Synthesis of the conservation value of the early-successional stage in forests of eastern North America

As a result of changes in natural and anthropogenic disturbance regimes, the extent of early-successional forest across much of eastern North American is near historic lows, and continues to decline. This has caused many scientists to identify the conservation of early-successional species as a high priority. In this synthesis, we discuss the conservation implications of this loss of early-successional habitats using examples from the literature on songbirds. Early-successional “shrubland” bird species require conditions and resources present in recently disturbed sites. These conditions are ephemeral and change rapidly over time as sites become dominated by later-seral species. Historical disturbance regimes such as wind-throw, fire and flooding have been altered or suppressed in eastern forests through human activity such as conversion of forests to younger aged stands more resistant to wind, fire suppression and mesophication of fire-adapted communities, and suppression of beaver activity and flooding. Furthermore, anthropogenic disturbance has shifted over much of the region to types of land use that provide less shrubland habitat of lower quality than historically. Despite scientific evidence in support of this concern, there is still misunderstanding about the role of disturbance in maintaining biodiversity, and public opposition to management remains a challenge to conserving these communities. Contemporary approaches use natural disturbance regimes to inform management practices that employ historical agents where possible or surrogates when necessary to achieve desired future conditions defined on the basis of regional population or community status. Conservation of early-successional communities occurs within the context of other potentially conflicting ecological values, such as the conservation and enhancement of biologically mature forest. Recent findings, however, show shrubland habitat can augment diversity in forested landscapes by providing seasonal resources for mature-forest species, such as food or predator-free space for juvenile forest songbirds that seek out early-successional habitats during the transition to independence. Balancing the conservation of early-successional shrubland species with other, sometimes conflicting values is an active area of current conservation research. In some cases the conservation of shrubland birds can be coordinated with commercial activities like silviculture or maintenance of infrastructure (e.g. powerline corridors), although our work indicates that deliberate efforts expressly directed at conservation of early-successional shrubland species are more effective.