The biodiversity challenge: Expanded hot-spots analysis

Summary This paper aims to throw light on the mass extinction that is overtaking Earth's species. Using an analytic methodology developed for an earlier partial assessment, it focuses on a series of hot-spot areas, these being areas that (a) feature exceptional concentrations of species with high levels of endemism, and (b) face exceptional threats of destruction. The paper identifies another eight such areas, four of them in tropical forests and four in Mediterranean-type zones. The analysis reveals that the four tropical-forest areas contain at least 2,835 endemic plant species in 18,700 km², or 1.1 percent of Earth's plant species in 0.013 percent of Earth's land surface; and that the four Mediterranean-type areas contain 12,720 endemic plan: species in 435,700 km², or 5.1 percent of Earth's plant species in 0.3 percent of the Earth's land surface. Taken together, these eight hot-spot areas contain 15,555 endemic plant species in 454,400 km², or 6.2 percent of Earth's plant species in 0.3 percent of Earth's land surface. This is to be compared with the earlier hot-spots analysis of 10 tropical-forest areas, with 34,400 endemic plant species in 292,000 km², or 13.8 percent of Earth's plant species in 0.2 percent of Earth's land surface.Taking all 18 hot-spot areas together, we find they support 49,955 endemic plant species, or 20 percent of Earth's plant species, in 746,400 km², or 0.5 percent of Earth's land surface. This means that one fifth of Earth's plant species are confined to half of one percent of the Earth's land surface — and they occur in habitats that are mostly threatened with imminent destruction.By concentrating on these hot-spot areas where needs are greatest and where the pay-off from safeguard measures would be greatest, conservationists can engage in a more systematised response to the challenge of large scale impending extinctions.Dr Norman Myers is a consultant in environment and development, a member of this journal's Advisory Board, and a regular contributor to the journal. He is a Senior Fellow of World Wildlife Fund — US. This paper enlarges on an important theme developed by Dr Myers in a contribution which appeared inThe Environmentalist,8(3), 187–208. The research for this paper has been supported by the MacArthur Foundation, Chicago, USA.     

Characteristics of Urban Natural Areas Influencing Winter Bird Use in Southern Ontario,Canada

Characteristics of urban natural areas and surrounding landscapes were identified that best explain winter bird use for 28 urban natural areas in southern Ontario, Canada. The research confirms for winter birds the importance of area (size) and natural vegetation, rather than managed, horticultural parkland, within urban natural areas as well as percent urban land use and natural habitat in surrounding landscapes. Alien bird density and percent ground feeding species increased with percent surrounding urban land use. Higher percent forest cover was associated with higher percentages of forest, bark feeding, small (<20 g) and insectivorous species. Natural area size (ha) was related to higher species richness, lower evenness and higher percentages of insectivorous, forest interior, area-sensitive, upper canopy, bark feeding, and non-resident species. Higher number of habitat types within natural areas and percent natural habitat in surrounding landscapes were also associated with higher species richness. Common, resident bird species dominated small areas (<6.5 ha), while less common non-residents increased with area, indicative of a nested distribution. Areas at least 6.5 ha and more generally >20 ha start to support some area-sensitive species. Areas similar to rural forests had >25% insectivores, >25% forest interior species, >25% small species, and <5% alien species. Indicator species separated urban natural areas from rural habitats and ordination placed urban natural areas along a gradient between urban development and undisturbed, rural forests. More attention is needed on issues of winter bird conservation in urban landscapes.     

A survey of trampling effects on vegetation and soil in eight tropical and subtropical sites

Impacts of recreation, especially of vehicles and walkers, were studied in eight tropical or subtropical public sites in Queensland. In each site, plant species number, vegetation cover, plant height, and species cover and frequency in untrampled, slightly trampled, moderately trampled, and heavily trampled areas were counted or measured. Soil penetration resistance and soil organic matter were also recorded. In two of these eight sites, plant cover, height, leaf length, leaf width, and leaf thickness of each species were measured. Some species of grass such asCynodon dactylon were present in areas subject to all degrees of trampling impact and some tussock species, particularlyEragrostis tenuifolia andSporobolus elongatus, were only present in trampled areas. Woody plants occurred only on untrampled areas. The number of species and all the vegetative measurements mentioned above were reduced as wear increased. Plant height was reduced dramatically by even light trampling. Tall plants appeared to be more sensitive to trampling than short plants. No clear relationship between soil organic matter content and trampling intensity was found.     

