4. The Commission shall ensure that data for monitoring programme implementation and results are collected efficiently, effectively, and in a timely manner. To that end, and in accordance with relevant methodologies, proportionate reporting requirements shall be imposed on recipients of Union funds to enable the collection of aggregable project-level output and impact indicators for all relevant specific environment and climate policy objectives, including in relation to Natura 2000 and the emissions of certain atmospheric air pollutants, including CO2.