If you're reading this, I probably don't need to waste my time trying to convince you that trees are great. They absorb carbon dioxide, they can be used to power small remote sensors and they're pretty darn nice to look at too. Now a new study by a team of scientists from Germany and the UK has discovered another beneficial property: they can block out the sun (and not just by providing shade), as The Guardian's David Adam reports.
Terpenes make forests nature's "climate air conditioners"
Boreal trees in countries like Canada, Scandinavia and Russia release chemicals known as terpenes that help thicken the clouds above them, producing an albedo effect that causes more sunlight to be reflected back into space. Terpenes, which are the major components of the essential oils found in many types of plants, have often been used as flavor additives for food, as fragrances for perfumes and in alternative medicine for aroma therapy. Some scientists think the trees may release them to protect themselves from air pollution or even to communicate (!).
Cutting down trees could be a double whammy for the climate
Dominick Spracklen, one of the study's leaders and the author of a forthcoming article in the Royal Society journal Philosophical Transactions A, believes this function makes trees the planet's "air conditioners." As a result, he says that cutting down trees could worsen climate change to a larger degree than was previously thought, and that protecting them, and planting new ones, should be one of our primary climate mitigation measures.
Adam explains the underlying sciences:
The team found the terpenes react in the air to form tiny particles called aerosols. The particles help turn water vapour in the atmosphere into clouds.
Spracklen said the team's computer models showed that the pine particles doubled the thickness of clouds some 1,000m above the forests, and would reflect an extra 5% sunlight back into space.
Discovery means trees could act as negative feedback on the climate
This may not sound like much but, as Spracklen puts it, every little bit helps. Since trees release more terpenes under warmer conditions, Spracklen and his colleagues think forests could act as a negative feedback on climate, weakening the impact of rising temperatures. While mainly found in forests of pine and spruce trees, they said that most other trees produced the chemicals as well (though maybe not as much) so the cooling effect should also be seen elsewhere.