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761.
Given that funds for biodiversity conservation are limited, there is a need to understand people's preferences for its different components. To date, such preferences have largely been measured in monetary terms. However, how people value biodiversity may differ from economic theory, and there is little consensus over whether monetary metrics are always appropriate or the degree to which other methods offer alternative and complementary perspectives on value. We used a choice experiment to compare monetary amounts recreational visitors to urban green spaces were willing to pay for biodiversity enhancement (increases in species richness for birds, plants, and aquatic macroinvertebrates) with self‐reported psychological gains in well‐being derived from visiting the same sites. Willingness‐to‐pay (WTP) estimates were significant and positive, and respondents reported high gains in well‐being across 3 axes derived from environmental psychology theories (reflection, attachment, continuity with past). The 2 metrics were broadly congruent. Participants with above‐median self‐reported well‐being scores were willing to pay significantly higher amounts for enhancing species richness than those with below‐median scores, regardless of taxon. The socio‐economic and demographic background of participants played little role in determining either their well‐being or the probability of choosing a paying option within the choice experiment. Site‐level environmental characteristics were only somewhat related to WTP, but showed strong associations with self‐reported well‐being. Both approaches are likely to reflect a combination of the environmental properties of a site and unobserved individual preference heterogeneity for the natural world. Our results suggest that either metric will deliver mutually consistent results in an assessment of environmental preferences, although which approach is preferable depends on why one wishes to measure values for the natural world. Preferencias de Cuantificación para el Mundo Natural Usando Estudios de Valor Monetario y No Monetario.  相似文献   
762.
The failure of fisheries management among multispecies coral reef fisheries is well documented and has dire implications for the 100 million people engaged in these small‐scale operations. Weak or missing management institutions, a lack of research capacity, and the complex nature of these ecosystems have heralded a call for ecosystem‐based management approaches. However, ecosystem‐based management of coral reef fisheries has proved challenging due to the multispecies nature of catches and the diversity of fish functional roles. We used data on fish communities collected from 233 individual sites in 9 western Indian Ocean countries to evaluate changes in the site's functional composition and associated life‐history characteristics along a large range of fish biomass. As biomass increased along this range, fish were larger and grew and matured more slowly while the abundance of scraping and predatory species increased. The greatest changes in functional composition occurred below relatively low standing stock biomass (<600 kg/ha); abundances of piscivores, apex predators, and scraping herbivores were low at very light levels of fishing. This suggests potential trade‐offs in ecosystem function and estimated yields for different management systems. Current fishing gear and area restrictions are not achieving conservation targets (proposed here as standing stock biomass of 1150 kg/ha) and result in losses of life history and ecological functions. Fish in reefs where destructive gears were restricted typically had very similar biomass and functions to young and low compliance closures. This indicates the potentially important role of fisheries restrictions in providing some gains in biomass and associated ecological functions when fully protected area enforcement potential is limited and likely to fail. Our results indicate that biomass alone can provide broad ecosystem‐based fisheries management targets that can be easily applied even where research capacity and information is limited. Of particular value, is our finding that current management tools may be used to reach key ecosystem‐based management targets, enabling ecosystem‐based management in many socioeconomic contexts.  相似文献   
763.
Geodiversity—the variability of Earth's surface materials, forms, and physical processes—is an integral part of nature and crucial for sustaining ecosystems and their services. It provides the substrates, landform mosaics, and dynamic physical processes for habitat development and maintenance. By determining the heterogeneity of the physical environment in conjunction with climate interactions, geodiversity has a crucial influence on biodiversity across a wide range of scales. From a literature review, we identified the diverse values of geodiversity; examined examples of the dependencies of biodiversity on geodiversity at a site‐specific scale (for geosites <1 km2 in area); and evaluated various human‐induced threats to geosites and geodiversity. We found that geosites are important to biodiversity because they often support rare or unique biota adapted to distinctive environmental conditions or create a diversity of microenvironments that enhance species richness. Conservation of geodiversity in the face of a range of threats is critical both for effective management of nature's stage and for its own particular values. This requires approaches to nature conservation that integrate climate, biodiversity, and geodiversity at all spatial scales.  相似文献   
764.
Oyster reefs form over extensive areas and the diversity and productivity of sheltered coasts depend on them. Due to the relatively recent population growth of coastal settlements in Australia, we were able to evaluate the collapse and extirpation of native oyster reefs (Ostrea angasi) over the course of a commercial fishery. We used historical records to quantify commercial catch of O. angasi in southern Australia from early colonization, around 1836, to some of the last recorded catches in 1944 and used our estimates of catch and effort to map their past distribution and assess oyster abundance over 180 years. Significant declines in catch and effort occurred from 1886 to 1946 and no native oyster reefs occur today, but historically oyster reefs extended across more than 1,500 km of coastline. That oyster reefs were characteristic of much of the coastline of South Australia from 1836 to 1910 appears not to be known because there is no contemporary consideration of their ecological and economic value. Based on the concept of a shifted baseline, we consider this contemporary state to reflect a collective, intergenerational amnesia. Our model of generational amnesia accounts for differences in intergenerational expectations of food, economic value, and ecosystem services of nearshore areas. An ecological system that once surrounded much of the coast and possibly the past presence of oyster reefs altogether may be forgotten and could not only undermine progress towards their recovery, but also reduce our expectations of these coastal ecosystems. La Pérdida de una Línea de Base Ecológica por Medio de la Erradicación de Arrecifes de Ostión de los Ecosistemas Costeros y la Memoria Humana  相似文献   
765.
