Global guidelines for the sustainable use of non-native trees to prevent tree invasions and mitigate their negative impacts

Abstract

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.

Forest inventory-based assessments of the invasion risk of Pseudotsuga menziesii (Mirb.) Franco and Quercus rubra L. in Germany

“…Responsible management of Douglas fir and red oak can deliver benefits with limited risks of invasiveness, if propagule sources close to sensitive ecosystems are removed, for example by installing appropriate buffer zones, and initial establishments in sensitive ecosystems are prevented. Such changes in management might be controversial and engagement with diverse stakeholders on the invasion risks posed by NNT and on the options for their management is recommended (Brundu et al 2020). Forest inventories continue to develop and provide increasing detail with every inventory period and thus could help track NNT invasion trends at national and regional scale.…”

Four priority areas to advance invasion science in the face of rapid environmental change

“…Similarly, many large-scale tree-planting programs have not led to the replenishment of degraded forests with native tree species, but rather to afforestation of nonforest land, including biodiverse grasslands, with monocultures of non-native trees. Such efforts include massive tree-planting campaigns using nonnative trees with the aim of mitigating the impacts of climate change and for poverty alleviation (Brundu et al 2020). Such plantings might not help offset greenhouse gas emissions as much as expected, owing to unforeseen fluxes and complex system dynamics (Covey et al 2012;Luyssaert et al 2018;Popkin 2019).…”

“…Such plantings might not help offset greenhouse gas emissions as much as expected, owing to unforeseen fluxes and complex system dynamics (Covey et al 2012;Luyssaert et al 2018;Popkin 2019). Indeed, inappropriate afforestation, especially in naturally treeless areas, can have serious consequences for sustainable development, biodiversity conservation, and ecosystem functioning (reviewed in Brundu et al 2020). Furthermore, many species used in such programs are highly invasive, which means that their impacts extend beyond areas identified for afforestation (Brundu and Richardson 2016;Brundu et al 2020).…”

Arboreta reveal the invasive potential of several conifer species in the temperate forests of western Europe

“…In comparison, we did not detect any regeneration for half of the studied species. If foresters want to diversify forest plantations, they should avoid introducing species with high invasiveness and prefer native species or low-risk alien species (Brundu et al 2020).…”