What energy source has the least harmful environmental effects?

Renewable energy sources, particularly solar and wind power, have the least harmful environmental effects compared to fossil fuels. They produce little to no greenhouse gas emissions during operation and have a minimal impact on air and water quality. While there are some environmental concerns associated with their production and land use, these effects are generally far less detrimental than those caused by coal, oil, and natural gas. Overall, transitioning to renewables is crucial for reducing environmental harm.