The moist tropical forest: Its conversion and protection

Summary Though strong concern over the rapid conversion of moist tropical forests may justifiably arise from any discipline, a growing interdisciplinary tide of voices is expressing its alarm over a particularly disturbing consequence of forest alteration and destruction: the reduction of species diversity through the extinction of numerous plant and animal species. Consequently, an array of ecologists land-use planners, botanists, zoologists and conservationsts are searching for means to enhance the protection and preservation of tropical forests' biotic diversity. Management schemes aimed at achieving this particular end are being investigated, particularly by UNESCO's Man and Biosphere (MAB) Project 8 of Biosphere Reserves Projects, by the International Union for the Conservation of Nature and Natural Resources (IUCN) tropical forests conservation program (UNEP, 1980) and by the World Wildlife Fund. In addition, many countries with a significant area of moist tropical forest (MTF) are beginning to pursue some form of conservation strategy. Currently Robert T. Perry is a full-time teacher of biology at a private school for a cademically gifted students in the Brooklyn area. In addition he has designed and is teaching courses in environmental chemistry and ethology to advanced high-schoolers. He is also an adjunct instructor for the City College of the City University of New York, where he is teaching graduate students in the Environmental Studies Programme. He graduated in Environmental Conservation from Cornell University, and has a Masters Degree in Environmental Biology from City University, New York.     

Impact assessment of a hydroelectric project on the flora in the Western Himalayan region based on vegetation analysis and socio-economic studies

This study provides an overview of the impacts of a proposed hydroelectric power project in the Western Himalayan region in India, using a primary database on floristic diversity and vegetation analysis. The remote sensing data revealed that in the submergence zone only mixed deciduous forest that occupies 807.5 ha area and has a wood biomass volume of 4,027,503 m³ is likely to be lost due to impoundment. A total of 165 plant species found in the submergence zone also occur in the influence and free draining catchment area of the project. In the influence zone of the project area only one tree species (Acer oblongum) is found under conservation threat category, which is also present in the free draining catchment of the project. The project affected population (6716 people) residing in the submergence and influence zone depend upon the surrounding forests for fuel wood, fodder, wild edibles etc., and most likely they will settle in the nearby areas, thus mounting more pressure on residual forests of the influence zone for various forest products. Further, from the vegetation analysis it is evident that several tree species (e.g. Lannea coromandelica, Terminalia alata, T. bellerica etc.), may face more pressure from exploitation as they provide a number of useful products and are represented in lower numbers in the forests of the project area. To compensate for the loss of various goods and services provided by the forests falling in the submergence zone and to offset the increased pressure of the project affected families on the forests of influence zone, a biodiversity management plan is suggested incorporating socio-economic considerations.     

Agricultural colonisation and floristic degradation in Nigeria's rainforest ecosystem

This paper attempts to characterise the common tree species that are now found in the tropical rainforest belt of Nigeria. The occurrence of species present in at least 10 percent of the quadrats studied were generated from field data. Simple correlation analyses were used to examine the strength of relationships among the species in the data sets. The results show that the nature and intensity of agricultural activities have influenced the types of floristic association found within different areas of the region. The ecological grouping of the species in the region shows distinct areas where regressive succession has led to floristic degradation of the rainforest belt.     

