The importance of residual ecological legacies for extinction debts in managed forests

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Habitat loss is the principal cause of species loss in boreal forests and many other ecosystems. However, recent theoretical advances suggest these impacts may be greatly underestimated and species loss may continue far into the future through a process called extinction debt. Despite this dire prediction, there are few empirical examples of extinction debt that provide the information necessary to predict when and which species will go extinct. As a consequence, it is unclear whether extinction debts will translate into long-term losses in ecosystem functions (`functional debt') and what kinds of conservation or restoration efforts could limit or reverse these losses.***Here, I present an integrated research program that will determine the likelihood, extent and duration of extinction debts following large-scale removal of deadwood by intensive harvesting and biomass removal in boreal forests. Through this research program I will train more than 12 HQPs. I will also provide a conceptually and experimentally unique approach based on direct measurement of colonization-extinction dynamics of deadwood-associated insects and fungi in individual deadwood habitats and across replicated, increasingly impacted landscapes. I will capitalize on three ongoing experiments where habitat loss occurred at different times thus providing a chronosequence of landscapes that spans 15 years and where the effects of extinction debt can be measured directly. I will then use empirical estimates of colonization-extinction dynamics to parametrize extinction debt models and evaluate the risks of long-term species loss under a large number of realistic, management scenarios. By focusing on communities and food webs in deadwood and their role in decomposition and carbon storage, I will further extend any long-term impacts of extinction debt to larger ecosystem impacts related to a functional debt. ***This framework presents a novel means to integrate conservation and restoration ecology through explicit consideration of colonization-extinction dynamics. With this information we can `customize' mitigation strategies that favour specific types of deadwood depending on the condition of the larger landscape. I also provide a means to unify deadwood management with notions of ecological resilience. This information is essential for land-managers, conservation stakeholders and policy makers who are currently planning guidelines and binding legislation for intensive biomass removal based on limited (if any) ecological information.**