Beneath this strange shelter is a rare glimpse into our future

In the middle of a Colorado grassland about 100km north-west of Denver, stand four domed structures – metal hemispheres to which sheets of plastic have been attached.

Built on top of a tiny parcel of the region’s sweeping grasslands, these structures form part of a crucial climate experiment.

Beneath the shelters, the ground looks like a backyard that has been home to an energetic dog, or a small army of highly active children – dead grass and exposed soil.

However the structures are surrounded by seemingly unblemished grassfields.

This ground-level juxtaposition is all part of an important, 4-year-long experiment on grass and shrublands across the planet to simulate potential real-world drought conditions that might be experienced in the future.

Similar structures have been built in 99 ecosystems on every inhabited continent as part of this major investigation involving 170 researchers.

But the study was led out of Colorado State University and it’s in these fields where lead author Professor Melinda Smith has been studying the effects of drought on her experimental plots of land.

Published today in the Proceedings of the National Academy of Sciences, the findings of the International Drought Experiment are a valuable, if concerning update to global drought projections.

“We have produced a truly unprecedented quantification of the effects of a single year of extreme drought – with the largest and most extensive field-based climate change experiment ever conducted,” Smith tells Cosmos.

Her international collaboration has achieved this unprecedented quantification by standardising how ecologists in different countries perform drought assessments.

By coordinating the methodology to build a unified dataset, the study found conditions that might be described as “1-in-100-year events” cause 60% greater loss of plant growth than more common, less extreme drought events.

That roughly translates to a similar measure of ecosystem function loss. That, the group argues, is important as grass and shrublands account for about 40% of ice-free land across the world.

Rather than relying on computer simulations, the use of physical barriers to rainfall as part of the experiment enhances, Smith argues, the “robust and generalisable” data produced by the experiment.

By carefully designing the rainfall structures, researchers in each location were able to accurately mimic natural drought events.

“The rainfall structures are passive, meaning that they consist of strips of plastic that cover the shelter so that each rainfall event is reduced by whatever percentage the structure’s roof is covered,” Smith says.

“For example, if the roof is covered 60% by strips of plastic, then each rainfall event is reduced by 60%, allowing 40% to reach the vegetation below.

“We have shown in a previous analysis that this approach mimics how drought naturally occurs via changes in precipitation. That is, fewer events, longer time between events.”

Although the structures aren’t capable of fully realising all drought conditions a region might experience during droughts, Smith says the restriction of rainfall is the primary drought driver and so is “broadly adopted” by scientists around the world for experimentation.

And not all grass and shrublands were negatively impacted by these events. While drier regions were more prone to extreme single-year droughts and vegetation loss, experiments in wetter parts of the world appeared to be more durable.

Smith argues that the focus for policymakers should be on finding effective ways to mitigate and adapt to drought in these dry areas.

“Our study revealed that even short-term drought should be of concern, but that the largest impacts are expected to occur in drier regions,” Smith says.

“Mitigation/adaptation efforts should be focused on grassland/shrubland ecosystems that occur in these drier regions of the globe.”

Drought conditions are expected to be exacerbated by climate change in coming years. In 2021, the Intergovernmental Panel on Climate Change indicated more agricultural and ecological droughts were already underway, with more to come in most regions with every increment of global warming.