Review Article |
Corresponding author: Giuseppe Brundu ( gbrundu@uniss.it ) Academic editor: Ingolf Kühn
© 2020 Giuseppe Brundu, Aníbal Pauchard, Petr Pyšek, Jan Pergl, Anja M. Bindewald, Antonio Brunori, Susan Canavan, Thomas Campagnaro, Laura Celesti-Grapow, Michele de Sá Dechoum, Jean-Marc Dufour-Dror, Franz Essl, S. Luke Flory, Piero Genovesi, Francesco Guarino, Liu Guangzhe, Philip E. Hulme, Heinke Jäger, Christopher J. Kettle, Frank Krumm, Barbara Langdon, Katharina Lapin, Vanessa Lozano, Johannes J. Le Roux, Ana Novoa, Martín A. Nuñez, Annabel J. Porté, Joaquim S. Silva, Urs Schaffner, Tommaso Sitzia, Rob Tanner, Ntakadzeni Tshidada, Michaela Vítková, Marjana Westergren, John R. U. Wilson, David M. Richardson.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Brundu G, Pauchard A, Pyšek P, Pergl J, Bindewald AM, Brunori A, Canavan S, Campagnaro T, Celesti-Grapow L, Dechoum M de S, Dufour-Dror J-M, Essl F, Flory SL, Genovesi P, Guarino F, Guangzhe L, Hulme PE, Jäger H, Kettle CJ, Krumm F, Langdon B, Lapin K, Lozano V, Le Roux JJ, Novoa A, Nuñez MA, Porté AJ, Silva JS, Schaffner U, Sitzia T, Tanner R, Tshidada N, Vítková M, Westergren M, Wilson JRU, Richardson DM (2020) Global guidelines for the sustainable use of non-native trees to prevent tree invasions and mitigate their negative impacts. NeoBiota 61: 65-116. https://doi.org/10.3897/neobiota.61.58380
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Sustainably managed non-native trees deliver economic and societal benefits with limited risk of spread to adjoining areas. However, some plantations have launched invasions that cause substantial damage to biodiversity and ecosystem services, while others pose substantial threats of causing such impacts. The challenge is to maximise the benefits of non-native trees, while minimising negative impacts and preserving future benefits and options.
A workshop was held in 2019 to develop global guidelines for the sustainable use of non-native trees, using the Council of Europe – Bern Convention Code of Conduct on Invasive Alien Trees as a starting point.
The global guidelines consist of eight recommendations: 1) Use native trees, or non-invasive non-native trees, in preference to invasive non-native trees; 2) Be aware of and comply with international, national, and regional regulations concerning non-native trees; 3) Be aware of the risk of invasion and consider global change trends; 4) Design and adopt tailored practices for plantation site selection and silvicultural management; 5) Promote and implement early detection and rapid response programmes; 6) Design and adopt tailored practices for invasive non-native tree control, habitat restoration, and for dealing with highly modified ecosystems; 7) Engage with stakeholders on the risks posed by invasive non-native trees, the impacts caused, and the options for management; and 8) Develop and support global networks, collaborative research, and information sharing on native and non-native trees.
The global guidelines are a first step towards building global consensus on the precautions that should be taken when introducing and planting non-native trees. They are voluntary and are intended to complement statutory requirements under international and national legislation. The application of the global guidelines and the achievement of their goals will help to conserve forest biodiversity, ensure sustainable forestry, and contribute to the achievement of several Sustainable Development Goals of the United Nations linked with forest biodiversity.
Biological invasions, code of conduct, environmental policy and legislation, invasion science, stakeholder engagement, stakeholder participation, sustainable forestry, tree invasions
Non-native trees (hereafter NNTs) and sustainably managed plantation forests of NNTs provide a wide range of forest goods and services and help to reduce the pressure on natural forests (
This large extent of NNTs is, in part, due to the rapid decrease in the extent of natural forests. Many on-going large-scale planting initiatives, sometimes with NNTs, aim to compensate for the loss of natural forests. Some examples of drivers of this loss are the reduction of natural forests caused by human activities in tropical regions of Brazil (
NNTs also represent a significant component of urban forests and are widely planted in urban greening projects worldwide (
Botanic gardens and arboreta, all hosting a large variety of NNTs, are increasingly recognised as key components of global plant conservation efforts through their living collections of endangered species, long-term archiving of seeds, taxonomic training, and public outreach (
A major change in the planting of trees has emerged recently, as massive tree-planting campaigns using NNTs are beginning to gain momentum globally as an assumed silver bullet to mitigate the impacts of climate change and for other purposes such as poverty alleviation (Table
Although sustainably managed NNTs can and do deliver economic and societal benefits with limited risk of escape and spread from planting sites into adjoining areas in many contexts, some widely used NNTs are invasive or have high potential to become invasive, sometimes causing substantial damage to biodiversity and related ecosystem services and functioning (
Invasive NNTs (INNTs) can be important ecosystem engineers, i.e. they “directly or indirectly modulate the availability of resources to other species by causing physical state changes by biotic or abiotic materials” (
As for many other groups of non-native species, perceptions regarding NNTs differ across interest groups, sometimes creating conflicts around their use and management (
The challenge is to maximise the socio-economic benefits and opportunities of NNTs, while minimising risks and negative impacts on the environment or compromising future benefits and land uses (
The GG-NNTs set out in this paper are addressed to all relevant stakeholders (including policy makers, the forestry and agroforestry industries, national forest authorities, certification bodies, environmental organisations, organisations and individuals involved in urban greening, landscape architecture, climate change mitigation, and all other endeavours that rely on the planting and management of trees). The GG-NNTs aim to reduce the risk of introduction of new INNTs and the negative impacts that might originate from their unregulated and/or unscrupulous use. To do so, these guidelines aim to enlist the co-operation of all relevant stakeholders to identify both robust scientific knowledge and technical knowledge and experience regarding the use and management of NNTs. Containment of NNTs to areas set aside for their cultivation or use must become an integral part of silviculture. Managers and planners need to consider the species and the environmental context and therefore should develop a stratified approach to take into account regional and habitat-specific management (
The eight recommendations (Rec.) in the GG-NNTs are clustered according to three overarching goals (Fig.
