Climate change is the greatest environmental threat humanity has ever faced. It is caused by the built-up of greenhouse gases from burning fossil fuels and destruction of areas that store massive amounts of carbon like the world’s rainforests. In recent years, global warming has been the subject of a great deal of political controversy.
Could plants help to slow the march of global warming?
Yes! It’s possible.
Biodiversity influences climate at local, regional and global levels, yet most climate models do not take biodiversity into consideration because its variables and effects are too diverse and complex to compute. Two recent studies, however, demonstrate the importance of being able to consider the response of vegetation to elevated levels of carbon dioxide in climate models as we try to predict our climate future.
Plants are incredible organisms. They tend to be very simple, only requiring a little CO2, water, and oxygen in order to live, but they’re capable of tremendous diversity and adaptability. Plants can grow big or small, fat or skinny, entirely based on some simple factors like how much light there is.
“Plant growth can have a considerable effect on the climate,” says Wolfgang Buermann, a geographer at Boston University. He explains that there are several ways in which plants can alter the temperature of the Earth’s atmosphere. Through the process of photosynthesis, plants use energy from the sun to draw down carbon dioxide from the atmosphere and then use it to create the carbohydrates they need to grow. Since carbon dioxide is one of the most abundant greenhouse gases, the removal of the gas from the atmosphere may temper the warming of our planet as a whole.
Because of these processes, many researchers believe plants may have a sizable impact on global climate in the future. As humans continue to generate carbon dioxide and other greenhouse gases, the Earth’s surface will likely warm at a faster rate than it has in a thousand years.
Plants also cool the landscape directly through the process known as transpiration. When the surrounding atmosphere heats up, plants will often release excess water into the air from their leaves. By releasing evaporated water, plants cool themselves and the surrounding environment. “It’s like sweating. When you sweat you cool the surface of your skin,” says Buermann. Over a forest canopy or a vast expanse of grassland, large amounts of transpiration can markedly increase water vapor in the atmosphere, causing more precipitation and cloud cover in an area. The additional cloud cover often reinforces the cooling by blocking sunlight.
Some aerosols–small atmospheric particles–can contribute to cooling because they help form clouds, which reflect sunlight. The albedo effect from increased cloud cover contributes to cooler temperatures. But the role of plant aerosols in this process was not well understood.
To investigate this, Finnish researchers collected data from forests in 11 locations around Earth. They measured aerosol concentrations, plant gases, average temperatures, and the height of something called the boundary layer, which is where aerosols and atmospheric gases mix together.
They found that plant emissions do impact climate warming, but only by a tiny degree. Globally, enhanced plant emissions counter about 1 percent of global warming. In forested areas where plants are concentrated, the effect is a more meaningful 30 percent, however. That could mean heavily treed areas–like the boreal forests of Canada, Siberia and Finland–could warm up more slowly than heavily populated areas in more southerly latitudes.