Addressing invasive species in ships’ ballast water - treaty amendments enter into force

Amendments to an international treaty aimed at preventing the spread of potentially invasive species in ships' ballast water entered into force on 13 October 2019.

Ships regularly take on sea water, in tanks, to ensure their stability. Known as ballast water, this can contain many aquatic species, including in microscopic or larval form. These can become invasive and harmful if the ballast water is released, unmanaged, in a new location at the end of an ocean voyage.

The International Convention for the Control and Management of Ships' Ballast Water and Sediments, 2004 (the BWM Convention)  was adopted by the International Maritime Organization (IMO), a specialized agency of the United Nations, to address this problem. 

The BWM Convention entered into force in 2017. The amendments formalise an implementation schedule to ensure ships manage their ballast water to meet a specified standard ("D-2 standard" - see below) aimed at ensuring that viable organisms are not released into new sea areas, and make mandatory the Code for Approval of Ballast Water Management Systems, which sets out how ballast water management systems used to achieve the D-2 standard have to be assessed and approved.

This will help ensure that aquatic organisms and pathogens are removed or rendered harmless before the ballast water is released into a new location – and avoid the spread of invasive species as well as potentially harmful pathogens. 

The amendments to the BWM Convention were adopted in April 2018. In essence, the schedule for implementation means that compliance with the D-2 standard set out in the Convention will be phased-in over time for individual ships, up to 8 September 2024. Over time, more and more ships will be compliant with the D-2 standard. (See the infographic).

In many cases, meeting the D-2 standard will be achieved through fitting ballast water management systems. There are now many such approved systems on the market, ranging from those which use physical methods such as ultraviolet light to treat the ballast water, to those using active substances (chemicals). Those that use active substances have to go through a thorough additional approval process. (A list of approved systems can be found here.)

Other amendments to the BWM Convention entering into force on 13 October 2019 relate to survey and certification.

The BWM Convention - D-2 standard

The D-2 standard specifies that ships can only discharge ballast water that meets the following criteria:

• less than 10 viable organisms per cubic metre which are greater than or equal to 50 micrometres in minimum dimension;
• less than 10 viable organisms per millilitre which are between 10 micrometres and 50 micrometres in minimum dimension;
• less than 1 colony-forming unit (cfu) per 100 millilitres of Toxicogenic Vibrio cholerae;
• less than 250 cfu per 100 millilitres of Escherichia coli; and
• less than 100 cfu per 100 millilitres of Intestinal Enterococci.

The BWM Convention and the SDGs

Implementation of the Ballast Water Management Convention contributes to achieving a number of the United Nations Sustainable Development Goals (SDGs), in particular, SDG 14 on life below water, which calls for sustainable use of the oceans; and SDG 15, which includes targets relating to biodiversity and curtailing the spread of invasive species.  

The BWM Convention requirements 

Since the Convention entered into force in September 2017, ships have been required to manage their ballast water to avoid the transfer of potentially invasive aquatic species. All ships must have a ship-specific ballast water management plan and keep a ballast water record book. Ships are also required to manage their ballast water to meet either the D-1 ballast water exchange standard or the D-2 performance standard. The amendments in force from 13 October 2019 formalise the implementation schedule for the transition from the D-1 to the D‑2 standard.