Related Rule
South Africa
Practice Relating to Rule 45. Causing Serious Damage to the Natural Environment
South Africa’s Revised Civic Education Manual (2004) states in its section on protected places: “Protocol 1 of the Geneva Conventions takes this [protection] further by forbidding means of warfare which are intended, or may be expected, to cause long-term damage to the environment.” 
South Africa, Revised Civic Education Manual, South African National Defence Force, 2004, Chapter 4, § 51(b).
South Africa’s ICC Act (2002) reproduces the war crimes listed in the 1998 ICC Statute, including in international armed conflicts:
intentionally launching an attack in the knowledge that such 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. 
South Africa, ICC Act, 2002, Schedule 1, Part 3, § (b)(iv).
South Africa’s Revised Civic Education Manual (2004) provides that “military use of environment modification techniques” is prohibited. 
South Africa, Revised Civic Education Manual, South African National Defence Force, 2004, Chapter 4, § 56(f)(iii).