In a previous report I tried to show that the widespread use of electric cars, both battery-powered and so-called ‘hybrid’ types (i.e. vehicles utilizing an electric motor powered by a battery in town, and a combustion engine on open highways), would not reduce, but rather increase, air pollution, because the electricity required to run them would have to be generated by a large number of additional fossil-fuel burning power plants, with a lower total energy efficiency (de Sabata 1995).

In the era of space travel, ecology has continued to gain relevance as the science of the ‘spaceship Earth’. In this context, it can be said to have a mission, which is to understand the complex network of the life-support systems that keep biospheric processes operating in a way suitable to sustaining living organisms and their environment (Odum & Sarmiento 1997). With the realization that ecology, in the broad sense, provides the means to understand the mechanics of nature, scholars are using ecological understanding at the interfaces of disciplines to: (1) prevent and reverse the demise of biodiversity in marine and terrestrial ecoregions (conservation biology), (2) reduce impacts of population pressure on the resource base of people (ecological anthropology), (3) establish more parsimonious economic activities to ensure optimum yields for the long term (ecological economics), (4) plan for an appropriately-equitable and socially-integrative sustainable development (environmental design), (5) restore degraded ecosystems and landscapes (restoration ecology), and (6) model hypothetical future scenarios where predictions from ecological theory may prove valuable for the future of mankind (environmental planning).

Critical loads studies (critical load is ‘a quantitative estimate of an exposure to one or more pollutants below which no harmful effects may occur’) have been used as the basis for assessing European strategies for reduction of sulphur emissions within the United Nations (UN) Economic Commission for Europe (ECE) Convention on Long-Range Transboundary Air Pollution (LRTAP). It is expected that the critical loads method will be applied to future international agreements under the Convention. Mapping of European critical loads conducted for the LRTAP Convention have progressed notably in recent years.

The concept of designing pollution control measures with the aim of protecting the most sensitive ecosystems, led to the creation of the Task Force on Mapping and Coordination Centre for Effects to implement these concepts on a European scale together with the corresponding National Focal Centres. The Russian National Focal Centre is used to illustrate how critical load data can be applied at the scale of a large country.

The policy implications resulting from the methods described in this review would support the development of an acidification protocol. While this has been suggested in the past, it is only now that scientific knowledge has advanced sufficiently to consider the feasibility of such a policy.

Arrested succession is conspicuous in the abandoned pastures of the Andean piedmont that have encroached upon the tropical montane forests toward higher limits and steeper slopes. Habitat 'shredding' is analysed to depict the current spatial configuration of tropical Andean landscapes, based on fragmentation patterns prompted by seed dispersal ecology and pasture encroachment.

Seed dispersal was studied to address the hypo-thesis that seed input constrains the recruitment of montane forest seedlings, thus impeding pasture conversion to forest. It turns out that a better competitor, the tussock grass Setaria sphacelata, is limiting dispersal success due to its bioarchitecture and planting patterns. Because of the variegation of fragments, the area is in danger of landscape homogeneity within a matrix of degraded pasture. Currently, protection of fragmented remnants and restoration of original landscape structure and function are urgent needs for land-use planning toward sustainable development in the region.

Restoration ecology is plausible as a means of conservation for degraded Tropandean forests, since human impacts have shredded landscapes entirely. Dispersal ecology may be used to facilitate pasture conversion to forest in equatorial landscapes, but the proactive approach of pasture removal or planting strategy should differ from that for lowland Amazonia, where abandoned pastures are different from those of montane environs. However, the region may be proactively managed only if political decisions include conservation as a goal of development.