Comparison of Agroforests and Protected Forests in the East Usambara Mountains,Tanzania

Comparative studies on plant species richness, endemism, floristic composition, and structure between protected and unprotected forests are few in the Eastern Arc Mountains, one of the most biodiverse ecosystems in Africa. This study from one mountain range, the East Usambaras, examines floristic and structural tree data from 41–0.5 ha plots in four types of Eastern Arc forest: active agroforests, recently abandoned agroforests, mature secondary forest, and natural forest. Active agroforests had significantly lower tree species richness, endemic species richness, and stand density compared to natural and mature secondary forest. Recently abandoned agroforests contained a higher tree species richness, density, and tree height than active agroforests. Active and abandoned agroforests were dominated by an invasive tree, Maesopsis eminii. This tree species makes up a large percentage of the stems in active agroforests (26%), recently abandoned agroforests (32%), and in the canopy of mature secondary forests ∼ 30 years post logging (30%). Through time the increasing dominance of this non-native tree in active agroforests is a concern when considering the role of agroforests in a landscape scale conservation strategy.     

Protected Area Safeguard Tree and Shrub Communities from Degradation and Invasion: A Case Study in Eastern Madagascar

Despite their prevalence in both developed and developing countries, there have been surprisingly few field assessments of the ecological effectiveness of protected areas. This study aimed to assess the effectiveness of a key protected area in eastern Madagascar, Ranomafana National Park (RNP). We established paired 100 × 4-m vegetation transects (400 m²) within RNP and in remnant forests in the park’s peripheral zone. In each 400-m² plot, all woody stems >1.5 cm in diameter at breast height were measured and identified to species. All species were also identified as native or non-native. We identified utilitarian species within all transects and they were sorted into use category. We calculated plot-level taxonomic biodiversity and functional diversity of utilitarian species; the latter was calculated by clustering the multivariate distances between species based on their utilitarian traits, and all metrics were tested using paired t-tests. Our results showed that there was significantly higher biodiversity inside RNP than in remnant forests and this pattern was consistent across all diversity metrics examined. Forests not located within the park’s boundary had significantly higher non-native species than within RNP. There was no statistically significant difference in functional diversity of utilitarian species inside RNP vs. remnant forests; however, the overall trend was toward higher diversity inside park boundaries. These findings suggested that RNP has been effective at maintaining taxonomic diversity relative to surrounding unprotected areas and restricting the spread of non-native plants. The results also suggested that low functional redundancy of forests outside of RNP might be of concern, because residents in surrounding villages may have few other substitutes for the services provided by species that are of critical importance to their livelihoods. This study highlights the challenges of trying to reconcile biodiversity conservation with human use of natural resources in economically poor, remote areas.     

Importance of Riparian Forests in Urban Catchments Contingent on Sediment and Hydrologic Regimes

Forested riparian corridors are thought to minimize impacts of landscape disturbance on stream ecosystems; yet, the effectiveness of streamside forests in mitigating disturbance in urbanizing catchments is unknown. We expected that riparian forests would provide minimal benefits for fish assemblages in streams that are highly impaired by sediment or hydrologic alteration. We tested this hypothesis in 30 small streams along a gradient of urban disturbance (1–65% urban land cover). Species expected to be sensitive to disturbance (i.e., fluvial specialists and “sensitive” species that respond negatively to urbanization) were best predicted by models including percent forest cover in the riparian corridor and a principal components axis describing sediment disturbance. Only sites with coarse bed sediment and low bed mobility (vs. sites with high amounts of fine sediment) had increased richness and abundances of sensitive species with higher percent riparian forests, supporting our hypothesis that response to riparian forests is contingent on the sediment regime. Abundances of Etheostoma scotti, the federally threatened Cherokee darter, were best predicted by models with single variables representing stormflow (r² = 0.34) and sediment (r² = 0.23) conditions. Lentic-tolerant species richness and abundance responded only to a variable representing prolonged duration of low-flow conditions. For these species, hydrologic alteration overwhelmed any influence of riparian forests on stream biota. These results suggest that, at a minimum, catchment management strategies must simultaneously address hydrologic, sediment, and riparian disturbance in order to protect all aspects of fish assemblage integrity.     

