Agriculture and Environment: Wood Pulp

Environmental Impacts of Production: Soil Erosion and Nutrient Loss

In plantations with intensive, short rotations, nutrients in the soil are depleted and soil becomes more acidic over time

Frequent management interventions, use of heavy equipment, and tree removal all disturb the soil, reduce organic matter, and increase erosion. Each of these impacts can contribute to other impacts as well. For example, soil erosion worsens the impacts of floods.

In Brazil, the policy of Aracruz Cellulose S.A. is to leave tree crowns and small branches on site after the harvest in order to help protect the soil (WRI et al. 1998). A study of fast-growing species in the tropics concluded that 70-80% of the nutrients in the tree were removed from the plantation when timber and bark were harvested.

Removal of such large quantities of nutrients results in the need for large amounts of fertilizer to restore soil fertility. Leaving slash (branches and other residue) on the site after harvest could reduce nutrient loss by 25%. Leaving bark could reduce loss by another 5-10%.

Extending the time of harvest also reduces nutrient loss, as shorter harvest-and-replanting cycles remove more nutrients. Harvesting Gmelina arborea every 5 to 6 years causes significantly more nutrient loss than harvesting every 13 to 15 years (Wadsworth 1997).