Climate Change and River Ecosystems: Protection and Adaptation Options

Rivers provide a special suite of goods and services valued highly by the public that are inextricably linked to their flow dynamics and the interaction of flow with the landscape. Yet most rivers are within watersheds that are stressed to some extent by human activities including development, dams, or extractive uses. Climate change will add to and magnify risks that are already present through its potential to alter rainfall, temperature, runoff patterns, and to disrupt biological communities and sever ecological linkages. We provide an overview of the predicted impacts based on published studies to date, discuss both reactive and proactive management responses, and outline six categories of management actions that will contribute substantially to the protection of valuable river assets. To be effective, management must be place-based focusing on local watershed scales that are most relevant to management scales. The first priority should be enhancing environmental monitoring of changes and river responses coupled with the development of local scenario-building exercises that take land use and water use into account. Protection of a greater number of rivers and riparian corridors is essential, as is conjunctive groundwater/surface water management. This will require collaborations among multiple partners in the respective river basins and wise land use planning to minimize additional development in watersheds with valued rivers. Ensuring environmental flows by purchasing or leasing water rights and/or altering reservoir release patterns will be needed for many rivers. Implementing restoration projects proactively can be used to protect existing resources so that expensive reactive restoration to repair damage associated with a changing climate is minimized. Special attention should be given to diversifying and replicating habitats of special importance and to monitoring populations at high risk or of special value so that management interventions can occur if the risks to habitats or species increase significantly over time.     

Life on the Edge: Vulnerability and Adaptation of African Ecosystems to Global Climate Change

Donor countriesare providing financial and technicalsupport for global climate change countrystudies to help African nations meet theirreporting needs under the United NationsFramework Convention on Climate Change(UNFCCC). Technical assistance to completevulnerability and adaptation assessmentsincludes training of analysts, sharing ofcontemporary tools (e.g. simulationmodels), data and assessment techniques,information-sharing workshops and aninternational exchange programme foranalysts. This chapter summarizes 14African country studies (Botswana, Côted'Ivoire, Egypt, Ethiopia, the Gambia,Kenya, Malawi, Mauritius, Nigeria, SouthAfrica, Tanzania, Uganda, Zambia andZimbabwe) assessing vulnerabilities toglobal climate change and identifyingadaptation options. The analysis revealedthat the participating African countriesare vulnerable to global climate change inmore than one of the followingsocio-economic sectors: coastal resources,agriculture, grasslands and livestock,water resources, forests, wildlife, andhuman health. This vulnerability isexacerbated by widespread poverty,recurrent droughts, inequitable landdistribution, environmental degradation,natural resource mismanagement anddependence on rain-fed agriculture. Arange of practical adaptation options wereidentified in key socio-economic sectors ofthe African nations analysed. However,underdeveloped human and institutionalcapacity, as well as the absence ofadequate infrastructure, renders manytraditional coping strategies (rooted inpolitical and economic stability)ineffective or insufficient. FutureAfrican country studies should be moreclosely coordinated with development ofnational climate change action plans     

Vulnerability of land systems to fire: Interactions among humans,climate, the atmosphere,and ecosystems

Fires are critical elements in the Earth System, linking climate, humans, and vegetation. With 200–500 Mha burnt annually, fire disturbs a greater area over a wider variety of biomes than any other natural disturbance. Fire ignition, propagation, and impacts depend on the interactions among climate, vegetation structure, and land use on local to regional scales. Therefore, fires and their effects on terrestrial ecosystems are highly sensitive to global change. Fires can cause dramatic changes in the structure and functioning of ecosystems. They have significant impacts on the atmosphere and biogeochemical cycles. By contributing significantly to greenhouse gas (e.g., with the release of 1.7–4.1 Pg of carbon per year) and aerosol emissions, and modifying surface properties, they affect not only vegetation but also climate. Fires also modify the provision of a variety of ecosystem services such as carbon sequestration, soil fertility, grazing value, biodiversity, and tourism, and can hence trigger land use change. Fires must therefore be included in global and regional assessments of vulnerability to global change. Fundamental understanding of vulnerability of land systems to fire is required to advise management and policy. Assessing regional vulnerabilities resulting from biophysical and human consequences of changed fire regimes under global change scenarios requires an integrated approach. Here we present a generic conceptual framework for such integrated, multidisciplinary studies. The framework is structured around three interacting (partially nested) subsystems whose contribute to vulnerability. The first subsystem describes the controls on fire regimes (exposure). A first feedback subsystem links fire regimes to atmospheric and climate dynamics within the Earth System (sensitivity), while the second feedback subsystem links changes in fire regimes to changes in the provision of ecological services and to their consequences for human systems (adaptability). We then briefly illustrate how the framework can be applied to two regional cases with contrasting ecological and human context: boreal forests of northern America and African savannahs.     

