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Transitioning Ecosystems Under Threat
Picture a stretch of forest where the arid Chaco Seco meets the lush Yungas, a mountainous jungle descending from the Andes. In this delicate interface, unique species thrive that are found nowhere else. The Argentine National Parks authority highlights trees like the quebracho colorado (Schinopsis lorentzii), whose dense and hard wood earned it the nickname “axe breaker.” For over a century, this tree has been decimated by the tanning industry, which utilises its wood for leather production.
Accompanying the quebracho is the palo santo (Bulnesia sarmientoi), known for its dark, aromatic trunk, typically found in the wetter areas of the Chaco. Closer to the mountainous jungle, the striking lapacho rosado (Handroanthus impetiginosus) can reach 30 meters tall, adorning its branches with vibrant pink flowers during the dry season, creating a stunning contrast against the rest of the leafless forest.
Now, envision an abandoned oil well at the heart of this ecological corridor, drilled in 1983 and since then, leaking greenhouse gases and hydrocarbons uncontrollably. This is the reality in Lomas de Olmedo, located in northern Salta province, Argentina, where 20 hectares of this unique transitional forest have turned barren and lifeless, coated with an oily film that gives the landscape a terracotta hue. Locals have dubbed this area “the Argentine Chernobyl.”
The Legacy of Neglect
The LO-X10 well, located within the hydrocarbon area of Puesto Guardián, falls under the jurisdiction of Pichanal, approximately 260 kilometres from the provincial capital. Drilled by the state-owned Yacimientos Petrolíferos Fiscales (YPF) in 1983, it was never commercially exploited and was left without the necessary technical sealing required for abandoned wells.
Over the years, the area’s concession changed hands multiple times before reaching President Petroleum S.A., a company with British-Algerian capital that inherited the responsibility for the well without having drilled it, and which has been declared bankrupt in Argentina since 2024.
Biologist and biodiversity specialist Matías Arrigazzi, who took part in a Greenpeace exploratory mission in November 2025, recounts the challenges of reaching Lomas de Olmedo. “We arrived through a desperate contact from one of the few residents still there, despite the dangers,” he explains.
Environmental Impacts and Evidence of Contamination
Among the materials shared with the Greenpeace team were alarming videos, one showing a cow that died from asphyxiation, allegedly due to consuming contaminated water, as indicated by the fire that erupted from its vomit when exposed to a lighter. “We first saw a distant, strange cloud. Lowering the car window, we could smell it and hear a white noise, like a television losing signal,” Arrigazzi recalls, describing their approach to the contaminated area. “Then we found dead animals along the roadside—one after another, eventually encountering piles of carcasses.”
As they neared the well, the only signage was illegible and ineffective: “There’s a sign that says ‘no entry,’ but it’s obscured by the very gases that fall as oily rain when they escape the well. There’s nothing to prevent entry or warn of the real danger. It’s a place where stepping on the ground releases hydrocarbons,” Arrigazzi summarises.
This region, designated as a Priority Ecosystem for Conservation at the provincial level, is also recognised internationally as an Important Bird Area. Arrigazzi explains that this classification should indicate the presence of highly threatened species, making it crucial for conservation efforts.
A History of Regulatory Failures
Initially drilled by YPF in 1983, the LO-X10 well was allocated in 1991 to a consortium of three private companies through a national decree. Over the subsequent 24 years, the concession changed hands six times, until President Petroleum S.A. became the sole owner in 2015.
On August 22, 2023, following a report by President Petroleum S.A., Salta’s Mining and Energy Secretariat opened an administrative investigation to monitor potential hydrocarbon leaks from the LO-X10 well. A document from August 2026 released by the State Prosecutor’s Office confirmed active gas leaks at the wellhead and the presence of hydrocarbons in the surrounding area. However, the company delayed the definitive abandonment of the well, claiming its contractor was occupied elsewhere.