Main goals and recommendations of the Global Guidelines for the use of Non-Native Trees (GG-NNTs) in relation to the Sustainable Development Goals of the United Nations (UN SDGs).
Private forestry enterprises, local authorities, arboreta and public forest managers might wish to publicise their adherence to the GG-NNTs through adopting a symbol or logo indicating this commitment.
The GG-NNTs aim to implement and expand the geographical context of most of the principles and recommendations of the European Code of Conduct for Invasive Alien Trees as endorsed by The Standing Committee to the Convention on the Conservation of European Wildlife and Natural Habitats, acting under the terms of article 14 of the Bern Convention, on the 8th of December 2017 (Rec. No. 193/2017). The Bern Convention has endorsed two other Codes that included overlapping principles addressing NNTs used as ornamental species, i.e. the Code of Conduct on Horticulture and Invasive Alien Plants published by the Council of Europe (
In the context of the present GG-NNTs, and in accordance with the Convention on Biological Diversity (CBD) principles and definitions (Decision V/8 of the Conference of the Parties to the CBD), the term non-native trees (NNTs) has exclusively a biogeographical meaning, i.e. it refers to tree species, subspecies, lower taxa, or genotypes, introduced through human activity outside their past or present natural distributions, and includes any part, seeds or propagules of such taxa that might survive and subsequently reproduce. As such, the term NNTs carries no a priori connotation (negative or positive) relating to risks to biodiversity (or to the economy or public health). For a detailed discussion of the terms used in these GG-NNTs and how they relate to those used internationally see Annex 1, Glossary/Acronyms.
In the context of the GG-NNTs, the terms alien, allochthonous, non-native, non-indigenous, exotic, and introduced are considered synonymous. These synonyms are all used in international and national legislation and in various technical documents, although with different frequency and with sometimes subtle differences in the meaning they convey. Therefore, for consistency, we use the term NNTs in accordance with the CBD definition, and for the purposes of the GG-NNTs, the term invasive non-native trees (or INNTs) is herewith defined as a NNTs whose introduction and/or spread threatens or adversely impacts biodiversity and related ecosystem services, or causes ecosystem disservices (
Native tree species should be preferred over NNTs, and consideration should be given to the precise provenance of seeds and germplasm. If native tree species are not suitable, the consequent recommendation is to evaluate the use of NNTs with low invasion risk.
