make new friendships with CABI staff members who I may not have been able to meet through my usual line of work. It was a really nice experience walking into a CABI office I’d never been to but still feeling welcome and a sense of familiarity. We’re often reminded of the ‘One CABI’ ethos at work but those words mean so much more when you actually experience it. It was not just lovely to meet Kenyan staff, but also to work with Marion, René and Sarah from Egham, UK.


Overall, it was fantastic to be part of a project with the purpose of improving people’s lives. These factsheets will directly help farmers to more effectively manage and control invasive weeds, improving yields and so resulting in more food and income for their families. The workshop experience was a reminder that there is still more work that needs to be done, but that by working together we can really make a difference.

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