The resumption of war in Yemen comes as the country’s environmental resilience is already exhausted by more than a decade of conflict. Yemen ranks among the world’s most climate-vulnerable nations, with per capita water availability among the lowest globally. The war has further weakened water systems and environmental institutions, and impacted agricultural livelihoods and communities’ capacity to absorb climatic shocks.

Recent fighting has been concentrated along the West Coast and southwestern frontlines, precisely the areas where groundwater depletion and land dispossession have been most acute. The escalation has the potential to accelerate these environmental pressures, push environmental degradation into new geographic areas, and intensify competition over diminishing resources.

Between August 1 and September 29, over 150,000 people were displaced in Yemen. More than half have been hosted in Taiz (83,000), followed by Lahj (36,000) and Aden (15,000). The concentration of displacement shifts demand for water, sanitation, land, food, energy, housing, and waste services from frontline areas to receiving districts, which already face serious resource constraints.

Water Resources and WASH

The water crisis is a significant aspect of the recent escalation, directly inherited from Yemen’s pre-existing water vulnerability. As of June, water scarcity was reported in 301 out of 333 districts across Yemen. Approximately 15.4 million lack adequate access to clean water, and 17.4 million lack adequate sanitation and hygiene. By June 2026, only 14 percent of humanitarian WASH response requirements had been funded.

The recent fighting has also worsened the WASH situation through two indirect channels: electricity disruption, which has disrupted water pumping systems, limiting access to safe water; and displacement, which strips households of the livelihoods, infrastructure, and resources they relied on and concentrates them in new sites, which lack these from the outset. In Taiz, which hosts more than half of recent IDPs, only 21 of 88 wells linked with Taiz’s public water supply network are operational, while 60–70 percent of WASH facilities had been completely or partially damaged by conflict or conflict-related neglect. Aden also faces long-running power outages that repeatedly interrupt water provision. The arrival of more than 15 thousand newly displaced people consequently exacerbated already recurrent water problems. By late September, roughly 40 percent of recently displaced IDPs were relying on unprotected wells or surface water for drinking supplies, a figure that indicates deteriorating water quality, rising contamination risk, and heightened risk of waterborne diseases.

Current water scarcity and conflict-resulted governance vacuum have driven up the cost of water, forcing IDPs and vulnerable populations to rely on water points, expensive private water trucking, or contaminated shallow wells, thereby increasing their suffering and the risk of waterborne diseases. The World Health Organization (WHO) Emergency Director for the Eastern Mediterranean, Annette Heinzelmann, told reporters in Geneva that Yemen had recorded around 8,000 suspected cholera cases and 22 deaths, alongside 9,600 dengue cases and 37 deaths, since the start of the year, and linked rising transmission risks to “unsafe water and poor sanitation at temporary shelters” created by the new wave of displacement in Taiz, Lahj, Hudaydah, and Aden.

Farms Abandoned, Disrupted Livelihoods and Hunger

In September, IDPs in Al-Kadha, Maqbanah, and Jabal Habashi in western Taiz described abandoning their farms and livestock as fighting advanced, in some cases for the second or third time. Even before the September escalation, an estimated 5.4 million people, 51 percent of the population in government-controlled areas, faced acute food insecurity.

The widespread landmines and unexploded ordnance throughout the war have contaminated vast areas of farmland, water sources, and communities. Renewed fighting has further disrupted livelihoods and supply routes, forcing farmers and rural households to move. By October 2, displaced people around Aden and Taiz were arriving without adequate food or water, while 75 percent of families in the affected areas are going hungry due to ongoing fighting.

Years of protracted conflict have also had tangible ramifications on land degradation. One satellite-based assessment found that 257,000 hectares of Yemen’s most important agricultural areas had exhibited signs of degradation, particularly in wadi systems such as Zabid and Rima in the Tihama plain, precisely the coastal agricultural belt where recent fighting has occurred.

Another satellite-based study found that national vegetation health, NDVI (Normalized Difference Vegetation Index), and the aridity index partially recovered from 2016 onward, and that agricultural land area in some regions increased despite the ongoing war, a pattern the researchers attribute to displaced populations converting previously marginal or unused land into farmland out of necessity. Conflict in Yemen thus appears to have a dual effect on agricultural production: destroying highly productive farmland in contested zones while pushing displaced households to expand low-quality, marginal cultivation elsewhere, a dynamic we are likely to see expand with the current escalation.