Identifying priority areas for ecosystem service management in South African grasslands

Grasslands provide many ecosystem services required to support human well-being and are home to a diverse fauna and flora. Degradation of grasslands due to agriculture and other forms of land use threaten biodiversity and ecosystem services. Various efforts are underway around the world to stem these declines. The Grassland Programme in South Africa is one such initiative and is aimed at safeguarding both biodiversity and ecosystem services. As part of this developing programme, we identified spatial priority areas for ecosystem services, tested the effect of different target levels of ecosystem services used to identify priority areas, and evaluated whether biodiversity priority areas can be aligned with those for ecosystem services. We mapped five ecosystem services (below ground carbon storage, surface water supply, water flow regulation, soil accumulation and soil retention) and identified priority areas for individual ecosystem services and for all five services at the scale of quaternary catchments. Planning for individual ecosystem services showed that, depending on the ecosystem service of interest, between 4% and 13% of the grassland biome was required to conserve at least 40% of the soil and water services. Thirty-four percent of the biome was needed to conserve 40% of the carbon service in the grassland. Priority areas identified for five ecosystem services under three target levels (20%, 40%, 60% of the total amount) showed that between 17% and 56% of the grassland biome was needed to conserve these ecosystem services. There was moderate to high overlap between priority areas selected for ecosystem services and already-identified terrestrial and freshwater biodiversity priority areas. This level of overlap coupled with low irreplaceability values obtained when planning for individual ecosystem services makes it possible to combine biodiversity and ecosystem services in one plan using systematic conservation planning.     

Revisiting Evidence for Sustainability of Bushmeat Hunting in West Africa

Bushmeat hunting, a key source of dietary protein, has been implicated as a major extinction threat to tropical vertebrate species in West Africa. Ideally, any such hunting of wild species should be done sustainably, with off-take levels low enough to ensure viability of harvested species. Recent work purports to show that a mature bushmeat market in a major city in Ghana operates sustainably after depletion of vulnerable, slow-reproducing species (Cowlishaw and others 2005). I revisit two aspects of this work. First, I retest the prediction that larger species are transported to the market from greater distances, as expected if overexploitation depletes large species close to the city. Cowlishaw and others failed to find a significantly positive relationship between species-specific body mass and distance between capture site and the market. However, my reanalysis provides evidence for a positive relationship after all, consistent with unsustainable harvesting. In particular, ungulate species were harvested significantly farther from the market than smaller-bodied rodent species. Second, I caution that just because species “persist” in the marketplace in no way implies that they can withstand hunting pressure elsewhere and so should be of little concern to conservationists. I reveal that such species, despite their high intrinsic rates of population growth, are not robust elsewhere. Several of them have disappeared from a network of protected areas in Ghana (Brashares and others 2001). I show that faster-reproducing species are not necessarily more likely to persist in protected areas. The mere presence of fast-reproducing species in a mature bushmeat market should not be construed as generalizable robustness; criteria for ecological sustainability should ensure viability; and harvested species should be robust, not highly prone to extinction, in protected areas.     

Abundance of Jackfruit (<Emphasis Type="Italic">Artocarpus heterophyllus</Emphasis>) Affects Group Characteristics and Use of Space by Golden-Headed Lion Tamarins (<Emphasis Type="Italic">Leontopithecus chrysomelas</Emphasis>) in <Emphasis Type="Italic">Cabruca</Emphasis> Agroforest

