HABITAT LOSS INHIBITS RECOVERY OF PLANT DIVERSITY AS FORESTS REGROW

Agricultural expansion has resulted in loss of natural habitats worldwide, threatening remnant populations and communities. However, during the past several centuries in much of Europe and eastern North America, extensive forest clearance (usually resulting in <20% forest cover) has been followed by widespread expansion of forest onto abandoned agricultural land. Since ancient forests (those remaining at the peak of forest loss) provide seed sources for recolonization of recent (post‐agricultural) forests, the extent of forest loss should influence the rate of population recovery in recent forest. Data compiled from the literature for 10 regions of Europe and North America indicate that the proportion of ancient forest in a landscape can account for >65% of the variation in species diversity of “ancient forest herbs” in recent forests relative to ancient forests. This result suggests that ancient‐forest loss has had a strong influence on the recovery of herbaceous plant diversity in post‐agricultural forests. In addition, a simple mainland–island metapopulation model suggests that with increasing severity of habitat loss the return time to equilibrium patch occupancy in recent forests is greatly extended, perhaps for centuries after forest clearance has ceased and restoration begun. Corresponding Editor: E. Menges.