According to The Pentagon, Climate Change, and War by Neta C. Crawford and numerous other studies, the U.S. Department of Defense (DoD) is the largest institutional consumer of fossil fuels and the largest emitter of greenhouse gases in the world. National security has become inextricably linked with the protection and use of fossil fuels. Since 2001, the DoD has been responsible for 77 to 80 percent of all federal government energy consumption.

Emissions from the military tend to spike during active conflicts for obvious reasons. The transportation of heavy equipment by land, air, and sea requires vast amounts of energy, as does the maintenance of overseas military bases, logistics, and combat operations (including training and simulations). These energy demands, collectively known as “operational energy,” account for about 70% of the DoD’s total energy consumption, with jet fuel and diesel being the largest contributors. Petroleum resources themselves have even become targets of conflict, such as the destruction of oil fields in Iraq and Syria in 2015.

Beyond the direct energy consumption, the broader environmental costs of military operations are harder to quantify but significant. These include the pollution, toxins, and infrastructure damage caused during and after conflicts, as well as the loss of natural carbon sequestration. Forests and other natural ecosystems play a vital role in absorbing carbon dioxide, and their destruction in wartime exacerbates climate change. Protecting these lands can, therefore, be viewed as a national security concern in its own right, as their loss contributes to a negative feedback loop in global carbon levels.

While the U.S. military and other global armed forces have made some efforts to improve operational efficiency—such as adopting sustainable logistics practices—these measures are not yet sufficient. To significantly reduce emissions, the military could transition to renewable and alternative energy sources, eliminate dependence on foreign oil, close unnecessary bases, use LEED-certified standards for new construction, and reduce manufacturing of military goods. A more sustainable military posture would not only reduce emissions but could also have a ripple effect in encouraging similar changes globally.

As societies strive to build a resilient future in the face of the climate emergency, it’s increasingly practical to anticipate the impacts of conflict, migration, and geopolitical instability. In this context, it makes sense for the military-industrial complex to lead on sustainability, rather than exacerbating environmental crises. A more sustainable approach could enhance national and global security by addressing both climate change and the risks associated with continued reliance on fossil fuels.