Within a country or region, native tree species rather than NNTs, should be used, in planning and establishing large-scale plantings, afforestation or reforestation projects, planted forest, and agroforestry (
Name of the initiative | Geographical scope | Aim of the initiative, tree species considered | Web site / Reference |
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The Great Green Wall initiative (African Union) | Africa (the Sahel) | Restore degraded land, sequester carbon and create green jobs by 2030 to reduce desertification; no indication for species used. | http://www.unccd.int/actions/great-green-wall-initiative |
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http://time.com/5669033/great-green-wall-africa | |||
The Trillion Trees campaign (NGO) | Global | Plant and protect one trillion trees to mitigate climate change and promote prosperity by 2050; native tree species are preferred, but planting NNTs is considered when there is a clear socio-economic, ecological, or climatic reason. | http://www.trilliontrees.org/home |
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Tree Nation (NGO) | Global | Citizens and companies can compensate CO2 emissions by supporting tree planting projects worldwide; trees are being chosen of a list of 300 species, but without further information if native trees are preferred over NNTs. | http://tree-nation.com |
Plant for the Planet (NGO) | Global | Platform enables to support tree planting projects worldwide with the goal to plant 1.000 billion trees; no indication for species used. | http://www.plant-for-the-planet.org/en/home |
http://www.unenvironment.org/news-and-stories/press-release/planting-trees-has-never-been-easier | |||
The Bonn Challenge (launched by German) Government) | Global | Restore 150 million hectares of deforested and degraded land by 2020 and 350 million hectares by 2030 worldwide; no indication for species used. | http://www.bonnchallenge.org |
The “Seed Bombing” initiative (Thai Government) | Thailand | Reforestation programme in Thailand throwing “seed bombs” from planes; only native species are considered. | http://thelondonpost.net/tree-seeds-tree-seeds-bombing-thailand |
The Billion Tree Tsunami Afforestation Project (BTTAP) (Khyber Pakhtunkhwa Government) | Pakistan | The BTTAP in Pakistan’s northern Khyber Pakhtunkhwa province was launched in 2015. It has surpassed its target by restoring and planting trees in 350,000 hectares of degraded forest landscapes; no indication for species used. | http://ejatlas.org/conflict/billion-tree-tsunami-afforestation-project |
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The Billion Trees campaign (NGO) | Global | Afforestation campaign with the goal to plant a billion trees across the planet to mitigate climate change; no indication for species used. | http://www.nature.org/en-us/get-involved/how-to-help/plant-a-billion |
http://www.unenvironment.org/resources/publication/plant-planet-billion-tree-campaign | |||
The One Billion Trees Programme (New Zealand Government) | New Zealand | Afforestation and reforestation programme with the aim to plant one billion trees to diversify existing land uses across New Zealand and to improve socio-economic performance; planting native species is encouraged to improve biodiversity. | http://www.mpi.govt.nz/funding-and-programmes/forestry/one-billion-trees-programme/about-the-one-billion-trees-programme/ |
The Three-North Shelter Forest Program (Chinese Government) | China | More than 66 billion trees were planted since 1978 to stop expansion of arid regions; NNTs and native species have been used so far, but native vegetation will be preferred in future. | http://www.nature.com/articles/d41586-019-02789-w |
http://news.bbc.co.uk/2/hi/world/monitoring/media_reports/1199218.stm | |||
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The 300,000 Trees in Nicosia initiative (Cyprus Government) | Cyprus | Afforestation programme with the aim to plant about 50,000 trees to combat climate change and protect biodiversity; planting indigenous species, such as endemic and rare varieties, is encouraged. | http://www.themayor.eu/fr/nicosia-launches-large-scale-tree-planting-campaign |
The 60 Million Trees initiative (Madagascar Government) | Madagascar | Reforestation project with the aim to plant 60 Million trees across 40,000 hectares; endemic and agroforestry species, including NNTs and INNTs, are being used to balance economic and ecological interests. | http://www.ecowatch.com/madacascar-tree-planting-2644879937.html |
The 50 Million For Our Forests campaign (NGO) | USA | Reforestation campaign with the aim to plant about 50 million trees to combat forest loss due to natural disturbances; only native trees are being used. | http://www.nationalforests.org/get-involved/tree-planting-programs |
The 73 Million Trees in the Amazon initiative (NGO) | Brazil | Reforestation programme with the aim to plant 73 million trees in the Amazon rainforest to combat forest loss; only native tree species are being used. | http://www.smithsonianmag.com/smart-news/brazil-begins-effort-plant-73-million-trees-amazon-180967086/ |
The 350 million trees in 12 hours Guinness record (Ethiopia Government) | Ethiopia | Afforestation project with the aim to plant 4 billion trees to combat deforestation and climate change effects; 350 million trees were planted in 12 hours setting a new world record; no indication for species used. | http://albertonrecord.co.za/221373/afforestation-project-ethiopia-recently-resulted-350-million-trees-planted-one-day/ |
Conversion of Cropland to Forest Program (also called Grain for Green) (Chinese government) | China | Tree-planting enterprise (since 1999) that pays farmers to plant trees on their land and provides degraded land to rural families to restore; native and NNTs are being used. | http://forestsnews.cifor.org/52964/grain-for-green-how-china-is-swapping-farmland-for-forest?fnl=en |
