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Wildlife and Continuous Living Cover: What Does the Research Say?

By Meghan Filbert, Alisha Bower and Nick Ohde

Numerous studies show that continuous living cover – whether it’s perennial pasture, diversified crop rotation with small grains and hay, or cover crops in a corn and soybean system – benefit many species of wildlife, from birds – whether they are hunted or non-hunted species – to insects to fish. Here are a few that we’ve come across as we seek to use peer-reviewed research to inform our thinking about keeping roots in the ground year round.

Wilcoxen et al. Use of cover crop fields by migratory and resident birds. Agriculture, Ecosystems and Environment 252 (2018) 42-50.

This study conducted bird surveys in four counties in central Illinois on corn and soybean fields with and without cover crops. They found significantly more birds in cover cropped fields than non-cover cropped fields. The most common bird species observed in the fields were Red-winged Blackbird (agelaius phoeniceus, 27.5%), Common Grackle (Quiscalus quiscula, 10.4%) and American Robin (Turdus migratorius, 10%). Corn stubble fields with no cover crop were host to 2.2 birds per 100 m while cover cropped fields saw double that at 4.4 birds per 100 m. For soybeans, there were fewer birds observed likely because soybean stubble provides less vegetation on the field than corn. Soybean fields with no cover crop versus cover crops held 2.4 and 3.0 birds per 100 m respectively. Moreover, the species of birds found in cover cropped fields had a higher conservation value assessed by Avian Conservation Significance scores. These higher scores were largely driven by greater abundance of the Eastern Meadowlark and Red-winged Blackbird. The Meadowlark migrates early and thus suffers high mortality rates in early spring due to low vegetation in early spring windows when fields are typically bare in the cornbelt which can be mitigated by a well-established stand of cover crops.

Single grass species cover crops had higher bird abundance than cocktail mixes except in the case of American Robin, Killdeer, Lapland Longspur. Cereal rye had the greatest abundance of birds compared to any other single species or mixed species cover crop, likely due to its high vegetative density scores compared to other cover crops. The authors propose delaying cover crop termination to early May to increase early nesting success without running into later nesting species.

Ellis, K.E., Barbercheck, M.E., 2015. Management of overwintering cover crops influences floral resources and visitation by native bees. Environ. Entomol. 44, 999–1010.

This native bee habitat survey was conducted on fields in a corn-soybean-wheat rotation in Pennsylvania in 2012. The six cover crop treatments that were assessed are canola monoculture, canola/medium red clover/Austrian winter pea/cereal rye four-way mix and canola/medium red clover/Austrian winter pea/cereal rye/forage radish/oats six-way mix. During temperatures warm enough for bees to be active, pollinators were observed and specimens collected. Bee visitation rates were thus significantly higher in the monocultures than in the six way mix. Canola was the only species of cover crop to flower before cover crop termination on May 14 (winter pea and red clover did not flower before termination). But even the six way mix increased bee habitat over the fallow check.

An additional experiment was conducted that compared planting dates and winter survivability of canola monoculture, medium red clover monoculture, Austrian winter pea monoculture planted at four different dates from 1 August to 5 October. Canola flowered first around April 21-May 21, Austrian winter pea flowered second from May 21-May 28 and red clover flowered last from June 3-July 1. Canola monoculture produced 36 bee species sightings, while Austrian winter pea had 11 and red clover had only 7. Canola therefore emerged from both studies as the ideal cover crop to bloom within a common field crop rotation and attract the most diverse and largest population of bee species.

Schmitz, R.A., Clark, W.R. 1999. Survival of ring-necked pheasant hens during spring in relation to landscape features. Journal of Wildlife Management 63, 147-154.

Clark, W.R., Schmitz, R.A., Bogenschutz, T.R. 1999. Site selection and nest success of ring-necked pheasants as a function of location in Iowa landscapes. Journal of Wildlife Management 63, 976-989.

