Forest Invasive Species

Primary reference(s)

FAO, 2015. Invasive species: impacts on forests and forestry. Food and Agriculture Organization of the United Nations (FAO). Accessed 24 October 2020.

Additional scientific description

Forest invasive species occur in all major taxonomic groups from micro-organisms to mammals. The invasive species include bacteria, fungi, flatworms, nematodes, insects and arachnids, molluscs, amphibians, reptiles, birds, mammals, grasses, plants, trees and shrubs (FAO, 2009a).

The Food and Agriculture Organization of the United Nations (FAO) in 2009 reported that (FAO, 2009b):

• For insect pests, the most commonly reported pest species belong to the orders Coleoptera and Lepidoptera which together made up over 70% of all insect pest species reported. Hemipteran species were the third most important insect order at 16%. In Africa and Asia and the Pacific, both Coleoptera and Lepidoptera made up the majority of pest species reported. Europe reported more lepidopterans and Latin America and the Caribbean reported more coleopterans.
• For diseases, the majority of species were members of the phylum Ascomycota which represented almost 60% of all pathogens reported. Basidiomycota species were the next major group at 33%. Four of the regions reported more Ascomycota species while the Near East reported more Basidiomycota species.
• For the category other pests, Acarina species were the most common followed by Artiodactyla species (even-toed ungulates) and Santalales (mistletoes and parasitic plants). Nematodes, rodents and primates were also classified as important pests. Africa reported more primate species, Europe more Artiodactyla, Latin America and the Caribbean more mistletoes and parasitic plants, and the Near East more Acarina species. In the Asia and Pacific region, nematodes and rodents were equally reported.

Globally, many forests are continually subject to severe outbreaks of invasive species, which can have huge environmental and sociocultural impacts. Threat of forest invasive species is rising with increasing global trade and travel and is exacerbated by impacts of climate change. Managing invasive species and avoiding new introductions of species with known potential to become invasive require coordinated efforts by many actors, nationally, regionally and globally (FAO and UNEP, 2020).

It is very important to protect the world’s forests from harm. The global forest area is just over 4 billion ha, which represents 31% of the total land area (FAO, 2010). Forests are important global resources that provide a wide range of environmental, economic and social benefits. They provide a variety of valuable products, such as timber, fuelwood, fibre and other wood and non-wood forest products, and contribute to the livelihoods of rural communities. They provide vital ecosystem services, such as combating desertification, protecting watersheds, regulating climate, and maintaining biodiversity, and play an important role in preserving social and cultural values (FAO, 2011).

Metrics and numeric limits

No globally delivered solution is available for this complex issue but work continues by several organisations.

FAO Forestry Department activities: data gathered in the global review of the status of invasiveness of forest tree species outside their native habitat is available in database format (FAO, 2009c).

The Global Invasive Species Programme (GISP) was established in 1997 to address global threats caused by invasive species and to provide support to the implementation of Article 8(h) of Convention on Biodiversity. To increase awareness and provide policy advice, the Programme has prepared the Global strategy on invasive alien species, which outlines ten strategic responses to the invasive species problem (Global Invasive Species Database, no date).

Examples of drivers, outcomes and risk management

The FAO Forestry Department is addressing the pressing global issue of invasive species in the following ways:

• A review of forest insect pests and diseases (including invasive species) in both naturally regenerating forests and planted forests was carried out in 25 countries representing Africa, Asia and the Pacific, Europe, Latin America and the Caribbean and the Near East (FAO, 2020).
• Preparing profiles on a number of important pest species impacting forests and the forest sector worldwide were prepared (FAO, 2018a).
• Publishing a report on global forest health, including insect pests, diseases and invasive species (FAO, 2009b).
• With the financial support of the FAO-Netherlands Partnership Programme, carrying out a number of fact-finding studies to assess the extent and intensity of invasiveness by forest trees (FAO, 2018b).
• Making available the data gathered in the global review of the status of invasiveness of forest tree species outside their native habitat in database format (FAO, 2009c).
• Documenting the benefits and drawbacks of Prosopis spp. which have been introduced in many countries, especially in dry and semi-arid zones, because of its capacity to survive in harsh environments and its potential in the restoration of degraded lands (FAO, 2009d).
• Offering assistance to countries not only in response to pest outbreaks and emergencies but also in establishing long-term prevention and forest protection strategies (FAO, 2021).
• Serving as a neutral forum, bringing countries together to discuss technical and policy issues related to invasive species and the forest sector.
• Helping establish regional networks dedicated to the issue of invasive species and the forest sector (FAO, 2021).
• FAO is a member of the Inter-agency Liaison Group on Invasive Alien Species (IALG-IAS) of the Convention on Biological Diversity (CBD) which facilitates cooperation among relevant organisations to support measures to prevent the introduction and mitigate the impacts of invasive alien species (FAO, 2015).

The Global Invasive Species Database (GISD) is a free, online searchable source of information about alien and invasive species that negatively impact biodiversity. The database is managed by the Invasive Species Specialist Group (ISSG) of the International Union for Conservation of Nature (IUCN) Species Survival Commission. It was developed between 1998 and 2000 as part of the global initiative on invasive species led by the Global Invasive Species Programme (GISP). The United Nations Environment Programme (UNEP) World Conservation Monitoring Centre (UNEP-WCMC) has recently developed a set of issue-based modules summarising country obligations under the Convention on Biological Diversity (CBD) and other conventions, and in 2020 published a report on Building a Multidimensional Biodiversity Index - A Scorecard for Biodiversity Health (Soto-Navarro et al., 2020).

The objectives of the Forest Invasive Species Network for Africa, for example, are to: facilitate exchange of information and provide a link for communication about forest invasive species; alert and provide policy advice on transboundary movement, phytosanitary measures and other relevant information; raise regional awareness on forest invasive species issues; encourage the publication and sharing of research results, management and monitoring strategies; facilitate taxonomic support; act as a link between and among experts, institutions, networks and other stakeholders concerned with forest invasive species; facilitate the mobilisation of resources for critical activities in management of invasive species; and provide technical guides on research and control of invasive species for sustainable forest protection and health issues in Africa (FAO, no date).

Tree Cities of the World is an international effort, promoted by the FAO and the Arbor Day Foundation in the United States of America, to recognise cities and towns that are committed to maintaining, sustainably managing and celebrating their urban forests and trees. To receive recognition, a town or city must meet five core standards: establish authority; set the rules; know what you have; allocate the resources; and celebrate achievements (FAO and UNEP, 2020).