Related Rule
Netherlands
Practice Relating to Rule 45. Causing Serious Damage to the Natural Environment
The Military Manual (1993) of the Netherlands states: “It is prohibited to employ methods or means of warfare which are intended, or may be expected, to cause widespread, long-term and severe damage to the natural environment.” 
Netherlands, Toepassing Humanitair Oorlogsrecht, Voorschift No. 27-412/1, Koninklijke Landmacht, Ministerie van Defensie, 1993, p. IV-1, § 1.
The manual explains that the part of the 1977 Additional Protocol I concerning the general protection of the civilian population against the effects of hostilities repeats this prohibition (in Article 55) with the proviso that “the damage to the natural environment has to be such that the health or the survival of the civilian population is endangered”. 
Netherlands, Toepassing Humanitair Oorlogsrecht, Voorschift No. 27-412/1, Koninklijke Landmacht, Ministerie van Defensie, 1993, p. V-9, § 7.
The Military Handbook (1995) of the Netherlands states: “Attention must be paid to the protection of the natural environment against widespread, long-term and severe damage.” 
Netherlands, Handboek Militair, Ministerie van Defensie, 1995, p. 7-44.
The Military Manual (2005) of the Netherlands states:
Section 13 - Methods or means which alter the natural environment
0464. AP I [1977 Additional Protocol I] contains a prohibition of the employment of methods or means of warfare which are intended or expected to cause widespread, long-term and severe damage to the natural environment and thus endanger the health or chances of survival of the civilian population. In other words, the concern here is for environmental damage which meets all the conditions of a prohibited act. In this case the environment is a “victim” of a given weapon or method (though only if the health or chances of survival of the population are impaired).
During the 1974–1977 Diplomatic Conference which established the Additional Protocols, attention was paid to the large-scale deforestation during the war in Viet Nam (in the 1960s and 70s). However, the prohibition is couched in vaguer terms. Thus the Conference took the adjective “long-term” to mean a few decades. The damage caused to the environment during the 1990–91 Gulf War does not appear to fall within the scope of this definition. With hindsight, the damage caused by burning and leaking oil wells turned out less than expected, although approximately 100 million tonnes of oil leaked into the sea. 
Netherlands, Humanitair Oorlogsrecht: Handleiding, Voorschift No. 27-412, Koninklijke Landmacht, Militair Juridische Dienst, 2005, § 0464.
In its chapter on peace operations, the manual states that the use of methods and means which “cause widespread, long-term and serious damage to the natural environment, or are expected to do so,” must be avoided. 
Netherlands, Humanitair Oorlogsrecht: Handleiding, Voorschift No. 27-412, Koninklijke Landmacht, Militair Juridische Dienst, 2005, § 1216.
Under the International Crimes Act (2003) of the Netherlands, “intentionally launching an attack in the knowledge that such an attack will cause … widespread, long-term and severe damage to the natural environment which would be clearly excessive in relation to the concrete and direct overall military advantage anticipated” is a crime, when committed in an international armed conflict. 
Netherlands, International Crimes Act, 2003, Article 5(5)(b).
The Military Manual (2005) of the Netherlands states:
0466. While the prohibition of AP I [1977 Additional Protocol I] addresses the consequences of a method or means used, the Convention on the Prohibition of Military or Any Other Hostile Use of Environmental Modification Techniques (also known as the ENMOD Convention) takes a different approach to the environment. This Convention prohibits modification of the living environment (environmental modification techniques) in order to use the environment as a weapon. The threshold of application of this Convention is lower: the consequences must be widespread, long-lasting or severe (ENMOD Article I).
In the negotiations leading to the ENMOD Convention, the following explanations of the terms widespread, severe and long-lasting were accepted:
Widespread: the consequences should be noticeable over a surface area of several hundred square kilometres.
Serious: consequences leading to serious or marked disruption or damage of human existence, natural or economic sources of support, or other assets.
Long-lasting: consequences which are noticeable for a period of several months or around one season.
0467. Environmental modification techniques are defined as any technique for changing – through the deliberate manipulation of natural processes – the dynamics, composition or structure of the Earth, including its flora and fauna, lithosphere (the Earth’s crust), hydrosphere (water on Earth) and atmosphere, or of outer space (ENMOD Article II).
In the negotiations concerning the ENMOD Convention, the following examples were quoted:
provoking an earthquake or tsunami, disrupting the ecological balance of a region, changing weather patterns (clouds, precipitation, cyclones or tornados), changing the climate, the courses of rivers, the ozone layer or the ionosphere.
Thus the diversion of a river or construction of a dam will affect the river basin, thus having a long-lasting impact on water levels and weather conditions. 
Netherlands, Humanitair Oorlogsrecht: Handleiding, Voorschift No. 27-412, Koninklijke Landmacht, Militair Juridische Dienst, 2005, §§ 0466–0467.