||Depletion of vital resources is often put forward by environmentalists as one of the principal ways that environment influences human society. The idea was most spectacularly presented in The Limits to Growth, a book which used computer models to argue that current rates of increase in consumption of vital resources would lead to disastrous shortages within a few decades. The methods used to make these predictions were subsequently discredited, but the concern over resources remains.
Resources are natural products or processes which are used to provide materials or energy for human use. Their effective abundance depends on the natural processes that make them available and the social processes which decide which are actually used. Natural materials can only be used if they are identified and if technology is capable of extracting them and transforming them into useful products. In the modern world, they tend to be used only if they are cheaper than alternatives, though politics can also influence whether or not a resource is used.
Resources are categorized into two types. Stock resources are those which exist in finite quantities, usually as a result of geological concentration over very long timescales. Flow (or continuous or renewable) resources are those which can be used and reused as long as they are not damaged by over use. Resource depletion has different meanings for the two types.
The obvious examples of stock resources are metal ores and fossil fuels. In fact modern society uses much larger quantities of building stone or aggregate, but with rare exceptions such stone is of low value and is only transported short distances. The concept of an ore is tautologous because metals exist in almost all rocks, but only those with the highest concentrations of the most suitable chemical composition are regarded as ores. Different metals are exploited at very different concentrations. Iron, which is abundant in nature and makes up 95% of all metal traded, is only exploited when ores contain more than 25% iron; copper is extracted from ores with only 0.5%; metals like gold, uranium and mercury are extracted at much lower concentrations. In no case are ores likely to be exhausted: if the most concentrated ores are used up, the response will be more intensive prospecting, and even if that fails less-concentrated sources will be available. However, lower grade ores will be more expensive, will require more energy to refine and will produce larger voids and more spoil. Increasing cost may stimulate efforts to recycle metals or to substitute alternative products, and so it is unlikely that, with a few exceptions like silver, tungsten and tin, metals will be the most acute resource problem.
The stock resource most likely to cause problems of depletion is fossil fuel, especially petroleum and natural gas. During this century consumption has increased exponentially until more than half of commercial energy comes from these two sources. Unfortunately, they are geologically rare and it is proving more and more difficult to find new fields. Even optimists calculate that oil and gas will be acutely scarce in a few decades if current trends continue. Although coal has been used over a longer period, there appear to be sufficient reserves for a century or more. Given the dominant role of fossil fuels in energy supply, dramatic changes will be needed to conserve them even if the pollution impacts are ignored. It is also significant that oil is potentially more valuable in the long term as a source of raw materials for the chemical industry than it is as a fuel. There are thus several lines of argument which indicate a need to reduce use of fossil fuels for energy and hence a need to become more energy efficient and/or to use renewable energy resources.
Renewable energy is one of three kinds of continuous resource. Solar radiation is both a continuous resource in itself and also the motive power of natural cycles which supply air and fresh water as well as wind, hydro and wave energy. Natural ecosystems offer a harvest of animal and vegetable products or can be cleared to use the soil to grow agricultural crops. The throughput of energy through these systems is enormous: only 0.2% of the solar energy entering the atmosphere is used in photosynthesis, but this is 30 times as much as the total consumption of fossil fuel and nuclear energy. So the resource base exists for a move to renewable energy and the economics are competitive. What seems to be lacking at present in most countries is the political will, perhaps because renewable energy technologies are still seen as â€˜low-techâ€™ or â€˜alternativeâ€™, and therefore suspect. Also, a move to the use of continuous resources may require a move to a more dispersed supply, and so raise problems of organization and ownership in sustaining the resource and distributing the benefit. These problems are not easy to overcome, as shown in the case of the other flow resources. Human activities cannot significantly affect solar radiation or the wind and waves, but they can lead to soil erosion and desertification.
The technical problems of managing continuous resources are not all that difficult, but the social problems are harder to overcome. A particularly problematic situation is that of managing resources held in common. Garret Hardin crystallized the problem in his description of â€˜the tragedy of the commonsâ€™. If many people live on the produce of a common resource, such as an area of grazing land or the fish from a lake, each individual may gain by exploiting the resource more intensively. But if everybody does so the result is overuse and reduction of the output. Some mechanism is required to regulate exploitation to a level that does not damage the resource. Some experts advocate private ownership, though it is easier to achieve for the land rather than the lake and hard to contemplate for atmosphere or ocean, while others press for co-operative arrangements, whether between villagers or between countries. However, the continuing disputes over fisheries and whaling are an indication that sustainable management of common resources is an intractable problem. It is particularly so where the individuals or groups concerned are poor.
Deforestation is a particularly emotive resource-management issue, with widespread criticism by the First World of destruction of tropical forests and of trees in the semiarid tropics. But this is not a black and white issue: the effects of deforestation of hills, with soil erosion in the uplands and floods and deposition of stones and boulders in the lowlands, has been known in Mediterranean countries for 2,000 years. Massive deforestation has occurred in the old world and the eastern US, some producing productive farmland, but not always without flooding and erosion. Clearance of trees in the tropics is more hazardous than in temperate areas because the heavy rain makes erosion more likely. The potential benefits are often small because tropical soils are typically infertile. But most of those involved in clearance have pressing short-term reasons: demand from the First World gives logging companies the incentive, ranchers may get government subsidies for clearance to produce meat for export, landless peasants need land to grow food to survive, or have no other fuel to cook with. The solutions may lie, as the tragedy of the commons suggested, in changing patterns of land ownership and in international agreements on the terms of trade. Like the management techniques themselves, the social organization of resource management needs to take a long-term perspective, but such a perspective is hard to achieve when individuals are concerned with survival and companies are concerned with short-term profits rather than long-term assets. PS