Why are short journeys performed with a cold engine especially damaging to the environment?

You have answered correctly. Short trips with a cold engine harm the environment mainly because more fuel is consumed and the engine wears out faster. When an engine is cold, it runs less efficiently and burns more fuel, which increases emissions. Also, higher material wear means engine parts degrade quicker, which can lead to more frequent repairs and part replacements, producing additional environmental impact from manufacturing new parts and disposing of old ones. The vehicle's battery does not get overcharged on short trips, so that is not a correct reason. In the future, remember: cold starts use more fuel and increase engine wear, making frequent short trips particularly harmful to the environment.