Cabruca is an agroforest of cacao trees shaded by native forest trees. It is the predominant vegetation type throughout eastern part of the range of the golden-headed lion tamarins, Leontopithecus chrysomelas, an endangered primate endemic to Atlantic Forest. Understanding how lion tamarins use this agroforest is a conservation priority. To address this question, we documented the diet, home range size, group sizes and composition, density, number of litters and body condition of lion tamarins living in cabruca, and other habitats. Jackfruit, Artocarpus heterophyllus, was the most used species used by lion tamarins in cabruca and was widely available and used throughout the year. In cabruca, home range size was the smallest (22–28 ha) and density of lion tamarins was the highest (1.7 ind/ha) reported for the species. Group size averaged 7.4 individuals and was not significantly different among the vegetation types. In cabruca, groups produced one or two litters a year, and all litters were twins. Adult males in cabruca were significantly heavier than males in primary forest. Our study is the first to demonstrate that breeding groups of golden-headed lion tamarins can survive and reproduce entirely within cabruca agroforest. Jackfruit proved to be a keystone resource for lion tamarins in cabruca, and bromeliads were important as an animal prey foraging microhabitat. In cases where cabruca contains concentrated resources, such as jackfruit and bromeliads, lion tamarins may not only survive and reproduce but may fare better than in other forest types, at least for body condition and reproduction.     

Tree Structure and Diversity in Human-Impacted Littoral Forests, Madagascar

This research surveyed human-impacted littoral forests in southeastern Madagascar to determine (i) how forest structural features, indicative of human impact, are related to total, utilitarian, and endemic tree diversity; (ii) the distribution, abundance, and demographics of tree species groups (i.e., total, useful, endemic) across the landscape; and (iii) the amount of basal area available per human use category. We also use these data to consider issues of sustainable use and how human impact may influence littoral forest tree community composition across the landscape. Within 22 transects of 400 m² each, we recorded a total of 135 tree species and 2155 individuals. Seventy-nine species (58%) were utilitarian and 56 (42%) were nonutilitarian species. Of the 2155 individuals, 1827 (84%) trees were utilitarian species. We recorded 23 endemic species (17% of the total species) and 17 (74%) of these were utilitarian species. Basal area was significantly correlated with Shannon Weiner Index values for total (r = 0.64, P < 0.01), utilitarian (r = 0.58, P < 0.01), and endemic tree diversity (r = 0.85, P < 0.01). Basal area was significantly correlated with the Simpson’s index values for the endemic species (r = 0.74, P < 0.01). These correlations suggest that endemic tree species, of high global conservation value, may be the species group most influenced by changes in forest structure. Utilitarian species constituted 84% of the total basal area. The use category contributing the highest amount of basal area to the landscape was firewood. The results presented herein demonstrate that the landscape of southeastern Madagascar, commonly perceived as degraded, retains high value for both global conservation purposes and for local livelihoods. Thus, valuable opportunities may exist for developing conservation incentives that leverage both global and local conservation needs.     

Carbon management and biodiversity

International efforts to mitigate human-caused changes in the Earth's climate are considering a system of incentives (debits and credits) that would encourage specific changes in land use that can help to reduce the atmospheric concentration of carbon dioxide. The two primary land-based activities that would help to minimize atmospheric carbon dioxide are carbon storage in the terrestrial biosphere and the efficient substitution of biomass fuels and bio-based products for fossil fuels and energy-intensive products. These two activities have very different land requirements and different implications for the preservation of biodiversity and the maintenance of other ecosystem services. Carbon sequestration in living forests can be pursued on lands with low productivity, i.e. on lands that are least suitable for agriculture or intensive forestry, and are compatible with the preservation of biodiversity over large areas. In contrast, intensive harvest-and-use systems for biomass fuels and products generally need more productive land to be economically viable. Intensive harvest-and-use systems may compete with agriculture or they may shift intensive land uses onto the less productive lands that currently harbor most of the Earth's biodiversity. Win-win solutions for carbon dioxide control and biodiversity are possible, but careful evaluation and planning are needed to avoid practices that reduce biodiversity with little net decrease in atmospheric carbon dioxide. Planning is more complex on a politically subdivided Earth where issues of local interest, national sovereignty, and equity come into play.     

