COMMENTARY — Reforesting Brazilian mine sites

As part of a commitment to sustainable development, Mineracao Rio do Norte (MRN) and Alcan Aluminio do Brasil are participating in a renewal project in the Brazilian Amazon.

The Trombetas bauxite mine is in the northern state of Par, between the Amazon and Trombetas Rivers. Millions of species of animals, insects and vegetation coexist in a unique ecosystem. Consequently, from the outset, MRN sought to apply the strictest environmental conservation measures to every facet of the mining process.

In 1977, two years before mining began, an environmental adviser was hired to map out the strategies that would ensure sucessful reforestation of the mined areas. Employee education, surveys of the flora and fauna and the creation of an on-site plant nursery and seed collection program provided the basis for what has now become one of the most sucessful land reclamation projects in Brazil. More than 1.8 million transplants of at least 250 different endemic species were used to create stands of new growth.

The primary layer of organic soil is of great importance in the reforestation effort. In the rain forest, nutrients are concentrated in the topsoil, and so the roots of vegetation are shallow and spread out. It is therefore necessary to conserve the topsoil, with its decaying leaf matter and vegetation, before mining begins, so that it can be used later to nurture the replanted seedlings.

The topsoil is removed and either immediately laid down on adjacent land being restored or preserved for future use. Finally, the overburden is removed. After mining, the overburden is used to create a landscape similar to the unmined surroundings. The topsoil is then added together with nutrients and, finally, the seedlings are planted.

At Trombetas, MRN’s environmentalists and engineers are using an established technique that will enable reforestation of the mined area in conjunction with continuous disposal of the tailings from the bauxite washing process. The technique requires that the tailings, which consist of benign mud, be stored in holding ponds. Once the ponds are filled and the tailings have dried, the reforestation process continues.

The work at the nursery begins before the onset of mining with a species survey and seed collection program. Following this, fertilization, storage and germination work is carried out. The combined annual output is about 350,000 seedlings per year. All the information gleaned from the nurseries is shared and, in this way, know-how developed in the region benefits the entire Brazilian community.

>From a report by the International Council on Metals and the Environment.