There are countless reasons to conserve soil, water and wildlife on our nation’s 900 million acres of agricultural lands. Some practices help keep nutrients—like nitrogen and phosphorus—out of our waterways and drinking water. Others help rebuild the health of our precious topsoil. Some practices can help combat climate change or improve conditions for wildlife.

The practice of planting cover crops, in particular, can serve as a utility infielder and fill multiple roles—improve water quality and soil health while fighting climate change. These benefits have been well documented.

Less investigated has been the impact of cover crops on wildlife. Dr. Adam Janke of Iowa State University is one of the experts trying to better understand this connection. Between 2019-2021, he and his colleagues monitored breeding grassland birds in Iowa and their relationship with cover cropped fields.

There are three billion fewer birds in the U.S. and Canada than in 1970. Grassland birds—such as red-winged blackbirds, lesser prairie chickens and meadowlarks—are the canaries in the coal mine. They are the best indicator we have of the health of grassland ecosystems and environmental changes. In the period since 1970, the most severe decline in bird populations has been among grassland birds, which decreased by more than half.

Conservation Director Jared Mott and I sat down with Dr. Janke to discuss his research and findings. He said the best way to reverse the decline of grassland birds is to get more of the native habitat they need onto the landscape.

Dr. Adam Janke of Iowa State University has studied the impacts of cover crops on wildlife.

Q: What questions drove you to do this research?

Janke: Oftentimes when we look at the portfolio of goods that agricultural landscapes provide, we think about water, carbon, greenhouse gas, soil health, biodiversity. That’s how the bird experts became involved, to examine that biodiversity question. We wanted to try to understand if there are secondary positive outcomes associated with cover crops that may help us address some of the challenges we have with grassland bird declines.

The other side of the coin is that some people were worried that perhaps cover crops could actually be doing harm to grassland birds. There was concern they could be “falling for ecological traps” in which they might perceive the cover crops to be an attractive nesting habitat, just before farm work begins and makes it the opposite.

So, there were three plausible outcomes of our research. We could find that cover crops provide a boon for wildlife, helping them nest and thrive. They could be a trap for wildlife, exposing them to harm, risk, or failed reproduction. Or they could be totally neutral.

Q: What did you find?

Janke: My research specifically was looking at grassland birds and cover cropped fields in Iowa, wedged between the growing seasons for corn and soybeans. The conclusion we came to was the neutral scenario. No consequence. It seemed like almost nothing was using the cover crops differently to what we would see in a field without cover crops. It wasn’t a trap, but it also wasn’t a boon for nesting birds.

Additionally, the types of avian communities you find on cropland with cover crops and cropland without cover crops are very similar. Think horned larks, vesper sparrows, upland sandpipers. Plus red-winged blackbirds, dickcissels and meadowlarks in the landscape. In contrast, if you walked into a grassland environment, you would see much broader diversity and much greater abundance.

Q: How should we interpret this neutral relationship between cover crops and grassland birds in your study?

Cover crops are not going to reverse grassland bird declines, but they're also not going to imperil the grassland birds that we're worried about.

Janke: For me personally, the result was sort of like, “cool!” Because we have this portfolio of other benefits that cover crops provide—clean water, healthy soil, reduced erosion, improved economics, and more. And it happens at no cost to wildlife. That’s a pretty positive outcome. Cover crops are not going to reverse grassland bird declines, but they’re also not going to imperil the grassland birds that we’re worried about.

With that said, it depends on the context. There’s great work out of western Kansas that shows pheasants are thriving in cover crops that functionally replace a summer fallow with a diverse mix of annuals. So, you can’t say cover crops aren’t good for wildlife across the board, because in that example they’re amazing for wildlife.

But cover crops are not going to be our solution to declines in terrestrial wildlife diversity. To address that, I’d rather talk about how to put more grass out on the landscape.

Q: Can you tell us more about the plight of grassland birds?

Janke: We know from research there has been an estimated 54 percent decline in grassland bird populations. One that is relevant to corn belt states is a 75 percent decline in eastern meadowlark populations.

That is arguably exclusively driven by the loss of grassland ecosystems. The causes have varied, but conversion to annual cropping systems is a major one. That was especially true in the biofuel mandate era when a lot of land that was in grass was converted to annual crops. Then there are also forces like degradation of grassland ecosystems, mainly through invasive species.

The solution to reversing grassland bird declines is figuring out how to get more grass out into those landscapes where the birds are looking for it.

Q: What are the steps forward?

Janke: We’ve got to find ways to work within and around those cropping systems to make sure that they improve environmental outcomes while they feed us, fuel us, fiber us and all the other good they do.

But we also need to get more grass back into our systems. I always try to challenge people to think about ways they can integrate diversity and perennial vegetation back into the landscape, specifically along margins, flood-prone areas, eroded hillsides, et cetera.

Plus, there’s such a winning proposition between grass and cattle production positively coexisting with biological diversity. That’s what prevails across the Great Plains, which is unequivocally our grassland bird stronghold. Any efforts to try to expand that would also do right by rural communities, the soil, the climate and all the good that comes with perennial ecosystems.

Top photo: The eastern meadowlark (Sturnella magna) thrives in native grasslands, but three out of four have disappeared since 1970. Credit: Sandi Smolker, iStock.