The Importance of Shelterbelt Density

By Jenna Peneueta-Snyder

Shelterbelts are vital to retaining soil nutrients and reducing wind caused erosion. For communities dependent upon agriculture, a decline in shelterbelt density can mean a decline in healthy soil and crops.

During the 1930’s much of the land in the Great Plains had been cleared and converted for agricultural purposes. The excessive clearing, however, left the fields vulnerable to erosion. This, coupled with extreme drought conditions, plunged the country into the worst economic recession it had ever seen, otherwise known as the Great Depression.

Detection of Shelterbelt Density Change Using Historic APFO and NAIP Aerial Imagery was recently published in the MDPI journal Remote Sensing. The project set out to gauge how much land area in Grand Forks County is dedicated to shelterbelts and if there has been a decline in recent years.

The primary researcher for this project was Morgen Burke, former master’s degree student in the Department of Geography & GISc and current Ph.D. student in the Department of Earth System Science and Policy at the University of North Dakota.

Burke et al. 2019’s journal paper utilized aerial images from the National Agriculture Imagery Program (NAIP) and other U.S. Government aerial photography programs dating back to 1962. Geographic object-based image analysis (GEOBIA) was used to adequately identify various vegetation types in the NAIP imagery and determine shelterbelt density.

Grand Forks County, North Dakota, Largest Concentration of Tree Shelterbelts in the World
Photo by Morgen Burke

Burke’s interest in shelterbelts in the Grand Forks region was piqued when he first moved to town in 2014. “When you’re driving into town from the west, there’s a big sign on the side of the road that says Grand Forks County, shelterbelt capital of the world.”

“At the same time I was noticing that in the Grand Forks Herald or NDSU’s Ag Week, they were saying these trees are being removed, and there was really nothing to back it up,” Burke said. “It was just kind of a question of how many trees are there and how have they actually changed.”

The results showed a doubling of shelterbelt densities from 1962 to 2014, as well as a relatively small decline between 2014 and 2016.

“The Prairie States Forestry Project had a goal to plant shelterbelts from Texas to the Canadian border. When we looked at the 1960 imagery, we expected most of the trees we were seeing then to have come out of that planting,” said Burke. “From the 1960’s on it was really the Soil Conservation Service pushing to get more and more trees planted.”

Morgen Burke, pictured here in his office in Clifford Hall, University of North Dakota
Photo by Jenna Peneueta-Snyder

Burke attributes the subtle decline from 2014 to 2016 to technological advancements in crop tillage and the increasing size of machinery.

Farmers that practice conservation tillage, which leaves stubble from previous crops on the field, help secure the root system, preventing erosion. Some farmers may also be choosing to remove their shelterbelts due to the massive size of machinery and the inconvenience of navigating around fallen trees.

Additional researchers on this journal include Dr. Bradley Rundquist, Interim Dean of Arts and Sciences and Professor of Geography and Dr. Haochi Zheng, Professor of Environmental Economics in ESSP, both at UND.

“My role in this research was to help interpret how farmer’s decision-makings on land uses may have an impact on observed changes in shelterbelt density,” said Zheng. “Planting shelterbelts on private agricultural land is a typical conservation practice to mitigate soil erosion. However, not every individual landowner values the environmental benefits from this conservation practice.”

In 2015, the North Dakota Forest Service was awarded $1.8 million to help maintain the state’s shelterbelts. Burke, however, noted a lack of enforcement when it comes to government subsidies and shelterbelt maintenance.

“[Farmers] could plant the trees and then 5 years later, or an even shorter period, they could just decide to remove them,” said Burke. “There’s no penalty for that. Although, some of the shelterbelts have been put into the Conservation Reserve Program.”

The Conservation Reserve Program is administered by the Farm Service Agency and provides a financial incentive in exchange for protecting or removing environmentally sensitive lands from agricultural production.

Although more research will need to be conducted down the line to further determine the status of shelterbelt densities in the region, Burke’s research showcases the importance of planting and maintaining shelterbelts.