About Forest Invasive Alien Species (FIAS)

About Forest Invasive Alien Species (FIAS)

Alien species (insects, micro-organisms and plants) are species found outside of their natural range. They can be pests diseases, insects or weeds. Other alien species are competitors of indigenous species rather than pests. They do not cause damage to trees and plants, but they do change the natural biological diversity of local ecosystems by crowding out indigenous species. These species are termed invasive if they are able to modify indigenous ecosystems either as pests or competitors. The introduction of alien pests into a new environment, sometimes far away from their original environment, is most often accidental. Some plants introduced for horticultural or ornamental reasons become invasive weeds that invade and threaten natural ecosystems if allowed to grow wild.

To prevent damage by these alien pests, the Government of Canada has set up an Invasive Alien Species Strategy for Canada based on the prevention, early detection, rapid response and eradication, containment and control of invasive alien species in forests (IASFs) that nonetheless succeed in entering Canada. The Canadian Food Inspection Agency, the Canadian Forest Service of Natural Resources Canada and Environment Canada have put forward an Action Plan for Invasive Alien Terrestrial Plants and Plant Pests that outlines how the national strategy will be implemented in the forest and agricultural sectors.

There are numerous alien insects and diseases trying to enter Canada. However, very few succeed in establishing a home here because of Canada’s generally effective natural barriers, such as climate, a vast land mass and topography. Invasive alien species also have special requirements and can only establish themselves sustainably under certain conditions, such as the absence of predators, presence of a compatible host and temperatures promoting their reproduction. Of the species that manage to establish themselves in Canada, only a few can be termed invasive alien species or pests because of the extensive damage they cause and threats they pose to the integrity of our forest ecosystems. A very well known example is Dutch elm disease, which completely ravaged the countryside of the St. Lawrence Lowlands and many of Canada’s major cities. In Quebec alone, 600,000 elm trees were destroyed or chopped down between 1945 and 1965 because of this disease.

A growing phenomenon

The risk of introducing alien species (insects and diseases) will increase in Canada over the next few years for various reasons:

  • More and more species reach our borders, particularly because of increased free trade;
  • Modern-day forests are more vulnerable because they have been significantly modified by human activities;
  • By definition, alien pests cause more damage than indigenous species because they have no natural enemies in Canada;
  • Lastly, environmental considerations will limit the use of some control and eradication measures.

Entry points

How do alien insects and diseases get into Canada? Like any traveler coming from abroad, they arrive by air, water or land. In fact, they can be found in all living or unprocessed plant matter (plants, seeds, tubers and greenhouse material) and in wood logs purchased outside Canada. It is suspected that the large-scale importing of pine logs from New England led to the introduction of pine shoot beetles into Quebec. They are also found in lumber used for packaging or securing cargo (wooden pallets, casings, dunnage, etc.), and even in the massive wooden spools imported from China that are used to wind cables, when these various products are made of green lumber. In short, the entry points for these unwanted guests are often the entry points of international trade. Because the United States, the world’s biggest importer, is our principal trade partner, many, if not the majority, of the alien pests that enter Canada have entered the United States beforehand. Moreover, with Canada building more and more trade links with other partners, such as Japan, China, South America and Europe, the origin and identity of alien pests entering Canada is changing. The introduction of these pests is usually accidental, but other pests may have been introduced intentionally, although their dispersal into nature can be accidental. For example, European gypsy moths were imported from France by an amateur entomologist who wanted to produce silk. In 1869, a few of the moths escaped and rapidly propagated. Today, this species is one of the major pests in Canada’s deciduous forests.

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Invasive insects and diseases that attack Canada’s ecosystems and forests, and often its urban forests, are known to have ecological, economic and social impacts.

In ecological terms, the pests can cause significant damage to indigenous trees and plants that lack natural defenses against these invaders. They can slow their growth or kill them over vast areas. Consequently, they change the internal dynamics and possibly rupture the characteristic equilibrium of ecosystems, because the damage they cause adds to various natural or human disturbances. They attack plantations and certain valuable species, such as pine, elm, oak and butternut trees. Invasive alien species can become competitors or predators of indigenous species and their activities can eliminate habitats for some wildlife species through diminished biological diversity and even, in extreme cases, through the disappearance of particular species. As a result of chestnut blight, a disease introduced into Canada in the early 20th century, the chestnut species was placed on Canada’s endangered species list. Purple loosestrife has already altered many wetland areas in Canada.

In economic terms, alien pests have a considerable impact. They slow down growth, kill trees and plants, and reduce the quality of lumber and harvests. They also cause a reduction in activities related to plant resources, such as lost jobs and income in the forest, recreation and tourism industries. Restrictions on and reductions in commercial activities and related income (sale of products, taxes, etc.) are other impacts produced by alien pests.

In addition, a considerable investment has to be made in regulatory controls, possible processing of products intended for export, scientific monitoring of introduced pests, detection and control of epidemics, reforestation and sanitary measures, and, of course, prevention. It is difficult to calculate all of the expenditures related to alien pests, and the expenditures vary from one year to the next. But solely in terms of timber losses, we know that forest pests destroy about 400,000 ha of forest every year in Canada, which is slightly less than half of the 930,000 ha harvested annually by the forest industry.

