What Humans Have Done with Deciduous Woodlands?

Most of Europe was once covered with climax deciduous forests except at high elevations and in places where standing water created marshes.

The forest canopy was so dense that, it has been said, a squirrel could travel from central Russia to the Atlantic coast without ever touching ground. On much of the continent the dominant species were oaks, but in some regions elms, beeches, and birches were prominent.

Fire and Axe. Many of these forest succumbed to fire or the flint axe. At first people cut trees mainly to obtain building material or fuel, but sometimes trees were felled merely to clear the land. Initial clearing were often abandoned and recovered by forest, as has been shown by the study of pollen buried in the mud of nearby lakes and bogs. Decreases in pollen of oak ivy (a native understory vine) mark the first clearing of the forest.

This stage is followed by high levels of weed pollen, which indicate a period of cultivation. Later peaks in hazel pollen show when these shrub by trees, took over fields that must have been abandoned.

Vast tracts of climax forest still flourished in Roman times. Throughout that period the forest edge expanded and contracted with wars and other changes in human fortunes.

Eventually, the relentless demand for plowed land and forest products doomed the woodlands. As commerce and trade grew, more and more timber was needed for ship building. Glass and soap manufacture required wood ashes as raw materials.

The smelting of tin, lead, copper, and iron depended on charcoal made from wood. By the eighteenth century these industries had scalped the forests of England, and the British had turned to digging coal. The woodlands of western Europe disappeared a short time later.

Such drastic alternation of the landscape naturally had far reaching effects. Rains began to wash the soil from the naked land. It is no coincidence that several British seaports filled with slit during the twelfth and thirteenth centuries and were abandoned when their waters were no longer deep enough to float seagoing vessels.

Erosion is still evident in parts of England. Some fields have been farmed with the same hedgerow boundaries ever since the land was cleared. In places where the hedges run across the middle of slopes, the soil is as deep as six feet on the upward side of the hedgerow but so thin on the lower side that rocks lie exposed. We have no idea how much more soil eroded away entirely and washed into the ocean.

Domestic animals prevented regeneration of most British woodlands. A great sheep industry thrived in England during the middle Ages; grazing was so heavy that the seedlings had no opportunity to grow out of reach of livestock. As sheep-rearing decreased, rabbits, introduced from the Continent, increased dramatically. The rabbits stripped bark from the young trees and did so much damage that few seedlings survived.

Conversion to Grassland and Moor. In many deforested areas of Britain the climate, soil, and grazing animals interacted to create a habitat favorable to coarse grasses. Manure from the sheep and rabbits returned minerals to the soil, established an efficient nutrient cycle, and permitted the formation of a crumbly soil that supported a heavy turf.

Not all the deforested British lands went to grass. On some soils the loss of trees raised the underground water level enough to create bogs.

There is a simple explanation for this drastic change. Each day during the leafy season, large trees transpire tremendous volumes of water. Deforestation reduces this drain on the groundwater. Therefore cutting certain forest can lead to their replacement with bogs or wet, peaty moors that support low shrubs.

Fate of the Forests. Wherever civilization flourishes, forests are destroyed. The history of other forests differs little from that of European forests.

The Chinese began clearing ground for crops at least four thousand years ago. The Mediterranean forests were already seriously damaged by Plato’s times. As a rule, few forests remain where civilization has long thrived.

Although we must infer much of the history of Eurasian vegetation, we know a great deal about what happened in North America. Along the East Coast, the abundance of land and the need for a lightweight crop they could be traded in Europe promoted slash-and-bum tobacco farming.

Not only did cutting and burning the trees clear the land, but it provided ashes that contained sufficient minerals to support a few crops of tobacco.

However, these minerals were soon lost from American soil. The mineral-rich tobacco leaves were shipped to Europe and connerted again to ashes, this time in foreign pipes. The broken nutrient cycles and rapid erosion quickly ruined the tobacco plantations. Whenever that happened, the owners merely moved westward and cut another area. In this way the forests around Chesapeake Bay were destroyed before the American Revolution. So much soil washed into streams and rivers and settled into the bay that the shoreline we know is quite different from the one the early settlers found.

Wherever the tobacco fields, were abandoned, the vegetation began to regenerate. Probably some fields in Virginia and nearby states have been cleared three or four times over as many centuries.

A few bear climax vegetation today, but because of the chestnut blight, we have not a single forest just like those the first planters cut down. Chestnut blight is a fungus introduced into New York early in this century on disease-resistant Chinese chestnuts. Soon the blight swept through the eastern part of the United States leaving great stands of dead trees. Some old chastnuts still have live roots that sand up new shoots, but there are on new trees, because the blight is lethal to sprouts.