South Dakota State University senior Jay Holm wants state legislators to know about an encroaching tree species that is threatening native grassland bird populations.
Holm, a Dell Rapids native studying wildlife and fisheries sciences, is among two SDSU undergraduates who will showcase their research in front of South Dakota lawmakers early next month. He and Madison Fitch will travel to Pierre on Feb. 7 for the 2023 South Dakota Student Research Poster Session.
Student researchers from Black Hills State University, University of South Dakota, Dakota State University, South Dakota Mines and Northern State University will also present their work.
Encroaching on grasslands
For the last year or so, Holm has been investigating the spread of the eastern redcedar, a woody juniper tree species, in the Northern Great Plains. Due to fire suppression, planting in windbreaks and overgrazing, the ERC has been encroaching on native grasslands in the region.
“If you drive around the countryside in South Dakota and look at the fields, you might see a bunch of scattered little pine trees,” Holm said. “Those are probably eastern redcedars.”
While the ERC isn’t necessarily an invasive species, the wildlife biology community is concerned that the spread of ERC could have a destructive impact on grassland bird populations, which include species like sedge wren, bobolink, western meadowlark, grasshopper sparrow and Savannah sparrow. Because of its widespread use among farmers in shelter belts, the ERC, often found in woodland areas, has been extending outside of its native range. ERCs are now sprouting—and growing—in grassland areas.
ERCs, along with invasive species, are contributing to the decline of native grasslands around the world. Other threats to grassland destruction include overgrazing, crop clearing and unsustainable agricultural practices. Since the ’80s, grasslands have declined by 50%, Holm said.
“The decline of many of the native grassland bird species have declined alongside the grasslands,” Holm said. “With this study, I wanted to compare grassland that has been encroached by the ERC and grassland that hasn’t and see if there’s any difference in the bird communities between the two.”
What Holm found, at first, was surprising. He was expecting to see a decline in species population’s diversity metrics, distribution and richness. What he found instead was those metrics had actually increased.
“This was confusing—did this mean the encroachment was actually a good thing for the bird populations?” Holm said. “We then looked at some literature and found that this was pretty much expected.”
What was happening in the areas that Holm studied (public land in the surrounding Brookings area) is what he calls a “temporary ecotone effect,” which is a transitional area between two distinct habitats, grasslands and woodlands. The native grassland bird species are able to persist in this transitional period when the trees are not fully grown, alongside woodland species that are moving into this new habitat.
In other areas of the country where the ERC has encroached, like Kansas, the trees are much taller and have pushed out many of the grassland birds. Previous research has suggested that with a 25% canopy cover, grassland birds are no longer able to persist in their native, encroached habitat, Holm explained.
“I did some GIS imagery to see what our canopy cover was at for my study sites,” Holm said. “We are only at about 9%, so there is a ways to go.”
Considering the 9% canopy cover, there is still time to reverse the trend, Holm said. While a singular solution has yet to be fully developed, there are a number in the works. One of the more interesting solutions is the use of goats.
“What they do is they’ll eat the bark off the ERC trees, which effectively kills them,” Holm said. “A grad student here at SDSU is investigating to see if this is a feasible control method.”
The “mechanical” method is by using a bulldozer to basically “chop them down,” Holm said.
The other, most proven method is the use of prescribed burns, which would do an adequate job of eliminating many of these trees in their early stages (and would allow for native plants to grow and flourish), but as Holm explains, private landowners have become wary of allowing agencies to carry out these types of burns.
“The prevailing thought is that they started to become afraid of (burns) because of the Smokey the Bear campaign to prevent forest fires back in the ’80s,” Holm said. “There’s a lot of extension going on right now to try and educate them about burns and how safe and beneficial they are.”
Without any interventions, grasslands will continue to decline which will then lead to the decline of native grassland species—which are essential to a healthy, balanced ecosystem, Holm said. Further, as habitats merge, species tend to evolve into more generalists, rather than specialists.
“When this happens, you basically see a drop in biodiversity,” Holm said. “Biodiversity makes an ecosystem more resilient to environmental change, essentially, because you have more species with different adaptions.”
As Holm notes, this is one of the chief reasons why biologists harp on “preserving biodiversity” and why individual ecosystems, like grasslands, must be preserved.
Holm will graduate this spring and then is hoping to move on to grad school, where he will pursue a master’s degree in environmental education. He’s also considering a more research-focused grad school option in which he will continue with similar studies.
“I’m very interested in public outreach and educating people,” Holm said.
As for his post academic career, Holm isn’t 100% sure what he wants to do, but he is interested in outreach, education and teaching.
“I wouldn’t mind being a wildlife education program coordinator, and I wouldn’t mind being a professor either,” Holm said. “K-12 education would be good to as would being a wildlife biologist for a state agency. I’m leaving my options open.”