Evidence is provided for an internal CO₂ sink in forest soils, that may have a potential impact on the global CO₂-budget. Lowered CO₂ fraction in the soil atmosphere, and thus lowered CO₂ release to the aboveground atmosphere, is indicated in high N-deposition areas. Also at forest edges, especially of spruce forest, where additional N-deposition has occurred, the soil CO₂ is lowered, and the gradient increases into the closed forest. Over the last three decades the capacity of the forest soil to maintain the internal sink process has been limited to a cumulative supply of approximately 1000 and 1500 kg N ha⁻¹. Beyond this limit the internal soil CO₂ sink becomes an additional CO₂ source, together with nitrogen leaching. This stage of “nitrogen saturation” is still uncommon in closed forests in southern Scandinavia, however, it occurs in exposed forest edges which receive high atmospheric N-deposition. The soil CO₂ gradient, which originally increases from the edge towards the closed forest, becomes reversed.

Research on the terrestrial carbon cycle is an important component in the study of global change. Soil organic carbon, as the main part of the terrestrial carbon reservoir, plays an important role in the Earth's carbon cycle. To accurately estimate soil organic carbon storage, its composition and dynamic change must be determined. This presents a challenge to research on the soil carbon cycle, especially in China where the nationwide soil organic carbon reservoir largely remains unknown. This paper reports a research project that attempts to estimate the nationwide soil organic carbon reservoir. Data from 2473 soil profiles from the second national soil survey were collected and GIS technology was employed to quantify the national soil carbon reservoir. The analytical results show that the total amount of soil organic carbon is about 92.4 Pg (Pg = 10¹⁵ g) and that the average carbon density is about 10.53 kg C m⁻². The spatial distribution of soil organic carbon was also analyzed and mapped. This study presents basic data and an analysis method for carbon-cycle studies and also provides scientific support for policy-making efforts to control CO₂ emissions in China.

Nutrient pollution and associated eutrophication of freshwaters threaten the ecological integrity and the services provided to humans by lakes. We examined how human residential development influenced the level of lake eutrophication in the Seattle, WA, USA, region. We surveyed 30 lakes and measured 3 indicators of eutrophication: concentrations of chlorophyll-a and phosphorus, and the proportion of algae that are inedible to zooplankton. We classified lakes based on the waste-treatment method for shoreline homes: septic, sewer, and undeveloped lakes. Septic lakes occurred along the urban-rural fringe while sewer lakes occurred near urban centers. Septic lakes were more eutrophic than sewer lakes and undeveloped lakes, as indicated by higher levels of phosphorus and chlorophyll-a. These results suggest that septic systems contribute to the high levels of eutrophication in lakes at the urban-rural fringe. Lakes at the urban-rural fringe represent an opportunity for proactive management of urban expansion to minimize lake eutrophication.

Indigenous knowledge of edible fungi and their utilization by local populations were investigated in southern Cameroon from 1996 to 1999. Some 100 participants from the major ethnic groups, comprising Bantu farmers and Bagyeli (Pygmy) hunter-gatherers, were interviewed. Mushroom usage by 30 families, (319 persons), was monitored daily for over a year. Mushroom knowledge among both groups was extensive. Over 50 vernacular names were provided by respondents. In Bantu house-holds, women and children, and to some extent hunters, harvest mushrooms. In contrast, the whole Bagyeli house-hold participates. Bantu harvest mushrooms preferentially in secondary forests while Bagyeli collect them pre-dominantly in primary forests. Mushroom consumption is low for both groups, 1.1 and 1.4 kg of fresh mushrooms per person per year, respectively, a rate that is much lower than in central and eastern Africa. The apparent discrepancy between extensive mushroom knowledge and rather infrequent mushroom consumption probably relates to the social valuation of mushrooms.

In rural Africa, wild foods provide diversity, vitamins and minerals in the diet. They are also important at times of food shortage. This paper discusses issues concerning wild food use in semiarid West Africa, and presents the results of a study of the use of wild plant foods in northeast Nigeria. Interviews with farmers and herders identified a total of 67 wild foods, coming from 53 species of plant. Knowledge of wild foods varied according to ethnic group and gender. Some wild foods caused side effects if eaten in excess. Land-use change due to agricultural expansion seems to be increasing the areas where wild foods are most commonly found. Wild foods are important as a supplement to daily diet, and at times of food scarcity. In addition, they provide an opportunity to generate income when they are collected and traded. The paper concludes that wild foods are an important coping strategy for rural communities. Further research is needed to determine whether local institutions and community-based natural resource management regimes are sufficient to conserve this resource

Prior to construction of the Aswan High Dam, the annual Nile flood delivered about 7–11 × 10³ t of biologically available phosphorus (P), at least 7 × 10³ t of inorganic nitrogen (N), and 110 × 10³ t of silica (Si) to the Mediterranean coastal waters off Egypt. These nutrients stimu-lated a dramatic “Nile bloom” of diatoms which supported a productive fishery. After closure of the dam in 1965, flow from the Nile was reduced by over 90%, and the fishery collapsed. It remained unproductive for about 15 years. The fishery began a dramatic recovery during the 1980s, coincident with increasing fertilizer use, expanded agri-cultural drainage, increasing human population, and dra-matic extensions of urban water supplies and sewage collection systems. Calculations of the potential anthro-pogenic contribution of nutrients (P and N, but not Si) are consistent with the hypothesis that human sewage and agricultural drainage now support the fertility once provided by the Nile, though the nature of the productive ecosystem now supporting the fishery appears to be quite different from the historical one.

