TREES & AIR QUALITY When an AQMA has been declared in an area, the District council is required to investigate options which would result in an improvement of air quality.  These can range from measures such as parking enforcement campaigns and vehicle emissions testing to engaging with the community and providing information on green travel. While investigating options it has been found that there are many benefits from planting trees.  These include improving health, providing shade, increasing biodiversity and creating a nicer community for everyone.  Some tree species are better at improving air quality than others.  The way pollutants interact in the atmosphere can be complex, and some trees species emit volatile organic compounds which can contribute to the creation of ground level ozone.