http://www.cifor.org/publications/pdf_files/articles/APutzel1601.pdf | |||
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Millennium show forest (Chinese government) | China (new city “Xiongang New Area”) | Massive urban afforestation project to construct a close-to-natural urban forest with the aim to minimise invasive species impacts; prioritisation of local species and seedlings. | ( |
Eden Reforestation Programme (NGO) | Global | Reforestation project with the aim to reduce poverty and restore forests by hiring local villagers to plant trees; no indication for species used. | http://edenprojects.org |
WeForest Making Earth Cooler (NGO) | Global | Forest and landscape restoration programme with the aim to mitigate climate change, conserve biodiversity, and reduce poverty of local communities; no indication for species used. | http://weforest.org |
OneTreePlanted (NGO) | Global | Reforestation programme to protect biodiversity, restore degraded soils, improve climate, and reduce poverty; no indication for species used. | http://onetreeplanted.org |
60 Million trees (60 Milioni di Alberi) | Italy | Planting one tree for each Italian citizen to fight climate change. It is recommended the use of native or non-native non-invasive trees. | http://www.alberitalia.it |
Multiple organisations have suggested, under certain conditions, the promotion of native trees over NNTs, including, for example, FAO (FAO 2006; FAO 2010 – Principle 9 – “if native trees are equal to or better than introduced species for the intended purpose”) and UNFCC (
PEFC certification system sets international Sustainable Forest Management benchmarks (see PEFC ST 1003:2018, Sustainable Forest Management – Requirements); within the framework provided by these benchmarks (11 criteria and 48 guidelines), national stakeholders develop their own national standards with the open participation of interested parties in a consensus-driven decision making process. All 54 recognised national standards require that origins of native species that are well-adapted to site conditions shall be preferred for reforestation and afforestation. Only those NNT species, provenances or varieties shall be used whose impacts on the ecosystem and on the genetic integrity of native species and local provenances have been scientifically evaluated, and if negative impacts can be avoided or minimised (
Native tree species exhibit multiple local adaptations to the climate of their habitat, guaranteeing optimal growth and survival under stable environmental conditions (
With global change, the link between climate and local adaptation may be disrupted, leading to local provenances of native tree species no longer providing the required ecosystem services (
When native tree species cannot be used, it is necessary to evaluate the use of NNTs with an expected low risk of invasiveness. Standard weed risk assessment tools can be successful at distinguishing between INNTs and non-invasive NNTs; see
Trees for urban environments are generally selected on the basis of pragmatic criteria, such as suitability for the site, pest resistance or tolerance, availability of stock, and the cultural and aesthetic preferences of local people (
At a country level, the recommendation of using native trees in preference of NNTs should be based on sound knowledge of the natural ranges and distribution of native tree species within the country and its regions, to limit translocations across biogeographical regions and safeguard biological integrity of Important Plant Areas (
Those engaged in the introduction, breeding, and use of NNTs and in the planted forest sector in general need to be aware of and comply with their obligations under regulations and legislation to prevent the introduction of INNTs and to minimise conflicts with regulatory authorities.
There is a substantial corpus of legally binding and non-binding conventions, regulations, and agreements on invasive non-native species at international, national, and regional levels. The CBD and its Parties recognised that there is an urgent need to address the impact of invasive alien species, and have adopted guidance on prevention, introduction, and mitigation of impacts of alien species that threaten ecosystems, habitats or species, and have taken a number of relevant decisions on invasive alien species, and forest biodiversity (e.g., COP 9 Decision IX/5). The CBD, the UN Climate Change, and UN Desertification Conventions may act synergistically to reduce the negative impacts of INNTs, promoting integrated, coherent, and multi-disciplinary approaches to these related issues and guiding the national forest authorities.
These international conventions have direct and indirect impacts on the everyday work in the planted forest sector and in the use of NNTs. Indeed, international conventions addressing issues of invasive alien species have been ratified by many countries (
The Regulation (EU) No. 1143/2014 has included in the “list of invasive alien species of [European] Union concern” a number of NNTs – Acacia saligna, Ailanthus altissima, Prosopis juliflora, and Triadica sebifera (syn. Sapium sebiferum) – totally banning any use of these species in the European Union. This is a very stringent ban, as invasive non-native species of concern in the European Union may not be intentionally: (a) brought into the territory of the Union, including transit under customs supervision; (b) kept, including in contained holding; (c) bred, including in contained holding; (d) transported to, from or within the European Union, except for the transportation of species to facilities in the context of eradication; (e) placed on the market; (f) used or exchanged; (g) permitted to reproduce, grown or cultivated, including in contained holding; or (h) released into the environment.
