Look through the boxes in your kitchen cabinet and you’ll likely see the word “natural” somewhere. Co-opted by marketers, it’s devolved into one of the most meaningless of words. The actual definition, “existing in or caused by nature; not made or caused by humankind” implies that it’s possible to draw a line between human and non-human causation (an increasingly difficult task in the age of the Anthropocene!) But if any place could be descibed as natural, it would surely be a forest, right?
This little fragment of nature most definitely stretches our notion of what is natural. Both in its past history, and our current attempts to revive native habitat, there’s a heavy hand of human causation. And some grey areas too – such as invasion by non-native plants. Is this natural or not? Though they were at one time intentionally planted, most invasive plants have spread throughout the landscape with the “natural” assistance of birds and water. Even some native plants, such as Osage orange, are only widespread because they were planted as hedges. And then there’s the subject of human transported pests such as the Emerald ash borer, which has killed at least 40% of the oldest trees in this forest.
If all this sounds like mere semantics, it’s not. Increasingly the forests of the world are becoming depauperate in species through logging, fragmentation, and non-native plant invasions. The link below details the increasing stresses on urban forests in particular:
Though “natural areas management” may sound like an oxymoron, it’s actually a strategy to keep parks and nature preserves from becoming monocultures of a few invasive plant species. Controlled burning, mowing, foliar spraying of herbicides, planting of native seed and plants are all routinely used to protect or revive the plant communities of natural areas.
When I first started doing this work as a volunteer, some twenty years ago, the focus was only on invasive plant removal. Admittedly the problem was huge, since this urban fragment had been unmanaged for several decades. We always felt a sense of accomplishment after cutting and treating a large section of Bush honeysuckle or Privet. I don’t get that good feeling anymore; in fact I’d rather not remove invasive shrubs at all unless there’s a plan to replace them with sustainable native ones. For wildlife habitat, something is better than nothing.
In this little forest, for the most part, native shrubs and trees aren’t regenerating “naturally” anymore. How can this be? White-tailed deer top the list of impacts, since their browsing and trampling is vastly more damaging than any other factor. Recruitment of young trees and shrubs is also suppressed by the shady, closed canopy created by Bush honeysuckle and older trees. Finally, the impoverished seed bank only contains the seeds of what’s been growing here for the past decades. Altogether, this means the removal alone of invasive plants is a fruitless effort, doomed to failure.
Planting is now the only way to recover a level of diversity that will benefit wildlife, and help prevent reinvasion by non-native plants. But what to plant? A forest with degraded soils, an impoverished seed bank, and high numbers of deer will not be able to support the kind of rich, diverse plant community that may have thrived here three hundred years ago. Common trees, shrubs, and herbaceous plants found on similar, but less damaged, sites are a good place to start.
The young spicebush and sycamore trees in the scene above look as though they belong here, and they do – both are thriving on this moist bottomland site. But they didn’t get here on their own; they were planted as part of an Eagle Scout project about five years ago. Both are mostly “deer proof” so can survive without protection from browsing.
Spicebush is one of just two native shrubs that have managed to hang on and even increase their populations as more light has become available. In a few areas, Spicebush is recruiting so abundantly from seed that small plants are competing for light and nutrients.
Transplanting these small ones to places that have none is a great way to speed things up. Spicebush is relatively shallow rooted, and good sized shrubs can be moved with little damage to the roots.
It may seem like a paradox – unnatural intervention to help return a forest to a more natural condition. But forests are no mere collection of trees, anymore than a neighborhood is just a collection of houses. It’s the amazing variety of life a forest can support that makes the difference – and much of that life depends on a rich diversity of native plants.
This year we’ll be planting a greater variety of native shrubs than ever before, including Smooth sumac, Fragrant sumac, Bladdernut, Carolina buckthorn, Silky dogwood, American hazelnut, Elderberry, Ninebark, Serviceberry, False indigo, Wahoo, Spicebush, Coralberry, and Buttonbush. Initially, many of these will need caging to protect them from deer. But in ten or twenty years there will be a revived shrub layer, at least in some parts of the forest – and insects, birds, and other animals including deer will benefit.