Natural resource managers are often expected to achieve both environmental protection and economic development even when there are fundamental trade‐offs between these goals. Adaptive management provides a theoretical structure for program administrators to balance social priorities in the presence of trade‐offs and to improve conservation targeting. We used the case of Mexico's federal Payments for Hydrological Services program (PSAH) to illustrate the importance of adaptive management for improving program targeting. We documented adaptive elements of PSAH and corresponding changes in program eligibility and selection criteria. To evaluate whether these changes resulted in enrollment of lands of high environmental and social priority, we compared the environmental and social characteristics of the areas enrolled in the program with the characteristics of all forested areas in Mexico, all areas eligible for the program, and all areas submitted for application to the program. The program successfully enrolled areas of both high ecological and social priority, and over time, adaptive changes in the program's criteria for eligibility and selection led to increased enrollment of land scoring high on both dimensions. Three factors facilitated adaptive management in Mexico and are likely to be generally important for conservation managers: a supportive political environment, including financial backing and encouragement to experiment from the federal government; availability of relatively good social and environmental data; and active participation in the review process by stakeholders and outside evaluators. Mejorando los Objetivos Ambiental y Social Mediante el Manejo Adaptativo en el Programa de Pagos por Servicios Hidrológicos en México  相似文献   
766.
Most species face multiple anthropogenic disruptions. Few studies have quantified the cumulative influence of multiple threats on species of conservation concern, and far fewer have quantified the potential relative value of multiple conservation interventions in light of these threats. We linked spatial distribution and population viability models to explore conservation interventions under projected climate change, urbanization, and changes in fire regime on a long‐lived obligate seeding plant species sensitive to high fire frequencies, a dominant plant functional type in many fire‐prone ecosystems, including the biodiversity hotspots of Mediterranean‐type ecosystems. First, we investigated the relative risk of population decline for plant populations in landscapes with and without land protection under an existing habitat conservation plan. Second, we modeled the effectiveness of relocating both seedlings and seeds from a large patch with predicted declines in habitat area to 2 unoccupied recipient patches with increasing habitat area under 2 projected climate change scenarios. Finally, we modeled 8 fire return intervals (FRIs) approximating the outcomes of different management strategies that effectively control fire frequency. Invariably, long‐lived obligate seeding populations remained viable only when FRIs were maintained at or above a minimum level. Land conservation and seedling relocation efforts lessened the impact of climate change and land‐use change on obligate seeding populations to differing degrees depending on the climate change scenario, but neither of these efforts was as generally effective as frequent translocation of seeds. While none of the modeled strategies fully compensated for the effects of land‐use and climate change, an integrative approach managing multiple threats may diminish population declines for species in complex landscapes. Conservation plans designed to mitigate the impacts of a single threat are likely to fail if additional threats are ignored. Manejo de Incendios, Reubicación Administrada y Opciones de Conservación de Suelo para Plantas de Vida Larga con Sembrado Obligado bajo los Cambios Globales en el Clima, la Urbanización y el Régimen de Incendios  相似文献   
767.
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.  相似文献   
768.
农林复合生态系统氮素平衡及其评价   总被引:4,自引:0,他引:4  
农业生态系统中养分的平衡状况及其合理性评价,是探讨农业生产和环境变化的前提和基础。选择三峡库区上游川中丘陵区一典型农林复合生态系统,依据系统养分循环概念模型,进行了农田和林地定位监测、耕地和盆钵模拟试验以及参与式农户调查等,研究系统的氮素各收入支出参数,计算系统的氮素平衡并对平衡合理性进行评价。结果表明,本复合生态系统旱地和整个农田子系统氮素略有盈余,盈亏量分别为56.1 kg/hm2·a和42 kg/hm\2·a,实际盈亏率为10.4%和8.2%;而水稻田和复合系统有少量亏缺,盈亏量分别为-13.21 kg/hm2·a和-37.5 kg/hm2·a,实际盈亏率分别为为-3.2%和-7.8%;林地亏缺较大,盈亏量为-165.9 kg/hm2·a,实际盈亏率为-39.2%。模型计算的允许盈亏率(旱地23.4%,水稻田-37.2%)评价表明,旱地和水稻田目前的氮素平衡基本上是合理的。与1960s系统氮平衡比较,可以看到林地在减少水土流失、促进养分的合理循环方面发挥了重要作用,应受到充分的重视。  相似文献   
769.
本文以四川水土流失情况为例,着重分析论述了水土流失对农业生态系统的严重危害,从而阐明了水土保持对农牧业生产的重要性和紧迫性,并从省情出发,总结提出了当前乃至今后相当一个时期,农牧部门应积极采取的几项行之有效的防治对策措施,可供各级政府和领导决策参考。  相似文献   
770.
Sincetheinternationalgeophysicalyear(IGY,1957—1958),Antarcticahasbeentheobjectofintensivescientificinvestigationbyteamsofscientists...  相似文献   
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