Topsoil is essential to abandoned mines and has to be stock-piled separately for post-mining land reclamation. If the storage period exceeds the 'shelf life' of the topsoil, it cannot be preserved by technical reclamation only. Opencast coal mining production in India is predicted to increase from the present level of 180 million tonnes per year to approximately 256 million tonnes per year by the year 2000. At that time about 60 km2 of land per year would be damaged by direct coal mines and 75 km2 per year would be affected by external overburden dumps and topsoil dumps. A large opencast coal mine was studied to evaluate the effect of stock-piling topsoil. Soil characteristics of soil dumps of six different ages (1, 3, 4, 6, 9 and 10 years old) were compared with those of surrounding unmined sites. Soil profiles were found to change greatly with age. Physico-chemical characteristics of soil dumps were found to deteriorate with respect to unmined soil. It was observed that, as the age of soil dumps increased from one to 10 years, the concentrations of suitable plant growth nutrients in soil gradually decreased and, after six years, the soils were found to be stagnant. This may be considered to be the 'shelf life' of topsoil. Biological reclamation must be adopted to preserve the topsoil if the storage period exceeds the shelf life period. The methodology provides guidelines for assessing the shelf life of topsoil in other areas.

Although the Government of Indonesia has good data on forest cover and population, it does not have data on how many people live on state-claimed forest land. The objective of this study was to assess the extent of this deficiency and to develop a methodology for overcoming it, based on field research in the province of West Kalimantan. The project retrieved and combined government data on forests and people, analysed their significance in terms of numbers of forest-dwelling people, compared these results with government estimates and an empirical field-check, and sought to explain why knowledge of forest dwellers on state-forest lands is problematic. Results suggest that 20 to 30% of the population of West Kalimantan (approximately 650 000 to one million people) live on state-claimed forests. The main reason why it is difficult to determine how many people live on state-claimed forest lands is that a large number of villages remain unmapped and thus it is not possible to unite census data with forest boundaries in a spatially-precise manner. While the Indonesian Ministry of Forestry has not placed a high priority on determining how many people live on state-claimed forests, this study suggests that the lack of information on forest population densities is as much a consequence of the lack of information on village locations as it is a result of political or institutional interests.

Predicting the distribution of endangered species from habitat data is frequently perceived to be a useful technique. Models that predict the presence or absence of a species are normally judged by the number of prediction errors. These may be of two types: false positives and false negatives. Many of the prediction errors can be traced to ecological processes such as unsaturated habitat and species interactions. Consequently, if prediction errors are not placed in an ecological context the results of the model may be misleading. The simplest, and most widely used, measure of prediction accuracy is the number of correctly classified cases. There are other measures of prediction success that may be more appropriate. Strategies for assessing the causes and costs of these errors are discussed. A range of techniques for measuring error in presence/absence models, including some that are seldom used by ecologists (e.g. ROC plots and cost matrices), are described. A new approach to estimating prediction error, which is based on the spatial characteristics of the errors, is proposed. Thirteen recommendations are made to enable the objective selection of an error assessment technique for ecological presence/absence models.

The implications of world population growth for future fertilizer use and impact on the environment have scarcely been predicted. We investigated world protein production using a global nitrogen balance model. The model assumes that world population continues to grow and crop yield per unit area is closely related to nitrogen fertilizer use. About five times more cereal protein is needed to produce meat protein through farming. Advanced countries consume more meat than people in developing countries. Assuming the world's arable land remains constant in area in the next century, and if the meat consumption in advanced countries is matched by the rest of the world, the demand for fertilizer will increase and reach 220 Tg y-1 by the middle of the next century. This is approximately three times more fertilizer than is currently used, and would accelerate environmental deterioration. The world would be suffering from conflict between supplying sufficient protein and greater nitrogen pollution of the environment.

Tropical forest destruction jeopardizes wildlife habitat. In many countries, hunting by low-income households also poses a direct threat to many species. This paper reports a study of the wildlife hunting practices of an indigenous cultural community in the Philippine province of Palawan. A survey of hunting practices was conducted among farmers living along the forest margin. The survey collected information on hunting frequency, hunting techniques, and species hunted. These data were combined with household income and demographic data to learn how socioeconomic factors influence hunting patterns and practices. Descriptive statistical procedures and regression analysis show that hunting pressure during the study period was typically greatest among resource-poor households. Poor households used the widest range of hunting implements, including modern implements such as air rifles, and low living standards were associated with greater hunting effort. Households with small farms were more likely to hunt, and were also more likely to expend greater hunting effort. Hunting was a supplementary source of food acquisition for most farmers and was found to be inferior to agricultural production, in the sense that households with large farms tended to hunt less often than households with small farms. Indirect evidence suggests that higher population pressure correlates positively with hunting pressure, and that non-agricultural employment negatively correlates with hunting probability and intensity.

