Repeal of the SEA guide for astronomical areas: the law remains in force and early action is key

Although the Environmental Assessment Service repealed the instrument that guided the evaluation of light pollution impact on astronomical areas, legal obligations remain fully intact. This new scenario opens an opportunity that calls for early action. Fundación Cielos de Chile examines its implications.

On 20 March, the Environmental Assessment Service (SEA) published a resolution in the Official Gazette revoking the SEA guide for astronomical areas, the technical instrument that since 2024 had guided the environmental assessment of projects with artificial light emissions in zones of scientific value for astronomy.

However, the repeal of the guide does not suspend legal obligations. What is established in Article 11 of Law 19.300 remains in force: every project submitted to the Environmental Impact Assessment System must demonstrate that it is not susceptible to affecting areas of astronomical value. This obligation stems from a 2019 legal amendment that introduced three fundamental changes: artificial light was incorporated as a pollutant, projects were required to demonstrate they would not affect astronomical areas, and the Ministry of Science was tasked with defining which areas qualify. All of the above remains in effect.

Reasons behind the repeal of the SEA guide and what comes next

The repeal responded to concerns raised by the astronomical and scientific community following a Fundación Cielos de Chile publication demonstrating that no project submitted to the SEA had been found susceptible to affecting astronomical areas, revealing that the parameters in use were too lenient and therefore failed to meet their preventive purpose. In a conversation with Radio Infinita on 23 March, Daniela González, Executive Director of Fundación Cielos de Chile, explained that “the repealed guide was based on considerably outdated criteria,” and that projects had consequently been evaluated without the required level of scrutiny.

From the Foundation’s perspective, the repeal of the SEA guide represents an opportunity. Last year, the Advisory Commission of the Ministry of Science worked on reviewing the 29 astronomical communes and their protection criteria. Its conclusions were clear: the susceptibility threshold should be set at 1% alteration of the natural sky brightness, a standard supported by technical bodies and the scientific community alike.

“The work has been done,” González stated on the Mundo Infinito programme. “What is needed now is political will. We call on the Minister of Science and the Minister of the Environment to expedite this process, because the entire astronomical community invested in these issues is fully prepared to ensure that the second version of this guide genuinely fulfils its purpose of protecting astronomical sites.” She also addressed a topic that has dominated the governmental agenda: the so-called issue of “permisología”, the complexity of regulatory permitting. From the Foundation’s standpoint, having clear and updated criteria directly supports this goal: “Permitting delays are largely driven by lengthy processing and review times. When criteria are clear and evidence-based, that is reduced, because there is no room left for interpretation,” González explained.

Dark skies as a strategic asset

Beyond their scientific and cultural value, Chile’s dark skies represent a concrete economic asset. The international observatories installed in the country constitute direct foreign investment. Chile currently hosts more than 40% of the world’s astronomical observation capacity, a figure that will exceed 60% once the new mega-telescopes become operational. Protecting this natural capital is not incompatible with productive development; it means reconciling different visions of progress. “The sooner we can resolve a second edition of the SEA guide for astronomical areas, the more we will reduce the uncertainty that project holders also face,” said the Foundation’s Executive Director.

A call for early action

For companies and projects operating in areas close to astronomical zones, the temporary absence of an updated guide is not a signal to pause, it is a “yellow light” that calls for early design review. Incorporating the light dimension from the outset, assessing how much light is truly needed and how to ensure operational safety without over-illuminating, is a strategic decision. Good lighting design not only ensures regulatory compliance: it can also generate long-term savings.

Fundación Cielos de Chile is actively working to contribute to the development of the new SEA guide for astronomical areas and to support project holders in responsibly incorporating the light dimension into their operations.