Environmental benefits of trees
Trees, whether individuals or in woodland, have many environmental benefits more or less related to sustainability.
1. Trees intercept rainfall so that it percolates into the soil instead of adding to run-off, moderating flood hazard and facilitating flood-water management.
2. Trees cleanse the air by trapping pollutants in leaves and bark. They also absorb carbon dioxide and give off oxygen, and may be pleasingly fragrant.
3. Trees provide shelter which can extend up to 20 times the height of the tree on the leeward side.
4. Trees cast shade, moderating summer temperatures, particularly in the urban environment.
5. Trees bind the soil and protect it, reducing soil erosion and helping to conserve banks, ditches and other landscape features.
6. Trees help to restore the fertility of soils that have been disturbed or degraded by providing abundant organic matter and by promoting good drainage and aeration to a considerable depth.
7. Trees, particularly big and veteran trees, can be very advantageous to wildlife.
8. Trees contribute to local distinctiveness, particularly in otherwise anonymous housing developments.
9. Trees and other vegetation in the suburban context increase privacy and dampen noise.
10. Trees can be hundreds of years old, creating a sense of continuity and having diverse historical and cultural associations. As such they may represent a fitting setting for other historic features such as listed buildings.
11. Trees have visual landscape or architectural value in framing the human scale of activity, creating space and adding pleasing colour, texture and structure to any urban, suburban or rural scene.
12. Trees, especially big trees, have powerful character and 'presence', which many people feel have spiritual connotations.
12. Overall, trees tends to reduce stress in people, particularly in the urban dweller, contributing to good mental health.
13. Trees sequester carbon dioxide in their woody biomass over the lifetime of the tree. This wood is therefore a relatively benign source of energy for heating.
The heat content of different woods is very similar weight for weight when the wood is completely dry, about 20 MJ (megajoules) or 5 kWh (kilowatt hours) per kilogram. Different woods have different densities, affecting handling and stoking rates, but the biggest variable in combustion behaviour is moisture content.