|Alien or new species that become invasive are considered to be a major direct driver of biodiversity loss across the globe.357 The socio-economic costs of prevention, control and mitigation, as well as the indirect impact on ecological services, can be extremely high.358 However, it should be pointed out that not all alien or new species would have a detrimental effect on ecosystems of international watercourses. As noted by Davis and others, ‘increasingly, the practical value of the native-versus-alien species dichotomy in conservation is declining’.359 The latter authors call for a more considered assessment of the environmental impact of new or alien species, and observe that, ‘the effects of non-native species may vary with time, and species that are not causing harm now might do so in the future. But the same is true of natives, particularly in rapidly changing environments’.360
The text of Article 22 is sensitive to the latter concerns in that it does not completely ban the introduction of alien or new species. Instead the Article requires states to take all measures necessary to prevent the introduction of alien or new species, ‘which may have effects detrimental to the ecosystem of the watercourses resulting in significant harm to other watercourse states’.
The obligation in Article 22 therefore firstly incorporates a precautionary approach through the use of the term ‘may’, and secondly sets the threshold at ‘detrimental effects resulting in significant harm to other watercourse states’.
Additionally, as with the obligation contained in Article 21, the obligation in Article 22 is one of due diligence, thus requiring states to take all ‘appropriate’ measures necessary to prevent the introduction of alien or new species (see Figure 4.6).
‘Species’ is defined by the ILC as including ‘both flora and fauna, such as plants, animals and other living organisms.’361 ‘Alien’ relates to ‘species that are non-native’, while ‘new’ covers ‘species that have been genetically altered or produced through biological engineering.’362 The provision is intended to cover the introduction of species into the watercourse itself, rather than fish farming or other activities conducted outside the watercourse, with no detrimental impact on the latter. 363
Guiding Principles for the Prevention, Introduction and Mitigation of Impacts of Alien Species That Threaten Ecosystems, Habitats or Species, Decision V1/23, Conference of Parties to the 1992 Convention on Biological Diversity
Guiding Principle 1 – Precautionary Approach:
Given the unpredictability of the pathways and impacts on biological diversity of invasive alien species, efforts to identify and prevent unintentional introductions as well as decisions concerning intentional introductions should be based on the precautionary approach, in particular with reference to risk analysis, in accordance with the guiding principles below. The precautionary approach is that set forth in principle 15 of the 1992 Rio Declaration on Environment and Development and in the preamble of the Convention on Biological Diversity. The precautionary approach should also be applied when considering eradication, containment and control measures in relation to alien species that have become established. Lack of scientific certainty about the various implications of an invasion should not be used as a reason for postponing or failing to take appropriate eradication, containment and control measures.
Guiding Principle 2 – Three-stage hierarchical approach:
Guiding principle 3: Ecosystem approach:
Measures to deal with invasive alien species should, as appropriate, be based on the ecosystem approach, as described in decision V/6 of the Conference of the Parties.
Guiding principle 4: The role of states:
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