Deforestation and unsustainable logging are also likely to intensify, driven by growing demand for firewood and limited access to affordable energy sources. IDPs further intensify this pressure, as they often have few alternatives but to rely on firewood for cooking and heating. Yemen today loses an estimated 6.7 million trees a year, resulting in the degradation of nearly 16,900 hectares of forested land and protected areas.

Qat Cultivation and Solar-Powered Irrigation

An enduring feature of Yemen’s war has been the widespread use of qat among combatants. Qat is a long-standing civilian consumption habit that war has reinforced along the economic structures that sustain it. Qat’s supply chains have continued to operate even across active front lines where almost nothing else can. Young men join fighting, knowing that they’ll be compensated in part with qat. Since the outbreak of war, qat consumption has risen among the general population, and is increasingly being used —alongside cash and tobacco — as an incentive for the recruitment of child soldiers and as a lubricant before they enter direct hostilities.

Yemen’s protracted war has also accelerated qat cultivation, degrading fragile groundwater systems amid weakened control over war-exacerbated illegal drilling. Qat uses more water than any other crop, and its cultivated areas expand by over 40 percent in some regions. Meanwhile, the widespread adoption of solar-powered irrigation, as an adaptation to conflict-induced energy shortages, has reduced pumping costs but has simultaneously become a curse for vulnerable water basins, aggressively displacing essential food crops and drying up fragile aquifers to feed a wartime market that prioritizes instant profits over long-term survival.

The Environmental Cost of Red Sea Insecurity

Behind the headlines on the Red Sea lies an increasingly pressing environmental crisis. Fighting in the Red Sea, the Gulf of Aden, and Bab al-Mandeb poses a distinct environmental risk. The targeting of petroleum facilities and commercial vessels poses a huge threat to marine ecosystems and the livelihoods of coastal areas. Since July, there have been twelve attacks or attempted attacks on commercial vessels in the southern Red Sea. This includes attacks on the Encelia and Layla on July 22, the Tihamah in the Bab al-Mandab Strait on August 11, and an attack on Saudi oil tankers at Amzan on August 24. The scale of these and previous attacks on oil, chemical, and cargo tankers poses risks to the deteriorating ecosystems in the Red Sea.

The fighting also impacts fishing access along the coast. The recent escalation of conflict has affected more than 30,000 fishermen along the West Coast, leaving them struggling to meet their basic needs. Yemen’s fisheries have been severely affected by the conflict. Fish production has fallen to around half of pre-war levels, while exports have declined substantially. Coastal fishing communities have faced rising fuel costs, restrictions on access to fishing grounds, the loss of boats and equipment, displacement, and disruptions to fishing along parts of the Red Sea coast.

Yemen’s biodiversity faces additional threats from the recent escalation. Protected areas, wetlands, and World Heritage sites have suffered significant environmental degradation since the conflict began. The advance of fighting along Yemen’s southern Red Sea coastline, including the capture of Mayun (Perim) Island near the Bab al-Mandab, places military activity directly on or adjacent to coastal and island habitats.

Sabotaging Ecological Recovery

War is not limited to human casualties and the destruction of infrastructure. It leaves behind a trail of pollution, water resource depletion, and ecosystem and biodiversity degradation that can persist for decades after the war ends. Environmental losses are characterized by their cumulative nature, and some are irreversible or impossible to compensate. This makes the environmental costs of war among the most profound and enduring consequences, despite their frequent exclusion from assessments of war-related losses.

Yemen’s ecosystem is experiencing an irreversible hollowing out of its natural heritage, rendering full ecological recovery in the post-conflict period increasingly improbable. Today, the resurgence of open hostilities, deep political fragmentation, and Red Sea shipping disruptions continue to disrupt imports of vital food, fuel, and equipment. Yet despite directly jeopardizing the survival of millions of Yemenis, this environmental collapse remains almost entirely invisible to both local authorities and the international community. The economic costs of war are measurable, but they also entail hidden environmental costs that are far more difficult to quantify. The environmental impacts of war are slow-moving and long-lasting, which makes them far more dangerous than they initially appear.