CSU Researchers: Colorado’s shortgrass prairies could face a new dust bowl as extreme droughts become more common

What remains of the stunning shortgrass prairie of eastern Colorado is at even more risk of die-off than previously thought, threatened by increasingly common extreme droughts.

The same fate awaits many of the world’s pastures and shrublands, but the impact could be worse in Colorado because shortgrass prairies exist in drier environments. That’s according to a newly published research paper that for the first time has modeled the impact of extreme droughts on different grass and shrublands across the globe. The paper appeared in the Journal of the Academy of Sciences on Jan. 8.

The study, involving 173 researchers, was led by Colorado State University Professor Melinda Smith, a biologist and big fan of Colorado’s high plains prairies. Her co-author is Kate Wilkins, the Denver Zoo’s regional conservation director for Colorado.

Deep droughts in the past have only occurred every 100 years or so. That rarity has made them difficult to study. So the researchers, using historic records, found old sites on six continents that had experienced an extreme one-year drought.

They then built special structures to apply water, mimicking rainfall. On roughly half of the sites extreme drought conditions were created and analyzed, while others created less extreme drought conditions.

Fresh Water News sat down with Smith to get her perspective on what this research means for Colorado and the other places included in the study, and to hear why she’s optimistic about what could be considered alarming findings.

Question: We all know the Earth is warming and drying. How does this research improve our ability to understand climate change and strategies for adapting?

Answer: On average we saw a 60% greater loss in plant growth in these extreme droughts than had previously been identified. It was surprising to us. In just a single year we can have much larger losses.

This finding is important because if we want to forecast impacts, we have to have some sense of what will happen. Across the sites we looked at there was a huge amount of variation. Some showed huge losses, some showed great resistance to drought.

Question: Which grasslands were the most vulnerable and which proved to be the toughest?

Answer: Shortgrass prairie was one of the most vulnerable sites, for a couple of reasons. The blue grama grasses that dominate the Front Range go below their wilting point when soil moisture levels drop. It can cause mortality and push them to a point of catastrophic loss.

But go out to Kansas to the tallgrass prairies and eastern Kansas, and those are quite resistant because they are wetter. You might think a grassland is a grassland but it depends on how wet a system is to begin with. The tallgrass prairie, with a wetter climate, has greater soil moisture levels that help buffer the grassland from short-term drought. The shortgrass prairie does not.

We also found that natural systems with a diverse group of plants were better able to survive than those with fewer plant species and those with rarer plants.

Question: Why are these grasses so important?

Answer: Shortgrass prairie does great with livestock because it allocates a lot of growth below ground and it keeps carbon below ground. It also spreads outward, not up, and that is great for grazing. It’s just amazing grass.

Question: What can be done to help them survive in a drier world?

One of the lessons we can learn is, how do we incorporate periodic extreme drought into the management of these grasslands. We use a lot of these grasslands for livestock grazing. How do we maintain that really important industry and help livestock growers manage them better?

It may be that we have to consider more proactive practices. A lot of livestock managers use native grasses that aren’t tilled or plowed, but after the Dust Bowl (in the 1930s) there was active restoration of grasslands. … How can we hasten recovery after these events? This research is just the beginning but it has revealed important priorities.

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