2.1. Literature Review: The Role of Trade in the Spread of Alien Species
Plant import, and more generally plant material import, is known as a possible avenue by which nonnative pests from specific territories are introduced. Several studies have examined various contributions to the problem, assessed the risk of invasion, and identified some possible tools for prevention and control of the spread. The analysis is complicated due to numerous implications of the problem, including biological, physiological, ecological, environmental, economic, and social aspects.
Among the various contributions, a set of properties has been established for identifying the invasion of a species and increasing frequency of alien invasions is expected due to changes in global biogeochemistry [
13]. An analysis of the terminology used in 1172 studies on plant invasions provided a definition of the nomenclature currently in use, distinguishing “native” as indigenous species, “alien” as exotic or introduced species, and “invasive” as naturalized species, with “in expansion” as an extension of the range [
14].
Other research has focused on experimentation and defining a model for predicting invasions, considering the ecological properties of the species and the conditions required for risk and damage, thereby threating biodiversity [
15].
From an economic point of view, biological invasions represent an unwanted consequence of human activity, with real costs for society that vary according to risk and human behavior, requiring the use of economic instruments and the development of institutions and policies for prevention, monitoring, eradication, and control. As such, the control of potentially invasive species is a “public good,” since society must be protected from the risks of invasive species by placing moral responsibility on the importers [
16].
The invasion risk analysis of alien species is increasingly linking biology and the economy, as required by international and national policies for the management of invasive species. In these cases, specific bioeconomic models have been developed for the estimation of biological invasion through the dynamics of interaction between species (introduction, establishment, diffusion, and impact), ecological and economic systems, and management problems, considering financial consequences and the identification of alternative strategies. Prevention has been shown to be capable of generating the highest long-term net benefits [
17].
Bioeconomic modeling through the use of endogenous risk theory has facilitated jointly grasping the ecological and economic aspects of production systems to improve risk assessment and the related cost–benefit value. A company can undertake various strategic options for risk management, eradication, control, and adaptation to address invasion and dissemination [
18].
An evaluation of the potential economic consequences derived from the introduction and spread of harmful organisms is known as pest risk analysis (PRA), which is based on the use of different techniques such as partial budgeting, partial equilibrium analysis, input output analysis, and computable general equilibrium analysis [
19]. These techniques differ from each other due to the market mechanisms considered (relationships between supply, demand, and prices), the links between agriculture and other sectors of the economy, and the ability to assess direct and indirect effects (for example, at the economic level) of the introduction of parasites [
20].
According to the International Plant Protection Convention (IPPC) and the World Trade Organization Agreement on Sanitary and Phytosanitary Measures (SPS Agreement), assessments of the economic impact of an invasion are generally developed using a qualitative approach, but this approach often lacks transparency and demonstrable objectivity. A quantitative approach is needed to help improve transparency, even if specific data and models are required that can better support a decision on pest quarantine status or justify management measures [
21].
Other control evaluations [
22] have focused on the following:
The role of the least developed countries, which are not always equipped with the means or technology to manage invasive species.
The role of private interest groups in the design and implementation of invasive species management policies, since, in some cases, the political contributions of these groups can lead to choosing a control level that is not optimal from a social point of view [
23].
The leadership role of some countries or areas in international cooperation and the ability to promote investments in strategies able to increase the capacity of other nations for managing invasive species problems.
The level of awareness of the causes and consequences of invasive species to increase the ability of governments to prevent, control, and reduce the costs of invasive species management.
Any possible avenue for spreading alien organisms is aggravated by the development of international trade in nonnative species, so a specific line of research has focused on the economic benefits connected to this trade and on the consequential risks of introducing harmful invasive species. At the international level, different countries have implemented liberal policies that can support a growing demand for non-indigenous species, which can be introduced until they prove to be problematic [
24]. Screening tools for nonnative species have improved, as has their use for the purpose of possible invasive forecasts; these can be combined with impact estimates to effectively manage the trade-off between the benefits and costs of this trade. Despite the precision, these tools are often imperfect and not always suitable for supporting the decision-making process and/or not always understood as useful by policy makers [
25].