An example of national-level regulation is that of Mesquite (Prosopis juliflora) in the Sudan. This species, native to Mexico, Central America, and northern South America, was introduced to the Sudan in 1917 from South Africa and Egypt and was planted in Khartoum for research purposes. The success of this species in tolerating drought and stabilising sand dunes led to it being introduced to more drought-prone areas. In the 1990s, P. juliflora was introduced as part of dune stabilisation programmes in the spate irrigation systems of the Gash and Tokar. However, soon after its introduction P. juliflora became invasive. Tens of thousands of hectares were invaded in these areas and a 1995 presidential decree pledged to eradicate the species from Sudan (
Those engaged in the planted forest sector and otherwise in the introduction and use of NNTs need to be aware of the potential for NNTs to become invasive and/or have negative impacts, and to use such information to inform decisions about the selection of trees and the management of plantations. This awareness should be based on the best available knowledge, on experience from elsewhere, and on appropriate assessments of risk, taking into account the existence of time lags in NNTs species spread and impacts (i.e. the “invasion debt”,
The fact that some NNTs have not yet spread from the sites where they were planted should not be taken as definitive evidence that spread and negative impacts will not occur in the future. Experience with the same NNTs in planted forests or gardens in other parts of the world, including areas where the species have long residence times (
INNTs included in legally-binding prohibited species or in advisory lists (such as the IUCN list of “100 of the world’s worst invasive species”, which includes, e.g., Acacia mearnsii, Cinchona pubescens, and Leucaena leucocephala) should not be used in the countries or regions where they are listed, nor released in the environment, nor planted along transport networks, nor used for new planted forests. For example, all new plants (including trees) currently not in New Zealand are banned unless permitted (
More than 100 risk assessment and risk analysis schemes for plant species have been proposed (
It has been suggested that importers, breeders, and growers who are responsible for introducing potentially invasive non-native species should be responsible for damages to the environment (i.e. the “polluter pays” principle), rather than allowing the burden to be borne by tax payers or neighbouring private landowners (
Climate change could affect the dynamics of invasions of NNTs in many interacting ways, for example: (a) by causing modification in the ecosystems that potentially modify opportunities for establishment, naturalisation, and spread of both native trees and NNTs (e.g.,
Under climate change, outbreaks of pests on native trees might increase, giving a greater momentum to planting NNTs, but these NNTs are also susceptible if pest/pathogens are subsequently accidentally introduced. For example, there has been an alarming increase in impacts of bark beetle outbreaks in conifer forests in recent years in Austria, the Czech Republic, Germany, Slovakia, and in North America (
Managed relocation or assisted migration has been proposed as an approach to mitigate climate change impacts on biodiversity by intentionally moving species to climatically suitable locations outside their natural range (
All stakeholders involved in the many activities related to NNTs use, from the nursery industry to the design of plantation, and from silvicultural management to timber harvest, should design and adopt tailored practices to ensure the sustainable use of NNTs and minimise the risk of the escape of NNTs. The nursery industry and public nurseries are key stakeholders (Table
Stakeholder groups and their expected involvement in the implementation and use of Global Guidelines for the use of Non-Native Trees (GG-NNTs). The classification of stakeholder groups is modified from
Stakeholder Group | Description | R1 | R2 | R3 | R4 | R5 | R6 | R7 | R8 |
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Regulators/Governors/ | National, regional and local governments involved in policy, law making, law enforcement, and incentives. National and regional environmental and forest authorities, public forest agencies, public forest nurseries, protected areas. | Y | Y | Y | Y | Y | Y | Y | Y |
Public Administrators | |||||||||
Commercial agro-forestry business & industry | Private businesses involved in timber production, harvesting, processing, transport, and trade; water companies; and energy suppliers. Includes confederations of industries. | Y | Y | Y | Y | Y | |||
Commercial nursery industry | Private businesses involved in tree collection, breeding, trade, etc. Turf and substrata industry. | Y | Y | Y | Y | Y | |||
Forest certification organisations | Independent, non-profit organizations setting standards under which forests and companies are certified. | Y | Y | Y | Y | Y | |||
Professionals and their organisations or confederations | Individuals providing specialist advice and support, urban forest professionals, landscape architects. | Y | Y | Y | Y | Y | Y | ||
Academia, science and education | Broad group of individuals and organisations conducting research on biodiversity, forest ecosystems related issues, urban forestry, and providing education. National or international scientific associations such as IUFRO. | Y | Y | Y | Y | Y | Y | Y | Y |
Botanic gardens and arboreta | Public or private institutions, including historical gardens where trees are grown for scientific study and display to the public. Confederations such as BGCI. | Y | Y | Y | Y | Y | Y | ||
Private forest owners and their organisations or confederations | Broad groups of individuals and organisations responsible for plantations and woodland management. | Y | Y | Y | Y | Y | Y | ||
Local or indigenous communities | Local, tribal, and indigenous groups involved either formally or semi-formally in running or managing local woodlands. | Y | Y | Y | Y | ||||
Individuals | Individuals (local) who use (the nearby) woodland or urban forest for numerous purposes, e.g. recreational activities, collection or non-wood forest products, as bee-keepers, hunters, agriculture and grazing. | Y | |||||||
General public | Citizen and consumers and their organisations, non-directly using the plantations or the urban forests. | Y | |||||||
Media and social media | Media professionals and their organisations, private individuals and organisations, broadcasting and social media platforms. | Y | Y | Y | Y |
Standard biosecurity protocols (
Standards, guidelines, criteria, and indicators for sustainable forest management (SFM) have been developed by intergovernmental processes, international organisations, certification schemes (e.g., Forest Stewardship Council, FSC, and Programme for the Endorsement of Forest Certification schemes, PEFC) (
Best-management practices include criteria such as that biodiversity issues must be considered in the design of planted forests (Conference of the Parties COP 11 Decision XI/19, 8–19 October 2012, Hyderabad, India). For example, the shape of planted forests comprising NNTs should minimise edges at right angles to prevailing winds during the seed-release season. The establishment of representative natural forest should be encouraged within planted forests and, where possible, natural forests should be restored on appropriate sites (Secretariat of the Convention on Biological Diversity 2009). Plantings of NNTs should be avoided near protected areas or endangered habitats. Because the seeds or other propagules of many INNTs are dispersed in water, consideration must be given to the proximity of planting sites to streams and rivers. Suitable practices for planted forest and urban forestry should also include all available methods to limit the spread of pathogens and pests within planted forests and from infested sites to native forest and other ecosystems (e.g.,
Land managers and owners of planted forests should be informed of forestry activities that favour or limit the spread of NNTs outside plantations (
The New Zealand guidelines for the use of the Decision Support System (DSS) “Calculating Wilding Spread Risk from New Plantings” (Paul and SCION 2015) are intended to guide individual landowners, consultants, and planners in carrying out initial assessments of wilding spread risk for new afforestation projects. The assessment applies a DSS known as the Wilding Spread Risk Calculator to assess wilding spread risk in a transparent, consistent and repeatable manner using the step-by-step description and examples.