Changes in climate are occurring around the world and the effects on ecosystems will vary, depending on the extent and nature of these changes. In northern Europe, experts predict that annual rainfall will increase significantly, along with dramatic storm events and flooding in the next 50–100 years. Scotland is a stronghold of the endangered freshwater pearl mussel, Margaritifera margaritifera (L.), and a number of populations may be threatened. For example, large floods have been shown to adversely affect mussels, and although these stochastic events were historically rare, they may now be occurring more often as a result of climate change. Populations may also be affected by a number of other factors, including predicted changes in temperature, sea level, habitat availability, host fish stocks and human activity. In this paper, we explain how climate change may impact M. margaritifera and discuss the general implications for the conservation management of this species.

Total mercury content was evaluated in water and suspended sediment samples of the Moji-Guaçu river and in water and bottom sediment of its 3 marginal lagoons (Catingueiro, Barrinha, and Rio das Pedras), located down-stream of the sampling point in the main channel. In all situations, low Hg concentrations were found in suspended and bottom sediments. Aluminum was used as a geo-chemical tracer to normalize the Hg concentrations in the sediment cores from the Rio das Pedras lagoon (r = 0.92). It was estimated that the Moji-Guaçu river transports up to 19 kg Hg yr⁻¹, 65% in the dissolved form and 35% adsorbed onto particulate matter. Following an acute toxic stage observed in the years 1970–1980, the basin has been restored to its original conditions mainly by natural recovery and a general reduction in Hg input to the eco-system.

On 25 April 1998, a breach of the tailings dam of the Los Frailes pyrite mine in southwestern Spain resulted in the release of 6 million m³ of acidic water and toxic sludge high in heavy metals. Contaminated material extended 40 km downstream, affecting agricultural land and parts of the wildlife-rich Doñana Natural and National Parks, including the Entremuros, a very important area for birds. We report on the concentrations, distributions and bioavailability of zinc and cadmium in soil and vegetation from the Entremuros in November 1998 and October 1999, following 2 ‘cleanup’ operations. Levels of Zn and Cd in soil increased significantly over this period, although this was not reflected consistently in metal concentrations in emergent macro-phytes. We recommend monitoring of further cleanup attempts in order to develop means of minimizing potential impacts to wildlife in the area.

Integrated Conservation and Development Projects (ICDPs) aim to stimulate conservation without the previous negative experiences for local people, but pay little attention to their long-term impact such as immigration. The rehabilitation of the Logone floodplain in North Cameroon, the core activity of the Waza-Logone ICDP, has led to a 34% increase of sedentary fishermen and a multiple number of temporary fishermen. Whereas livestock pressure tripled, kob antelopes, a key floodplain species, have not increased, reducing their competitiveness. The virtual disappearance of wildlife in nearby Kalamaloué National Park (NP), due to advanced human encroachment forms, is therefore a bleak perspective for Waza NP. Examples from the Central African Republic (CAR), Galapagos, Nigeria and Zimbabwe also showed that in open-access systems, improvement in living standards (development) may stimulate immigration, jeopardizing the stability necessary in protected areas (conservation). Most ICDPs lack demographic monitoring, masking its possible immigration risk. To counter the immigration risk in Waza, a policy was formulated based on local stakeholder categorization and subsequent privileges, resulting in the voluntarily displacement of a village out of Waza NP. It is further recommended that ICDPs should be involved in regional land-use planning and discourage development activities that stimulate immigration.

Based on 1997–1998 field investigations in the Changjiang river mouth, rain sampling from the river's upper reaches to the mouth, historical data, and relevant literature, the various sources of Total Nitrogen (TN) and Dissolved Inorganic Nitrogen (DIN) in the Changjiang river catchment and N transport in the Changjiang river mouth were estimated. The export fluxes of various form of N were mainly controlled by the river runoff, and the export fluxes of NO₃-N, DIN and TN in 1998 (an especially heavy flood year) were 1438 10³ tonnes (t) yr⁻¹ or 795.1 kg km⁻² yr⁻¹, 1746 10³ t yr⁻¹ or 965.4 kg km⁻² yr⁻¹ and 2849 10³ t yr⁻¹ or 1575.3 kg km⁻² yr⁻¹, respectively. The TN and DIN in the Changjiang river came mainly from precipitation, agricultural nonpoint sources, N lost from fertilizer and soil, and point sources of industrial waste and residential sewage discharge, which were about 56.2% and 62.3%, 15.4% and 18.5%, 17.1% and 14.4%, respectively, of the N outflow at the Changjiang river mouth; maximum transport being in the middle reaches.

India has a very extensive coastline of about 7515 km, rich in diverse living resources. These resources continue to deteriorate with rampant harvesting or are altered for other uses such as aquaculture and fisheries. The present paper deals with degrading coastal habitats in northeastern India, and projects the intensity of the stress arising from the collection of tiger prawn seeds (Penaeus monodon) for aquacultural farms and molluskan shells for poultry feed and edible lime. Indiscriminate exploitation of these resources leads to a heavy reduction of the species concerned and other associated marine communities. The magnitude of such destruction has been quantified. The impacts of biodiversity loss and their after-effects on the ecobalance of this coastal system have become a matter of great concern to ecologists to maintain security and sustainability. The authors propose a public awareness program on themes relating to the importance of biodiversity for human livelihoods.