Effect of introducing prenatal diagnosis on the reproductive behaviour of families at risk for cystic fibrosis. A Cohort study

We studied 101 couples to determine how far their reproductive behaviour was affected by the diagnosis of cystic fibrosis (CF) on its first occurrence in the couple's progeny and by the availability of prenatal diagnosis (PD). The couples were all resident in the Veneto and Trentino regions and attending the Verona CF Centre. CF had been diagnosed in the first affected child, during the period 1 January 1980-1 July 1990, before the age of 1 year. Couples received a questionnaire regarding socio-demographic status, reproduction data, and awareness of PD. Reproductive history was divided into three phases: prior to diagnosis of CF in the first affected child; from this time until PD was made available; and after the couples had learned of PD. In phase 2 (awareness of the genetic risk but not of PD), 54 couples showed a marked decrease in reproduction, none of the few pregnancies that occurred being taken to term. When couples became aware of PD, some resumption of reproductive activity occurred and 11 per cent of the 101 couples had another child; PD was used in 65 per cent of pregnancies and the abortion rate decreased to 35 per cent. All couples who opted for PD had no children without CF.     

Mosaicism or pseudomosaicism: The problem of hypermodal cells in amniotic fluid cell culture

A series of 2029 consecutive amniotic fluid specimens studied for prenatal genetic diagnosis were reviewed and reassessed so as to evaluate the frequency and clinical significance of hypermodal cells in amniotic fluid cell cultures. Hypermodal cells were defined as those with more than 46 chromosomes, and were characterized by an additional structurally normal or structurally abnormal chromosome. Of 2029 specimens, 47 (2.31 per cent) contained a total of 167 hypermodal cells. True fetal mosaicism was detected in three cases (0.14 per cent). All had hypermodal cells in more than one culture flask or colony which contained the same aberrant chromosome complement. In all but one case the babies were normal when only one cell was hypermodal, or when several cells were hypermodal but present in only one colony or one culture vessel. One case had an extra No. 20 chromosome in one cell. Although the child had multiple anomalies, they were not characteristic of trisomy 20, and subsequent chromosomal study on the baby postnatally revealed a 46,XX karyotype. The in situ coverslip technique is recommended as the preferred method for prenatal diagnosis, and it is useful as an aid in differentiating true mosaicism from pseudomosaicism.     

Biogeochemistry of mercury in the Amazonian environment

In this paper, the processes that affect mercury (Hg) cycling in the Amazonian environment were reviewed, criticized and new directions of research are proposed. The discussion of the origin of the mercury contamination, whether natural or anthropogenic is marked by a lack of fundamented arguments from both sides. Undoubtedly mercury inputs from gold mining have locally increased environmental concentrations, but in the whole Amazon, these loads would be insignificant, considering the high concentrations observed by some authors in remote soils. A reasonable process that should explain these elevated concentrations in soil is that B horizons function as a mercury "sponge" that have been accumulating mercury over a geological time scale, releasing it back to cycling during erosion and forest fires. The environmental degradation of the Amazonian forest due to human activities is probably enhancing the release of that mercury to the cycle. Mercury transformations in reduced, anoxic environments--sediments and waters--are also a key problem for the understanding of the environmental methylation. The studies that have been carried out in the Amazonian environment are too restricted and results permit only circumstantial conclusions. Large efforts must be directed to monitoring programs considering time and space variability.     

