ENMOD: Dodo, Dormant or Presciently Divine?

[Vanessa Murphy and Helen Obregón Gieseken are Legal Advisers at the Legal Division of the International Committee of the Red Cross (ICRC) in Geneva]

At the 34^th International Conference of the Red Cross and Red Crescent in October 2024, Nigeria and European Union Member States pledged, among other things, to consider acceding to the Convention on the Prohibition of Military Use of Environmental Modification Techniques (ENMOD). This post seeks to refresh memories as to ENMOD’s potential and outline why such accessions are worthwhile. 

For those less familiar with it, ENMOD is a 1977 convention that prohibits its contracting parties from engaging in “military or any other hostile use of environmental modification techniques having widespread, long-lasting or severe effects as the means of destruction, damage or injury to any other State Party” (Article I). It is the treaty at the source of Principle 17 of the UN International Law Commission’s Principles on the Protection of the Environment in Relation to Armed Conflict, and Rule 3.B of the ICRC Guidelines on the Protection of the Natural Environment in Armed Conflict. The International Law Commission commentary observes that ENMOD deserves particular attention “as the first and, so far, the only international treaty to specifically address means and methods of environmental warfare.”

What does ENMOD actually prohibit? As defined in Article II, the term “environmental modification techniques” refers to “any technique for changing—through the deliberate manipulation of natural processes—the dynamics, composition or structure of the earth, including its biota, lithosphere, hydrosphere and atmosphere, or of outer space”. A technique that falls under Article II must cause destruction, damage or injury that meets the widespread, long-lasting or severe threshold of Article I to be prohibited by the Convention. Unambiguous examples of phenomena that could be caused by environmental modification techniques – listed in the “Understanding” relating to Article II, produced by its drafting delegations to accompany the treaty – include “earthquakes; tsunamis; an upset in the ecological balance of a region; changes in weather patterns (clouds, precipitation, cyclones of various types and tornadic storms); changes in climate patterns; changes in ocean currents; changes in the state of the ozone layer; and changes in the state of the ionosphere”.

Dodo? ENMOD’s Reputation as the (Extinct) Bird that Never Flew

Often thought to be old-fashioned and out-moded, ENMOD has not been the subject of much multilateral attention since its Cold War inception. Already in 1977, commentators rued its restricted scope as irrelevant to real warfare. It has never given rise to a formal complaint nor litigation, and with only 78 States parties, is not as widely ratified as most other treaties pertaining to the law of armed conflict. In the last 20 years, there have been only nine new accessions or ratifications (Cameroon, China, Estonia, Honduras, Kazakhstan, Kyrgyzstan, Nicaragua, Palestine, Slovenia). In the cultural landscape of international law, many have relegated it to a “Cold War relic.”

Dormant? ENMOD as a ‘Sleeping Giant’

A closer look starts to tell a different tale: asleep not extinct. While ENMOD is not extensively ratified, its State party list does feature China, the Russian Federation, the United States and the United Kingdom – i.e. all of the permanent members of the UN Security Council bar France. It applies, for example, in the current international armed conflict between the Russian Federation and Ukraine. Reflecting on its potential in 2024, Jarose cast it as a ‘sleeping giant’. 

Notwithstanding its potential, it is certainly dormant in a procedural sense. Its mechanism for review hasn’t convened since its two Conferences of States Parties (‘Review Conferences’) held in 1984 and 1992. Unlike certain disarmament treaties whereby such conferences recur after fixed periods of time, ENMOD’s depend either on the will of a majority of States (under Article VIII (2)) or a minimum of 10 States Parties (under Article VIII (3)). The solicitation of views of States parties on the convening of a Third Review Conference, conducted by the UN Secretary General in 2013, returned fewer than 10 affirmative responses and so no Conference was convened at the time. Today, the prospect for a Third Review Conference depends on renewed will from States parties. But conference or no conference, under Article V (1), requests to the UN Secretary-General (the Depositary of the Convention) can be made by any State party to convene a Consultative Committee of Experts to make appropriate findings of fact and provide expert views relevant to any problem raised in relation to the Convention. 

Presciently Divine? ENMOD’s Future-fit Potential 

ENMOD’s restriction on the use of environmental modification techniques is newly important in modern warfare for four reasons. 

First, the concern voiced by some scholars regarding ENMOD is that the techniques it prohibits are largely hypothetical; beyond the grasp of contemporary science. This critique is fading (among other reasons) because, almost half a century since its adoption, technology and science have leapt past where they were at ENMOD’s inception. Vöneky points to speedy advances of biotechnology; Kolpack warns that potential weaponisation of geoengineering technologies cannot be dismissed; McGee, Brent, McDonald, and Heyward argue that ENMOD “offers a potentially promising forum for contributing to international solar radiation governance that has been largely overlooked”. 

Indeed, unilateral environmental modification techniques in peacetime are now more a part of our lives. Global competition in the ‘green tech’ domain is driving innovation. The suitability of climate-altering technologies and measures are increasingly debated in the scientific community (including their potential to “promote conflict”) and are controversial. Faced with the up-tick in advocacy for geoengineering as a climate solution, Mann sums up “the fundamental problem with geoengineering, in the end, is that tinkering with a complex system we don’t fully understand entails monumental risk.” A resolution aimed at improving regulation of climate-related geoengineering ultimately failed at the 2019 UN Environmental Assembly, UNESCO published a report on the ethics of climate engineering in 2023, and solar radiation modification continued to be divisive at UNEA-7 in December 2025. 

In sum, governments and their militaries now have at their disposal greater technical capabilities to cause unequivocal violations of ENMOD. In 1977, such techniques may have been considered “non-existent or imaginary”. In 2025, scientific frontiers have caught up with the seventies-era imagination.