Tree seedling establishment in dry tropics: an urgent need of interaction studies

The current anthropogenic activities and climate change are increasingly becoming a growing global concern for dry tropical forests. Worldwide, these ecologically important forests have degraded considerably since the past few decades due to such factors. These factors have harmful consequences on the vegetation structure and diversity especially tree seedlings, which may further aggravate climate change. Generally, the vegetation recovery is very slow and unpredictable in the dry tropics due to complex interaction among tree seedling, site (particularly, soil) and climatic conditions. We inculcated that a better understanding of the behavior of individuals of different tree species at seedling stage in dry forests is of immense importance. It is increasingly being recognized for explaining and managing the future composition of plant communities under changing environmental conditions. In this regard, the multi-factorial interaction studies under various resource–disturbance combinations are needed in dry tropical ecosystems to understand the: (1) impact of relative variability in resources and disturbances on the responses of tree seedlings of native species and (2) how the later relates to distinct functional and life history traits of the individual tree species. Most importantly, such studies would improve our limited understanding of how variation (natural and man-made) in nutrient availability, under the influence of other local environmental factors (such as water, light, grass competition, herbivory, fire, allelopathy and enhanced CO₂ conditions), would affect the dynamics of dry tropical forest community. It may help in the proper management of these forests. Moreover, it may prove helpful in the current climate change scenario, as change in forest community dynamics may have consequences on soil C sequestration and CO₂ efflux at global scale.     

Implications of Land Use Changes on Carbon Dynamics and Sequestration—Evaluation from Forestry Datasets, India

Forests and soils are a major sink of carbon, and land use changes can affect the magnitude of above ground and below ground carbon stores and the net flux of carbon between the land and the atmosphere. Studies on methods for examining the future consequences of changes in patterns of land use change and carbon flux gains importance, as they provide different options for CO₂ mitigation strategies. In this study, a simulation approach combining Markov chain processes and carbon pools for forests and soils has been implemented to study the carbon flows over a period of time. Markov chains have been computed by converting the land use change and forestry data of India from 1997 to 1999 into a matrix of conditional probabilities reflecting the changes from one class at time t to another class time t+1. Results from Markov modeling suggested Indian forests as a potential sink for 0.94 Gt carbon, with an increase in dense forest area of about 75.93 Mha and decrease of about 3.4 Mha and 5.0 Mha in open and scrub forests, if similar land use changes that occurred during 1997–1999 would continue. The limiting probabilities suggested 34.27 percent as dense forest, 6.90 as open forest, 0.4 percent mangrove forest, 0.1 percent scrub and 58 percent as non-forest area. Although Indian forests are found to be a potential carbon sink, analysis of results from transition probabilities for different years till 2050 suggests that, the forests will continue to be a source of about 20.59 MtC to the atmosphere. The implications of these results in the context of increasing anthropogenic pressure on open and scrub forests and their contribution to carbon source from land use change and forestry sector are discussed. Some of the mitigation aspects to reduce greenhouse gas emissions from land use change and forestry sector in India are also reviewed in the study.     

Plant Diversity in Live Fences and Pastures,Two Examples from the Mexican Humid Tropics

This study analyzes the potential uses of live fences and pastures as reservoirs of plant diversity for two regions with different management histories, Los Tuxtlas (LT) and Uxpanapa (UX), Veracruz, México. We studied two habitats, live fences and pastures, analyzed their species richness, diversity, structure and plant composition and classified species according to plant regeneration modes (light-demanding and shade tolerant), seed dispersal syndrome and their local uses. We recorded 62 species of trees at LT and 48 at UX. Live fences were more diverse than pastures in both regions. The LT site showed to analyze the relationship a higher diversity of plants in regeneration stages than the one at UX. However, UX had higher diversity of adult plants in the pastures than LT. Composition and structure of live fences were different between regions, as well as within live fences and pastures, 53 % of species were light-demanding and 40 % were shade tolerant; 70 % of the species were dispersed by birds. Differences between sites are associated with the modifications in live fences structure, which changed according to managerial practices and the use of local species; this may influence plant regeneration modes as well as the visits of avian dispersal agents. In LT, all species found in live fences were useful to humans, whereas in UX, less than half were used by the local population. Our results underline the importance of live fences and isolated trees in pasture habitats as potential sites to host native and useful species from tropical rain forests in livestock landscapes.     

