Quantifying Long-Term Urban Grassland Dynamics: Biotic Homogenization and Extinction Debts

• Main Authors: Marié J. du Toit, D. Johan Kotze, Sarel S. Cilliers
• Format: Article
• Language: English
• Published: MDPI AG 2020-03-01
• Series: Sustainability
• Subjects: time lags; conservation; landscape history; urban vegetation; legacy effects
• Online Access: https://www.mdpi.com/2071-1050/12/5/1989

Sustainable urban nature conservation calls for a rethinking of conventional approaches. Traditionally, conservationists have not incorporated the history of the landscape in management strategies. This study shows that extant vegetation patterns are correlated to past landscapes indicating potential extinction debts. We calculated urban landscape measures for seven time periods (1938−2019) and correlated it to three vegetation sampling events (1995, 2012, 2019) using GLM models. We also tested whether urban vegetation was homogenizing. Our results indicated that urban vegetation in our study area is not currently homogenizing but that indigenous forb species richness is declining significantly. Furthermore, long-term studies are essential as the time lags identified for different vegetation sampling periods changed as well as the drivers best predicting these changes. Understanding these dynamics are critical to ensuring sustainable conservation of urban vegetation for future citizens.