Second, ENMOD’s protections are freshly relevant because militaries not only have access to heightened capabilities, they also arguably may be more inclined to use environmental modification due to the climate crisis. Mann warns “one could easily imagine a whole new form of global conflict wherein rogue states employ geoengineering to control the climate in a way that is optimal for themselves”. Hulme and military commentators point out that the weather has long been influential in military strategic planning; a force-multiplier or a spanner in the works. Recognizing it as a cause of an increasingly unpredictable operating environment, climate change has become a foresight issue for militaries; NATO established a Climate Change and Security Centre of Excellence in 2023, with a mandate to “support the integration of climate security into NATO’s military operations, planning, and facilities, ensuring that the Alliance is prepared to address the growing security risks posed by climate change.” 

Third, ENMOD’s protections are more important because the natural environment is increasingly fragile even before it is damaged by militaries. Climate change is leading to widespread adverse impacts and damage to nature (IPCC, 2023), and biodiversity is declining faster than at any time in human history (IPBES, 2019). Thus modified environments might take longer to recover (if they ever do): for example in places like Fao, south of Basra, Iraq, people attribute their water and farming problems – exacerbated by climate-related water stress – to the cutting of emblematic date palms for military purposes during the Iran-Iraq war (ICRC, 2020). And ENMOD is all the more relevant because of its potential to protect increasingly fragile environments from a wide range of environmental modification techniques: Jarose has explained that the definition provided in Article II does not require a certain level of technological sophistication – indeed does not require the “sci fi” level of technological sophistication that commentators too often associate with ENMOD. Low-technology methods of intentional environmental modification that cause the requisite threshold of damage are also prohibited by Article II, for instance “more prosaic methods such as burning, poisoning and physical shifting” (Jarose, 2024). One such example identified by States parties in the final document of the Second Review Conference is the use of herbicides “if such use upsets the ecological balance of a region, thus causing widespread, long-lasting or severe effects as the means of destruction, damage or injury to any other State party.” Protections from this wide array of techniques are all the more urgent as biodiversity nosedives and pollution climbs. 

The fourth and final reason for ENMOD’s newly salient potential is humankind’s greater scientific ability to monitor, document, and analyze environmental damage caused by warring parties. Civil society is leveraging emerging technologies to do this in conflict zones; a growing number of organizations – among them UNEP, CEOBs and PAX – document conflict-related environmental damage regularly; citizen science coalitions have coalesced around this purpose. In 2024, the UN Environmental Assembly adopted UNEA Resolution 6/12, mandating UNEP to identify and develop technical guidance, including new and emerging practices, on the collection of data on environmental damage associated with armed conflict. 

This means that States, international organizations and civil society have improved capacity to document and assess whether ENMOD’s threshold of damage has been met. Namely, whether damage is “long-lasting” in that it endures “a period of months, or approximately a season”; “widespread” in that it impacts “an area on the scale of several hundred square kilometres,” and “severe” in that it involves “serious or significant disruption or harm to human life, natural and economic resources or other assets” (see “Understanding” to Article I). ENMOD established limits, and there are now more tools to police them. 

Why Should More States Ratify or Accede to ENMOD?

ENMOD’s preamble states its aim is to “sav[e] mankind from the danger of using new means of warfare” (within the scope of the treaty), and recognizes “that scientific and technical advances may open new possibilities with respect to modification of the environment.” For States seeking a shield from hostile modification of their environments – modifications rendered more feasible by contemporary science and technology, and environments rendered more fragile by the global environment and climate crisis – ENMOD offers some shelter. 

States who have not already acceded would benefit from doing so. ENMOD’s prohibitions only apply between its 78 States parties, meaning that if a State seeks to protect its national environment from modification, it must join ENMOD. Perhaps heartening is that among current States parties are those who have the most developed environmental modification capabilities at their disposal. The State party list is particularly sparse among African and Middle Eastern States – yet these states are on the front lines of climate change and environmental degradation. They have good reason to protect their environment from modification. 

States already party to ENMOD should ensure it is implemented into national law, policy and/or military doctrine. This can be done in many ways, starting with military manuals. For example, Canada’s 2021 Law of Armed Conflict Manual does so in its section on lawful and unlawful tactics, Denmark’s 2020 Military Manual contains a section on ENMOD in its chapter on prohibited weapons, and Norway’s 2025 Law of Armed Conflict Manual sets out ENMOD’s prohibition in its section on the natural environment. The Australian Defence Forces’ 2024 Guide to the Legal Review of New Weapons, Means or Methods of Warfare contains an ENMOD legality check. Beyond military manuals, some States have criminalized violations of ENMOD: Uruguay’s Law on Cooperation with the ICC (2006),  Arts 26.1 and 26.3.48, establish as a war crime “[u]sing environmental modification techniques for military, combat or other hostile purposes which have widespread, long-lasting or severe effects”, and Senegal’s Penal Code (1965, amended 2007), Article 431-5, establishes as a crime acts prohibited by ENMOD. 

For those interested, instruments of ratification or accession are to be deposited with the Secretary-General of the UN. The UN Office for Disarmament Affairs (Geneva Branch) is the ENMOD Secretariat, and can advise as the treaty’s custodian. In addition, the ICRC is available to advise States considering acceding to ENMOD and/or incorporating it into their domestic frameworks. The ICRC’s IHL Advisory Service supports States to adopt IHL treaties and other relevant instruments, including ENMOD, and to put in place national legislation implementing the treaty. To this end, a short ICRC factsheet on ENMOD sets out what States need to know (in Chinese, English, French, Russian, and Spanish). As global concern for the environment mounts, the normative value of ENMOD is worth a fresh look. 

Photo attribution: Photo by Marc Schulte on Unsplash