ecosystem of a watercourse, this link between the “introduction” of the species and appreciable harm wa8 included in the artfcls. As in the case of peragraph 2 of article 23, the use cf the word “may@’ indicates that precautionary action is necessary to guard against the very serious problems that alien or new species may cause. While the term“environment” was included for purposes of emphasis in paragraph 2 of article 23, it perhaps goes without saying that the “appreciable harm to other we.tercourse States” contemplated in the present article includes harm to the environment of those States. Finally, as is true of other aspects of the protection of international watercourse[s] [systems], joint, as well as individual action may be called for in preventing the introduction of alien or new species into international watercourse [s] [systems]. e 25 Watercourse States shall, individually or jointly, take all measures with respect to an international watercourse [system] that are necessary to protect and preserve the marincj environment, including e8tuaries, taking into account generally accepted international rules anc7 sten%ards. (1) Article 25 addresses the increasingly serious problem of pollution that is transported into the marine environment by international watercouree[sJ [systems]. While the impact of such pollution upon the marine environment, including estuaries, has been recognized only relatively recently, it ).s now dealt with, directly or indirectly, in a number of agreements. In particular, - 169 -the obligation not to cause pollution demaqe to the marine environment from land-baaed aourcea ie recogaiaed both in the 1982 United Nations Convention on the Law of the Sea 2JQ/ and in conventions cloncerning various regional 8888. 2121 (2) The obligation set forth in artful6 25 is not, however, to proteat the marine environment, per U, but to take the meaeurea “with resgeot to an international watercourse [system]” that are necessary to protect that
**Analysis**
The text discusses the protection of the marine environment and the measures to be taken by States to prevent harm to the environment of other States through the introduction of alien or new species into international watercourses. It also mentions the obligation to prevent pollution of the marine environment. These topics are closely related to the concept of environmental protection and the management of natural resources.

**Category**
Natural resources and environment, International trade