Tailored management practices should be followed in the case of planted forests with NNTs for bioenergy production (Short Rotation Forestry SRF, Short Rotation Coppice SRC): choosing new planting sites; mitigating negative impacts on biodiversity (
Finally, it is very important to design and adopt good practices for harvesting and transport of timber and other forest products or materials, to mitigate the unintentional spread of reproductive material of NNTs by harvest and transport of timber, to reduce the spread of seeds of other weeds, pathogens, and pests inside and outside the plantations. A key requirement of best practice in this regard is to keep forestry machinery out of water bodies and riparian margins. Machinery needs to be cleaned and checked regularly where the transfer of propagules of NNTs species is an identified risk. Although the role of such dispersal has only been studied in a few cases (e.g.,
Forest personnel and city council staff responsible for working with urban trees should be trained to recognise and report unusual pests and symptoms of diseased or infested trees, to report escape events, and to carry out practices that reduce the risk of pest, NNTs and other non-native species or propagules moving to other locations (Rec. 6). Personnel should wear outer layers of clothing and footwear that are not “seed friendly” (sensu
Forest roads (usually built with the primary aims of supporting forest management and harvesting), fire-control ditches, and road and railways networks should be periodically monitored to prevent the escape of NNTs, especially during harvesting or other silvicultural operations that can promote the accidental spread of propagules (
It is very important to regularly monitor plantings for the spread of NNTs and to act rapidly to control spread so that invasions can be managed before they become widespread and costly to control. Early detection and initiation of management to promptly remove INNTs can make the difference between being able to prevent invasions and having to either spend substantial resources controlling widespread invasions or accept or mitigate against whatever negative impacts they have (
The relatively long initial lag phase between introduction and naturalisation/invasion (
Any NNTs detected outside cultivation areas – especially NNTs recognized elsewhere as invasive and/or if occurring in areas of high conservation value – should be georeferenced, reported, and controlled or contained. All records and sightings will help to determine the extent of the INNT problem in a given area and facilitate a rapid response where necessary. They can also help to better understand species distribution, habitat suitability, and thus support better management. Such data should ideally be collected and quality-controlled by a (national / state) coordination centre, so that it can directly inform policy and management. Owing to the huge number of species observations that can be collected by non-professional scientists, citizen science has great potential to contribute to data collection, scientific knowledge on invasive non-native species, and to support early detection for NNTs outside cultivation areas. The recent adoption of information and communications technology in citizen science (e.g., web or mobile application-based interfaces for citizen training and data generation) has led to a massive surge in popularity, mainly due to reduced geographic barriers to citizen participation (
A rapid response capacity implies the availability of skilled personnel, contingency plans (where responsibilities are clearly determined), and technical guidelines for controlling invasive NNTs. Guidelines exist for many NNTs (e.g., PM-9 for Ailanthus altissima,
Establishing a new sentinel garden or joining a network of sentinel sites is an important tool for supporting early detection and early waring strategies. This approach provides the unique opportunity to monitor NNTs in sentinel site networks (
Efficient monitoring activities require carefully planning, large and permanent funding and skilled personnel, but important contributions can be done even with limited resources. For example,
If an INNT species has been introduced and started to spread beyond a planting site, early detection and rapid response is crucial to prevent its establishment. The preferred response is to eradicate the INNTs as soon as possible (UNEP/CBD/COP VI/23, principle 13). If eradication is not feasible, containment, and long-term control measures should be implemented. It is often not clear how INNTs can be successfully managed, but there are examples from Australia and South Africa where integrated management approaches are applied, including chemical, physical, biological (
It is necessary to develop and adopt species-specific and site-specific guidelines for the restoration of sites previously occupied by INNTs or by planted forests of NNTs, to minimise or reverse disturbances caused by the previous land use or INNTs. In fact, recent international commitments have paved the way for the implementation of large‐scale ecological restoration programs in the upcoming decades (https://www.decadeonrestoration.org/), such as the Initiative 20×20 in Latin America and the Caribbean (https://initiative20x20.org/) that seeks to restore 20 million hectares of degraded land by 2020, the AFR100 African Forest Landscape Restoration Initiative (afr100.org) that aims to bring 100 million hectares of degraded land under restoration by 2030 (
Restoration objectives have been broadly classified into overarching strategies, such as rehabilitation, reconstruction, reclamation, and replacement (see
The Atlantic Forest in the Brazil biodiversity hotspot is being threatened by its replacement for Eucalyptus plantations (
Active restoration of ecosystems degraded by INNTs to pre-invasion or pre-degradation conditions is impractical in some situations for logistical or financial reasons. In such cases, options for managing such ecosystems sustainably to optimise biodiversity and considerations relating to key ecosystem services should be explored, and guidelines should be formulated for integration into regional management plans (e.g.,
