See especially the 1972 London Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter, mww, vol. Xi (19721, p. 1294. This agreement separates harmful wastes into three categories: those whose discharge is prohibited altogether) those whose discharge is subject to a prior special permit) and those whose discharge is subject only to a prior general permit. 2421 Illustrations of such agreements are provided in the precediny footnote. au/A/CN.4/412/Add. 1, pares. 38-88. i&Q41 J. Lanuners, a:~, note 193, pp. 124 et seq. See also the survey by J. J.A. Salmon, conducted in connection with the study by the Institute of International Law of“Les obligations rel;*‘,ives a la protect!on du milieu aquatique”, in Annuaireded__Inslk&-BWdroit.mti.,.. L979, vol l 56, Part One, pp. 195-200 and 268-271. - 166 -of international non-governmental organisstions concerned with international law and groups of experts in this field has been particularly rich, &Q5/ These authorities evidence a long-standing concern of States with the problem of pollution of international watercourses. States have stepped up their efforts to deal with the problem aa water pollution has become more serious, and as they have become increasfngly aware of the close and interdependent relationship between nature and humankind. These considerations are reflected in article 23, which contains a set of general obligations that are necessary for the protection of watercourse States against pollution. 24 Watercourse States shall take all measures necessary to prevent the introduction of species, alien or new, into an international watercourse [system] which may have effects detrimental to the ecosystem of the international watercourse [system] resulting in appreciable harm to other watercourse States. (1) The introduction of alien or new species of flora or fauna into a watercourse can upset its ecological balance and result in serious problems including the clogging of inttikes and machinery, the spoiling of recreation,
**Analysis**
The text discusses international agreements and obligations related to the prevention of marine pollution, specifically the introduction of alien or new species into international watercourses. The focus is on the protection of the ecosystem and preventing harm to other watercourse States. This suggests that the topic is closely tied to environmental concerns and the management of natural resources.

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