Using landscape biodiversity metrics to assess rewilding: A comparison of the Knepp Estate and an agricultural baseline at Boothby Wildland

Abstract The biodiversity crisis is often framed in terms of the reduction of species found at a site: α (alpha) diversity. However, changes in species composition across a landscape—β (beta) diversity—caused by biotic homogenisation are part of the same crisis. Much biotic homogenisation in British terrestrial landscapes in the post‐war period (1945 onwards) has been driven by agricultural conversion and intensification. Restoration efforts must therefore contend with restoring agricultural land to some desired state, and rewilding has emerged as a potential solution to this problem. Here we quantify rewilding success by comparing α‐ and β‐diversity of plant assemblages across two study systems in different stages of rewilding. Boothby Wildland is an arable farm recently given over to rewilding, while the Knepp Estate is an ex‐arable and dairy farm currently >20 years into rewilding. We assessed α‐diversity within and β‐diversity across these two landscapes using 3 years of plant survey data (2022–2024). We confirmed expected differences between a baseline and rewilded landscape and explored the changes in a brand new rewilded landscape during its early years of progress. As expected, the plant community at the Knepp Estate is relatively stable while that of Boothby Wildland is changing rapidly and we discuss the landscape impacts of different herbivory regimes on recovery. Practical implication. We show that spatial metrics for phylogenetic diversity can distinguish between a rewilded and degraded landscape. This suggests that changes in the structure of biodiversity across landscapes can be quantified using analyses that account for spatial structure in metrics. We call for further research to test if a spatial approach of this kind can be used as a general metric of success in rewilding.