Scientists have always been puzzled by the fact that the rainy season in the Amazon begins two or three months before the other regions of Latin America. Now a team of researchers at the University of California believe that they have the answer: these trees make their own rain. It is done through transpiration, which is a well-known part of photosynthesis that starts when moisture is drawn up through a plant’s roots. It then gathers on the leaves and eventually evaporates into the atmosphere. These scientists believe that in the Amazon rainforest this process goes one step further. They say that the exceptional amounts of moisture that their transpiration releases into the atmosphere actually help to make it rain. The trees pump so much moisture into the air that it triggers a shift in wind patterns which brings in more moisture from the ocean.
Lead researcher Dr Rong Fu and her colleagues used NASA’s Aura satellite to observe the water vapour levels over the Amazon rainforest. She told ‘Science’ magazine that the satellite showed vapours consistent with transpiration that is strong enough to be the cause of rain clouds. Previous research had already shown that the Amazon rainforest releases aerosols that encourage the formation of rainclouds, so this new study reinforces the belief that these plants are not just passive recipients of moisture from the atmosphere. This is one more reason to support the ongoing efforts to stop deforestation. Scientists and environmental campaigners have long championed rainforests like the Amazon as the lungs of the planet – breathing in carbon dioxide and breathing out oxygen. Cutting down these rainforests to make way for agricultural land has been described as one of our greatest challenges to creating a sustainable ecology.