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EFFECT OF TREE COVER IN SUBURBAN AREAS ON AVIAN DIVERSITY

Abstract

Habitat loss is the main cause of biodiversity loss at a global scale and urban sprawl is one of the contributors to habitat loss, which is. In the Piedmont region of the USA, 17% of the forest canopy has been lost to urbanization. Our hypothesis was that canopy cover in suburban areas in this region will benefit avian diversity. We calculated Shannon Diversity Index from data collected through bird counts at 10 points in each of three locations in Gwinnett County, Georgia. We used ArcGIS Pro to determine housing and population density from block-level U.S. Census data at 30 m and 100 m radius from each point, as well as canopy landcover using the combined area of the three forest classes defined by the National Land Cover Data. When then tested for the effects of these covariates on diversity using a linear mixed effect analysis. The best model according to AIC was the global model with canopy at 30 m radius, population density at 30 m radius and season with random effect of year and location. With canopy cover not being part of the best model, we failed to reject our null hypothesis. The best model indicated a significant (p<0.01) decrease of -0.16±0.04 in diversity for each m2 increase in canopy cover per hectare and significant (p<0.01) decrease of -0.03±0.004 in diversity for each increase in population density per hectare, so we used this information to estimate bird diversity in the county.

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