Because they take vast amounts of carbon dioxide out of the atmosphere, rainforests are an important part of the planet’s carbon cycle and their conservation is playing front and center in major international efforts to combat global warming.
In a study published recently in Nature, scientists at NASA’s Jet Propulsion Laboratory used lidar data captured by satellites to map changes in forest canopy in the Amazon following a particularly severe drought in 2005.
Lidar, which stands for "Light Detection and Ranging" uses lasers to measure distances and create three-dimensional representations of surface features like canyons, craters, and, in this case, trees.
If the drought continues too long, the tree will die.
Big trees also sequester a disproportionate amount of carbon dioxide, so their loss means a forest is not able to store as much carbon as it once did.
And as the big trees decompose, their stored carbon is released back into the atmosphere, tilting a forest’s carbon budget from sink toward source.
Last year, scientists discovered that much of the rain that falls in a rainforest comes from water vapor that trees release through their leaves.
But if a drought makes trees lose their leaves, then this water doesn’t get added back to the atmosphere, making it likelier that another drought will happen.
The study only looked at the years following the 2005 drought, which was so severe that it would normally be a once-in-a-century event.
The researchers write that if this is indeed the new normal for the Amazon rainforest, then the consequences could be dire both for the Amazon and for a world that depends on it to regulate the global climate: "Our results clearly indicate that the Amazon forests may lose their role as a robust sink of atmospheric carbon in the face of repeated severe droughts."