Agriculture and Environment: Wood Pulp

Environmental Impacts of Production: Changes in the Water Cycle

The environmental impacts of plantations on the water cycle are not fully understood.

However, it is clear that changes occur. The amount of water falling on the soil is different after a plantation is established because the new trees and foliage are uniform; they do not have the same diversity of size and shape as the flora found in native forests.

Runoff and absorption of rainfall also vary in response to factors such as the amount of leaf litter generated by the plantation and the type of humus produced by that litter as it decomposes. Heavy equipment compacts soil, which increases the speed and amount of runoff and reduces absorption. Some plantation trees use a large amount of water per hectare, although some studies have shown that they consume no more water than other herbaceous vegetation (Wadsworth 1997).

In Kenya plantation softwoods managed on 20-year rotations actually consume less water per hectare than natural forests, and only 10% more than perennial pasture grasses (Pereira 1967, as cited in Wadsworth 1997).

There is, however, a direct correlation between a species' rate of growth and total water consumption, so plantations that use fast-growing species such as eucalyptus have high water use. This high rate of water use can cause problems in areas surrounding the plantation, as less water is available for crops, freshwater ecosystems, and the generation of hydroelectric energy and other industrial activities.