Pheasant hunting used to be a big part of Iowa’s economy. Hunters from across the nation swarmed hotels and coffee shops across the state, injecting thousands of dollars into small businesses and the rural economy in general. “I still remember filling our cafes and hotels every pheasant season,” said PFI member Seth Watkins at Pheasant Fest (the national convention of Pheasants Forever and Quail Forever) in Des Moines in 2015, “And that was good for commerce. That sustained my community.” But as perennial habitat has declined in Iowa since the 1960s, so have pheasant numbers. As pheasant numbers have declined, so have hunting numbers, and South Dakota has long overtaken Iowa as the pheasant hunting capital of the United States.

Two papers published in the late 1990s based on long-term research by Iowa State University and the Iowa Department of Natural Resources (IDNR) still guide wildlife management and recommendations for habitat-focused groups like Pheasant Forever and the IDNR. (The other perennially useful resource is a book written by Allen L. Farris, Eugene D. Klonglan, and Richard C. Nomsen in 1977 called “The Ring-Necked Pheasant in Iowa.” ) The research study compares two landscapes – one with more perennial cover vs. one dominated by row crops – to see how those landscape features influence pheasant reproduction and therefore pheasant populations. While honing in on some of the finer-scale processes that can guide land managers on how to configure limited perennial habitat in the best way possible for wildlife, the research reemphasizes a big point: a diverse landscape with more blocks of perennial cover will provide more habitat for pheasants to find mates, find food, successfully nest, and avoid predators.

A good takeaway that could benefit farmers looking to diversify (from Clark, Schmitz & Bogenschutz, 1999): “In the 1940s and 1950s, a diversified agriculture with small grains, hayland, pastureland, and odd areas that were rotated constantly provided the landscape management that wildlife professionals are challenged to recreate under today’s policies.”

Zimmerman, J.K.H., Vondracek, B., Westra, J. 2003. Agricultural land use effects on sediment loading and fish assemblages in two Minnesota watersheds. Environmental Management 32, 93-105.

 A primary issue for the success of trout populations is sediment in the water. Trout hunt by sight, and cloudy water caused by suspended sediment inhibits their ability to find prey. While trout can only survive in coldwater streams, sediment is also an issue for site predators in warm water streams. This study looked at the impact of agricultural land use in two streams and their watersheds in Minnesota – one, a coolwater stream, Wells Creek, and the other, a warmwater stream, the Chippewa River.

Using models that simulate land use changes, the authors compared the modeled outcomes of four scenarios looking at different proportions of the landscape using different agricultural practices. In short, the scenario with the most continuous living cover – having more diversified crop rotations including cover crops – led to the least number of days a year with potentially lethal sediment loads for fish.

A big management implication from the study: “Changing land use to provide more permanent cover in the uplands and increased vegetation in riparian areas… may shift the fish assemblage to one more characteristic of a coldwater stream,” i.e. one more favorable to trout species.

Teague, W.R., 2018. Forages and Pastures Symposium: Cover Crops in Livestock Production: Whole-System Approach: Managing Grazing to Restore Soil Health And Farm Livelihoods. Journal of Animal Science.

A few key takeaways:

“To ensure long-term sustainability and ecological resilience of agroecosystems, agricultural production should be guided by policies that ensure regenerative cropping and grazing management protocols. Changing current unsustainable high-input agricultural practices to low-input regenerative practices enhances soil and ecosystem function and resilience, improving long-term sustainability and social resilience.”

“Ruminant livestock are an important tool for achieving sustainable agriculture and with appropriate grazing management, can increase C sequestered in the soil to more than offset ruminant GHG emissions while they support and improve other essential ecosystem services for local populations such as increase water infiltration, reduce soil erosion, improve nutrient cycling, soil formation, carbon sequestration, biodiversity, and wildlife habitat.”

“Research conducted on managed landscape shows that ecologically managed adaptive multi-paddock (AMP) grazing strategies incorporating short, high impact grazing with long recovery periods can regenerate ecosystem function on commercial-scale agro-ecological landscapes. These include: 1) build soil carbon concentrations and soil microbial function; 2) enhance water infiltration and retention; 3) control erosion more effectively; 4) build soil fertility; 5) enhance watershed hydrological function; 6) improve livestock production and economic returns and the resource base; 7) enhance wildlife and biodiversity; and 8) increase soil function as a net greenhouse gas sink.”