Biosecurity measures are aimed at preventing the introduction of non-native species. After habitat destruction, invasive non-native species (INNS) are viewed as the second biggest threat to further biodiversity loss. This is because ecosystems that have been traditionally isolated by natural barriers (such as oceans and climatic conditions), have been increasingly connected by global trade, transport, tourism and climate change.

There are approximately 65 established non-native marine species in Great Britain. Once established it is practically impossible to remove an aquatic non-native species. Non-native species become invasive where they threaten or adversely affect biodiversity by displacing native animals or plants by competing with them for space, light or food, or preying on native species. Therefore the focus of biosecurity is placed squarely on prevention; this is also viewed as the most cost-effective option.

Over half of the total number of INNS introduced to Britain are thought to have been associated with shipping, where the organisms are either transported in the ballast water or by attaching to the hull (known as 'hull fouling' or 'biofouling'). Biofouling will be considered next month in Part 2 to this article.

Global response

At the international level, the UN Convention on the Law of the Sea 1982 (UNCLOS) requires State parties to take all measures necessary to prevent, reduce and control the pollution of the marine environment resulting from intentional or accidental introduction of species, alien or new, to a particular part of the marine environment, which may cause significant and harmful changes thereto (Article 196).

However, UNCLOS is generally considered to be a framework agreement and further detailed international agreements are required to create specific operative regulations for many of its provisions. Therefore the International Convention for the Control and Management of Ships' Ballast Water and Sediments (BWM Convention) was developed by the International Maritime Organization (IMO) and was adopted on 13 February 2004.

The BWM Convention will not enter into force, and therefore be binding on signatories, until 12 months after over 30 States representing 35% of the world's merchant shipping tonnage have ratified the Convention. The most recent ratification by Peru on 10 June 2016 means that 51 States representing 34.87% tonnage have now ratified the convention, though it is hoped that Finland will quickly follow with its 0.14% tonnage (as at end-May 2016, though this is subject to change and therefore tonnage is currently being analysed by the IMO on a monthly basis).

The BWM Convention will require ballast water to be treated before being released in a new location so that any microorganisms or other non-native marine species are killed off. As the IMO explains:

"Under the Convention, all ships in international traffic are required to manage their ballast water and sediments to a certain standard, according to a ship-specific ballast water management plan. All ships will also have to carry a ballast water record book and an international ballast water management certificate. The ballast water management standards will be phased in over a period of time. As an intermediate solution, ships should exchange ballast water mid-ocean. However, eventually most ships will need to install an on-board ballast water treatment system." i

A number of Guidelines have been developed and adopted by the IMO's Marine Environment Protection Committee (MEPC) to support the uniform implementation of the BWM Convention, including Guidelines for the approval of ballast water management systems (G8).

The IMO notes that the potential impact of aquatic invasive species in ships' ballast water is a complex and multi-disciplinary problem and it is currently in the pioneering knowledge-gathering phase. The Guidelines will therefore be kept under review and updated to reflect the introduction of new technologies and improvements in the knowledge base. Whilst not yet in force, UK-registered ships are encouraged by the Maritime and Coastguard Agency to comply with the Guidelines.