It is a misconception to classify tidal power as a renewable energy source. In reality, large-scale extraction of tidal energy could produce environmental impacts more severe than those associated with fossil fuels. Tides arise from Earth’s rotation relative to the gravitational pull of the Moon and the Sun on ocean water. Although tidal patterns appear to move relative to observers on Earth, the tidal bulges remain essentially fixed with respect to these celestial bodies. This decoupling exerts a braking torque on Earth’s rotation, dissipating rotational energy and gradually lengthening the day. Over the past 400 million years, this natural process has slowed Earth’s rotation from roughly 420 to 365 days per year. Harvesting tidal energy would accelerate this deceleration by removing additional rotational energy from the Earth. This study provides quantitative estimates showing that even modest reliance on tidal power could produce significant environmental disruption on short geological timescales. Based on global energy consumption trends over the past 50 years, meeting only 1% of global energy demand with tidal power could cause Earth to become tidally locked to the Moon in roughly 1,000 years. In such a state, a single day would span an entire lunar month, with one hemisphere experiencing perpetual sunlight and extreme heating, while the other would remain in continuous darkness and severe cooling. These extreme thermal contrasts would render large portions of the planet uninhabitable, potentially leading to widespread ecosystem collapse and the extinction of most life on Earth.