Restoration of mined lands—using natural processes

Mining causes soil damage and destruction. In the process of removing the desired mineral material, original soils become lost, or buried by wastes. In many countries legislation now requires that surface soils be conserved and replaced, but there is a vast heritage of degraded land left by past mining that requires restoration. Since the industry that created this heritage has often gone and there is no money left, the restoration needs to be achieved as cheaply and yet as effectively as possible. The processes of natural succession demonstrate that nature can achieve restoration unaided, and develop fully functioning soils. Although there are problems set by the processes of dispersal, once they are established plants demonstrate that they can readily provide organic matter, lower soil bulk density, and bring mineral nutrients to the surface and accumulate them in an available form. Most importantly, some species can fix and accumulate nitrogen rapidly in sufficient quantities to provide a nitrogen capital, where none previously existed, more than adequate for normal ecosystem functioning. It will normally (but not always) be necessary to introduce artificially, the plant species most appropriate for the restoration process. But natural ecosystem development can then be left to occur on its own. In mined lands, however, certain extreme soil conditions may occur that prevent plant growth, particularly physical conditions, gross lack of certain nutrients and toxicity. It can be important that these are identified and relieved first, otherwise the whole restoration process may either not begin, or fail after a few years. But even so, ecosystem restoration can be achieved at low cost, and the product be self-sustaining in the long term, ecological engineering of the best kind.