The relationship between global commercial networks and large-scale distribution of non-indigenous species has been addressed with the implementation of the 10 connectivity indices, which represent the potential role of commercial networks, air transport links, geographic proximity, climatic similarity, and the wealth of the country of origin in facilitating species invasion [
26]. The theory is demonstrated according to which invasion is favored by imports of live plants and/or agricultural products from countries where the focal species is present that are climatically similar to the importing country, facilitating the development potential of a predictive framework to improve risk assessment, biosecurity, and surveillance of invasions.
Finally, with regard to protection tools, one possibility is to adopt tariff-type barriers to reduce import risks, for example, by imposing a fixed or variable import tax, also useful for the establishment of funding for research, screening of imported species, education, and eradication of past invasions [
27,
28,
29]. Taxation poses two types of problems: (1) acceptance by sector operators (subjects offering plants or parts of plants) and potential demand (consumers, in general) and (2) the level of taxation that is proportionate to the seriousness of the problem, the potential susceptibility, and the availability of reliable and official statistical data on trade flows by species to prohibit those potentially invasive species.
In the literature, mandatory or voluntary-type policy options have been suggested given the difficulty in ex ante estimating the possible damage, since it is necessary to have detailed information at the sector level about potential sales and costs for nurseries. In this context, some evidence emerged, such as in North America and Canada, demonstrating that establishing an annual fee for the control of potential risks and damages is possible using the consequences encountered in other, similar infestations. For example, Barbier et al. [
30] indicated that it is possible to establish an annual fee for controlling the potential risk and damage derived from the importation of nonnative plants by the North American nursery industry; however, these determinations are not generalizable in time and space. The design and implementation of market control tools need adequate ecological information on the parasite, pathogen, or organism (latency, assertion of the invasion, potential damage, etc.) and on the acceptability of the market intervention by the recipients with respect to alternative forms of protection with less impact on company profits and the demand for products. Modern screening methods can quickly and cheaply identify the potential invasiveness of nonnative species for nurseries [
31]; the major international competitors, before implementing market control tools, can apply a screening policy, then progress to quarantine and phytosanitary risk assessment policies, and, finally, to a selective application of annual licenses and import taxes [
32].
2.2. Plant Health Control System in EU and Related Policies
Market globalization and climate change have significantly changed the scenario of the defense of both agricultural and forestry plants. In Europe, the alarm is very high whenever there is the spread of new unknown diseases in the area, in the face of limited interceptions at official control points [
33]. In fact, the agricultural, rural, forest and landscape heritage, biodiversity, ecosystem services, and public and private green areas in the European Union, and consequently the possibility of their achieving income, employment, innovation, and food security, are at risk [
34].
The phytosanitary system is regulated by international standards that arise from general agreements on the exchange of goods and services. Among them, the EU joined the IPPC, an agreement originally signed in 1952 by 182 countries within the Food and Agricultural Organization (FAO), with the aim of protecting cultivated and spontaneous plants from introduction and the spread of harmful organisms (HOs).
In this context, the FAO published the International Standards for Phytosanitary Measures (ISPM), procedures on phytosanitary measures that were revised over time to take the SPS Agreement. The IPPC also set up scientific organizations with specific phytosanitary tasks at the regional level; among these is the EPPO. The EPPO, an intergovernmental organization responsible for cooperation in plant health within the Euro-Mediterranean region, operates under the aegis of the IPPC, with the aim of cooperation and harmonization of plant protection systems.
Within the European Union, legislative tasks are assigned to the Directorate General for Health and Food Safety (SANTE), the main body of the European Commission, which issues the mandatory phytosanitary regulations for all member states. This is accompanied by the EFSA, an EU scientific and technical consultancy organization. Most of the EFSA’s work is undertaken in response to requests for scientific advice from the European Commission, the European Parliament, and the EU member states. Within the latest updates, the National and Regional Phytosanitary Services connected online through a phytosanitary committee, with functions of surveillance, intervention in case of risk, and participation in the Permanent Phytosanitary Committee of Brussels.