Stakeholder engagement and public participation are key in the management of risks posed by NNTs and INNTs. The crucial role of stakeholder engagement is increasingly recognized globally, but engagement still implemented mostly in a top-down fashion (
Forest and forestry issues have become more complex in recent decades. The many uses of forests, of NNTs, and the related types of land uses, now benefit a wider stratum of people than ever before, and is subject to a large range of social and environmental demands. An example of one possible classification of the major stakeholder groups involved in forest and forestry issue, and which are differentially affected by the GG-NNTs, is reported in Table
It is always important to consider that many NNTs, planted for production or for other purposes, have strong direct positive economic impacts on the local and national economies of many countries, including poverty alleviation, but often lead to sharp conflicts of interest when the NNT species become invasive, and have negative impacts on the ecosystem (
Besides land managers, forest owners, and local or indigenous communities, engagement with the general public is very important for issues related to NNTs, from their use in gardening and landscaping to forests and forestry. The active and informed participation of communities and stakeholders affected by planted forest management decisions is critical to the credibility and acceptance of management processes. Public awareness-raising and communication activities play critical roles in informing and educating the public (
An increasing number of tourists are interested not only in experiencing unique natural and cultural environments and landscapes but also learning more about them. Forest-based tours are an ideal opportunity to share information about different types of forest environments, native and NNT species, restoration actions, wildlife and landscapes, how they function, and how they came to be. Visitors are also likely to be interested in the lifestyles, cultures, and social and political histories of local communities living near forest areas and making use of local tree species. Citizen science projects such as online apps for collecting data on distribution and impacts of INNTs (
Since 1992, the UNCED Statement of Forest Principles (
In formulating legislation on NNTs and INNTs a further application of the participatory approach from regulators, governors, and the public administration in general is envisaged. The aim of participatory forestry is to ensure that all stakeholders are included in all aspects of forest management, decision-making and policy formulation (
Participatory forestry in the context of NNTs should include professionals from the invasion science sector, as scientific knowledge and evidence are usually conceived outside of policy systems and legislation corpus, and then brokered or disseminated into the policy process, with varying degrees of success (
Global networks, collaborative research, and information sharing are crucial for supporting the implementation of the recommendations of the GG-NNTs and for achieving their goals. Thus, this final recommendation is cross-cutting and relevant to all the other recommendations.
For example, the preferential use of native trees has to be supported by large-scale efforts for the conservation and evaluation of forest genetic resources (
Another important field, and a critical aspect of collaborative research in the management of NNTs and INNTs, is the need for defining and identifying NNT species, since species are the unit tied to regulatory policies and management (
Fast and reliable identification of NNTs and INNTs is also a prerequisite of early detection and rapid response (Rec. 5). Global networks and collaborative research can advance application of novel techniques, such as remote microscopy facilitating real‐time identification of NNTs (
Global networks (
The scientific community should support the improvement of standard and accepted methods to assess negative impacts of INNTs, establish priorities for intervention, and provide improved tools for comparing species (
Information on NNTs and INNTs and strategies for dealing with them is critical for the implementation of all the recommendations in the GG-NNTs. Science-based strategies to tackle biological invasions depend on recent, accurate, well-documented, standardised, and openly accessible information on non-native species (
However, there is the need to improve the quality and quantity of the available information, and support and use systems for information sharing. For example, the precise geographical distribution of plantations of NNTs is not available for many countries. Harmonised and quality-controlled data at the regional scale (e.g., for the European Union) are needed for robust assessments of responses of forest tree species to climate change (
Information sharing systems would greatly improve the ability of authorities to prevent the introduction and spread of INNTs (
Global networks, collaborative research, and information sharing are also crucial to adequately design and promote forest and forestry biosecurity training programmes, in building and developing capacity. In fact, the effective management of NNTs and INNTs, from prevention to early detection and rapid response, from habitat restoration to stakeholder engagement, requires a breadth of expertise from field to laboratory, and specialised knowledge and skills that can only be developed over time. The capacity and awareness of landowners, forestry officials, nursery personnel, and other stakeholders are crucial for effective implementation of the recommendations of the GG-NNTs, as is their hands-on experience to help design training programmes or adjust and improve existing guidelines.