Social impacts are even more difficult to assess, but the following, which are or may be affected to varying degrees, can be pointed out:

  • Stability and well-being of rural communities, particularly those associated with the forest industry;
  • Traditional Aboriginal activities;
  • Esthetic and spiritual values that people associate with forest and natural ecosystems;
  • The attraction of jobs in the forest and wildlife sectors;
  • Health problems related to forest industry work and higher risk of accidents in disturbed ecosystems;
  • Public perceptions of forestry and forest industry activities; and
  • Credibility of governments in the area of forest and ecosystem management.
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A list of our worst pests

The following is a list of the principal alien pests, along with their preferred hosts and estimated dates of arrival in Canada:



Ash dieback, caused by the Chalara fungus, prompts re-evaluation of current protocols to protect UK trees and other plants; taskforce recommends threats to plant health be taken as seriously as animal disease

The UK needs to be better prepared for threats to plant health. In the last few years alone, several previously unknown pests and pathogens have emerged, posing significant risks to the UK’s crops as well as trees in woodlands, commercial forests and in urban environments.

Professor Chris Gilligan, chair of the taskforce and Professor of Mathematical Biology and Head of the School of Biological Sciences at the University of Cambridge

As the fungus responsible for ash dieback continues to devastate ash tree populations throughout the UK and other threats to the countryside continue to emerge, experts convened by Defra are advocating for stronger measures to protect the UK’s trees and plants.

The independent Tree Health and Plant Biosecurity Expert Taskforce was established by Defra’s Chief Scientific Adviser, Professor Ian Boyd, late last year to address the current and emerging threats to the UK’s trees and plants. Working with an advisory group made up of various stakeholder organisations, to include industry, Defra, and the Forestry Commission as well as Border Force, the taskforce is proposing a number of initiatives aimed at minimising the risk of plant pests and diseases.

Professor Chris Gilligan, chair of the taskforce and Professor of Mathematical Biology and Head of the School of Biological Sciences at the University of Cambridge, said: “The UK needs to be better prepared for threats to plant health. In the last few years alone, several previously unknown pests and pathogens have emerged, posing significant risks to the UK’s crops as well as trees in woodlands, commercial forests and in urban environments.

“By increasing our understanding of what pests and diseases are the biggest threats and how best to mitigate their impact, we can minimise potentially devastating outbreaks.”

The scientists believe that the threats have increased because of globalisation in trade and travel and the subsequent escalation in volume and diversity of plants and plant products entering the UK, all of which potentially harbour plant pests and pathogens. Once established, pests and pathogens can wreak havoc on biodiversity, timber and crop production, the landscape and, in certain circumstances, human health. (In addition to Chalara, recent examples include horse chestnut leaf mining moth, oak processionary moth, bleeding canker of horse chestnut and Dothistroma needle blight on pines.)

Professor Charles Godfray, a member of the taskforce from the University of Oxford’s Zoology Department & Oxford Martin School said: “Globalisation poses many challenges including to the health of our trees and other plants; the taskforce has tried to suggest proportionate measures that will materially lessen the risks to the nation’s trees and forests without adding unnecessary barriers to trade and commerce.”

Although the remit was to focus on trees and related woody species, the taskforce noted that many of the principles addressed in recommendations for tree health are applicable to pests and diseases that affect other plants (including agricultural, horticultural and biomass crops, indigenous vegetation and ornamental plants).

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Taskforce recommendations

Currently, there are numerous risk assessments for individual pests and pathogens at both the national and European level. The taskforce recommends a single national Risk Register for plant health. This new UK Plant Health Risk Register would serve to identify and prioritise pests and pathogens that pose a threat to the UK and to identify what actions must be taken should the threat materialise.

The taskforce is also advocating an individual at a senior level who is responsible for overseeing the UK Plant Health Risk Register and providing leadership for managing those risks. The Chief Plant Health Officer would work in a similar fashion as the Chief Veterinary Officer, who oversees animal-related emergencies.

The appointee would also be responsible for developing and implementing procedures for preparedness and contingency planning to predict, monitor and control the spread of pests and pathogens. There was also a recommendation that current governance and legislation needed to be reviewed, simplified and strengthened.

Because of globalisation, more and more people and goods are travelling greater distances at an increasingly greater rate. As a result, there is a significant increase in the risk of introducing non-native pests and pathogens. In order to minimise the risks of introduction at the border, the taskforce has made several recommendations regarding the import of trees and other plants. They propose that no plant material for personal use be imported from outside the EU.

The import of live plants, foliage, branches and other plant parts has seen a 71 per cent increase since 1999, dramatically increasing the risk a pathogen or pest might be introduced. Therefore they also propose the Plant Passport scheme, which currently only applies to some plants associated with pests and pathogens, be strengthened and also applied to seeds as a means of ensuring traceability (showing all ports of calls within the EU and last port before entry to the EU).

Dr Jens-Georg Unger, taskforce member and Head of the Institute for National and International Plant Health in Germany, said: “There have been too many introductions of serious new pests in recent years into EU countries — improvements are needed urgently. Efficient protection can only be achieved by more complete and faster exchange of information between countries and more focussed and better coordinated action in all EU countries. The UK taskforce is an extremely important step for the initiation of such improvements on the national and the EU level.”

Additional recommendations include improving the use of epidemiological intelligence from EU/other regions and work to improve the EU regulations concerned with tree health and plant biosecurity, developing a modern, user-friendly, system to provide quick and intelligent access to information about tree health and plant biosecurity, and addressing key skills shortages.

For more information about this story, please contact: Genevieve Maul, Office of Communications, University of Cambridge. Email: [email protected]; Tel: 01223 765542.

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