Are pre-Columbian conditions relevant baselines for managed forests in the northeastern United States

Populations of a number of taxa associated with shrublands, early-successional forests, and other disturbance-generated habitats (collectively referred to as thickets) are declining in the northeastern United States. To assure that species dependent on thicket habitats persist, intervention is warranted. However, conservationists concerned with the status of thicket-dependent species are confronted with two important questions. How much habitat is needed? And how should these habitats be distributed? Natural disturbance regimes have been recommended as a baseline that managers should consider while providing thicket habitats. Within the Northeast, historic disturbance regimes varied substantially among forest types. Coastal regions were characterized by extensive barrens where regular and often times large-scale disturbances that resulted in >15% of the area being covered by regenerating forest stands. Among inland forests, natural disturbances were usually small and resulted in seedling-sapling stands and beaver (Castor canadensis) impoundments covering <6% of the area. Under these conditions, thicket-affiliated species were probably distributed in small, disjunct populations that shifted in space and time. Current efforts to maintain thicket habitats must deal with a range of current land-uses and a legacy of historic uses. Additionally, the effectiveness of management protocols that mimic natural disturbances is limited among many forests. Increasing ownership parcelization, a relatively young forest, and landscape fragmentation substantially reduce the practicality and suitability of small-scale disturbances for generating thicket habitats. Large, clustered patches may be more practical and beneficial, especially in urbanized landscapes. In rural areas, silvicultural manipulations should be applied on a “sliding scale” relative to forest age. Timber harvests that emulate the range of variability of natural disturbances may become appropriate in these areas as forest stands mature. Addressing the needs of thicket-dependent species in the northeastern United States will require creativity, a willingness to explore a variety of solutions, and public support.