Recovery Takes Time

In modern science, studies have to be conducted so that results can be verified and reproduced if necessary. There is a control group and then an experimental group, so that researchers can see how their particular hypothesis acts in relation to a group that is not being acted upon by an external stimulus. However in some areas of scientific research, conclusions can be reached with computer models. In the era of Big Data, all kinds of numbers can be crunched and conclusions can be reached. The numbers don't lie, right? Not exactly.

In a recent study of the effects of drought in forests across the globe, it was found that trees take much longer to recover after a drought than the virtual models had assumed.

William R.L. Anderegg, an assistant professor of biology at the University of Utah, the lead author of the study published recently in the Journal Science said in a press release, "This really matters because in the future droughts are expected to increase in frequency and severity due to climate change. Some forests could be in a race to recover before the next drought strikes."

Having proper data on forest tree recovery is crucial because it's these trees that play a large part in mitigating the effects of climate change by getting rid of large amounts of carbon dioxide emissions. Previous computer model studies had scientists believing that the trees stored large amounts of carbon dioxide, which made drought recovery faster, but the new information shows that recovery is taking longer because the trees are not retaining as much carbon dioxide as originally thought.

So if the computer models were not presenting an accurate picture of drought recovery, how did the researchers on Anderegg's team come up with their figures? The old-fashioned way, it seems. The rings in the interior of tree trunks are a much better indicator of tree health, recovery and yes age.
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Using ring counts from the International Tree Ring Data Bank, the team, which included colleagues from universities in Arizona, New Mexico, Nevada and New York as well as officials from NOAA, was able to look at actual drought recovery rates from over 1,300 forests all over the world. With these hard facts on growth rates and carbon uptake the study found that while a few forests were doing better than the virtual model estimates, recovery was taking anywhere from two to four years after a drought.

The researchers found that a few forests showed positive effects, that is, observed growth was higher than predicted after drought, most prominently in parts of California and the Mediterranean region. But in the majority of the world's forests, trees struggled for years after experiencing drought that was about 9% slower than earlier estimates for the first year of recovery. Pine trees were especially vulnerable since those trees continue to use large amounts of water and can't adjust well to changes in the availability of water.

Rising temperatures also had a significant effect. When it's hotter, rainfall deficits make a bigger impact on forest growth and recovery.
The team stressed that more study is needed now that the computer models have been shown to be less than accurate. Professor Anderegg summed up the results by saying, "In most of our current models of ecosystems and climate, drought effects on forests switch on and off like a light. When drought conditions go away, the models assume a forest's recovery is complete and close to immediate. That's not how the real world works."

Check out the video below to see how another team, from UC Berkeley, hopes to study drought effects and recovery directly as opposed to virtual models.