Current and Future Redcedar Encroachment: Potential Implications for Central Nebraska Landscapes

Abstract

Woody plant encroachment is one of the primary threats to the grasslands of the North American Great Plains. Woody plant encroachment not only reduces biodiversity but also alters ecosystem services, such as groundwater recharge and livestock forage production, which are vital to the socio-economy of the region. In this study, we used machine learning, Markov chains, and cellular automata modeling to map the current and future cover of eastern redcedar (Juniperus virginiana). Eastern redcedar, a native species to the United States, is a dominant woody evergreen species in landscapes of the Central Great Plains. We used a multilayer perceptron to classify Landsat image archives (2000, 2010, and 2020) with training samples generated from the classification of high-resolution National Agriculture Imagery Program images. A sampling-based approach was used to estimate the encroachment rate between 2000 and 2020. We used transition probabilities between 2000 and 2010 to represent four different encroachment scenarios and predicted redcedar encroachment using transition potentials for the years 2020, 2050, and 2100. Results from image classification indicated that redcedar increased annually by 0.34–3.31% in 2000–2010, 3.88–4.15% in 2010–2020, and 2.10–3.73% in 2000–2020. The most encroachment occurred in counties with high proportions of loess canyons and hills. Redcedar’s distribution, predicted using Markov chains and cellular automata modeling, increased by > two-fold (3 999 km²) in 2050 and four-fold (7 226 km²) in 2100 compared with an area of 2 006 km² in 2020. Our results demonstrate that despite differences in transition probabilities and accompanying rates of spread, redcedar is likely to continue spreading at the expense of grassland ecosystems. Redcedar encroachment scenarios with various encroachment patterns can be used to guide proactive conservation, inform decision-making, and provide inputs for biophysical models to simulate the effects of encroachment on various ecosystem services in the absence of large-scale management success.