This section is a classical classroom exercise that does not require any outside activities. It is combined with a writing exercise and discussion on ethics that should appeal to teachers of science or equally of language.

Group discussion 1: How do we prevent rats from jumping off a ship?

This example was selected to promote a classroom discussion and later lead to a discussion on how much more difficult it is to control marine species. There are several ways for rats to jump ship. The following list illustrates the main ones:

•  Down the main gangway. This can be raised so that it doesn't touch the quayside and guard posted to check who gets on and off the ship, human or non-human!

•  Along the ropes tying the ship to the quay. These can be fitted with rat guards shaped like empty cones with the open end facing towards the ship – the rats cannot climb over.

•  On the cargo. Large items of cargo have to be inspected before being unloaded.

Of course, the students might come up with innovative solutions. Why not keep a ship's cat? This used to be a practice but a cat is no match for a ship infested with fierce rats. When a ship is seriously infested it may be quarantined (not allowed to tie up at the port) until the rats are eliminated.

Group exercise

Ship-owners are currently not legally obliged to exchange ballast waters in mid ocean. Think of some good arguments to persuade them to do this and write a letter to the owner of an oil tanker that travels between America and the Black Sea asking him to ensure that his ship follows the guidelines.

This is an exercise in creative writing that could be set as homework. In 1993, the International Maritime Organisation introduced a set of voluntary guidelines for ship-owners aimed at minimising the environmental damage of ballast water discharge. These guidelines are voluntary at present, and include recommendations that ships should discharge their ballast water in open sea and not in ports. Ensuring compliance with voluntary guidelines is not easy. The letter might contain arguments showing that invasory species have caused huge damage in the past and that the measures proposed would help to prevent the loss of species and habitats and would also protect the income of the many people that rely on the Black Sea . It could mention that the measures proposed are not expensive and should not delay the ship form operating. Students should learn that to be persuasive does not require threatening or strong language but an appeal to the better side of human nature.

The moral maze

This section has been included in order to trigger a wider debate and help students to discuss questions of ethics. Science cannot guarantee that a particular vision of ecosystem intervention will lead to the best outcome. This is because ecosystems are highly complex in nature and our understanding of their function is far from complete. All decisions are therefore accompanied by a degree of uncertainty. The issue of uncertainty however, has often been ignored or understated in science education. The scientific method itself is based on continuous questioning that sometimes results in the overturning of previous theories.

One response to uncertainty has been the Precautionary Principle that was widely recognised at the time of the Earth Summit in Rio de Janeiro in 1992. In its marine context, the Principle affirms that preventative measures are to be taken when there are reasonable grounds for concern that an activity may increase the risk of presenting hazards to human health, harm living /Resources and marine ecosystems, damage amenities or interfere with other legitimate uses of the sea, even when there is no conclusive evidence of a causal relationship between the activity and the effects . In other words, greater caution is required to protect the environment when information is uncertain, unreliable or inadequate . In terms of this principle, scientists and politicians were right to disallow the introduction of new species to the Black Sea as the uncertainty with the fish species in question was considerable.

The Precautionary Principle has not been introduced into the student text. It is felt that they themselves should probe the need for a written ethical code. The teacher can introduce the Principle as a way of helping a positive outcome to the debate.

Further reference material for teachers can be found on the IMO website at the address below, in English and Ukrainian: http://globallast.imo.org/AwarenessMaterials.htm Prof. Zaitsev's material can be found in: Zaitsev, Yu and V. Mamaev (1997). Biological Diversity in the Black Sea : A study of change and decline. Zaitsev, Yu. (1998) Vol. 6. The Most Blue in the World, (an introduction to the Black Sea ). Black Sea Environmental Series Vol. 3. (Russian), UN Publications, New York . This material is available free of charge to teachers from the Black Sea Environmental Programme office in Istanbul .