Wipfel as wind factory
Forests influence the weather - scientists have known that for a long time. The water in their leaves evaporates, creating clouds and rain. A controversial theory suggests that forests also create the winds that move clouds across continents.
Every summer, Anastassia Makarieva leaves her lab in Saint Petersburg for a vacation in the vast forests of Northern Russia. The nuclear physicist camps amid spruce and pine trees on the shores of the White Sea and kayaks along the region's broad rivers, taking notes on nature and the weather. "The woods are a big part of my inner life," she says. Additionally, after 25 years of making her annual pilgrimage north, forests have increasingly become a significant part of her professional life.
For over a decade, Makarieva, along with her mentor and colleague at the Institute of Nuclear Physics in Saint Petersburg, Victor Gorshkov, have been developing a theory of how Russia's boreal forests (the world's largest tree area) regulate the climate in northern Asia. It's a relatively simple physical model that describes how the water vapor emitted by trees drives air currents: winds that cross the continent and carry humid air from Europe to Siberia to Mongolia and China; winds that bring rains that feed the vast rivers of eastern Siberia; Winds that water the North China lowlands, the breadbasket of the world's most populous nation.
Large forests absorb carbon dioxide from the air and release oxygen - which is why they are often referred to as the lungs of our planet. However, according to Makarieva and Gorshkov, they are also its beating heart. "Forests are complex, self-sustaining systems that produce rain. They also drive atmospheric circulation on Earth," says Makarieva. According to their theory, the huge clumps of trees carry enormous amounts of water into the air and also create winds that pump moisture around the world. The first part of this idea - forests as rainmakers - came from other scientists and has now been proven. The second part, however, according to which groups of trees cause winds, which Makarieva calls a "biotic pump", is far more controversial…