A number of universities offer graduate and postgraduate certification and diplomas on plant biosecurity. Skill development includes, for example, knowledge of the legislative frameworks underlying the regulation of transboundary movement of potentially invasive non-native species, the identification and analysis of pathways and vectors, writing risk assessments for new species (pre-border and post-border), developing incursion response plans, biodiversity management plans, and research proposals, as well as gaining advanced science communication skills. Other important topics include training on pest and pathogen risks to forestry (
A large and growing number of NNTs are invasive in their new ranges and have diverse negative impacts on biodiversity and ecosystem functioning, as well as on Nature’s Contribution to People (
The GG-NNTs outlined in this paper are general; they need to be modified for implementation in different national, regional, and local-scale contexts, in consultation and with full engagement of all relevant stakeholders. Different groups of stakeholders have different fundamental and unreplaceable roles in formulating workable management strategies. For example, in the stakeholder group that includes regulators, governors, and public administration, key expectations are to: make pledges to mobilise resources; build and develop capacity; mainstream the GG-NNTs into national and sub-national policies, regulations, strategies and plans, to prevent NNTs invasions and ecosystem degradation; and to support collaborative scientific research and delivering of technical solutions for the sustainable management of plantations of native trees and NNTs.
The GG-NNTs offer general recommendation on NNTs and provide a basic framework and suggestions on tools for planning and implementing sustainable use of NNTs in nationally appropriate and scientifically sound practices that account for national and sub-national needs. It is important to bear in mind that national circumstances vary considerably in terms of biophysical conditions (e.g., NNT species, forest types, and forest and forestry utilization practices), institutional and legal frameworks, economic challenges and possibilities, management, and use, among other factors. Therefore, no “one-size-fits-all” approach can be applied in the implementation of the GG-NNTs. Instead, various technical and organisational options must be combined to achieve efficient implementation of the guidelines.
Global networks, collaborative research, and information sharing are crucial for supporting the implementation of the recommendations of the GG-NNTs and for achieving their goals. This is the main cross-cutting recommendation. However, other recommendations or parts of them are somewhat cross-cutting and relevant to the whole set of GG-NNTs, such as the need to consider global change trends and to engage with all relevant stakeholders. In fact, tree species, provenance, and site selection, plantation management, evaluation of risks and benefits in the use on NNTs, restoration, and conservation activities are all expected to be strongly influenced by changes in climate and land use.
Finally, in the implementation phase, intersectoral collaboration within the country or within regions should be promoted. Sectors such as agriculture, environmental protection, biodiversity conservation, ecotourism development, and other social fields will be interested in the process of local implementation and in the results of applying the GG-NNTs to the country scale. This involvement may lead not only to greater value at the national level, but also to greater understanding, acceptance of and support for the guidelines. Ideally, the goals of the GG-NNTs should be embedded in national strategies on biodiversity and invasive non-native species. Forest certification schemes are important instruments for mainstreaming the recommendations in the GG-NNTs.
We thank the Czech Academy of Sciences, Institute of Botany, Department of Invasion Ecology, Czech Republic, for hosting a workshop on GG-NNTs in September 2019 and for creating the space that facilitated the production of this paper. We also gratefully thank Rodrigo Pintos for the GG-NNTs logo, Ingolf Kühn, and Benjamin Caldwell for fruitful discussion and suggestions. AN, JP, PP and MV acknowledge funding from EXPRO grant no. 19-28807X (Czech Science Foundation) and long-term research development project RVO 67985939 (Czech Academy of Sciences). AP and BL were funded by Fondecyt 1180205, CONICYT PIA AFB170008 and NERC-CONICYT NE/S011641/1. DMR acknowledges the DSI-NRF Centre of Excellence for Invasion Biology, the National Research Foundation of South Africa, and the Oppenheimer Memorial Trust (grant 18576/03) for support. GB acknowledges the University of Sassari (UNISS) for support through the “fondo di Ateneo per la ricerca 2020”. JLR acknowledges start-up funding from Macquarie University’s Faculty of Science and Engineering and Department of Biological Sciences. JRUW thanks the South African Department of Forestry, Fisheries, and the Environment (DFFtE) for funding, noting that this publication does not necessarily represent the views or opinions of DFFtE or its employees. MW was supported by Research Programme P4-0107 financed by the Slovenian Research Agency. PEH was supported through grant C09X1611 “Winning against Wildings” from the New Zealand Ministry of Business, Innovation and Employment. US was supported by the Swiss Programme for Research on Global Issues for Development (r4d) for the project “Woody invasive alien species in East Africa: Assessing and mitigating their negative impact on ecosystem services and rural livelihood” (Grant Number: 400440_152085) and by CABI with core financial support from its member countries (see www.cabi.org/about-cabi/who-we-work-with/key-donors).
Global guidelines for the sustainable use of non-native trees to prevent tree invasions and mitigate their negative impacts (GG-NNTs) Background information (Annex to the GG-NNTs)
Data type: Additional materials
Explanation note: Terms and definitions, Acronyms, and additional Tables: Non-native tree species in planted forests and for other uses: historical and recent pathways of introduction; Main types of negative impacts of INNTs (after Richardson et al. 2000); Major international initiatives and legislation pertaining to invasive alien species and INNTs.