Politically, the EU, in an attempt to not contrast free international trade and to respect the agreements signed in the WTO, issued directives which, despite being integrated and modified over time, have maintained three basic elements: (1) the general structure that regulates trade with third countries and circulation within the EU; (2) the delegation of control directly to the places of production of the plants; and (3) the plant passport.
After the first phytosanitary directive 77/93/EEC, Directive 2000/29/EC followed, consisting of annexes frequently updated by a special working group, which lists the nocive organisms under quarantine and the phytosanitary requirements that the plants must meet in order to be marketed. To these was added Regulation 873 of 2016, which lists the EU protected areas that must be particularly protected by the introduction of quarantined nocive organisms. To be able to circulate in these areas, the propagation material must have reinforced phytosanitary requirements, certified by the protected zone (PZ) passport.
Plant products and foodstuffs from third countries (outside the EU) are checked, from a phytosanitary point of view, at authorized entry points (ports, airports, etc.), defined as border entry points (BEPs).
The monitoring of the national territory is organized on production entities (nurseries, above all), forest areas, urban areas, and naturalistic areas with visual inspection and with the aid of monitoring systems such as attraction traps. Support of the monitoring activity has been activated by the laboratories within the phytosanitary services, which also provides an agreement with research institutions (universities and other research centers). There is also a national monitoring program (co-financed by the European Union) of the HOs, which provides for a minimum number of checks (official investigations) to define the phytosanitary status and delimit the areas of national territory.
The plant protection authorities routinely perform analyses of nurseries and other production categories (e.g., citrus and potatoes) by visual checks, and randomly with samples for laboratory analysis. Nurseries that sell to professionally engaged operators (e.g., fruit growers) must be accredited as suppliers of propagating material, which at least meets the Community Agricultural Conformity (CAC) requirement. There is also a “voluntary” certification system that ensures higher phytosanitary guarantees of the material produced. The primary purpose of these periodic checks by the phytosanitary services is to ensure that requirements are maintained to issue the plant passport.
When the presence of a quarantine HO is verified, eradication or containment measures must be applied. For this reason, the operators of the supply chain (nurserymen, fruit growers, marketing firms, etc.) and all potentially involved subjects (nonprofessional nurserymen, consumers, etc.) who are invited to avoid the exchange of propagation material (scions, grafts, buds, etc.) or the purchase of plants of dubious origin, play an extremely important role.
Despite this organizational apparatus, 20 years after the issuance of Directive 2000/29/CE, various problems were unsolved, such as [
5]:
Insufficient attention paid to prevention as a result of increased imports of high-risk goods;
The need to prioritize harmful agents at the EU level;
The need for better tools to control the presence and natural spread of harmful organisms if they reach territories of the EU;
The need to modernize and update the instruments concerning intra-EU movements (plant passports and protected areas);
The need to find adequate additional resources.
Regulation (EU) 2016/2031 was thus issued, which entered into force on 14 December 2019. It establishes the rules for determining the phytosanitary risks represented by any species, strain, or biotype of pathogen, animal, or parasitic plant harmful to plants or plant products and measures to reduce these risks to an acceptable level. It is complementary to:
Regulation (EU) 2017/625 of 15 March 2017, relating to official controls carried out by the competent authorities to verify whether professional operators are compliant with phytosanitary legislation and other official activities, which replaces Regulation (EC) 882/2004.
Regulation (EU) 2014/652 of 15 May 2014, which establishes provisions for the management of expenses relating to the food chain, animal health and welfare, plant health, and plant reproductive material.
Regulation (EU) 2014/1143 of the European Parliament and the Council of 22 October 2014, containing provisions aimed at preventing and managing the introduction and spread of invasive alien species, issued in the context of the EU’s biodiversity strategy.
Ultimately, the regulatory effectiveness is changed, since the legislation is transformed from a directive to a regulation; the emphasis is on priority and prevention, transforming the current Annexes I and II of Directive 2000/29/EC, in which the regulated harmful organisms are listed according to their technical characteristics, regardless of their priority for the Union; the procedures by which the plant passport is issued and the systems of the protected areas are updated; and greater sharing of responsibilities with professional operators is envisaged.