What did forests once look like?
It has been understood, taken as gospel, that the “Bambi Factor” which prevents hunting and management culls of too large deer populations is leading, in large parts of eastern North America, to a severe loss of forest understory as out of control deer eat pretty well everything with reach of their teeth. This results in a pronounced thinning out of the lower layers of the forest and consequently, it is said, inadequate and insufficient shelter and nesting sites for birds as well as a notably changed flora below the trees. Too many deer in the forest leads to reduced biodiversity.
We all know this to be “true” – but is it?
I recently read an essay by David Haskell, a biology professor in Tennessee, who puts a wholly different spin on things. Perhaps what we see in the deer-rich and more open forests today is closer to the natural status than we think.
He argues that the truly dense forest understory we harken back to as being the historic norm has only been so for at most a couple of hundred years. It came about as a result of early settlers shooting and eating huge numbers of forest herbivores that prior to settlement used to keep the forest much more open. In the centuries prior to European settlement, indigenous populations used to harvest deer too but they were not so “efficient” and so herds were not extirpated as happened with the arrival of European guns. In fact, ancient forests have always interspersed dense areas with connected open glades.
Thus the dense, biodiverse forest we think of as normal is a fairly recent artefact.
Nowadays, with modern hunting restrictions (this is not a pro-hunting article, by the way) and outright bans in some places, the deer have had a heyday in recent decades and the forest is opening out again as it has not done for a long time. Perhaps, though, opening out too much. The fact that we have also removed all or most of the natural predators such as wolves and the larger cats from our forests has not helped. There are now four to 10 times more deer in North America than prior to European settlement 300 or so years ago. As human populations and their farmland and towns have increased, deer forest habitat has shrunk drastically, mostly giving way to suburban lawns, gardens and farms that can also provide a deer’s food sources.
Early settler writings tell us that “ … there is such infinite herds that the whole country seems but one continued park” (Thomas Ashe – 1682) and “I cannot express what quantities of deer and turkeys are to be found in these woods” (Baron de la Hanton – 1687).
Going back even further in evolutionary history, the great eastern forests were once browsed by now extinct giant herbivores such the giant sloths (picture on left) and the mastodons amongst others. More recently the forests were inhabited by woodland musk oxen, woodland bison and more, now extinct species of deer. These really were huge animals and opened the forest lower layers even further from the ground than did the deer. It has been postulated that the reason many shrubs and trees, such as the hollies for example, don’t bother producing thorns or prickly leaves much above ten feet height is that that was the browse height when the giant sloths were in the forest. Evolution does not usually move rapidly. The fossil relics of these animals are to be found across the continent.
Haskell writes that “North American Forests have experienced 50 million years of heavy browse, followed by ten thousand years of drastically reduced mammalian herbivory, then one hundred strange years of no browse at all”. Yet it is those hundred or so years that today we consider to be the lost Arcadia and “the way things ought to be”.
In other words, while today we undoubtedly have too many herbivores in the forests and some management culling would be helpful, to try to restore the forests to a density that was itself only created relatively recently by the activities of our ancestors would be inappropriate.
Ideally, we would benefit the forest biodiversity by reintroducing predator species such as wolves (this has been shown to work in Yellowstone, for example but could be a hard sell closer to large centres of population). Instead we should put an end to the Bambi thinking and invest in managed culling of deer herds – yes, wolves would be wonderful, but I doubt they will be welcomed so we have to do the controlling ourselves, and that means guns.
Doing this would open up parts of the forest to create lighter glades and forest rides which would in turn encourage a more varied flora while still ensuring enough areas of denser shrubs at lower levels in which birds would be able to nest.
I find it very interesting that we so often think of the status quo ante during our grandparents’ lifetimes as being the “normal” status of our wilder habitats when, of course, that is far from the truth. Similar things could be said for our opinions of what is a normal insect population for example.
In the image below, to the right of the fence is a forest with a large deer population, while to the right is a regenerating area of forest from which deer have been excluded. Altogether denser. The ideal is to have areas of both – which means deer, but not too many deer.