Latitudinal and seasonal capacity of the surface oceans as a reservoir of polychlorinated biphenyls

The oceans play an important role as a global reservoir and ultimate sink of persistent organic pollutants (POPs) such as polychlorinated biphenyls congeners (PCBs). However, the physical and biogeochemical variables that affect the oceanic capacity to retain PCBs show an important spatial and temporal variability which have not been studied in detail, so far. The objective of this paper is to assess the seasonal and spatial variability of the ocean's maximum capacity to act as a reservoir of atmospherically transported and deposited PCBs. A level I fugacity model is used which incorporates the environmental variables of temperature, phytoplankton biomass, and mixed layer depth, as determined from remote sensing and from climatological datasets. It is shown that temperature, phytoplankton biomass and mixed layer depth influence the potential PCB reservoir of the oceans, being phytoplankton biomass specially important in the oceanic productive regions. The ocean's maximum capacities to hold PCBs are estimated. They are compared to a budget of PCBs in the surface oceans derived using a level III model that assumes steady state and which incorporates water column settling fluxes as a loss process. Results suggest that settling fluxes will keep the surface oceanic reservoir of PCBs well below its maximum capacity, especially for the more hydrophobic compounds. The strong seasonal and latitudinal variability of the surface ocean's storage capacity needs further research, because it plays an important role in the global biogeochemical cycles controlling the ultimate sink of PCBs. Because this modeling exercise incorporates variations in downward fluxes driven by phytoplankton and the extent of the water column mixing, it predicts more complex latitudinal variations in PCBs concentrations than those previously suggested.     

Biodegradability of wheat gluten based bioplastics

A large variety of wheat gluten based bioplastics, which were plasticized with glycerol, were subjected to biodegradation. The materials covered the total range available for the biochemical control parameter Fi, which expresses the percentage of aggregated proteins. This quantity can be related to the density of covalent crosslinks in the wheat gluten network, which are induced by technological treatments. The biodegradability tests were performed in liquid medium (modified Sturm test) and in farmland soil. All gluten materials were fully degraded after 36 days in aerobic fermentation and within 50 days in farmland soil. No significant differences were observed between the samples. The mineralization half-life time of 3.8 days in the modified Sturm test situated gluten materials among fast degrading polymers. The tests of microbial inhibition experiments revealed no toxic effects of the modified gluten or of its metabolites. Thus, the protein bulk of wheat gluten materials is non-toxic and fully biodegradable, whatever the technological process applied.     

Fungi and nematodes occurring in different composts used in Uruguayan agriculture

Forty three thermophilic, thermotolerant and mesophilic fungal species and nematodes from five trophic groups were found in four compost types. Aspergillus fumigatus and A. niger were the most frequent species. Plant pathogenic fungi viz. Fusarium oxysporum, F. acuminatum, F. nygamai and F. solani were found in some of the composts in low frequency. The most abundant species of nematode corresponded to bacterivores. Tylenchus, a phytophagous nematode was scarcely found.     

Help or disperse? Cooperation in termites influenced by food conditions

Ecological factors have been claimed paramount for the evolution and maintenance of cooperative group living in eusocial termites, as well as in cooperatively breeding birds and mammals. However, a clear demonstration of the role of any specific ecological factor in termites has been lacking. In the termite Cryptotermes secundus, individuals have two options, staying as helpers at the natal nest or developing into winged sexuals that disperse to found new colonies. An important ecological factor expected to influence the course of termite development is food availability; C. secundus nests inside a single piece of wood that serves as the sole source of food for the duration of the colony. As wood is consumed, the longevity of the colony is reduced, thus diminishing the potential fitness gains of staying at the nest. We experimentally investigated the occurrence of cooperative behavior and development under abundant- and limited-food conditions. Workers exposed to food-limited conditions were more likely to develop into dispersing sexuals and increased selfishly their food-acquisition behaviors. Proximately, a reduced frequency of proctodeal trophallaxis may have interfered with the distribution of pheromones that inhibit sexual development. Ultimately, decreased inclusive fitness benefits in food-limited, and thus short-lived nests, appear to explain the development of dispersing sexuals, supporting (1) the benefits-of-philopatry hypothesis as developed for the occurrence of cooperative breeding in vertebrates, and (2) predictions of reproductive skew theories.Communicated by L. Keller