A. D. Bradshaw

Restoration of mined lands—using natural processes

Abstract 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.

The use of natural processes in reclamation - advantages and difficulties.

The damage to soil and vegetation caused by mining, unless prevented by careful planning, is usually extreme, because the original ecosystems have had to be grossly disturbed or buried by the mining process. Radical reconstruction is therefore required. In nature this takes place by the well-known processes of primary succession, without human assistance. In the interest of economy and the maintenance of our natural resources, reclamation should attempt to involve the same processes. But primary succession on raw substrates can take several centuries to complete. This paper attempts to analyse what seem to be the factors that limit the processes involved and how they can be overcome by ameliorative treatments. It examines in particular how long this amelioration will take and how much it is likely to cost. Knowing this we are then be able to include a natural approach in land reclamation effectively.

The biology of land restoration

Disturbance of land is an inevitable consequence of modern civilization which has resulted in a substantial “heritage” of degraded land on which the original ecosystems, plants, animals and soils have been totally destroyed. All that is left is skeletal soil material. The restoration of functional, self-sustaining ecosystems on these materials is a considerable challenge.

Ecosystem development on reclaimed china clay wastes. I. Assessment of vegetation and capture of nutrients.

(1) In a survey of sixty-eight reclaimed china clay wastes, vegetation was scored for overall cover, legume cover and the number of ingressed species, and the accumulation of biomass and major plant nutrients was measured at forty-three sites. (2) Vegetation cover was adequate for slope and sand stabilization, and at certain sites there was a high legume component which contributed to the nitrogen economy of the vegetation. There was limited ingression of new species into these reclaimed areas. (3) Organic matter and most major plant nutrients accumulated in these new ecosystems. An overall nutrient budget comparing inputs from atmospheric deposition and fertilizer sources to net accumulation within these ecosystems showed a net loss of all elements measured with the exception of nitrogen and to a lesser extent phosphorus. In the case of nitrogen there was an overall accumulation in excess of measured inputs reflecting the influence of leguminous species.

Technology Lecture: Land Restoration: Now and in the Future

Derelict and degraded land destroys amenity, causes pollution and is a waste of productive land surface. Despite the worldwide activity to restore it there is an enormous backlog, which in England has increased since 1974. In the past much of this restoration was empirically based and not always successful. But natural ecosystems develop unaided on raw starting materials by natural ecological processes. A proper understanding of these has led to more reliable and inexpensive restoration techniques. At the same time we have come to realize that, because, at the start, the slate has been wiped clean, many different end points are possible. Derelict land is a challenge and opportunity for creative manipulation of our landscape. Yet what is achieved in practice is often pedestrian, unscientific and uneconomic. Often the simple treatments that would minimize the impact of industrial activity, and would set the restoration off early and in the right direction, are not carried out. Yet there are plenty of good examples of what can be done. It appears that once more we may be victims of the British failure in technology and imagination transfer. For this the fault seems to lie broadly, not only with planners, industrialists and government, for not always making sure something is done, but also with scientists, for not applying their ecological knowledge sufficiently to problems of hard practice.

Conservation problems in the future

Change in existing ecosystems is usually considered to damage nature conservation interest. Yet many of the changes that have occurred in the past since woodland was cleared by primitive man have lead to enhanced interest by providing diversity in a wide variety of sub-climax ecosystems. But the ecosystems are sensitive and liable to further change. Many of the local problems of present-day nature conservation stem from this. But there are also pervasive changes which because they are widespread are leading to wholesale loss of ecosystems and species. They are important not only on a local scale but also in their effects on the totality of wild life. In these circumstances it appears that we will have to change our attitudes and take account not only of areas which we recognize because of their naturalness, but also man-made habitats. We shall have to consider the restoration as faithfully as possible of areas that have been grossly disturbed, the reintroduction of species into areas from which they have been lost, and the creation of new areas of conservation interest in totally degraded areas such as gravel pits, quarries and even chemical waste heaps. Some man-made areas are already of considerable interest and value to nature conservation. But others require deliberate modification and the introduction of appropriate species. Some steps have already been taken in this direction, but there is a wealth of further opportunity. Such work will require the application of scientific knowledge to practical ends: in its turn it can provide us with critical information on the subtleties of plant and animal behaviour.

Ecosystem development on reclaimed china clay wastes. II. Nutrient compartmentation and nitrogen mineralization.

(1) The accumulation of biomass and nutrients in three compartments (plant shoots, roots and surface soil) in developing ecosystems in two types of reclaimed china clay waste, sand tips and mica dam walls was measured. Biomass and nitrogen accumulated mainly in the root compartment whereas all other elements measured with the exception of potassium in mica dam wall soils, accumulated in the soil fraction. (2) The accumulation of nutrients in the shoot and root pools was not due to redistribution of nutrients from the soil pool as accumulation was demonstrated in all three pools. (3) Soil nitrogen mineralization tests showed an increase in mineralizable nitrogen in the reclaimed waste compared to the raw waste. A significant correlation with age since treatment was demonstrated for sand tip soils. (4) The importance of nutrient cycling and of nitrogen cycling in particular in recently established ecosystems, such as reclaimed china clay wastes is emphasized. The relative contributions to nitrogen cycling from mineralization and grazing sources are discussed.

Tolerance ofHolcus lanatus andAgrostis stolonifera to sodium chloride in soil solution and saline spray

SummaryInland and sea cliff populations of bothAgrostis stolonifera L. andHolcus lanatus L. were subjected to soil NaCl treatments, of 100 and 200 mol m−3 NaCl, and tolerance examined using plant dry weight data. A parallel experiment subjected them to salt spray treatments of 2.5%, 5% and 10% NaCl in distilled water, and tolerance assessed from leaf damage.Both populations of each species were equally sensitive to soil NaCl. When subjected to salt spray the sea cliff populations however showed marked resistance to leaf damage. Soil salinity resistance and salt spray resistance thus appear to be independent characteristics in these two species.

Rehabilitating Damaged Ecosystems

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Ecology and Planning

The United Kingdom was one of the first countries to provide for formal planning procedures through legislative action with the introduction of the Town and Country Planning Act of 1947. During its formative years planning as a profession was largely concerned with improving public health particularly in decaying urban centres in post-war Britain. Subsequently the emphasis in planning has shifted through engineering considerations, sociological and economic aspects and latterly environmental quality, reflecting changing concerns amongst society at large. In addition to these changes in the flavour of planning the formal procedures themselves, the framework within which decisions are taken, have also evolved to meet the society’s changing requirements.