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961.
Surface sediments of the lagoons of Lomé, Togo, were analyzed for mercury, methylmercury, and trace elements. Concentrations
were greater than typical for natural lagoon sediments, and with greater variability within the Eastern lagoon compared to
the Western one. The Eastern lagoon is larger and has been dredged in the past, while the Western lagoon, which also receives
major waste inputs, has not been dredged and shows less tidal flushing. Accordingly, one naturally believes that the Eastern
lagoon is cleaner and probably safe to use due to its natural resources, including fishes to eat. Unexpectedly, we describe
here that mercury methylation was greater in the Eastern lagoon, indicating increased bioavailability of mercury, as probably
facilitated by past dredging that decreased solid-phase retention of inorganic mercury. Urbanization has historically been
more developed in the southern part of the lagoons, which is still reflected in contamination levels of sediment despite dredging,
probably because sources of contamination are still more important there today. Such urban contamination emphasizes the need
to regulate waste discharges and possible airborne contamination in growing cities of developing countries, and implements
environmental and public health monitoring, especially in relation to misbelieves systematically associated with the cleansing
effect of dredging activity. 相似文献
962.
963.
This study projected responses of forest net primary productivity (NPP) to three climate change scenarios at a resolution
of 5 km × 5 km across the state of Louisiana, USA. In addition, we assessed uncertainties associated with the NPP projection
at the grid and state levels. Climate data of the scenarios were derived from Community Climate System Model outputs. Changes
in annual NPP between 2000 and 2050 were projected with the forest ecosystem model PnET-II. Results showed that forest productivity
would increase under climate change scenarios A1B and A2, but with scenario B1, it would peak during 2011–2020 and then decline.
The projected average NPP under B1 over the years from 2000 to 2050 was significantly different from those under A1B and A2.
Forest NPP appeared to be primarily a function of temperature, not precipitation. Uncertainties of the NPP projection were
due to large spatial resolution of the climate variables. Overall, this study suggested that in order to project effects of
climate change on forest ecosystem at regional level, modeling uncertainties could be reduced by increasing the spatial resolution
of the climate projections. 相似文献
964.
The aim was to describe spatiotemporal patterns of colonization of spruce branches by algae and lichens and the relationship
with decreasing deposition of N and S. Coverage was estimated annually over 10 years for four Swedish Integrated Monitoring
catchments with varying deposition levels. Initial hypotheses were that algal coverage would be positively correlated with
deposition and that lichen coverage would be negatively correlated with S and positively with N deposition. Data were analyzed
using regression, ANOVA, and partial least square regression. The results showed a temporal decrease in the coverage of algae
but an increase in colonization rates, while lichens showed less uniform patterns. Within catchments, algae and lichen coverages
were positively correlated with mainly S deposition. Across catchments, coverage of algae increased, while the coverage of
lichens decreased with increasing N and S deposition. Colonization rates of both algae and lichens showed weak correlations
with both spatial and temporal trends in N and S deposition. Thus, while N and S deposition had an effect on the colonization
and coverage of algae and lichens, other factors are also important. 相似文献
965.
Land use conflicts are becoming increasingly apparent from local to global scales. Surface gold mining is an extreme source
of such a conflict, but mining impacts on local livelihoods often remain unclear. Our goal here was to assess land cover change
due to gold surface mining in Western Ghana, one of the world’s leading gold mining regions, and to study how these changes
affected land use systems. We used Landsat satellite images from 1986–2002 to map land cover change and field interviews with
farmers to understand the livelihood implications of mining-related land cover change. Our results showed that surface mining
resulted in deforestation (58%), a substantial loss of farmland (45%) within mining concessions, and widespread spill-over
effects as relocated farmers expand farmland into forests. This points to rapidly eroding livelihood foundations, suggesting
that the environmental and social costs of Ghana’s gold boom may be much higher than previously thought. 相似文献
966.
Globally, urban growth will add 1.5 billion people to cities by 2030, making the difficult task of urban water provisions
even more challenging. In this article, we develop a conceptual framework of urban water provision as composed of three axes:
water availability, water quality, and water delivery. For each axis, we calculate quantitative proxy measures for all cities
with more than 50,000 residents, and then briefly discuss the strategies cities are using in response if they are deficient
on one of the axes. We show that 523 million people are in cities where water availability may be an issue, 890 million people
are in cities where water quality may be an issue, and 1.3 billion people are in cities where water delivery may be an issue.
Tapping into groundwater is a widespread response, regardless of the management challenge, with many cities unsustainably
using this resource. The strategies used by cities deficient on the water delivery axis are different than for cities deficient
on the water quantity or water quality axis, as lack of financial resources pushes cities toward a different and potentially
less effective set of strategies. 相似文献
967.
Supply of international environmental public goods must meet certain conditions to be socially efficient, and several reasons
explain why they are currently undersupplied. Diagnosis of the public goods failure associated with particular ecosystem services
is critical to the development of the appropriate international response. There are two categories of international environmental
public goods that are most likely to be undersupplied. One has an additive supply technology and the other has a weakest link
supply technology. The degree to which the collective response should be targeted depends on the importance of supply from
any one country. In principle, the solution for the undersupply lies in payments designed to compensate local providers for
the additional costs they incur in meeting global demand. Targeted support may take the form of direct investment in supply
(the Global Environment Facility model) or of payments for the benefits of supply (the Payments for Ecosystem Services model). 相似文献
968.
Rundqvist S Hedenås H Sandström A Emanuelsson U Eriksson H Jonasson C Callaghan TV 《Ambio》2011,40(6):683-692
Shrubs and trees are expected to expand in the sub-Arctic due to global warming. Our study was conducted in Abisko, sub-arctic
Sweden. We recorded the change in coverage of shrub and tree species over a 32– to 34-year period, in three 50 × 50 m plots;
in the alpine-tree-line ecotone. The cover of shrubs and trees (<3.5 cm diameter at breast height) were estimated during 2009–2010
and compared with historical documentation from 1976 to 1977. Similarly, all tree stems (≥3.5 cm) were noted and positions
determined. There has been a substantial increase of cover of shrubs and trees, particularly dwarf birch (Betula nana), and mountain birch (Betula pubescens ssp. czerepanovii), and an establishment of aspen (Populus tremula). The other species willows (Salix spp.), juniper (Juniperus communis), and rowan (Sorbus aucuparia) revealed inconsistent changes among the plots. Although this study was unable to identify the causes for the change in shrubs
and small trees, they are consistent with anticipated changes due to climate change and reduced herbivory. 相似文献
969.
This study was conducted in the Swedish sub-Arctic, near Abisko, in order to assess the direction and scale of possible vegetation
changes in the alpine–birch forest ecotone. We have re-surveyed shrub, tree and vegetation data at 549 plots grouped into
61 clusters. The plots were originally surveyed in 1997 and re-surveyed in 2010. Our study is unique for the area as we have
quantitatively estimated a 19% increase in tree biomass mainly within the existing birch forest. We also found significant
increases in the cover of two vegetation types—“birch forest-heath with mosses” and “meadow with low herbs”, while the cover
of snowbed vegetation decreased significantly. The vegetation changes might be caused by climate, herbivory and past human
impact but irrespective of the causes, the observed transition of the vegetation will have substantial effects on the mountain
ecosystems. 相似文献
970.