Pleas,plights and environment: Part I

Summary The depletion of the world's natural resources continues relentlessly. Plants and animals alike are being trapped into ever more numerous shrinking pockets, as man advances to incorporate virgin estates into areas of productivity. The immediate consequence of such an all-out attack in the tropical areas of under-developed countries is the destruction of habitats and the likely break-up of food webs. The attendant disastrous effects on the reproduction of species, hence, puts natural selection at a premium. This scenario has distinctly impressed different people in different places. This suggests diverse sensitivity even for causes voiced in public as matters of sheer truism. The study concentrates on the examination of the dialectic nature/nurture controversy to see whether this may account for the state of disharmony recorded between man and nature. Conversion of nature is traditionally considered a realm of the scientific establishment. The study tries to suggest that the humanities cannot be left out in any debate on the interpretation of the environment. The synthesis reveals a blatant refusal of social determinism as causal agent and, with some reservation, projects biological determinism into sharp focus for pertinent consideration. The cautious reconciliation with parts of sociobiological tenets was regarded as inevitable once grasped that will, knowledge, and sensitivity, were interpreted as the foundation of the main teleological argument.Dr Antonio Allem is trained as a plant taxonomist. His research has focused on the collection of plant genetic resources germ plasm. He has recently written (with J.F.M. Valls) a book entitledRecursos Forrageiros Nativos do Pantanal Mato-Grossense, published by the Departamento de Difusão de Tecnologia, EMBRAPA, Brasilia. He has an interest in the taxonomy of cultivated plants and has recently solved the origin of the cassava plant (Manihot esculenta, Euphorbiaceae). Dr Allem is a member of staff of thein situ conservation unit at Centro Nacional de Recursos Genéticos e Biotecnologia da Empresa Brasileira de Pesquisa Agropecuária.     

西藏农村能源消费及环境影响研究

西藏农村人口现有220多万,占全区总人口80％以上,农村经济落后,城乡差距很大。西藏农村能源资源主要有水力、地热、太阳能、风力、林木和畜粪等,煤炭、石油、天然气等高热值的优质能源很少。在这种经济发展水平及能源资源基础条件下,农村能源消费中高热值的现代能源比重很低,主要以生物质能如薪柴、牛粪、草皮等为主。这种低水平的能源消费结构已经对西藏脆弱的生态环境造成了巨大的破坏,西藏未来的能源发展战略迫切需要改变农村目前的消费结构,应发展太阳能、风能、农村小水电及输入高热值的化石能源替代目前生物质能的消费,减少因能源消费对西藏生态环境的破坏。     

Effects of Management on Understory Diversity in the Forest Ecosystems of Northern Spain

Pine plantations are an alternative to marginal agriculture in many countries, and are often presented as an option that improves biodiversity. However, these plantations can have adverse environmental effects if improperly managed. To evaluate the effect of forest management practices on biodiversity, the diversity, species richness, dominance and frequency of understory woody plant species in different forests of the Basque Country (northern Spain) were compared. Plantations of exotic conifers (Pinus radiata [D.] Don) of different ages were compared with deciduous forests of Quercus robur L. and Fagus sylvatica L. The effects of different types and intensities of management were taken into account. The differences observed were mainly conditioned by the intensity of forestry management, although the response varied according to forest type and age. In unmanaged pine plantations, the diversity and species richness of the understory increased rapidly after planting (while dominance decreased), remained stable in the intermediate age range, and reached a maximum in plantations more than 25 years of age. Management practices resulted in decreased understory diversity and species richness, as well as greater dominance. This was more pronounced in younger than in older stands. Moderate management, however, favored a greater diversity of the understory in deciduous forests. The species composition of the plantations and deciduous forests were different, the latter having a wider range of characteristic species. Knowledge of how forestry practices influence biodiversity (in terms of diversity, richness, dominance, and species composition) may allow predictions to be made about the diversity achievable with different management systems.