Hydroelectric dams in tropical forest areas emit carbon dioxide and methane. How these emissions and their impacts should be calculated, and how comparisons should be made with global warming contributions of alternative energy sources such as fossil fuels, can lead to sharp differences in conclusions on the relative advantages of these options. The example of Brazil's Tucuruí Dam is examined to clarify these differences. The present paper extends an earlier analysis to 100 years and explores the differences between these and comparable fossil fuel emissions.

Factors considered here in calculating emissions for Tucuruí Dam include the initial stock and distribution of carbon, decay rates and pathways (leading to carbon dioxide and methane), and losses of power in transmission lines. Factors not considered include forest degradation on islands and reservoir shores, nitrous oxide sources in drawdown zones and transmission lines, additional methane emission pathways for release from standing trees, water passing through the turbines, etc. Construction-phase emissions are also not included; neither are emissions from deforestation by people displaced by and attracted to the project. A complete accounting of the alternative landscape is also lacking. Standardization of the level of reliability of the electricity supply is needed to compare hydroelectric and thermoelectric options.

Types of emission calculations commonly used include the ultimate contribution to emissions, the annual balance of emissions in a given year, and emissions over a long time horizon (such as 100 years). The timing of emissions differs between hydroelectric and thermal generation, hydro producing a large pulse of carbon dioxide emissions in the first years after filling the reservoir while thermal produces a constant flux of gases in proportion to the power generated. The impacts of emissions are related to the atmospheric load (stocks) of the gases rather than to the emissions (flows), and therefore last over a long time. According to the calculations in the present paper, the average carbon dioxide molecule in the atmospheric load contributed by Tucuruí was present in the atmosphere 15 years earlier than the average molecule in the comparable load from fossil fuel generation. This means that, considering a 100-year time horizon, a tonne of CO2 emitted by Tucuruí has 15% more global warming impact than a tonne emitted by fossil fuel, assuming no discounting. If discounting is applied, then the relative impact of the hydroelectric option is increased.

Time preference, either by discounting or by an alternative procedure, is a key factor affecting the attractiveness of hydroelectric power. At low annual discount rates (say 1–2%), the attractiveness of Tucuruí, although less than without discounting, is still 3–4 times better than fossil-fuel generation. If the discount rate reaches 15%, the situation is reversed, and fossil-fuel generation becomes more attractive from a global-warming perspective. Tucuruí, with a power density (installed capacity/reservoir area) of 1.63 W m-2 is better than both the 0.81 W m-2 average for Brazilian Amazonia's 5500 km2 of existing reservoirs and the 1 W m-2 estimated by Brazil's electrical authorities as the mean for all planned hydroelectric development in the region.

Conservation projects around the world have been impeded by conflicting land uses. In Greece, although agriculture is considered to have significant impacts on wetlands and adversely to have affected conservation, the attitudes of Greek farmers to wetlands and conservation have not been assessed. Data on demographic variables of farm operators, characteristics of the farming operation, irrigation practices, attitudes towards environment and the wetland resources, knowledge on the impact of agriculture on the local environment and opinions on the Common Agricultural Policy reform, were collected through a survey using personal interviews from a random sample of 196 farmers operating in two wetlands, Lakes Mikri Prespa and Kerkini (Ramsar sites), and 141 farmers operating in a plain, in Macedonia, northern Greece.

Analysis of the data revealed that farmers practise crop and stock agriculture more intensively in wetlands than in the plain, and exploit wetland resources excessively. Hunting, fishing and wood harvesting are practised, and lake water is used intensively for irrigation by both groups of farmers, with no care for loss of the resources. Alternative methods of irrigation for improving efficiency of water use or alleviating hydrological pressures on the wetlands are not considered. Sustainability of agriculture is at risk as present practices result in impoverished soils, salinization of the fields and waste of water resources. Wetland farmers seemed to have a more negative attitude toward the wetland resources and seemed to be more ignorant of conservation issues or the impact of their practices on the environment than plain farmers. Moreover, their awareness and willingness to adopt an environmentally-friendly type of farming was very low.