Before August 2023, the prosecutor’s office noted there had already been “multiple controls, technical interventions, and complaints about environmental liabilities concerning the LO-X10 well.” Aureliano Reyes, a livestock producer from “El Estanque,” adjacent to the well area, filed a complaint in 2023, reporting the death of 350 cattle and horses due to soil and groundwater contamination on his property.
Legal Proceedings and Environmental Accountability
Following President Petroleum’s bankruptcy, Salta province declared the concession’s cancellation through a decree, returning the area to state control. By December 2025, it was temporarily managed by REMSa, Salta’s state energy and mining company. However, an agreement signed at the end of 2025 limited their actions to “emergency safeguarding,” preserving installations and preventing further damage while conducting an initial environmental study.
In response to the lack of action regarding his complaint, Aureliano Reyes contacted Greenpeace, which launched the “Chernobyl of Salta” campaign following its initial visit in November 2025. Currently, no remediation efforts are ongoing in Lomas de Olmedo.
Technical Challenges in Sealing Abandoned Wells
Properly sealing an oil well eliminates any risk of leakage, according to Jorge Martín Camargo, a petroleum engineer with over thirty years of industry experience. “When you seal something, like closing a soda bottle, nothing should escape,” he explains. The simultaneous release of methane and liquid hydrocarbons from LO-X10 indicates that “it was left open,” he asserts.
Camargo elaborates that if the well had been correctly sealed, there would be no methane emissions. “Companies often neglect this process because it incurs costs, and while they attempt to comply with regulations, they don’t always ensure wells are adequately sealed,” he adds.
In Argentina, the abandonment of hydrocarbon wells is governed by Resolution 5/96, enacted in 1996, which mandates companies to seal inactive wells, including those that were merely drilled, like LO-X10. Wells located in forested areas, or within 200 metres of water bodies, were required to be sealed within ten years, with a possible one-year extension. Based on this timeline, LO-X10 should have been sealed by around 2006.
Health Risks Associated with Contamination
To approach the LO-X10 well, masks are necessary. In footage shared by Greenpeace, Arrigazzi describes the odour resembling that of an open petrol station. During their visit, they discovered ponds containing hydrocarbons approximately 500 metres from the well, a phenomenon not observed in 2024. This is the same air that the few families remaining in Lomas de Olmedo must breathe.
The gas detector they carried recorded high concentrations of methane, propane, and butane. “I’m not a doctor,” Arrigazzi states, “but it’s clear that being there isn’t good for your health.” Residents reported feeling unwell in the area, and during a visit from provincial authorities, they were advised not to sleep in their homes.
They expressed that evenings and nights are particularly hazardous when pressure in the well rises, making it impossible to approach. They are increasingly worried about hydrocarbon-laden water flowing from the well, which is spreading further each day.
Implications for Biodiversity and Future Conservation
The provincial government is aware of the hazardous air quality surrounding the well. Following an inspection on June 4, 2025, the Crisis Committee reported that the situation had worsened and preliminarily established a safety radius of 200 to 300 metres from the wellhead. Among the agreed measures was the opening of an alternative route for local herders to avoid the areas with the highest gas concentrations.
Weeks later, local media reported that the fluids spewing from the well contained high levels of hydrogen sulfide, a substance highly detrimental to health. Residents have been compelled to live with masks due to air toxicity.
What does it mean for human health to live in proximity to such a leak for three years? A report published in September 2026 by the Foundation for Environment and Natural Resources (FARN), authored by toxicologist Francisco Tomás Dadic, cautioned that abandoned wells can release pollutants for decades. According to the report, hydrocarbons primarily enter the body through respiration, but can also be ingested or absorbed through the skin. Hydrogen sulfide, reported in Olmedo, is classified as a “histotoxic” gas because it directly impacts cellular respiration: it irritates at low concentrations and can cause respiratory failure at higher doses.
The Path Ahead and Long-Term Consequences
Sealing the LO-X10 well will merely be the first step. Some plant species may revive