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Study says hiking, biking and other nature-loving activities are major threats to rare plants

The endangered running buffalo clover.
U.S. Fish and Wildlife Service

Outdoor activities like hiking and camping can help people appreciate nature and encourage public support for conservation, but a new study finds that such recreation can also be harmful to the environment. 

In the most comprehensive survey of threats to rare plants conducted in 20 years, researchers from the Missouri Botanical Garden and the University of Missouri-St. Louis analyzed data on threats to nearly 3,000 rare plants in the United States. As scientists report in the journal Biological Conservation, they discovered that outdoor recreation was the most common threat to plants, above residential development and agriculture.

"That's not what I expected," said Adam Smith, a Missouri Botanical Garden researcher and a co-author of the study. "To be honest, we've gotten some disbelief when I presented these results." 

However, some ecologists and others who work in wildlife management weren't surprised by the results, Smith said.

One of his students, for example, told him that there are areas in Illinois where photographers taking photos of plants will trample on other plants by accident.

The study's lead author, Haydée Hernandez, a recent UMSL graduate, also was initially surprised. But after some thought, she found it rather logical. 

A chart that ranks and shows how common each type of threat is to rare plants.
Credit Provided by the Missouri Botanical Garden
The results from the study indicate that recreation is the most common threat to plants.

"People go off of roads all the time and if you're camping with your RV or whatever, you will probably step on plants you shouldn't be trampling on," Hernandez said. "So it does make a lot of sense when you see it that way." 

Smith said many of the adverse effects on plants were caused by people driving off-road vehicles, which can create potholes and remove soil.

But the researchers could only measure how common the threats were, not how severe. Agriculture, for example, has a pretty severe impact on plant species. 

"Obviously plowing something up is far worse than hiking over it," Smith said. "'Common' just means that [the threat] affects a large number of species, but it doesn't reduce their population by a lot. A severe threat is one that reduces or eliminates much of a population of a species." 

The researchers couldn't use the available data to determine how each of the threats they analyzed could affect rare plants indirectly. For example, hikers can unintentionally pick up and spread seeds from invasive species. Smith mentioned being told that the Appalachian Trail is "one very, very long line of invasive species" that's made worse by hikers.


Smith also enjoys hiking, but said it's important to note that about one out of five plants in the world are at great risk of going extinct. 

"The very last thing we want to say is that people should stay inside to preserve rare plants," he said. "There's a lot of research saying that if people go outside, they tend to value the natural world more. But I think that more generally, what [the study] says is that if we see a trail closure, we should observe that."

Follow Eli Chen on Twitter: @StoriesByEli


Eli is the science and environment reporter at St. Louis Public Radio.