That is what scientists at Biosphere 2 in Arizona did in 2019. In a Science paper , Werner and colleagues describe how they turned off the rain for 9.5 weeks and watched what happened to the trees, soil, and air. If you forget to water a houseplant for a week or two, it will droop quickly. Now imagine doing that to an entire rainforest on purpose. The goal was to explore how a severe drought affects a forest’s carbon and water dynamics.
It’s a rare place for scientists to control the rain and watch an entire ecosystem respond. They also followed labeled carbon dioxide and deep water through the forest to see where the carbon and water ended up. The surprising part was this: researchers had assumed the drought-sensitive trees would immediately tap into the deep soil water, but they did not.
Biosphere 2 is a University of Arizona research facility located in Oracle, Ariz. Its glass-enclosed rainforest, about the size of seven tennis courts, has 90 species of plants. 80 international scientists participated in the project co-led by Christiane Werner of Germany’s University of Freiburg, Laura Meredith, and Scott Saleska of the University of Arizona , according to University of Arizona News . They installed nearly 2 miles of Teflon tubing and more than 133 sensors throughout the forest to collect data on carbon, water, and soil processes.
Instead, Werner said, the trees drastically cut their water use and turned to deep reserves only under very extreme drought, conserving them for as long as possible.
The team found a roughly 70% drop in the carbon storage in the rainforest as the drought deepened. Because the forests absorb carbon dioxide from the air, and scientists are concerned about how well they can continue to do that as the climate changes, that’s important. The headline figure is hard to miss. Then the rain came again. As the water returned, the plants started to respond, and the forest started to recover. The findings have limits, however, since a glass rainforest is not the Amazon. But severe droughts are a threat to ecosystems around the world, and tests like this help scientists understand what might happen outside the lab. Some plants play it safe and slow down; others continue on their way and take more risks. These differing plant strategies shape how hard drought hits an ecosystem and how exposed it is to climate change. Meredith added that future studies and models should consider plant groups, soil, and the atmosphere together.
Meredith said the diversity of plant types helped the forest retain more carbon and maintain water cycling at the height of the drought, and recover quickly once moisture returned. In some ways, Meredith said, the forest was “surprisingly resilient” to drought. Even so, the 70% drop shows the damage was real: “resilient” here means the forest kept functioning and bounced back, not that it escaped harm.
